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Dioxin emissions from small-scale combustion of bio-fuel and household waste
Umeå University, Faculty of Science and Technology, Department of Chemistry.
2005 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [sv]

Denna avhandling behandlar rökgasutsläpp av persistenta organiska föroreningar, framförallt dioxiner, vid förbränning av fasta biobränslen och torrt hushållsavfall i relativt små anläggningar (5-600 kW) utan avancerad rökgasreningsteknik.

Samförbränning av avfall och biobränsle i effektiva mindre biobränslepannor testades som en alternativ strategi till den vanligen förekommande storskaliga hanteringen och förbränningen fast hushållsavfall. Medan storskalig förbränning av avfall ger investeringsmässiga fördelar med rökgasreningsteknik etc. kan små lokala anläggningar ha transportmässiga fördelar och möjligheter till utnyttjande av lokala biobränsletillgångar. Källsorterat, torrt, brännbart hushållsavfall insamlades från hushåll i glesbygd och samförbrändes i brikettform med energigräset rörflen i 150-600 kW biobränslepannor. Endast undantagsvis understeg dioxinemissionerna gällande gränsvärden för avfallsförbränning och nivåerna av väteklorid i rökgas översteg gränsvärdena flerfaldigt. Det bedömdes att någon form av extra rökgasrening är nödvändig för att säkerställa nivågränserna. Dioxiner hittades också i det eldade avfallet, framförallt i textilfraktionen. Dioxinmängderna i rökgaserna var oftast lägre än i det ingående bränslet.

Intermittent pelletseldning gav oväntat höga utsläpp av dioxiner med en emissionsfaktor på 28 ng(WHO-TEQ)/kg. Vedeldning i en modern miljömärkt villapanna gav betydligt lägre utsläpp av dioxiner än eldning i en gammal kombipanna och eldning med full lufttillförsel, som kan jämföras med användning av ackumulatortank, resulterade i upp till 90% minskning av utsläpp av dioxiner jämfört med eldning med reducerat lufttillskott (’pyreldning’). Eldning av plastavfall i en vedpanna gav höga utsläpp av dioxiner.

Okontrollerad förbränning av trädgårdsavfall och hushålls avfall i tunna eller som öppen eld ’bakgårdsbränning’, gav stora variationer i utsläppsnivåer som bara delvis kunde kopplas till avfallsinnehåll. Resultaten visar att denna typ av förbränning kan vara en betydande källa till dioxiner i miljön, och ett emissionsfaktorintervall på 4-72 ng (WHO-TEQ)/kg föreslås för bedömningar av utsläpp från backgårdsbränning av avfall med låga eller måttliga klorhalter.

En sammanfattande slutsats av alla försök är att dioxin utsläpp beror på komplicerade samband mellan bränsleinnehåll och förbränningsbetingelser. Bränslen med mycket höga klorhalter av ger oftast högre utsläpp av dioxiner än bränslen med låga klorhalter medan små skillnader döljs av variationer i förbränningsbetingelser.

Abstract [en]

This thesis deals with emissions of persistent organic pollutants, primarily dioxins, from the combustion of solid biofuels and dry combustible household waste in relatively small facilities, 5-600 kW, without advanced air pollution controls.

Co-combustion of waste and biofuel in effective small boilers was tested as an alternative to prevailing large-scale management and combustion strategies for handling municipal solid waste. This approach includes no advanced air pollution control systems, but offers two advantages: limiting transport and providing scope to use local biofuel resources. Source-sorted, dry, combustible household waste was collected from households in a sparsely populated area and co-combusted as briquettes together with reed canary-grass in 150-600 kW biofuel boilers. Most trials showed difficulties to meet regulative limits for the emissions of dioxins valid for incineration of MSW and the regulated limits for emissions of hydrochloric acid were exceeded manifold. It was concluded that additional flue-gas cleaning will be needed to ensure that emissions are sufficiently low. Dioxins were also found in the waste, especially in the textile fraction. The mass of dioxins in the flue-gas emissions was generally lower than the mass in the fuel input.

Intermittent combustion of wood pellets in a residential boiler resulted in an unexpectedly high dioxin emissions factor of 28 ng (WHO-TEQ)/kg fuel. Combustion of wood in a modern environmentally certified boiler yielded considerably lower dioxin emissions than combustion in an old boiler, and combustion with a full air supply, i.e. with use of heat storage tank, resulted in up to 90% reductions in dioxin emission factors compared to combustion with reduced air supply. Combustion of plastic waste in a residential wood boiler resulted in high emissions of dioxins.

Tests of uncontrolled combustion of garden and household waste in barrels or open fires, ‘backyard burnings’, resulted in emissions with large variations that could only be partly correlated to the waste constituents. The results imply that this may be an important source of dioxins in the environment and an emission factor range of 4-72 ng (WHO-TEQ)/kg is suggested for estimating emissions from backyard burnings of lightly and moderately chlorine-contaminated waste.

