Wste-to-energy by Ronld G Hrley, Xicon Infrstructure This pper introduces the concepts behind municipl wste mngement, nd then gives more detils of the wste-to-energy process in prticulr. It compres the greenhouse gs emissions of trditionl power plnts ginst the WTE process, nd gives opertionl dt of tons per cpit for different countries. Then it gives detiled informtion of vrious countries. It is cler tht WTE plnts re being deployed rpidly cross the globe. Energy from wste (EfW) or wste to energy (WTE) refers to the process of turning municipl solid wste into source of het nd then into electricl energy. Municipl solid wste refers to wste generted by households, industries, construction nd demolitions, s well s sludge from wstewter in some cses. When MSW is not converted to energy, it is used for lndfill, or in developing countries, burned in open-ir (nd often illegl) dump sites. Although there re fcilities gered towrd the cpturing of gses relesed by lnd fill, not ll the greenhouse gses (GHG) re cptured. This cuses high levels of pollution, which WTE ddresses. There re severl methods used to convert MSW into energy s illustrted in Fig. 1. Pyrolysis is the degrding of MSW under pressure without the presence of oxygen, llowing for the formtion of chr, pyrolysis oil nd syngs. It is ccomplished with tempertures between 500 nd 1000 C. Gsifiction involves higher tempertures thn pyrolysis, nd includes smll mount of oxygen to form syngs. Plsm rc is useful for tretment of biomedicl wste due to the high temperture t which the process occurs, nd involves the decomposition of MSW into its bsic elements, resulting in hydrogen-rich plsm converted gs (PCG). Refuse derived fuel (RDF) is the process of converting sorted MSW into dense pellets tht burn more efficiently thn untreted, unsorted MSW. For the combustion process, tempertures vry from 800 to 1000 C, nd combustion is most efficient if the MSW hs less thn 50% moisture [7]. Process This pper focuses on the combustion method for WTE, nd the electricl energy produced thereby. The combustion process strts with receiving chmber, s illustrted in Fig. 2. The MSW my lredy be presorted, with recyclble items lredy removed. In RDF fcilities, the MSW is first shredded to produce better burning fuel source. The SEMASS fcility in Rochester, Msschusetts, in Fig. 3 is good exmple of n RDF-type plnt. The MSW is then moved to either mechnicl grte tht moves the wste through the combustion chmber, or seprted with some wste plced in circulting fluidised bed (CFB) tht hs upwrd-blowing jets of ir Fig. 1: Tretment options for municipl solid wste [7]. Fig. 2: Plnned lyout of the Sntigo, Chile WTE plnt. [24] Fig. 3: Exmple of n RDF type fcility, like the SEMASS fcility in Rochester, Msschusetts, USA, which hs cpcity of 0,9-million tons nnully [Themelis, 2003]. to increse the het trnsference. For exmple, the grte designed by Mrtin energize - August 2012 - Pge 71
combustion is used to crete stem which is then used to drive turbine connected to n electricl genertor, or sent out s source of district heting. The Bresci WTE fcility in Itly, shown in Fig. 4, is good exmple of cogenertion plnt. Fig. 4: Bresci WTE plnt. The plnt produces 650 kwh electricity per ton MSW combusted. [Themelis, 2003] After incinertion, the cooled shes, which my contin metl re sorted using mechnicl nd electromgnetic devices. Some nitrogen oxides will form during the burning process, nd mmoni or ure is injected into the hot flue gs to neutrlize