پسماند و مدیریت پسماند--Waste and waste management

Waste and waste management

Solid waste are just raw materials, we are too stupid to use. (Arthur C.Clark)

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Introduction:

The law of conservation of matter:

When a physical or chemical change occurs, no atoms are created or destroyed. All we can do is rearranging the elements and compounds in different spatial patterns (physical changes) or combinations (chemical changes). There is no “away” as in “throw away.” Everything we think we have thrown away remains here with us in some forms. We just can recycle or reuse some materials and chemicals but some quantities of wastes still remain a problem.

In nature essentially no waste because the wastes from one organism become nutrients for others.

Humans produce huge amounts of waste that pollute environment è but this amount can be drastically reduced.

There are 2 types of wastes:

1)      Pre-consumer(internal) waste: generated in a manufacturing process. 3/4  of wastes. 

2)      Post consumer(external) waste: generated by consumers. 1/4 of wastes.

Waste stream in US è 76% mining, 13% agriculture, 9.5% industry , 1.5% MSW

Waste management is the collection, transport, processing, recycling or disposal, and monitoring of waste materials which involve solid, liquid, gaseous or radioactive substances.

Mexico city, the largest city in the world generates some 10,000 tons of trash each day.

The cost of disposing a ton of solid waste in Philadelphia went from $20 in 1980 to more than $100 in 1990.

US now spends about %10 billion per year to dispose of trash and a decade from now it may cost them $100 billion per year to dispose of trash and garbage.

Suitable places for dispose are becoming scarce in many areas and citizens have become more concerned and vocal about health hazards as well as aesthetics.

MWS in US è paper & cardboard(37%), yard waste(12%), food waste(11%), plastics(11%) and metals(8%) è more than 180 million metric tons per year which equals to 2/3 of a ton per capita!

Each day the average American produces over 2 kilograms of MSW è  3/4 of it dumped in landfills or incinerated è  That is about twice the amount of solid waste per person in other industrialized countries such as Japan or Germany and 5 to 10 times that amount in most developing countries.

IWM (Integrated Waste Management) è First priority: primary pollution and waste prevention (produce less or waste minimization). Second: secondary pollution prevention (convert as much if it’s possible to less hazardous substances). third: waste management(put the rest in long term, safe storage).

4Rs approach to waste minimization: è Refuse, Reduce, Reuse, and Recycle.

 

1) Redesign manufacturing process & products to use les material & energy as well as produce less waste and pollution.  For example the weight of a typical car has been reduced by about 1/4  since the 1960s. By using lighter steel along with light weight plastics and composite materials. Soft drinks also contain 1/3 less aluminum today. 

2) Develop products that are easy to repair, reuse, remanufacture , compost or recycle and encourage reusing of second-hand products, and avoiding disposable products (such as disposable cutlery).

3) Eliminate or reduce unnecessary packaging or designing products to be refillable or reusable (such as cotton instead of plastic shopping bags) è Canada has set a goal of using these priorities to cut excess packaging in half.

4) Using Pay-As-You-Throw (PAUT) or Fee-per-bag waste collection systems but provision of free pick-up of recyclable and reusable items. By using this approach, the proportion of households recycling went from 21% to 85% è about $ 1 million per year revenue because of increased sales of recycled materials to industries. 

 

In fact, waste reduction priority have not been followed by most countries and most efforts are devoted to waste management (bury it or burn it).

Waste disposal methods è open dumps/ocean dumping, exporting wastes, Incineration and energy recovery, recycle and reuse, compost.

 

Open Dumps

Fields and holes in the ground which sometimes covered with soil. MSW in developed countries usually buried in landfills or burned in incinerators but in developing countries end up in open dumps.

Every year some 25,000 metric tons of packaging, including half a million bottles, cans, and plastic containers are dumped at sea.

Sanitary Landfill

Ø  Sanitary landfill is a waste disposal site on land in which wastes spread out in thin layers, compacted and covered daily with fresh layer of clay or plastic foam which keep them dry, lessen risk of fire, decrease odor, reduce accessibility to vermin.

According to EPA è All landfills eventually leak.

Advantages of sanitary Landfill: no open burning, little odor, low operating cost, can handle large amounts of wastes.

Disadvantages of sanitary landfill: dust, groundwater pollution, greenhouse gas emissions, slow decomposition if wastes.

Landfill percentage of MSW è in US(55%), Canada(80%), Japan(15%), Switzerland(12%)

 

Recycle and Reuse

 

Recycling is collecting and reprocessing a resource so that it can be made into new products.

Primary or closed loop recycling è material are recycled into new products of the same type.

Ø  Secondary recycling è materials are converted into different products. For example used tires can be shredded and turned into rubberized road surfacing ; Newspapers can be processed into cellulose insulation. Recycling fly ash produced by coal-burning power plants into bricks that cost at least 20% less than conventional bricks.

Advantages of recycling: reduce air and waste pollution, save energy, reduce mineral demand, decrease green house emissions, reduce solid waste production and disposal.

 Disadvantages of recycling: can cost more than burying in areas with ample landfills, reduce profits for landfills and incinerator owners, source separation may be inconvenient for some people.

By 2015, EU will require that 95% of any discarded must be reused or recycled in industry.

By 2020, EU must recycle 50% of its MSW and ban recyclable wastes from landfills.

Refillable glass beverage bottles & refillables soft drink bottles made of polyethylene terephthalate(PET) plastics è make 15 round-trips before become too damaged to reuse è save energy, reduce pollution, and wastes and stimulate local economies.

Parts of Canada & 11 US states have bottle laws that place a small deposit fee on all beverage containers.

In Finland 95% of the soft drink, beer, wine and spirits containers are refilled.

Ø  Cloth bags can be used instead of paper & plastic bags to carry groceries & other items. To encourage people to bring reusable bags, stores in Netherland & Ireland charge for plastic shopping bags.

Japan probably has the most successful recycling program in the world. Half of all household and commercial wastes in Japan are recycled while the rest is equally incinerated and landfilled.

Japanese families separate wastes into as many as seven categories each picked up on a different day.

Recycling 1 ton of aluminum saves 4 tons of bauxite (aluminum ore) and 700 kg of petroleum coke and pitch, as well as keeping 35 kg of aluminum fluoride out of air.

Large beverage industries have used their political & financial clout to keep most US states from passing bottle laws è arguing they lead to loss of jobs, and higher beverage costs for consumers.  

Households & workplaces produce 5 major types of materials that can be recycled: paper, aluminum, steel, and some plastics.

About 424,000 trees would be saved if every US household replaced just one roll of virgin fiber toilet paper(500 sheets) with a 100% recycled one!

Switzerland & Japan recycle about 50% of their MSW but US recycles about 24% of its MSW è with education and proper incentives may reach to 60-70%.

 

Incinerators

In US, more than 110 waste incinerators burn 45,000 tons of garbage daily.

A typical municipal incinerator costs between $100 million and $300 million.

EPA has found alarmingly high levels of dioxins, furans, lead, and cadmium in incinerator ash which is more concentrated in fly ash. Pollutants from incinerators include particulates, CO, and toxic metals such as mercury.

Globally, MSW is burned in more than 600 large waste to energy incinerators, which reduce the volume of solid wastes by 90%.

Advantages of incineration: reduce trash volume, less need for landfills, less water pollution, concentrate hazardous substances to ash, sale of energy.

Disadvantages of incineration: expensive to build, cost more than short distance landfill, difficult to site, air pollution and CO2 emission, encourage waste production.

 MRF(Material Recovery Facilities) è receives mixed urban wastes and in these facilities workers or machines separate the mixed wastes; Remains in this process like paper, plastic and other combustibles are burned; There are about 480 MRFs in US.

Composting

Decomposing organic waste, such as food scraps and yard trimmings, with microorganisms (mainly bacteria and fungi) to produce compost.  Compost is organic material that can be used as a soil amendment, soil conditioner or fertalizer as a medium to grow plants.

Hazardous or toxic wastes

Any discarded material, liquid or solid that contain substances known to be (1) fatal, (2) toxic, carcinogenic, mutagenic or teratogenic to humans or other life-forms, (3) explosive or corrosive. 

For example: industrial solvents, hospital medical wastes, car batteries, household pesticides, dry-cell batteries, and incinerator ash.

UN è developed countries produced 80-90% of world’s hazardous wastes.

World’s 10 most polluted places è Russia(3 places), China, India, Ukraine, Peru, Dominican Republic, and Zambia.

According to EPA, industries in US generate about 265 million tons of officially classified hazardous wastes each year, slightly more than 1 ton for each person in the country. And also 40 million tons of hazardous wastes which are not regulated by EPA. 

Exporting waste or garbage imperialism?

Ø  In 1988, the Greenpeace organization identified more than fifty plans to send wastes from US and EU to Africa, Latin America and the Middle East. 

It commonly cost $1,000 per barrel to dispose of toxic waste in US, but some African countries will take that barrel for $50.

Basel Convention: bans developed countries that participate in treaty from shipping hazardous waste(including E-waste) to or through other countries without permission. By 2007, this agreement ratified by 152 countries but not the US.

In 2000, Swedish parliament enacted a law that by 2020 will ban all chemicals that are persistent and can accumulate in living tissue è this law also requires industry to perform risk assessment on the chemicals they use to show that those chemicals are safe to use è chemicals assumed to be guilty until proven innocent.