A summarized conclusion from all of the experiments is that predicting emission levels from waste contents is not straightforward (except that fuels with very high chlorine levels will usually result in high levels of dioxins in flue-gas emissions). Moderate differences in chlorine levels will usually be masked by the effect of variations in combustion conditions.

Place, publisher, year, edition, pages
Umeå: Kemi , 2005. , 54 p.
Keyword [en]
Source-sorted waste, Household waste, Textile, Biofuel, Firewood, Pellets, Combustion, Wood boiler, Pellet boiler, Backyard burning, Garden waste, PCDD/F, dioxin, PCB, Emission factor
Keyword [sv]
Källsorterat avfall, Hushållsavfall, Textil, Biobränsle, Ved, Pellets, Förbränning, Vedpanna, Pelletpanna, Trädgårdsavfall, PCDD/F, dioxin, PCB, Emissionsfaktor
National Category
Environmental Sciences
Identifiers
URN: urn:nbn:se:umu:diva-593ISBN: 91-7305-956-0 (print)OAI: oai:DiVA.org:umu-593DiVA: diva2:143897
Public defence
2005-10-14, KB3B1, KBC-huset, Umeå Universitet, Umeå, 10:00
Opponent
Supervisors
Available from: 2005-09-21 Created: 2005-09-21 Last updated: 2017-03-24Bibliographically approved
List of papers
1. Emissions from small-scale energy production using co-combustion of biofuel and the dry fraction of household waste
Open this publication in new window or tab >>Emissions from small-scale energy production using co-combustion of biofuel and the dry fraction of household waste
2005 (English)In: Waste Management, ISSN 0956-053X, E-ISSN 1879-2456, Vol. 25, no 3, 311-321 p.Article in journal (Refereed) Published
Abstract [en]

In sparsely populated rural areas, recycling of household waste might not always be the most environmentally advantageous solution due to the total amount of transport involved. In this study, an alternative approach to recycling has been tested using efficient small-scale biofuel boilers for co-combustion of biofuel and high-energy waste. The dry combustible fraction of source-sorted household waste was mixed with the energy crop reed canary-grass (Phalaris Arundinacea L.), and combusted in both a 5-kW pilot scale reactor and a biofuel boiler with 140–180 kW output capacity, in the form of pellets and briquettes, respectively. The chlorine content of the waste fraction was 0.2%, most of which originated from plastics. The HCl emissions exceeded levels stipulated in new EU-directives, but levels of equal magnitude were also generated from combustion of the pure biofuel. Addition of waste to the biofuel did not give any apparent increase in emissions of organic compounds. Dioxin levels were close to stipulated limits. With further refinement of combustion equipment, small-scale co-combustion systems have the potential to comply with emission regulations.

Place, publisher, year, edition, pages
New York, N.Y.: Pergamon, 2005
Keyword
municipal solid-waste, reed canary-grass, fluidized-bed reactor, mass-balance, polychlorinated dibenzofurans, combustion conditions, organic pollutants, heating-systems, flue-gas, incineration
Identifiers
urn:nbn:se:umu:diva-4685 (URN)10.1016/j.wasman.2004.07.018 (DOI)
Available from: 2005-09-21 Created: 2005-09-21 Last updated: 2011-03-28Bibliographically approved
2. PCDD/F in source-sorted waste fractions and emissions from their co-combustion with reed canary-grass
Open this publication in new window or tab >>PCDD/F in source-sorted waste fractions and emissions from their co-combustion with reed canary-grass
2007 (English)In: Waste Management, ISSN 0956-053X, E-ISSN 1879-2456, Vol. 27, no 11, 1580-1592 p.Article in journal (Refereed) Published
Abstract [en]

The dry combustible fraction of source-sorted household waste, including material that would otherwise be recycled, was mixed with the energy crop reed canary-grass (Phalaris arundinacea L.), and combusted as briquettes in 150 and 600 kW biofuel-boilers without advanced cleaning systems. The source-sorted waste was further sorted and characterized according to its material and chemical contents. The bulk of the waste’s chlorine content came from the non-package plastic fraction, whereas 90–95% of ∑PCDD/F (74–90% of WHO-TEQ) originated from the textile fraction. The sources of the dioxins in the waste fractions are discussed. The balance of dioxin levels was negative, i.e., the amounts of dioxins output in the flue gas were lower than those input in the fuel, except when there were operational disturbances in the combustion. In one of the combustion trials the total levels of dioxins in the flue-gas and ashes were also lower than the input levels. The use of additional cleaning equipment will be needed to ensure that emissions of dioxins and hydrochloric acid will be below legal limits.