them. This is clled "selective non-ctlytic reduction". Fly sh then goes through the bghouse which collects the fine sh. After the sh hs been sorted, it is recycled nd cn be used t plces like cement fctories [10, 24]. In ddition to creting higher rtes of recycling, the WTE process lowers, nd in some cses elimintes the emission of GHGs nd reduces MSW mss by n verge of 90% [21] s illustrted in Fig. 5. Fig. 5: Nett globl climte chnge emissions. (Michels, 2007). Air emissions of wste-to-energy nd fossil fuel power plnts (Pounds per MW hour) Fcility type Crbon dioxide Sulfur dioxide Nitrogen oxides Col 2249 13 6 Oil 1672 12 4 Nturl gs 1135 0,1 1,7 Wste-to-energy 837 0,8 5,4 Tble 1: GHG emissions for col, oil, nturl gs, nd WTE [Michels, 2007]. Trents for GHG emissions from wste using () 1996 nd (b) 2006 PCC inventory guidelines extrpoltions nd projection (MtC0 2 -eq, rounded) Source 1990 1995 2000 2005 2010 2015 2020 2030 2050 Lndfill CH 4 760 770 730 750 760 790 820 b Lndfill CH 4 340 400 450 520 640 800 1000 1500 2000 Lndfill CH 4 (verge of nd b ) 550 585 590 635 700 795 910 Wstewter CH 4 450 490 520 590 600 630 670 Wstewter N 2 C 80 90 90 100 100 100 100 b Incinertion CO 2 40 40 50 50 60 60 60 70 70 Totl GHG emissions 1120 1205 1250 1345 1460 1585 1740 Notes: Emissions estimtes nd projections s follows: Bsed on reported emissions from ntionl inventories nd ntionl communictions nd ( for nonremporting c ountires) on 1996 inventery guidelines nd extrpoltion (US EPA, 2006) b Bsed on 2006 inventory gudleines nd BAU projection (Monnl et.3el., 2006). Totl includes lndfill CH 4 (verge), wstewter CH 4 wstewter N 2 O nd incinertion CO 2 Tble 2: Comprison of GHG emissions from vrious wste mngement systems [Bogner et l, 2007]. Lndfills nd wstewter re the two gretest producers of GHGs [9]. Not only do WTE fcilities reduce these GHGs, but the energy they produce lso helps substitute the need for burning fossil fuels. Tble 1 shows how the GHG emissions from WTE, prticulrly the crbon dioxide, re significntly lower thn from burning col, oil, or nturl gs. Tble 2 compres the GHG emissions from vrious wste mngement systems, nd shows tht totl emissions hve historiclly incresed, but between 1990 nd 2003 the percentge of totl globl GHG emissions from the wste sector declined 14 19%. Operting dt There re severl fctors tht determine whether or not WTE plnt is suitble for loction. These include the region's economic strength; the ntionl policies nd lws regrding the hndling of MSW; environmentl regultions; the infrstructure required to build, supply nd mintin WTE fcility; nd the public's perception [9]. Municipl jurisdiction usully controls the hndling of MSW in specific region; however, some sttes hve ntionl policies tht influence those regions. In other countries municiplities re left to decide on the hndling process, possibly leving the region with low forml recycling rtes nd lck of MSW services. A lrge possible obstcle to the building of WTE plnt is the negtive public perception of such fcilities. Since the implementtion of strict regultions on WTE fcilities, these fcilities hve significntly improved their emissions.[8]. GmbH in Munich, Germny, seems to be the most widely used round the world, followed by compny in Switzerlnd clled the Von Roll Inov Corp. [24]. Air is drwn through the receiving chmber to crete negtive pressure tht will drw the gses relesed by the wste bck into the furnce for neutrlistion. Het from energize - August 2012 - Pge 72 Tble 3 shows tht the emissions from the SEMASS WTE plnt in Msschusetts re significntly lower thn the EPA requirements. Emissions from WTE fcilities