 

New Advancements:

Comparison of aerobic and anaerobic degradation of municipal solid waste in bioreactor landfills

Two laboratory scale PVC reactors were constructed in a thermo-insulated room kept at a constant mesophilic temperature of 32 °C. Each reactor had a diameter of 0.35 m and a length of 1 m (about 96 L). These two landfill bioreactors were operated under aerobic and anaerobic conditions in a thermo-insulated room

Reactors were filled with 19.5 kg of shredded synthetic solid waste and operated by using leachate recirculation. Aerobic conditions maintained by using an air compressor.

 

Results:

The results of experiments indicated that aerobic reactor had higher organic, nitrogen, phosphorus and alkali metal removal efficiencies than the anaerobic one.

Stabilization time considerably decreased when using aerobic processes with leachate recirculation compared to the anaerobic system with the same recirculation scheme.

The anaerobic bioreactor landfill shows the highest levels of all parameters of pollution, with high concentrations of COD, TOC, BOD, ammonia, phosphorus and alkali metals in leachate.

The aerobic reactor was more effective in terms of COD reduction and waste stabilization. While aerobic reactor was completed within 374 days, anaerobic reactor was operated for 630 days.

Aeration of the waste mass produce a rapid oxidation of organics and nitrogen when compared to the anaerobic bioreactor landfill. More than 90% of COD was decomposed within 70 days in the aerobic bioreactor compared to 462 days in the anaerobic bioreactor.

Ø  The waste(TOC) settlement in the aerobic reactors occurred faster than the waste settlement in the anaerobic reactors.

 

Municipal solid waste incinerator residue recycling by

thermal processes

 

Ø  MSW generated annually in Japan is approximately 50 million tons and 75% of this MSW is incinerated, producing approximately 6 million tons of residue which is then landfilled, with leachate control.

Ø  One of the following four treatment methods must be applied to the generated by ash: (1) melting and solidification, (2) solidification with cement, (3) stabilization using chemical agents or (4) extraction using acid or other solvents.

The melting operation works by keeping the temperature at approximately 1400°C in a high-temperature furnace. After the residues' physical and chemical state changes, the mass and volume of the residues is greatly reduced, producing a high-density melted product.

Inorganic compounds like metallic elements, especially in fly ash, are redistributed after the melting treatment according to the boiling temperature.

The 1st stage of the melting process adopts promotive evaporation in the furnace, chloridizing and vaporizing heavy metals by chloride in fly ash, cooling the exhaust gas, and collecting the condensate dust by using a bag filter.

In the 2nd stage of wet treatment, dust is mixed with acid solution, transferring Zn, Cu into a liquid state by separating non-soluble Pb compounds by filter.

Slag produced from the melting of MSW residues can be used as fill for road surfaces, as a component in asphalt mixtures, in concrete structures and in secondary products (e.g. interlocking blocks, tiles, and bricks).

Recycling of incineration ash in thermal process and using ash in concrete production

Recycling of incineration ash in thermal process and using ash in concrete production Pouya Aghaseyedabolghasem December, 2009 ……………………………………………………………………………………… Abstract There is a growing trend in waste production in the world. This trend in EU countries with high share of incineration in waste management has lead to the problem of ash production. Although ash landfilling is an accepted way but it leads to heavy metal leakage after years. Two technologies, recycling of incineration ash and using ash in concrete production, proposed for dealing with this problem. In order to distinguish the market and promoting it in EU countries we need to define the most important factors that govern the process of diffusion. Also we need to know about current market share and state of diffusion of these innovations. All these attitudes and factors that govern the market are under direct and indirect influence of the system of innovation which consists of various components in different aspects and an active interaction among them.   …………………………………………………………………………………… 1.      Background Regulations on waste elimination make waste management a significant problem for the public authorities today. In France, for example, the law of July 13, 1992, forbids the discharge of municipal solid waste (MSW) in tips as from July 01, 2002. These lines of regulations are getting stricter day by day around the world especially in industrialized countries with strict criteria and public awareness. Among replacement solutions is incineration, which currently treats 35% of MSW in France and more and less same figure in more industrialized EU countries.   The main problem with incineration is that it produces waste in its turn, although in smaller quantities. The bottom ashes are reused, mostly as material for roads, but the fly ashes are considered as final residues for which the only lawful destination is the landfill (Mackenzie, 2002; Miller, 2008; Saigo, 1999). But landfill is not safe destination for incineration ash with considerable amount of heavy metals. According to EPA, all landfill eventually leak and this make ash landfilling a public health concern in EU countries with considerable and ever growing ash production (Tchobanoglous, 2002).   We propose two alternative technologies to dealing with incineration ash. First technology is recycling of incineration ash by a thermal process and heavy metal recovery and second is using treated incineration ash in concrete production instead of sand.     2.      Aim   The prime aim of our study is defining the most important factors that govern the process of diffusion of two mentioned technologies about incineration ash and consequently improving and facilitating this process of adoption for achieving a bigger market share in short and long term. To achieve this goal we define the market as municipalities and their partners in EU countries as units of adoption.     Also we try to define the types of innovations to pinpoint them in the market and to be able to focus on different aspects which affect their adoption. One other important aim in our study is defining the current market share and state of diffusion of incineration ash technologies which is closely related to identifying the system of innovation. There are five stages in innovation decision process (Rogers, 1995) which should be defined to understand the process of diffusion in our products.   3.      Methods   In order to understand the potentials of innovations in market we need to classify them. There are three different types of innovations with specific effect on the market and the system of innovation (Garcia, 2002). On the other hand, it is proposed that there are some internal characteristics in each innovation which affect the rate of adoption (Rogers, 1995). There is also a difference in characteristics of different units of adoption in terms of the time needed for adoption (Rogers, 1995) which in turn contribute to rate of adoption and market share.   Defining the rate of diffusion is also of great importance because innovations follow the same pattern and tend to pass same steps and there is a robust attributes of technological change (Grubler, 1998). There are six stages in life cycle of a technology: invention, innovation, niche market commercialization, pervasive diffusion, saturation and senescence that are different in terms of mechanisms, cost, commercial market share and learning rate (Grubler, 1998). This can be done using databases in EU countries and/or browsing world wide networks (e.g. The Internet) for them.   Innovation and diffusion result from the interaction between actors and constituents of an innovation system (Mahapatra, 2007). The most important aspects that influence the diffusion and market of incineration ash technologies are legislative, financial and fiscal aspects and also public participation.   4.      Results   Discontinuities in technology and market affect the future market and also system of innovation. Base on discontinuities in technology and market in macro/micro level, there are three types of innovations: radical, really new and incremental (Garcia, 2002). In the case of recycling of incineration ash by thermal process, there is a technological discontinuity at micro and macro levels, but there is only marketing discontinuity at micro level. So this innovation best fit the really new innovation category. And considering the usage of incineration ash in concrete, both technological and market discontinuity are at micro level. Therefore, this technology falls into incremental innovation category.   Innovativeness is a degree to which an individual or other unit of adoption is relatively earlier in adopting new ideas than other units of adoption (Rogers, 1995). Accordingly, there are 5 adopter categories: innovators, early adopters, early majority, late majority and laggards. Different municipalities in different EU countries fall in these categories on the base of their reaction to innovation which in turn is a function of system of innovation. It is estimated that more industrialized EU countries like Germany, France, and Sweden show more innovativeness and fall into innovators and early adopter categories but less industrialized EU countries like Portugal and Czech Republic be late majority and laggards.     One of important aspects of market is the rate of adoption of innovation. The characteristics of an innovation as perceived by members of a social system determine its rate of adoption (Rogers, 1995). There are 5 attributes of innovation in this sense toward our innovations which are relative advantage, compatibility, complexity, trialablity and observability.   These attributes for our innovations consist of some advantages of ash recycling and using in concrete production compare to problems of ash landfilling like leakage of heavy metals(Aubert, 2003), land scarcity in EU countries and strict environmental regulation in this case. On the other hand both technologies are considered as compatible with norms/rules and current infrastructure and technologies (Sakaia, 2000). We believe there are some technical complexities in the case of recycling of ash by thermal process. Trialablity and observability both are poor in these cases which may hinder the process of adoption and contribute to less market share.   Five stages in innovation decision process are knowledge, persuasion, decision, implementation, confirmation which all units of adoption pass through them. Change agents and opinion leaders (Rogers, 1995) play an important role in this process. Municipalities in EU countries receive information about innovations through different channels but they may also be influenced by change agents who provide them with educative materials in order to help them gain some ideas about the existence of incineration ash technologies and make a decision toward them. Then, municipalities continue this process toward implementation of technologies and finally the step of confirmation. Concerning stylized stages of technological development and typical characteristics (Grubler, 1998), we conclude that our innovations are in niche market commercialization stage. It characterizes by "learning by doing" which reduce the cost and improve the performance of technologies with experience, close relationships between suppliers and municipalities (units of adoption), high cost of production that declines with standardization of production and commercial market share less than 5% (Frank, 2001).     5.      Discussion   Innovation and diffusion result from the interaction between actors and constituents of an innovation system which complement each other and benefit from the positive externality of the interaction (Mahapatra, 2007; Edquist, 2004). Obviously there are so many different active constitutes in the system of innovation which affect the market in this case but the most important aspects which need change in order to creating a bigger market are legislative, social and financial aspects(Wikins, 2001).   In legislative aspect, making clear and robust governmental plans and targets in less industrialized EU countries like Ireland, Spain or Czech Republic ,for example, can promote the diffusion of the innovations in these countries and a therefore a better market in thinkable in this way (Wikins, 2001). In financial aspect, fiscal policies for provision of Research and Development, financing of innovation processes and other activities that can facilitate commercialization of knowledge and its adoption can decrease the capital needed for production per unit via “learning by doing” and “learning by using” which is crucial in making a bigger market share in future (Grubler, 1998). Public awareness and participation can force government and policy makers to change their approaches and attitudes about the way of dealing with the problem. This can be especially the case in EU countries like Switzerland, Sweden and Denmark which face land scarcity and higher share of incineration in waste management sector in one hand and more public participation and higher health criteria on the other.     References: Aubert, J.E., Husson, B., Vaquier, A., 2003, Use of municipal solid waste incineration fly ash in concrete, Cement and Concrete Research 34 (2004) 957–963 Edquist, C., 2004, Systems of innovation: perspectives and challenges, in Fagerberg, J, Mowery, D.C. and Nelson, R.R. (eds.) The Oxford Handbook of Innovation, Oxford University Press, pp. 181-208. Frank, W., Geels, 2001, Technological transitions as evolutionary reconfiguration processes: a multi-level perspective and a case-study, Research Policy 31 (2002) 1257–1274 Garcia, R. and Calantone, R., 2002. A critical look at technological innovation typology and innovativeness terminology: a literature review, The Journal of Product Innovation Management, 19: 110–132. Grubler, A., enovicH, N. N., Victor, D. G., 1998, Dynamics of energy technologies and global change, Energy Policy 27 (1999) 247-280 Jacobssona, S., Lauber, S., 2004, the politics and policy of energy system transformation—explaining the German diffusion of renewable energy technology, Energy Policy 34 (2006) 256–276 Mackenzie, F. T., Our changing planet, 2002, Pearson education, Inc, 3rd edition, USA  Mahapatra, K., Gustavsson, L.,  Madlener, R., 2007, Bioenergy Innovations: The Case of Wood Pellet Systems in Sweden, Technology Analysis & Strategic Management Vol. 19, No. 1, 99–125, January 2007 Miller, G. T., Spoolman, S., 2008, Environmental science, Thomson, Canada Rogers, E. M., 1995, Diffusion of Innovations, The free press, USA Sakaia, S. , Hiraokab,  M., 1999, Municipal solid waste incinerator residue recycling by thermal processes, Waste  Management 20 (2000) 249-258 Saigo, C., 1999, Environmental sceince, Mcgrow-Hill 5th edition, USA Tchobanoglous, G., Kreith, F., 2002, Handbook of solid waste management, Mcgraw-Hill handbooks, 2nd edition, USA Wikins, G., 2001, Technology transfer for renewable energy, Erathscan, London  