Place, publisher, year, edition, pages
Oxford: Pergamon Press, 2007
Keyword
municipal solid waste, dibenzo-P-dioxins, mass-balance, household waste, combustion, PCDFS, incinerators, strategies, industry, carbon
National Category
Environmental Sciences Environmental Engineering
Identifiers
urn:nbn:se:umu:diva-16370 (URN)10.1016/j.wasman.2006.08.008 (DOI)000250060500014 ()
Available from: 2007-09-18 Created: 2007-09-18 Last updated: 2017-03-24Bibliographically approved
3. Emission of PCDD/F, PCB, and HCB from combustion of firewood and pellets in residential stoves and boilers
Open this publication in new window or tab >>Emission of PCDD/F, PCB, and HCB from combustion of firewood and pellets in residential stoves and boilers
2006 (English)In: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 40, no 16, 4968-4975 p.Article in journal (Refereed) Published
Abstract [en]

To assess potential emissions of polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), polychlorinated biphenyls (PCBs), and hexachlorobenzene (HCB) from residential combustion of biofuels, experiments were performed in which various types of pellets and firewood were combusted in four types of stoves and boilers, with both full and reduced rates of air supply. Intermittent combustion of wood pellets resulted in emissions of 11 ng-(WHO-TEQ)/kg combusted fuel (dry weight). A modern, environmentally certified boiler yielded somewhat lower emissions of PCCD/F and PCB than a wood stove. Both gave <0.1 ng(WHO-TEQ)/m3n (1.3-6.5 ng(WHO-TEQ)/kg) and considerably lower emissions than an old boiler (7.0-13 ng(WHO-TEQ)/kg). No positive effect on emissions could be observed in full air combustion (simulating the use of a heat storage tank) compared to combustion with reduced air. Two of the wood combustion experiments included paper and plastic waste fuels. Chlorine-containing plastic waste gave rise to high emissions: ca. 310 ng(WHO-TEQ)/ kg over the whole combustion cycle. The homologue profiles of PCDD/Fs show characteristic differences between ashes and flue gas from combustions with different levels of air supply. These differences do not, however, seem to have any correlation to the relative amount of toxic congeners.

Place, publisher, year, edition, pages
Washington: American Chemical Society (ACS), 2006
Keyword
air pollutants, benzofurans, chlorine, environmental monitoring, environmental pollutants, fires, hexachlorobenzene, particle size, plastics, polychlorinated biphenyls, soil pollutants, temperature, tetrachlorodibenzodioxin, wood
National Category
Environmental Engineering Environmental Sciences
Identifiers
urn:nbn:se:umu:diva-11755 (URN)10.1021/es0524189 (DOI)000239684900029 ()16955894 (PubMedID)
Available from: 2007-03-08 Created: 2007-03-08 Last updated: 2017-03-24Bibliographically approved
4. Emissions of polychlorinated dibenzodioxins and dibenzofurans and polychlorinated biphenyls from uncontrolled burning of garden and domestic waste (backyard burning)
Open this publication in new window or tab >>Emissions of polychlorinated dibenzodioxins and dibenzofurans and polychlorinated biphenyls from uncontrolled burning of garden and domestic waste (backyard burning)
2005 (English)In: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 39, no 22, 8790-8796 p.Article in journal (Refereed) Published
Abstract [en]

To assess emissions of dioxins (chlorinated dibenzodioxins and dibenzofurans) and PCB from uncontrolled domestic combustion of waste ("backyard burning"),test combustions in barrels and open fires were monitored. The waste fuels used were garden waste, paper, paper and plastic packaging, refuse-derived fuel (RDF), PVC, and electronic scrap. Combustions including PVC and electronic scrap emitted several orders of magnitude more dioxins than the other waste fuels. Emissions from the other fuels had considerable variations, but the levels were difficult to relate to waste composition. Emission factors of PCDD/F and PCB from the backyard burning ranged from 2.2 to 13 000 ng (WHO-TEQ)/kg. The levels found in ash usually were less than 5% of the total. For assessment of total emissions of dioxins and PCB from backyard burning of low and moderately contaminated wastes, an emission factor range of 4-72 ng (WHO-TEQ)/kg is suggested. These figures imply that combusting waste in the backyard could contribute substantially to total emissions, even if the amounts of fuel involved are equivalent to just a few tenths of a percent of the amounts combusted in municipal waste incinerators.

Place, publisher, year, edition, pages
Washington: American Chemical Society (ACS), 2005
Keyword
household waste, mass-balance, P-dioxins, combustion, incineration, barrels, PCDD/F, air
National Category
Environmental Sciences Environmental Engineering
Identifiers
urn:nbn:se:umu:diva-13590 (URN)10.1021/es051117w (DOI)000233297100037 ()
Available from: 2007-05-11 Created: 2007-05-11 Last updated: 2017-03-24Bibliographically approved

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