Comprison of 1999 emissions from SEMASS No. 3 unit with EPA stndrds Emission EPA stndrd 1 SEMASS 2 Prticulte (gr/dcf) 0,010 0,002 Sulfur dioxide* 30 16,06 Hydrogen chloride* 25 3,6 Nitrogen oxides* 150 141 Crbon monoxide* 150 56,3 Cdmium** 20 1,24 Led** 200 30,03 Mercury** 80 5,09 Dioxins/furns(ng/dscm) 30 0,86 Gr.dscf: grins/dry stndrd cubic foot, *ppmdv:prts per million dry volume, ** u/dscm: microgrm per dry stndrd cubic meter; ng: nnogrm 1 The stndrds nd dt re reported for 7% O2, Dry bsis, nd stndrd condtions. 2 Averge of 1994 1988. Boiler N 0 3. Tble 3: Comprison of emissions for the SEMASS unit (Msschusetts, USA) [Weinstein, 2006]. Emission reductions from WTE fcilities between 1990 2000 in the US [134] Pollutnt Reduction (%) Dioxins/furns 99,7 Mercury 95,1 Cdmium 93,0 Led 90,9 Prticulte mtter 89,8 Sulfur dioxide 86,7 Tble 4: Emission reductions from WTE fcilities in the US over time [Bhd, 2007]. Pollutnts 1990 emissions (t/y) CDD/CDF TEQ bsis* 2005 emissions (t/y) Percent % reduction 4400 15 99% Mercury 57 2,3 96% Cdmium 9,6 0,4 96% Led 170 5,5 97% Prticultor mtter 18 600 780 96% HCL 57 400 3200 94% SO 2 38 300 4600 88% NO 2 64 900 49 500 24% Tble 5: Comprison of emissions from lrge nd smll WTE units before nd fter MACT retrofits [MICHAELS, 2007]. Chemicl comprison of wste in developing nd developed countries [17] Moisture content (%) Lowincome country High-income country 40 80 20 35 Density (kg/m 3 ) 250 500 120 200 Lower heting 800 1,100 1,500 2,700 vlue (kcl/kg) Tble 6: Chemicl comprison of wste in developing nd developed countries [Bhd, 2007] in the US hve decresed significntly over time s shown in Tble 4. Tble 5 compres emission in tons per yer for group of US WTE plnts operting in 1990 nd fter retrofitted with mximum chievble control technology (MACT) by 2005. The 2005 column clerly shows drmtic reductions. In some countries the ntionl lws regulte the seprtion of MSW. This could include complete seprtion by ctegory s found in countries like Germny.The moisture content of MSW is directly relted to the level of welth in given region. Tble 6 illustrtes the difference in moisture content, density nd lower heting vlue between typicl low income country nd high income country, nd shows tht the heting vlue for high income countries could be s much s twice tht of the low income countries. This mens tht MSW produced in developing countries is less suitble for WTE processing. Developing countries lso hve lower MSW genertion rtes thn lrger, industrilised countries s shown in Tble 7. Finlly, Tble 8 compres the mount of wste generted per person per dy for different countries vrying from low income to high income countries. Even in developed countries in Europe, the wste incinerted per cpit vries gretly s shown in Fig. 6. Performnce dt The potentil for energy recovery, s demonstrted by the following cse energize - August 2012 - Pge 74 studies, is lower for developing countries thn for industrilised ones. Globlly, in 2003/4, there were 600 WTE fcilities round the world, processing 130-million tons of MSW nnully. Mny re locted in countries tht re severely limited in spce, with dense popultions producing nywhere from round 1 kg of MSW per person per dy to 2 kg. In plces like Europe, lnd filling of sorted combustible MSW is illegl, nd lnd filling is txed. The number of WTE fcilities