نیروگاه ترکیبی گرما و الکتریسیته-Combined Heat and Power (CHP) Case study: Jamtkraft

Combined Heat and Power (CHP) Case study: Jamtkraft By Pouya Aghaseyedabolghasem Overview Cogeneration (also combined heat and power, CHP) is the use of a heat engine or a power station to simultaneously generate both electricity and useful heat. It is one of the most common forms of energy recycling. Conventional power plants emit the heat created as a by-product of electricity generation into the natural environment through cooling towers, flue gas, or by other means. By contrast CHP captures the by-product heat for domestic or industrial heating purposes, either very close to the plant, or—especially in Scandinavia and eastern Europe—as hot water for district heating with temperatures ranging from approximately 80 to 130 °C. This is also called Combined Heat and Power District Heating or CHPDH. Small CHP plants are an example of decentralized energy. (see fig.1) Fig1. simple chp based on combustion Cogeneration is a thermodynamically efficient use of fuel. In separate production of electricity some energy must be rejected as waste heat, but in cogeneration this thermal energy is put to good use. Thermal power plants (including those that use fissile elements or burn coal, petroleum, or natural gas), and heat engines in general, do not convert all of their thermal energy into electricity. In most heat engines, a bit more than half is lost as excess heat. By capturing the excess heat, CHP uses heat that would be wasted in a conventional power plant, potentially reaching an efficiency of up to 89%, compared with 55% for the best conventional plants. This means that less fuel needs to be consumed to produce the same amount of useful energy. The viability of CHP (sometimes termed utilization factor), especially in smaller CHP installations, depends upon a good base load of operation, both in terms of an on-site (or near site) electrical demand and heat demand. In practice, an exact match between the heat and electricity needs rarely exists. A CHP plant can either meet the need for heat (heat driven operation) or be run as a power plant with some use of its waste heat. The latter being least advantageous in terms of its utilization factor and thus overall efficiency. In such cases the heat from the CHP plant is also used as a primary energy source to deliver cooling by means of an absorption chiller. CHP is most efficient when the heat can be used on site or very close to it. Overall efficiency is reduced when the heat must be transported over longer distances. This requires heavily insulated pipes, which are expensive and inefficient; whereas electricity can be transmitted along a comparatively simple wire, and over much longer distances for the same energy loss. Cogeneration plants are commonly found in district heating systems of cities, hospitals, prisons, oil refineries, paper mills, wastewater treatment plants, thermal enhanced oil recovery wells and CHP is one of the most cost efficient methods of reducing carbon emissions of heating in cold climates.[6] Types of plants Topping cycle plants primarily produce electricity from a steam turbine. The exhausted steam is then condensed, and the low temperature heat released from this condensation is utilized for e.g. district heating or water desalination. Bottoming cycle plants produce high temperature heat for industrial processes, then a waste heat recovery boiler feeds an electrical plant. Bottoming cycle plants are only used when the industrial process requires very high temperatures, such as furnaces for glass and metal manufacturing, so they are less common. Large cogeneration systems provide heating water and power for an industrial site or an entire town. Common CHP plant types are: Gas turbine CHP plants using the waste heat in the flue gas of gas turbines. The gaseous fuel used is typically natural gasGas engine CHP plants use a reciprocating gas engine which is generally more competitive than a gas turbine up to about 5 MW. The gaseous fuel used is normally natural gas. These plants are generally manufactured as fully packaged units that can be installed within a plant room or external plant compound with simple connections to the sites gas supply, electrical distribution and heating systems. Combined cycle power plants adapted for CHPSteam turbine CHP plants that use the heating system as the steam condenser for the steam turbine.   Utilization of Combined Heat and Power (CHP) in Sweden CHP has had a minor importance in the history of Swedish power generation. Before 1965, hydropower dominated Swedish power generation, only giving space for thermal power during dry years and for peak loads. After 1980, nuclear power and hydropower together reduced the space for CHP in the power balance. Between l965 and l980, thermal power was needed in order to fulfil the power balance. During these years, both industrial CHP and municipal CHP was used to a large extent in order to reduce the demand of condensing power. Industrial CHP is mainly connected to steam demands in the Swedish pulp and paper industry, while municipal CHP refer to CHP in connection with district heating. All municipal CHP- plants and most of the industrial plants were oil-fired during these years. In 1981, when several new large nuclear power stations came into operation and when the oil price had risen, the total share of CHP in the power balance sunk to 4,5 % from being almost 10 % in 1980, see figure 4. Depending on supply of hydropower and demand of electricity in the country, the share of CHP in the power balance has varied between 3 and 4,5% during the 80's. Many municipal CHP-plants converted to coal-firing during the first half of the decade in order to reduce the cost of heat and power generation. The annual national overall electricity yield is defined as the difference between power generation and electricity consumption in the district heating systems divided by the total heat generation. Electricity consumption consists of power for distribution pumps , electric boilers , large heat pumps etc. During the 70's, this national electricity yield varied between 0,12 and 0,20, as can be seen in figure 6. This implies that the individual electricity yields of the existing CHP-plants were moderate. During the 80's, the national electricity yield has gone negative, since CHP generation has fallen and some new heat generation sources have been based on electricity consumption (electric boilers and heat pumps). This interesting conclusion reveals that the Swedish district heating systems have become power-consuming during the 80's from being power-generating during the 70's (Eriksson 1988). Fuels and energy sources used The low share of heat from CHP in the heat generation balance during the 80's has created a unique mixture of heat sources in order to reduce the dependence of fuel oil. Heavy fuel oil was the main fuel during the first three decades of district heating in Sweden. The presence of CHP and a price difference between light and heavy fuel oil gave competitive district heating prices. Nowadays, fuel oil is only used for peak loads and reserve capacity. Coal as fuel in CHP-plants appears in Västerås, Norrkäiping, Stockholm, Helsingborg, Örebro, Linköping, Uppsala, and Borås. Major users of coal for heat generation only are Södertalje/Södertörn, Malmö, and Göteborg. Wood chips consist of wood waste from the forest industry and are delivered by forest owners' societies, forest companies, and saw mills. Major users of wood chips are Borås, Linköping, Växjö Eskilstuna, and Östersund. Peat is extracted from peat bogs. Major users of peat are Uppsala, Karlskoga, Växjö and Östersund. In November 1990, the intermediate peat storage in Uppsala was accidentally burned in a huge fire. Major refuse incineration plants appear in Göteborg, Stockholm, Uppsala, Malmö, Linköping , and Umeå (Bergström & Gustafsson 1987). Some small refuse incineration plants exist, but new environmental demands reduce the economy of small units. Presently, a refuse incineration plant must burn at least 100 000 tons of refuse per year in order to cover its own costs. Waste heat recovered from industrial processes is utilized in Göteborg, Helsingborg, Malmö, Landskrona, Köping, Piteå, and Vänersborg. In Göteborg, the heat source is the Shell refinery (Eriksson 1980), while a ferro alloy furnace is the heat source in Vänersborg. Large heat pumps with heat capacity outputs in the range between 5 and 40 MW have been popular during the 80 ' s. During the first half of the decade, the electricity price in Sweden was very low compared with the oil-price, giving a driving force for installations of large heat pumps. Major installations of large heat pumps have been made in Stockholm, Göteborg, Solna/Sundbyberg, Lund, Örebro, Borlänge, Eskilstuna, and Malmö. The heat pumps built use heat sources like sea water and purified sewage water. In Lund, low- temperature geothermal water is used. During 1988, the average overall coefficient of performance for all large heat pumps installed in Swedish district heating systems was 3.1. This means that 1 MWh of electric energy fed into the heat pumps gave 3.1 MWh of heat generated. Electric boilers were built during the first half of the 80's in order to utilize surplus electricity for heat generation. This electricity is mostly available in Sweden during the spring, summer, and autumn seasons due to surplus capacity of nuclear power and hydropower without water storage possibilities. Natural gas arrived in the south of Sweden in 1985. Nowadays, natural gas is used by Malmö and Göteborg for heat and power generation in existing CHP-plants. Natural gas for heat generation only is used by Lund. But in this town, a simple cycle gas turbine with heat recovery is being built. A small combined cycle CHP- plant with natural gas as fuel is being built in Ängelholm. Further expansion of the natural gas system in Sweden is being discussed. Due to a favourable energy tax, LPG for heat generation has been interesting since 1987/88. But nothing lasts forever, the energy tax of LPG was increased by 307% on January 1, 1991. A CHP- plant in Luleå has used blast furnace gas since 1982. Minor utilization of digester gas from sewage water treatment and refuse gas from refuse disposals also occur for generation of heat.   Case study: Jamtkrat Ostersund is the far biggerst electricity consumer (77.9%) in Jamtland  followed by Are (0.8%), Krokom(0.8%), Vattenfall(20.6%). (See fig2 and 3) Fig2. Jamtland in Sweden   Fig3.Jamtkraft CHP plant location in Ostersund Total electricity production in Jamtland is equal to 1.100 GWh/year. This amount of electricity is produced by 17 hydro-electric plants (80%), 1 biofuel CHP-plant(20%) and 1 wind power plant(1%).   Fig4. Fuel use in Ostersund between 1981-2004   There are several district heating networks within Ostersund-Froson which cover 80% of the district heating in this town(500 GWhth) and 20% of the total electricity production(200 GWhe).(see fig.4) In 2005, the emission of NOx, NH3, N2O and CO from CHP-plant Jamtkraft AB in Ostersund are 25, 1, 7 and 10 mg/MJ respectively which seems to be acceptable figures.   Fig5. Lugnvik, Ostersund Biof-fule plays an important role her. Bio-fuel consist of 85% wood(foreat residues, sawdust, woodcgips, bark, and woodbased waste) and 15% peat. In general fuel flow is about 18 kg/s in full load(average 50 trucks with trailer per day). 85% of this amount of fuel is available within a radius of 150 km from the plant (see fig.5, 6 and 7 ). Produced ash is equal to 2-3% of fuel input. Electric filters can seperate as much as 99.9% of particles in emitted gas.    Fig6, Percentage of available biomass from tree   Fig7. Aggregation of logging residues.    Further reading: http://en.wikipedia.org/wiki/Cogeneration http://www.uschpa.org/i4a/pages/index.cfm?pageid=1 http://www.localpower.org/ http://www.chpa.co.uk/ http://alfagy.com/index.php?option=com_weblinks&view=category&id=12&Itemid=44/

چشم انداز جهانی و رویکرد های مدیریت پسماند Global E-waste Perspective and Management Approaches

Global E-waste Perspective and Management Approaches

Definition

•       Electronic waste or e-waste is a generic term embracing various forms of electric and electronic equipment that have ceased to be of any value to their owners.

•       “Any appliance using an electric power supply that has reached its end-of- life.”(OECD, 2001)

 

Categories of WEEE

•       Categories 1–4 account for almost 95% of the WEEE generated

 

Content of WEEE

 

•       E-waste contains more than 1000 different substances, many of which are toxic, such as lead, mercury, and so on which create dioxin emissions when burned. These toxins can cause brain damage, allergic reactions and cancer (Puckett and Smith, 2002).

 

 

•       Every computer, including the monitor, on average contains between 1 and 2 kg of lead (20% of the weight of monitor is lead).

•        Thus 340,000 tonnes of lead can be extracted from the 315 million computers in US between 1997 and 2004 (Milojkovic and Litovski, 2005).

 

The current and future global production of E-waste

•       It is estimated that in 2005 approximately 130 million mobile phones will be retired. Similar quantities of electronic waste are expected for all kinds of portable electronic devices such as PDAs, MP3 players, computer games and peripherals (O’Connell, 2002).

 

The flux of these contaminants on a global scale: the fate of E-waste

 

 

•       Basel Convention restricts

    transboundary trade of

    E-waste.

•       From non-ratifying

    countries, such as the

    USA, 50–80% of the

    collected domestic

    e-waste is not recycled

    domestically but rather

    shipped to destinations

    such as China.

 

 

E-waste management approaches and initiatives

 

•       Currently, most attention is focused on brown goods, white goods, automobiles and batteries which require special handling and treatment.

•       Traditionally, the legislative approach toward environmental problems has been one of ‘command and control’, largely addressing ‘end-of-pipe’ pollution problems

•       Emphasis is changing towards producer responsibility whereby those who produce goods are then responsible for the environmental impacts throughout the whole of their life cycle.

 

•       EPR is a method of integrating sustainable development principles into international trade based on an international environmental law principle known as the “Polluter Pays Principle” (Kibert, 2004).

•       Reasons for take-back of WEEE

•       There are both economic and ecological concerns. WEEE can contain hazardous materials that could be released into the environment during incineration.

•       Darby and Obara (2005) observed that more than 90% of WEEE is landfilled, incinerated or recovered in the UK without any pre treatment.

Extended producer responsibility (EPR)

•       “an environmental policy approach in which a producers’ responsibility for a product is extended to the post-consumer stage of a products life cycle including its final disposal” (OECD, 2001).

•       The ultimate goal of EPR is sustainable development through environmentally responsible product development and product recovery (Milojkovic and Litovski, 2005).

•       The EPR policy is considered by OECD as well as the EU as one of the most promising means to combat the increasing generation of waste and pollution.

•       Prioritization of preventive measures over end-of-pipe approaches, enhancement of  lifecycle thinking and a shift from the “command-and-control” approach to a non-prescriptive, goal-oriented approach.

•       Incorporation of incentive mechanisms for industries to continuously improve their products and process.

•       The policy instruments that lie under EPR umbrella include advance recycling fees (ARFs), product take-back mandates, virgin material taxes, pay-as-you-throw, waste collection charges, and landfill bans.

The main goals of EPR

waste prevention and reduction;

• product reuse;

• increased use of recycled materials in production;

• reduced natural resource consumption;

• internalization of environmental costs into product prices;

•  and, energy recovery when incineration is considered appropriate (Langrova, 2002).

•       These changes would include improving product recyclability and reusability, reducing material usage, downsizing products, etc. (Walls, 2006).

 

A study of usefulness of recycling as a waste management practice using LCA, CBA and MFA

A study of usefulness of recycling as a waste management practice using LCA, CBA and MFA

بررسی اثربخشی بازیافت بعنوان یک گزینه مدیریت پسماند با بهره گیری از ال سی ای، سی بی ای، و ام اف ای

Pouya Aghaseyedabolghasem

January, 2010

 

Abstract

.................................................

Waste generation remains a global challenge since increasing exploitation of resources by developed and developing countries don’t tend to mitigate in a short or even long term. Considerable efforts have been done in the waste management area and innovative approaches are everywhere. Recycling as a useful tool in waste management should be legitimized by comprehensive and holistic approved studies both for policy makers and ordinary people as important role players. We employed Life Cycle Assessment, Cost benefit Analysis and Material Flow Analysis to study different aspects of this practice.

……………………………………………

 

1.   Introduction

Solid waste generation is increasing alarmingly throughout the globe in recent decades. Annual municipal solid waste (MSW) generation in the United States, for example, has increased from 88 million tons in 1960 to approximately 254 million tons in 2007 (USEPA, 2007). The escalating waste generation combined with concerns over landfill costs and availability of space have prompted regulators and policymakers to reform MSW policies at all levels, from the community to the state level.