round the world ppers in Fig. 7, with Jpn nd Tiwn in the led. Jpn, with n verge MSW genertion of 314 kg per cpit nnully [or 1,1kg/ per cpit/dy] (2004) incinertes 80% of its MSW to produce both electricity nd heting. This mens tht 40-million of the 50-million ton of MSW generted nnully is incinerted, with Jpn's instlled cpcity t 1000 MW power genertion. Europe (in 2002) hd cpcity of 40-million tons nnully, from which 41-million GJ of power ws generted. The EU-15 (2006) incinertes 20 25% of its totl MSW in 400 WTE fcilities with n verge cpcity of round 500 tons/dy. The distribution of WTE sites round Europe ppers in Fig. 8, together with the tons per yer incinerted in 2003. In 2007, there were 87 WTE fcilities in the United Sttes, processing 28,7-million tons of MSW, with genertion cpcity of 2720 MW. Annully, the US genertes pproximtely 17-billion kwh. While the US processes 8% of its totl MSW in WTE fcilities, 64% is lndfilled nd only 28% is recycled [21]. It is estimted tht if the US were to incinerte ll of its combustible MSW, the power generted would be ble to provide 3 4% of the ntion's electric needs. [6] The US does not hve lrge district heting, decresing the benefits of cogenertion. With the lndfills filling up nd some sttes driving MSW by truck to other sttes for buril, the prospect of reducing MSW by 90% mkes incinertion n ttrctive option. In 2003, 500 600 kwh of electricity ws produced for every ton of MSW processed. 770 000 t of ferrous scrp metl ws lso slvged from the shes in these fcilities. Fig. 9 illustrtes the loction of WTE fcilities in the different sttes in the US. In 1991 the Integrted Wste Services Assocition (IWSA) ws formed in the US. Municipl solid wste-genertion rtes nd reltive income levels Country Low income Middle income High income Annul income ($/cp/yr) 825 3255 3256 10065 >10066 Municipl solid wste genertion rte (t/cp/yr) 0,1 0,6 0,2 0,5 0,3 to >0,8 Note: Income levels s defined by world bnk (www.worldbnk.org/dt/wd?2005) Sources: Bermche-Perez et l., 2001 Cllrecovery, 2004, 2005, Diz nd Eggeth, 2002,Griffiths nd Willims, 2005 Idris et l., 2003, Kse v et l., 2002 Ojed-Benitez nd Berud-Lozno, 2003, Hung et l., 2006, US EPA, 2003. Tble 7: Municipl solid wste genertion rtes nd reltive income levels [BOGNER ET AL, 2007]
2005 mde the lnd filling of untreted MSW illegl. Fig. 6: Averge mount of wste incinerted. [Michels, 2007]. Sweden hs since 2002, outlwed lnd filling of presorted combustible MSW [9]. The Swedish popultion of 9-million produced MSW rte of 462 kg per person nnully. 22 183 000 t ws collected, nd 46,7% of the household MSW ws incinerted for cogenertion. In 2004, 9,3 TWh energy ws recovered. [22]. Overll, the Swedish incinerted 3188 000 t of MSW, nd generted 740 GWh of electricity nd 9300 GWh of overll energy. The Cndin popultion considered in the proposl ws 32-million, nd produced roughly 640 kg MSW per cpit nnully. Overll, 1,017-million t of MSW ws collected, nd 975 000 t thereof could be incinerted to generte n expected 417 GWh of electricity nd 2635 GWh of overll energy. The WTE plnt tht ws used s bse for the Toronto proposl is clled Sävenäs, nd is locted in Gothenburg. It hs three furnces tht burn totl of 460 000 t of wste per yer. In Germny, roughly 340-million t of wste is produced, of which 48-million re municipl wste. 25-million t of these 48-million re recovered (incinerted) in 50 cogenertion plnts, 10 power genertion plnts, nd 9 het/stem plnts [18]. Broken down by cpcity, there is 20,2-million t per yer incinertion cpcity; 5-million refuse derived fuel (RDF) cpcity, nd roughly 2-million for cogenertion. 