 

Waste management practices such as source reduction, recycling, and composting have been instituted in order to reduce materials from entering the waste stream (Shaufique et al, 2009). A range of programs and policy instruments are available to policy makers for managing waste and recycling. Given the variety, analyses of the effectiveness of these practices are needed for improved policy decisions.

 

However, most policymakers evaluate the effectiveness of recycling and waste management programs by looking at improvements in the rate of recycling because the rate of recycling is able to capture movements in the amount of recycling and waste generation at the same time, as opposed to separate measurement of per capita quantities. On the other hand, these waste management practices need to be evaluated by holistic and elaborate tools to be publicized on a more powerful and easily accepted ground.

 

 

2.   Methods:

We analyze recycling process using three different analytical tools, Life Cycle Analysis (LCA), Material Flow Analysis (MFA) and Cost Benefit Analysis (CBA) in order to have a better understanding of different aspects of recycling process in different industrial areas. All these tools try to draw a picture on the basis of its own framework and procedure and finally we would have a holistic view of recycling as an important waste management practice.

 

2.1.      LCA

In this study we employed LCA as an assessment tool to analyze recycling and landfill disposal of spent fluorescent lamp (SFLs). A long straight tube SFL (36 watts, 200 g and 13,600 h for mean time before failure) was selected as a product model. The system boundary starts at the site where SFLs were transported. Its result would provide the environmental impacts due to the SFLs recycling at different recycling rates (or percent) compared with the landfill and could be used as a guideline for decision makers to decide on SFL disposal facilities.

 

Poonphunchai studied the stabilization of heavy metal sludge containing chromium, mercury, and iron of industrial wastewater, by adding sodium sulfide before solidifying waste with ordinary Portland cement and lignite fly ash. The results indicated that the stabilization efficiency of mercury were about 91.40% and 99.40% when using sodium sulfide at 1.75 and 3.00 times the stoichiometric amount, respectively, with the waste/binder ratio of 0.25 (Poonphunchai, 1996).

 

The various technologies for the disposal of spent fluorescent lamps are available. In this study, for SFL recycling, an existing technology, the Japanese SFL recycling technology, is selected from that being used broadly in commercial scale and can recover more useful materials of SFL. A simplified diagram of the selected technology in Fig.1 shows current technology for the SFL recycling process in Thailand.

 

 

Fig.1 Current technology for the SFL recycling process in Thailand.

 

 

The explanation of each processing step is provided as follows: cut and blow step, tube crushing process, metal caps sorting process, phosphor purification and mercury distillation. The study was conducted by using the newest LCA definition as an analytical method (ISO 14044, 1998). The goal of this study was to evaluate environmental impacts for various rates of SFLs recycling in Thailand. The functional unit is a long tube SFL (36 watts, 200 g and 13,600 h for mean time before failure). The scope is to characterize and compare the environmental impact between specified recycling technology and the secure landfill.

 

At present, as all SFLs to be disposed have to be transported to a landfill site, the system boundary of the study will be considered after the SFLs have arrived at the site. The activities included in this system boundary were mainly both recycling and then study was conducted by using the newest LCA definition (ISO 14044, 1998) as an analytical method. The goal of this study was to evaluate environmental impacts for various rates of SFLs recycling in Thailand. The functional unit is a long tube SFL (36 watts, 200 g and 13,600 h for mean time before failure). The scope is to characterize and compare the environmental impact between specified recycling technology and the secure landfill. At present, as all SFLs to be disposed have to be transported to a landfill site, the system boundary of the study will be considered after the SFLs have arrived at the site. The activities included in this system boundary were mainly both recycling and FL were excluded.

 

The considered system boundary is shown in Fig. 3. SFLs were separated for either recycling or safe disposal (non-recycling). Rates of recycling in this study were varied as 100%, 80%, 60%, 40%, 20% and 0% (100% landfill), respectively. For recycling, the activities started at the disassembly process (at recycling plants) and terminated at the disposal process of residual waste from the disassembly process. The rest of the SFLs that were not sent to the recycle process would be sent to safe disposal (non-recycling process) (Apisitpuvakul et al. 2008). Thus, the activities started at the landfill sites, SFLs would be stabilized and solidified before being secured at the landfill sites. Raw materials and energy production considered in this study were cement, water, sodium sulfide, glass and electricity production as well as natural gas extraction. The recovered material is glass cullet.

 

Fig. 3. The system boundary of the SFLs disposal alternatives. The amount of SFLS sent to recycling plant and solidification plant depends on the rate of recycling.

 

 

 

For recycling process, inputs of the inventory data were measured by following explanation. The amount of SFLs fed to recycling plant was collected by manually counting and the amount of electricity used in each detail process such as disassembly, glass tube crushing, wet scrubber processes was obtained by reading out from electricity gauge meter. The amount of natural gas and water consumption in the processes were also collected in the unit of cubic-meter (m3). Of these, all data were recorded once a month. These data were collected for 12 months or 12 records a year.

 

The allocation of each input to a SFL was calculated by dividing the total amount of each input with the total amount of SFLs sent to the plant in a year. For output inventory data, the amount of cullet was collected by weighting the recovery each month for 12 months or 12 times a year. Eco-indicator 99 (I) version 2.1 was selected to assess the impacts which were classified into three main groups: human health, ecosystem quality, and resource depletion. The first group concerning human health (unit: DALY ¼ Disability adjusted life years; this means different disabilities caused by diseases are weighted) was composed of carcinogens, respiratory organics, respiratory inorganics, climate change, radiation and ozone layer.

 

The second group concerning ecosystem quality (unit: PDF*m2year; PDF ¼ Potentially disappeared raction of plant species) was composed of ecotoxicity, acidification/ eutrophication and land use. The last one concerning resource depletion (unit: MJ surplus energy, additional energy requirement to compensate lower future ore grade) was focused on minerals. Environmental impact factors (Characterization factor) from Simpro 6.0 database (SimaPro, 2005) were reviewed as shown in Table 1. The fuel mix for electricity production was obtained from PRET project (Uddin et al. 2008). The mixture was composed of coal (33.46%), natural gas (62.21%), bunker oil (4.2%), and diesel (0.12%).

 

Table 1

Environmental impact data for both material and energy productions and the pollutant emissions by using eco-indicator (I) version 2.1 (SimaPro, 2005)

 

 

2.2.      CBA

According to the statistics of Taiwan Environmental Protection Agency, the total amount of solid waste produced daily in Taiwan grew from 11726 t in 1984 to 23268 t in 1994, translating to an annual increase of 7.1% over the 11-year period. During the same period, the per capita MSW generated increased from 0.67 to 1.10 kg/day (Leu and Lin 1997). Of the daily 23268 t of MSW production, only about 5% was incinerated and the rest used landfill. The rapid increase in the total amount of MSW placed a considerable strain on the landfill and incineration facilities nationwide.

 

To alleviate the MSW disposal problem, measures of waste minimization and recycling appear to be the only alternative. It is noted that the combustible portion constitutes the great majority of the MSW (Leu and Lin 1997). The MSWs can also be divided into recyclable and non-recyclable categories. The materials that have been mandated by the Taiwan EPA for recycling include waste paper, plastics (bottle, sheet and others), metals (iron, aluminum and copper) and glass. Based on the fact that an MSW consists of approximately 82% of the general type and 18% of the market type (Leu and Lin 1997), Table 2 shows that the recyclable materials amount to more than 55%. Thus, at least theoretically, recycling of all recyclable materials can lead to an MSW reduction of more than one-half. This provides a very strong impetus for promoting waste minimization and recycling.

 

Table 2.  MSW percent composition in Taoyuan County and in Taiwan

 

 

The Lungtan Resource Recovery Center (LRRC) is managed by a director who performs all managerial and planning duties. A secretary handles all office work. Other employees include eight drivers and five on-site workers. Two drivers are assigned to a truck which goes out daily to collect the recyclable materials from the collection points along a pre-assigned route. The on-site workers are responsible for sorting the recyclable materials collected.

 

Seven kinds of recyclable materials were collected by the LRRC center: waste paper, plastics, PET bottles, steel cans, aluminum cans, copper and glass. PET (polyethylene terephthalate) bottles, widely used as soft drink, mineral water, cooking oil and soy sauce containers, were separated from the plastics as a single category because of the nationwide compulsory customer deposit levied on each of these bottles. Hence their resale value was considerably higher than that of other plastic materials.

Among the recyclable materials, papers were by far the largest collected (Leu and Lin, 1997). Table 3 demonstrates that papers constitute about 66% of the total 13600 t of recyclable material collected by the center over the 3-year period from September 1992 to September 1995. This was followed by steel cans (14.2%), PET bottles (13.2%) and plastics (2.9%). The rest of the recyclable materials constituted only about 3.7%.

Table 3 also shows the average monthly amount (t/month) for each type of recyclable material collected since September 1992. The total amounts, which are the sum of all figures across each row, are 677.8, 417.9, 297.5 and 251.1 t/month for 1992, 1993, 1994 and 1995, respectively.

 

Table 3

The monthly average amount (t/month) of each recyclable material collected by LRRC

 

 

2.3.      MFA

In order to understand the relationships between environmental problems and current socio-economic activities as characterized by massive use of materials, it is essential to quantify comprehensively the flows of materials and energy between the economy and nature, as well as those among the various economic sectors. Material flow accounting (MFA) is a powerful tool for such a comprehensive analysis. Here we describe concept and framework of MFA, and examine the present state of recycling and waste management from the viewpoint of MFA.

 

One typical use of MFA considers an aggregated total of all the material flows which accompany a national economy (see fig. 4). This is known as bulk-MFA. Another use of MFA, in a broader sense, traces the flows of specific substances of priority concern (for example, heavy metals, toxic chemicals, nutrients) (Moriguchi, 1999). This is often called SFA (substance flow analysis) in order to distinguish it from bulk-MFA.

 

 

Fig 4. Basic framework of material flow accounting

 

 

Recycling from the viewpoint of MFA

As is often debated, recycling activities have several different objectives. The reduction of the absolute volume of waste for final disposal is one of the main targets, particularly in Japan, where we suffer from a shortage of disposal sites. Another essential purpose is the reduction of new inputs of nonrenewable and renewable material resources of high environmental concern. This will also contribute to the reduction of ecological rucksacks behind new inputs. Recycling sometimes also contributes to avoiding inputs of energy and outputs of pollutants and wastes from the material production processes from virgin resources, although we should carefully assess the fact that recycling activities themselves are also accompanied by additional inputs and outputs.

 

From macroscopic analysis by MFA, it seems that absolute flows of recycled materials are relatively small compared with total material throughput. However, we have to keep in mind that the goal is not an increase in the absolute amount of recycled materials, but a reduction of resource inputs and waste/pollutant outputs by promoting recycling activities. The consistent and comprehensive framework of MFA will contribute to such an understanding. For example, material inputs avoided by recycling are a candidate indicator to measure the performance of recycling activities.

 

What we ultimately have to do is to manage the whole cycle of materials, from the so-called from-cradle-to-grave viewpoint, rather than manage known, defined, specific, limited types of waste. In the same context, the concept of recycling should be applied to the whole cycle of materials, rather than the recycling of wastes under the auspices of waste management authorities. The reason why we have to use the term “re”-cycle is that the loop of the usual material cycle is not closed without intentional “re”-actions. Ultimately, the term recycle may lose its raison d’être when the closed loop is successfully integrated everywhere in our society.

 

 

3.   Results

3.1.      LCA

After all available data are collected. The quantified inputs and outputs for disposing one SFL at the end of life at various recycling rates (raw material use, energy use, solid waste generation as well as emissions to air and water) are calculated and results are shown in Table 4. Fig. 5 shows a linear relationship among various inputs with the reduction of the recycling rate from 100% to 0%. The amount of electricity consumption is increased from 0.0036 to 0.0051 kWh/SFL. The amount of sodium sulfide, cement and new glass are also increased from 0.0019, 0.03, and 0 kg/SFL to 0.014, 0.20, and 0.172 kg/SFL, respectively. On the contrary, the amount of water and natural gas consumption are decreased from 0.00021 and 0.000046 m3/SFL to 0.00020 and 0 m3/SFL, respectively.

 

Table 4. The quantified inputs and outputs for each activity to dispose one SFL (0.2 kg) at the end of life at various recycling rates

 

 

Raw materials and energy production considered in this study were cement, water, sodium sulfide, glass and electricity production as well as natural gas extraction. The recovered material is glass cullet. The unrecovered cullet would be compensated by new glass production. Main emissions from these processes were solid waste and mercury. Inventory analyses (ISO 14041, 1998) were conducted to identify and quantify inputs and outputs (raw material use, energy use, solid waste and mercury emitted to air and water) from each related unit process as shown in Fig. 6.

 

Fig. 5. The inputs for each activity to dispose one SFL (0.2 kg) at the end of life at various recycling rates.

 

 

From Table 4, when the total amount of the consumed materials and energy in the SFL disposal system were compared between 100% recycling (called as recycling) and 0% recycling (called as non-recycling), the results here indicate and confirm that the recycling process consumes less material and energy than the non-recycling one. The result here indicated and confirmed that recycling gives the advantage over non-recycling. It helps to reduce the amount of consumed materials and energy in the SFL disposal system. For instance, the amount of electricity, sodium sulfide, and cement for recycling are less than the non-recycling by about 1.42, 7.36 and 6.67 times, respectively. Moreover, the amount of new glass consumption for the non-recycling is about 0.172 kg/SFL more.

 

The water consumption in each approach is comparatively the same. When considering the products and pollutant emissions from both recycling and non-recycling processes, the amount of cullet generated from recycling process is 0.17 kg/SFL. This implies that 0.17 kg of glass/SFL will be reduced from resource extraction. It is also shown that recycling generates less amount of mercury vapor than the non-recycling. The reason is that the existing recycling technology has a wet scrubber for reducing mercury vapor released from disassembly process before emitting to the ambient air. Consequently, the amount of mercury released to ambient air is not exceeded the emission standard. In addition, the analysis showed that non-recycling generates 0.35 kg of solid waste/SFL, more than that of recycling.

 

 

Fig 6. The system boundary of the SFLs disposal alternatives. The amount of SFLS sent to recycling plant and solidification plant depends on the rate of recycling.

 

 

 

3.2.      CBA

 

In performing the cost–benefit analysis of the center, the income and all expenses need to be considered. The income of the center comes solely from the sale of sorted recyclable materials to manufacturers as raw materials. The expenses include operating cost of the center and prices paid to persons in charge of the field collection points. Both are expected to be sensitive to price fluctuation of the raw materials in the market place.

 

The operating cost of the center consists of salaries for employees, utilities (telephone, water, electricity, etc.), upkeep of trucks (insurance, taxes, maintenance, gas, etc.), annual depreciation of trucks and machinery, and site rental. The total expenses for each year are listed in Table 4. The center has two large trucks (10.5tons), one medium-size truck (8.8 t) and four small ones (3.5 t). In addition, it also has a compacting machine, a shredder, a conveyor and a weighing station. The total initial investment for truck and machinery came to slightly less than $245000 (all cost figures are in US currency). The usable life of the equipment permitted by the government is 8 years.

 

table 4. Operating costs (US currency) of LRRC.

 

 

Assuming an 8% interest rate, the annual depreciation of equipment amounts to $56680. The other cost figures in this table were based on the data supplied by the center. The cost–benefit analysis is performed and listed in Table 5. The second row represents the total amount of recyclable materials sold by the center for each year and the third row the income derived from the sale. The average unit sale price was obtained by dividing the income by the total amount of recyclable materials. The total purchase price is that paid to the person in charge of the field collection point.

 

The net income represents the total sale income less the operating cost and the purchase prices. Based on the sum of operating cost and purchase price, the average unit cost of recyclable materials is computed and listed below the net income. The benefit derived from recycling was computed on the basis of $57.5/t. The rationale for this benefit is that recycling is equivalent to MSW reduction. Without recycling, the recyclable materials need to be landfilled at a current landfilling cost of $57.5/t and such a cost has to be borne by the town or city governments. Hence, the benefit of waste reduction can be legitimately regarded as part of the income of the recycling center.

 

Table 5. Cost–benefit analysis of resource material recycling

 

 

According to Table 4, the total amounts of monthly collection decreased steadily from 677.8 t/month in 1992 to 251.1 t/month in 1995. These monthly amounts of recyclable material collections were larger than the amounts of monthly sale shown in Table 5, which are 564.4, 392.4, 286.4 and 162.6 t/month for 1992, 1993, 1994 and 1995, respectively.

 

 

4.   Discussion

 

4.1.      LCA

An application of LCA to assess the environmental impacts of SFL disposal at the various recycling rates (0-100%) in Thailand was conducted. The analysis carried out in this study shows that the main contributors to the environmental impacts are cement production, sodium sulfide production, and electricity production, respectively. Of these, at all recycling rates, cement production is the main contributor (more than 90%) to carcinogen, climate change, acidification/eutrophication and land use, while sodium sulfide production was the second contributor of respiratory organics, respiratory inorganics, climate change, radiation, ozone layer, ecotoxicity, acidification/eutrophication, land use and minerals.

 

Moreover, about 16% of contribution to carcinogens, respiratory organics, respiratory organics, climate change, ecotoxicity and acidification/eutrophication is coming from electricity production. New glass production shows a small contribution (about 1%) to the respiratory organics, respiratory inorganics and ozone layer. Mercury vapor emission also shows a little contribution to carcinogens and ecotoxicity. For solid waste landfill, a small contribution to respiratory organics and inorganics, ozone layer, acidification/eutrophication and minerals is observed.

 

 Other activities during the life cycle of a fluorescent lamp were not observed for their contribution to these 10 environmental impact potentials. However, it is anticipated that impacts would be reduced when rate of recycling is increased. Therefore, all selected environmental impacts would be reduced when reducing the use of cement in disposal process or improving the process of producing cement. This conclusion was supported by the result from inventory analysis. It indicated that non-recycling process (100% landfill) consumed cement more than the recycling one as most of the cement was consumed in stabilization and solidification processes before landfill.

 

 

4.2.      CBA

 

The present study examines the operation of a recycling center organized and operated by a private, non-profit environmental protection foundation and subsidized by the county government in Taiwan. The monthly amounts of recyclable materials collected by the center since its inception are reported. According to the data supplied by the recycling center for the past several years, waste paper constitutes the bulk of the recyclable materials (66%). This is followed by steel cans (14.2%), PET bottles (13.2%), and plastics (2.9%). All other recyclable materials represent only about 3.7%.