14-billion kwh of het is produced nnully, s well s 7-billion kwh of electricity. Germny hs strict rules for source seprtion of MSW, nd hs since Denmrk ws the first Europen country to bn the lnd filling of combustible MSW. With 29 fcilities, 3,5-million t of wste is treted, including 20% of the sludge from wstewter, equivlent to pproximtely 26% of the totl MSW produced in 2005. In 2003, the totl MSW produced ws YOUR PARTNER IN ENERGY EFFICIENCY AND THE ENVIRONMENT >>CLEAN ENERGY SOLUTIONS<< Tel: +27 11 704 0580 emil: enquiry@cbz.co.z website: www.cbz.co.z energize - August 2012 - Pge 75
Wste genertion in selected countries (kg/person/dy) [150] Low-income countries* High-income countries Indi 0,46 Germny 0,99 Nepl 0,50 Denmrk 1,26 Vietnm 0,55 Hollnd 1,37 Chin 0,79 Austrli 1,89 Sir Lnk 0,89 USA 2,00 *Wste genertion rtes in urbn res Tble 8: Wste genertion in selected countries. [Bhd, 2007] hd 3,29-million t of MSW incinertion cpcity in 2004 for its 28 WTE fcilities. [www.swissworld.org]. Tiwn (2005) produces totl of 8,38-million tons of MSW nnully, round 381 kg per cpit. The verge wter content of Tiwn's MSW is 50%, leving the 2005 expecttions for power genertion in the 21 plnned WTE fcilities t 1850 000 MWh of electricity nnully, while processing 65% of the totl MSW generted. Prior to 2005, the expected revenue from the WTE fcilities ws $47-million [20]. Mumbi, Indi, hs popultion of pproximtely 12-million (2008), nd its residents produce n verge of 0,18 t of MSW per person per yer. In 2008 proposl by grdute student Perinz Bhd t Columbi University, n RDF fcility t one of the lndfill sites ws proposed. It would produce 500 kwh per ton of MSW processed [7]. Fig. 7: Number of WTE fcilities round the world. [Renosm]. A WTE fcility with 1000 metric tons per dy cpcity, generting 600 kwh per ton of MSW ws suggested in 2006 for the city of Sntigo, Chile [24]. The plnt is expected to produce 720 kwh/ t of MSW, of which 600 kwh could be sold. A 20 MW WTE plnt hs been proposed for El Gucl, Colombi to be constructed t lndfill. The fcility would tke in 650 t per dy of MSW nd convert it into refuse derived fuel, totlling 400 t per dy. The process would generte 20 MW of electricity.. There is potentil for 47 MW cpcity in the four min cities in Colombi. It is expected tht the fcility would generte 470 MWh per dy of electricity. Additionl informtion For more detiled informtion on WTE fcilities round the world, see: www. industcrds.com/ppworld.htm, s well s http://yeroc.us/wte-db Fig. 8: Amount of wste incinerted in Europe per yer. [Renosm]. round 12,7-million t, of which 3,3-million tons were incinerted. For every ton of MSW incinerted, 2 MWh of het nd 0,67 MWh of electricity is produced. In 2003, round 98% of the remining sh ws recycled s well. The overll electricity generted in 2003 ws 1,47-million MWh. (Renosm; Dnish Environmentl Protection Agency). Switzerlnd, which since 2000, lso requires combustible MSW to be incinerted, nd References [1] Energy Recovery - Europen Countries. WTERT. www.ses.columbi.edu/erth/wtert/ globlwte_europe.html [2] Energy Recovery. WTERT. www.ses. columbi.edu/erth/wtert/globlwte.html [3] Fesibility study for the 20 MW wste to energy plnt t El Gucl lndfill. Instituto pr el Desrrollo de Antioqui (IDEA). December 7, 2010. Medellín, Colombi. [4] Fesibility study for the Turkey: ISTAÇ Wste to Energy plnt. Istnbul Environmentl Mngement Industry nd Trding Compny. 1 November 2010. Istnbul, Turkey. [5] The most efficient wste mngement system in Europe: Wste-to-energy in Denmrk. RenoSm. http://viewer.zmgs. com/showmg.php?mid=wsdps [6] ASME. Wste-to-Energy: A Renewble Energy Source from Municipl Solid Wste. Solid Wste Processing Division nd Energy Committee of ASME's Technicl Communities of Knowledge nd Community. 2008. [7] P Bhd, N Themelis, Drft nwtec16-1930: energize - August 2012 - Pge 76