 

The financial data reveal that the financial health of the recycling center is strongly influenced by the prices of raw materials in the market place. Cost–benefit analysis of the operation shows that, for the period of high raw material prices, like that of this year, the recycling center can operate in the black by resale of the sorted recyclable materials alone. At lower raw material prices like those in 1994 and before, the financial health of the recycling center is in worse shape and government subsidy is necessary.

 

However, the monetary benefit derived from the waste reduction due to recycling is found to be sizable in comparison to the income from the resale of recyclable materials. The rationale for considering the benefit as part of income is that recycling is directly related to saving in municipal solid waste disposal by landfill. Considering this monetary benefit as indirect income, the resource material recycling center would be in excellent financial shape except for the first few months after its inception in 1992.

 

 

References

 

Apisitpuvakul, W., P. Piumsomboon, D. J. Watts, and W. Koetsinchai. 2008. LCA of spent fluorescent lamps in Thailand at various rates of recycling. Journal of Cleaner Production 1046-1061

 

ISO 14041, 1998. www.iso.org/iso/catalogue_detail.htm?csnumber=38498. Accessed January 2010

 

Leu. L., and S. Lin. 1998. Cost–benefit analysis of resource material recycling. Resources, Conservation and Recycling 23: 183–192

 

Moriguchi, Y. 1999. Recycling and waste management from the viewpoint of material flow accounting. J Mater Cycles Waste Manag (1999) 1:2–9

 

Poonphunchai, A. 1996. Solidification of heavy metal sulfide sludge using cement and lignite fly ash as binders. Masters thesis, Department of Environmental Engineering, Chulalongkorn University, Thailand

 

Shaufique, F. S., S.V. Joshi, F. 2009. Lupib. Factors influencing the rate of recycling: An analysis of Minnesota counties. Resour Conserv Recy, doi:10.1016/j.resconrec.2009.08.006

SimaPro. 2005. SimaPro 6.0 demo version program. PRé Consultants bv, Amersfoort , The Netherlands. www.pre.nl/simapro/support/default.htm , Accessed 24 March 2010

Uddin, S.N., R. Taplin and X. Yu. 2008. Towards a sustainable energy future, exploring current barriers and potential solutions in Thailand. Journal of Environment, Development and Sustainability  1387-585X (63-87)

USEPA. 2007. Municipal solid waste in the United States, 2007 facts and figures. http://www.epa.gov/epawaste/nonhaz/municipal/pubs/msw2008rpt.pdf, Accessed January 2010

 

هم سنجی اثرات زیست محیطی زباله سوزها و دفن بهداشتی A Comparison of the Environmental Impacts of Inc

A Comparison of the Environmental Impacts of

Incineration and Landfilling

By Pouya Aghaseyedabolghasem

2010

Abstract

Life cycle assessment (LCA) was used in order to compare the environmental impact of incineration and the landfilling in dealing with municipal solid waste. Incineration with energy recovery and landfilling treatment systems were assessed. Also some incineration scenarios with different ash treatment systems were evaluated. Two landfilling scenarios were evaluated, namely, with and without energy recovery. Energy consumption, recovered resources, and emissions to the air and water were quantified and analyzed in terms of their impact potentials. Incineration with ash disposal to a landfill site resulted in the lowest impact values for all impact categories assessed in this study. Among the incineration scenarios, the reuse of ash for brick production resulted in a higher environmental impact due to an increase in energy consumption. Overall, landfilling had a higher environmental impact than incineration.

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 Introduction

Dealing with waste and rapid increase in the amount of waste stream is one of the considerable challenges around the world. Waste management systems having lower global and regional environmental impacts are desirable, apart from health and safety concerns, because of the wider effects of waste management on the environment.

Environmental life cycle assessment (LCA) is a tool that attempts to predict the overall environmental impact of a process over its entire life cycle. Different waste management systems and their various environmental effects can be evaluated by applying LCA. White et al. (1999) constructed a life cycle inventory (LCI) model called integrated solid waste (ISW) management which facilitates the assessment of the environmental and economical aspects of municipal solid waste management (MSWM).

LCA studies of solid waste management systems are very rarely performed in developing countries like Brazil. From this standpoint, it would be worth extending the LCA application to MSWM to the largest Brazilian city, São Paulo. In this city, the 10 million inhabitants produce 10,000 t of residential solid waste daily (Mendesa et al. 2003). Currently, almost all the waste is buried in landfill sites.

However, there is both a lack of new landfill sites and a concern about the environmental effects of this practice. Incineration was chosen because it decreases the volume of waste considerably, while energy can be recovered. On the other hand, as São Paulo used to have old incinerators with high emissions, people now are against incineration (Mendesa et al. 2003). We aim to present a comparison of landfilling and incineration of the residential fraction of the MSW of São Paulo City regarding some environmental parameters.

 

Methodology and Scope

A LCA study is a tool able to evaluate environmental burdens associated with a product, process, or service by identifying energy and materials used and emissions released to the environment (Cherubini et al., 2008); moreover it allows also an identification of opportunities for environmental improvements LCA methodology is the internationally standardized method that is considered one of the most effective management tools for identifying and assessing the environmental impacts related with waste management options. In particular, the broad perspective of LCA makes possible to take into account the significant environmental benefits that can be obtained through different waste management processes (Cherubini et al., 2008).

 

The LCA consists of four stages: goals and scope definition, life cycle inventory analysis, life cycle impact analysis (LCIA), and interpretation analysis or improvement analysis (Fava et al., 1993; Graedel, 1998; USEPA, 1995).

Table 1 includes the typical physical (moisture, ash) and chemical (C, H, O, S, N) composition of MSW according to Tchobanoglous et al. (1993). These values were used to calculate the total amount of each chemical element that enters the incinerator or the landfill.

 

In this study, the impact of the collection and transfer of solid waste is not considered. The basic assumption is that treatment facilities are located close to each other. Therefore, it is expected that the environmental impact from various collection alternatives would be similar, regardless of the treatment method used. Finnveden and Ekvall (1998) concluded that transportation (as long as it is reasonably efficient) will in general have no effect on the conclusions and is thus not a key issue in the choice between recycling and incineration of paper packaging materials with respect to environmental issues.

The environmental parameters chosen as of interest to this study were the net energy consumption, the air emissions of CO2, CH4, N2O, NO2, SO2, H2S, HCl, HF, NH3, and the water emissions of total-N and total-P. Those emissions were grouped into three environmental impact categories: GWP, acidification potential (AP), and nutrient enrichment (NE) (Mendesa et al. 2003).

 

System boundaries and scenarios

Possible improvements were investigated by establishing five scenarios that incorporated incineration and landfilling. Three incineration scenarios that used different ash treatments and two landfilling scenarios, one with and one without energy recovery were assessed for their environmental impacts. The processes in each scenario were chosen based on currently applied technologies.

In scenario 1, the waste is incinerated in a mass-burn incinerator having energy recovery efficiency of 15% of the lower heating value of the waste as heat and 15% as electricity. The incinerator consumes 123 kWh of electricity and 293 MJ natural gas/t of incinerated waste. The flue gas purification technology is the same as described by Kremer et al. (1998); it includes dust removal, gas scrubbing, absorption, selective catalytic reduction of nitrogen oxides, and spray drying of gas-scrubbing liquid emissions. The bottom, boiler, and fly ashes from the incinerator are disposed of in a landfill.

Nitrous oxide emission depends on the size, type, and operating conditions of the incinerator. The IPCC revised guidelines (IPCC, 1997) presents values for N2O emission in the range of 26–270 g N2O/t MSW incinerated.

In this study, N2O emission was assumed to be 100 g/t of MSW incinerated. Scenario 2 is a variation of scenario 1, however, the bottom, boiler, and fly ashes are melted in a furnace, producing slag, which is disposed of in the landfill. Energy consumption and emissions of the melting process were calculated based on the model of the thermal slag treatment (HSR process) developed by Hellweg (2000).

In scenario 3, the waste is burned in an incinerator similar to that described in scenario 1 and the bottom ash is reused for producing pavement bricks. The boiler and fly ashes resulting from their heavy metal content are assumed to be landfilled as hazardous waste (Mendesa et al. 2003). In this study, incineration bottom ashes are pressed forming the pavement bricks that are burned for 10 h with the maximum temperature reaching 1050 ◦C.

Since the release of heavy metals is not addressed in this study, it was assumed in scenarios 1 and 2 that ash and slag disposed in the landfill are stable and only occupy space. Fig. 1 presents the flowchart of scenarios 1–3.

 

Scenario 4 describes the spreading of all waste in a landfill. The diesel oil and electricity used in the landfill management were quantified as 0.8 l of diesel and 0.1 kWh of electricity/t of landfilled waste. 50% of the methane gas is released to the atmosphere. Carbon dioxide emitted from the landfill was not considered a contributor to the global warming potential, because it is not anthropogenic in origin (Mendesa et al. 2003).

The biogas naturally released from landfill is collected (about 50% of the total), treated and burnt (in situ) in order to produce electricity. The other part of the biogas is burnt in flares (25%) or released to the atmosphere (remaining 25%). As mentioned in the previous section, the CO2 released by biogas combustion is not accounted for in the GWP but it is included among the local emissions. The estimated energy content of the collected biogas is 3.12E‏09 MJ, thanks to a biogas lower heating value of 17.73 MJ/m3. The biogas is thus burnt in turbines at 28% efficiency to produce 2.43E‏08 kWh of electricity per year. Airborne emissions from combustion are calculated according to Cherubini et al. Material inputs for biogas collection and use are to be considered negligible in terms of mass contribution compared to the clay and earth for landfill walls.

 

Based on models about the fate of carbon in landfills (Dalemo et al., 1997; Nielsen and Hauschild, 1998), the assumption is that 1% of the carbon content in biodegradable wastes is emitted as COD to the leachate. One gram of carbon is assumed as equivalent to 3 g of COD (Dalemo et al., 1997). 50% of the nitrogen content of biodegradable components is assumed to be emitted as total-N within the leachate, 3% of the disposed sulfur is emitted to the landfill gas as H2S, and 1% to the leachate (based on Nielsen and Hauschild, 1998).

The assumption adopted about leakage is that over the life of the landfill, 70% of leachate will be collected and treated, and 30% will leak out without any treatment (Rieradevall et al., 1997; White et al., 1999). The leachate treatment consists of biological treatment, precipitation, chemical oxidation, sand filtration, activated carbon adsorption, and sludge treatment. Solid emissions from the LTP are treated and landfilled. Scenario 5 is a variation of scenario 4, in which the collected gas is passed though a wet scrubber to remove SO2 (95% removal efficiency) and then burned in a gas engine with 30% energy recovery efficiency. The energy content of the landfill gas depends on the methane content of the landfill gas. In this scenario, similarly to scenario 4, a gas collection with 50% efficiency is assumed.

The amount of gaseous emissions differ depending on which fraction of the landfill gas it refers to, i.e. if it is gas escapes to the atmosphere without any treatment, gas that is flared (scenario 4), or combusted in a gas engine (scenario 5). Table 2 lists the emissions of CO, NO2, HCl, and HF for both portions (based on White et al., 1999).

 

For a better understanding of the source of the environmental imact, the scenarios were divided into stages, as shown in Fig. 2. The main treatment (MT) corresponds to the incineration and landfilling processes. The ash treatment (AT) represents ash disposal in a landfill in scenario 1, the melting process in scenario 2, and brick production in scenario 3. The collected leachate is treated in an LTP in scenarios 4 and 5. The avoidance of environmental impact due to the production of electricity and brick is addressed in the energy recovery (ER) and materials recovery (MR) stages, respectively. These last two stages are represented only in Fig. 1 but are omitted in Fig. 2.

 

Life cycle inventory

In LCA tool, 'Inventory' involves data collection and modeling of the product system, as well as description and verification of data. This encompasses all data related to environmental (e.g., CO₂) and technical (e.g., intermediate chemicals) quantities for all relevant unit processes within the study boundaries that compose the product system.

The data must be related to the functional unit defined in the goal and scope definition. Data can be presented in tables and some interpretations can be made already at this stage. The results of the inventory is an LCI which provides information about all inputs and outputs in the form of elementary flow to and from the environment from all the unit processes involved in the study.

Energy consumption, input and recovery of resources, and pollutant emissions to the air (CO2, CH4, SO2, NO2, N2O, H2S, HCl, HF, NH3) and water (COD, total-N, total-P) were estimated for all scenarios. The emissions generated during production of auxiliary materials, fuels and electricity were also included. Since no life cycle inventory data for Brazilian electricity was available, an inventory was determined by applying the data for electricity production presented in the SAEFL Report 250 (1998) in the following proportions: hydropower (94%), oil (3%), coal (2%), and nuclear (1%). This inventory was used for indirect emissions from electricity use.

 

Life cycle impact assessment

Life cycle impact assessment aimed at evaluating the contribution to impact categories such as global warming, acidification, etc. The first step is termed characterization. Here, impact potentials are calculated based on the LCI results. The next steps are normalization and weighting, but these are both voluntary according the ISO standard. Normalization provides a basis for comparing different types of environmental impact categories (all impacts get the same unit). Weighting implies assigning a weighting factor to each impact category depending on the relative importance.

The emissions accounted for in the inventory stage were arranged into three environmental impact categories: GWP, AP, and NE. Within each impact category, each emission was multiplied by an equivalency factor to obtain an impact potential value. It is important to note that calculated impact values correspond to a potential impact that could occur and not in fact to an actual impact.

Acidification effects not only depend on the emitted substances but also on the receiving soil. Although nitrogen substances such asNO2 andNH3 only cause acidification in sensitive areas, we considered a case in which all emissions related to acidification are contributors to this impact category.

 

Results and discussion

Life cycle inventory analysis

Table 4 shows the input–output balance for the treatment of 1 t of MSW with the average composition in São Paulo calculated for all scenarios. This table presents the type and amount of fuels and auxiliary materials used in each scenario. Methane emissions in scenarios 4 and 5 are due to incomplete landfill gas collection while water emissions are due to leachate leakage. Incineration scenarios presented higher CO2, N2O, and NO2 emissions than landfilling ones. Conversely, landfilling scenarios presented higher emissions of CH4, H2S, and nitrogenous compounds (expressed as total-N). Finally, as expected, much more energy was recovered by incineration than by landfilling with energy recovery.

 

Life cycle impact analysis

The energy and auxiliary product consumption, and emissions for each scenario were associated with global warming, acidification, and nutrient enrichment potential impacts. In Figs. 3–5, the obtained impact potentials for the studied scenarios including both the final values (left) and the contribution of each stage (right) are shown. The contribution of stages is represented by a weighted value, in which the final impact potential of each scenario is expressed as 1.

The avoidance of environmental effects as a result of energy or materials recovery is expressed as negative values in the stage charts. The stages are expressed as follows: main treatment which corresponds to incineration or landfilling processes; ash treatment which corresponds either to ash disposal, melting or reuse; leachate treatment; energy recovery; and materials recovery.

 

Global warming potential

Fig. 3 presents the global warming potential (as kg of CO2) for the different scenarios assessed (left) and the contribution of each stage (right). As can be seen in the figure, landfilling presented a higher GWP than incineration.

Among the incineration scenarios, the one involving brick production had the highest GWP due to the high energy consumption for the process, while low avoidance of environmental impact could be achieved because the production of traditional brick consumes less energy. A process that mixes ash and clay would consume less energy than the one assuming the use of 100% pure ash for brick production.

Regarding the different stages, the GWP was essentially due to the main treatment for all scenarios. The GWP of landfilling was mainly a result of methane generation during the biological degradation of organic waste. In the case of incineration, the GWP is largely due to burning plastics, which creates anthropogenic CO2 emission.

Producing electricity did not decrease the GWP considerably in the scenarios involving energy recovery. The avoidance of an environmental impact due to the production of electricity was not so high because in Brazil electricity is mainly hydro-based. Despite the small reduction in the GWP, electricity production is beneficial due to the lack of electricity in the São Paulo area.

 

Acidification potential

Fig. 4 presents the chart of the total value (left) and the contribution of each stage (right) to the acidification potential expressed as g of SO2. Landfilling scenarios had much higher APs than incineration scenarios. Scenario 1, incineration with ash disposal, presented the lowest AP. Regarding ash treatment, since it was assumed that the ash disposed of in the landfill just occupies space and that no acid compounds are released, this procedure resulted in almost no AP. Ash melting and reuse had increased AP due to higher energy consumption and higher acid gas emissions during the thermal process.

For landfilling, almost 80% of the impact potential was attributable to the leachate treatment. This is caused by the high energy consumption. Hydrogen sulfide (H2S) is generated in the landfill (main treatment stage) and it is the most significant contributor to the acidification potential of the main stage. Despite the fact that H2S is converted into SO2 during gas flaring, the AP did not decrease because it depends on the amount of sulfur emitted and not on its form. However, the environmental impact of scenario 5 was lower because in addition to combusting gas to generate electricity there is also a gas treatment system in which the SO2 emissions are reduced. Producing electricity in the landfill (scenario 5) decreased the AP by almost 10%.

 

Conclusions

Results show landfill systems as the worst waste management options and that significant environmental savings are achieved from undertaking energy recycling. The higher the yields of energy recovered with waste disposal, the greater the savings. We are convinced of the effectiveness of the use of environmental life cycle assessment to investigate and discuss various aspects of MSW management. Landfilling of all waste, the current management practice in São Paulo City, presented the highest environmental impact in our investigation. In the landfilling scenarios, energy recovery only slightly reduced the environmental impact compared to landfilling without energy recovery.

 

Lowest environmental burden regarding the impact categories assessed in this study is devoted to incineration with ash disposal to a landfill. We conclude that in disposal of ash to a landfill site there is no contribution to global warming, acidification, or nutrient enrichment because ash and slag contain mainly inorganic compounds, and very low or insignificant amounts of carbon, nitrogen, and sulfur. However, the leaching of heavy metals can be toxic to the environment, while the production of slag would decrease the heavy metal leachability.

Finally, production of electricity did not reduce the GWP considerably. However, it is noteworthy that Brazil lacks sufficient electricity generation and so any energy production is welcomed. On the other hand, production of electricity reduced the AP considerably.

 

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