Fig. 9: WTE plnts in the US. [Themelis, 2003]. potentil for the FIRST WTE fcility in Mumbi (Bomby) Indi. 16th Annul North Americn Wste-to-Energy Conference. Proceedings of NAWTEC16. My 19-21, 2008, Phildelphi, Pennsylvni, USA. Deprtment of Erth nd Environmentl Engineering, nd Erth Engineering Center, Columbi University, New York, NY 10027 www. ses.columbi.edu/erth/wtert/nawtec16-1930_bhd_themelis. pdf [8] P Bhd, Fesibility nlysis of wste-to-energy s key component of integrted solid wste mngement in Mumbi, Indi. WTERT. Columbi University. 1 July 2007 [9] J Bogner, M Abdelrfie Ahmed, C Diz, A Fij, Q Go, S Hshimoto, K Mreckov, R Piptti, T Zhng, Wste Mngement, In Climte Chnge 2007: Mitigtion. Contribution of Working Group III to the Fourth Assessment Report of the Intergovernmentl Pnel on Climte Chnge [B Metz, OR Dvidson, PR Bosch, R Dve, LA Meyer (eds)], Cmbridge University Press, Cmbridge, United Kingdom nd New York, NY, USA [10] Cndin Wste to Energy Colition. Turning Grbge into Green Power. www.energyfromwste.c/energy/turning-grbge-into- Green-Power [11] Dnish Environmentl Protection Agency. Wste in Denmrk. Ministry of Environment nd Energy, Denmrk [12] www.covntenergy.com/en/list-of-fcilities/covnt-fcilities.spx [13] www.ses.columbi.edu/erth/ppers/globl_wste_to_energy.html [14] www.ses.columbi.edu/erth/wtert/sofos/bhd_thesis.pdf [15] www.ses.columbi.edu/erth/wtert/sofos/denmrk_wste.pdf [16] www.ses.columbi.edu/erth/wtert/sofos/wste_mngement_ Report_by_Netherlnds.pdf [17] www.wte.org/userfiles/file/asme%20wte%20white%20pper%2008. pdf [18] ITAD. Potentil Drivers nd Current Brriers of Wste-to-Energy. www.isw.org/filedmin/glleries/generl%20assembly%20nd%20 WC%202010%2011%20Hmburg/Presenttions/Spohn.pdf [19] Kusud, Tsuneo. Wste to energy project in Jpn. Electric Power Development Co.,Ltd. Tokyo Jpn www.enef.eu/history/2002/en/ pdf/kusud_aj.pdf [20] Lee Shng-Hsiu. Wste-to-Energy Fcilities in Tiwn. WTERT/Erth Engineering Center. www.ses.columbi.edu/erth/wtert/sofos/ Lee_TW.pdf [21] T Michels, The 2007 IWSA Directory of Wste-to-Energy Plnts. Integrted Wste Services Assocition. October 27, 2007. http:// energyrecoverycouncil.org/userfiles/file/iwsa_2007_directory.pdf [22] M Schönning, Swedish Wste Mngement. Cndin Urbn Institute, Toronto, June 14 2006, www.cnurb.com/medi/ Presenttions/UL_19/MSchonning140606.pdf [23] Nickols J Themelis, An overview of the globl wste-to-energy industry. Wste Mngement World (www.isw.org/), 2003-2004 Review Issue, July-August 2003, p. 40-47 [24] Pul Estevez Weinstein, Wste-to- energy s key component of integrted solid wste mngement for Sntigo, Chile: A cost- benefits ANALYSIS. Columbi University, My 2006 www.ses. columbi.edu/erth/wtert/sofos/estevez_thesis.pdf [25] www.swissworld.org/. Incinertion. Accessed: 01/07/2011. www. swissworld.org/en/environment/wste_mngement/incinertion/ print.html Contct Pt Nidoo, Pt Nidoo Consulting Engineers, Tel 031 409-3130, pt@ptnidoo.co.z energize - August 2012 - Pge 77