Recovery and Use of Landfill Gas in Adelaide, South Australia

Recovery and Use of Landfill Gas inAdelaide, South AustraliaTreloar, J. 1998AbstractAustralians rate amongst the highest producers of waste in the world, producing anaverage of 780 kilograms of disposable solid waste per capita annually (NOGIC1996). The accumulation of waste, deposited mainly in landfill sites, creates largeamounts of landfill gas that becomes an environmental pollutant and a re-useableenergy source.The main constituents of landfill gas are methane and carbon dioxide, both of whichare major contributors to global warming. Methane is also a highly flammable gas,making it a also a threat to public safety. This report looks at the potential impact onthe biosphere and atmosphere resulting from landfill gas as a pollutant, and alsodiscusses the risks to public health and safety. Some practical methods of minimisingenvironmental degradation, and using landfill gas as a valuable commercial resourcein terms of current usage and future potential are also discussed.Key Words: Gas, Methane, Landfill, Power generation, Adelaide.IntroductionScopeLandfill sites remain the most common means of waste disposal in the Adelaidemetropolitan area. Unless properly planned and managed, landfill sites threaten tobecome a significant source of environmental degradation and air pollution. Gasesgenerated by microbiological breakdown of organic waste material can create anenvironmental liability, but paradoxically the major component gas, methane, can beused as a non-polluting fuel source.AimsThe aim of this report is to consider the following aspects of landfill gas:• Source and analysis of landfill;• Location and description of sites within the Adelaide metropolitan area;• Implications for public health and safety;• Effects of soil contamination and biotic degradation, air pollution and Greenhousegas emission;

• Waste management practices for landfill gas extraction and control;• Applications for methane as an economically viable energy source;• Waste management alternatives for the future.RationaleThe emission of landfill gas from waste provides an opportunity to convert a potentialliability into an economic asset whilst reducing environmental degradation. Thesolutions are technically feasible, requiring incentives enforced by a regulatoryframework to provide the impetus for further exploitation of this resource.DiscussionSource and analysis of landfill GasThe main components of landfill gas are by-products of the decomposition of organicmaterial, usually in the form of domestic waste, by the action of naturally occurringbacteria under anaerobic conditions. A typical landfill gas analysis is shown in Table1.Methane and carbon dioxide production typically rises to peak within 6 to 12 monthsof the site closure, then gradually declines over a 30 to 50 year period. The rate of gasproduction is influenced by the interaction of several environmental factors. Thesefactors determine the decomposition rate which, in turn, affects the volatility andproductive life of a site. Figure 1 illustrates the interaction of the factors that influencethe gas production process.Table 1: Typical analysis of raw landfill gas.ComponentContentMethane (CH 4 ) 40-60%Carbon Dioxide (CO 2 ) 20-40%Nitrogen N 2 ) 2-20%Oxygen (0 2 )

Complex Organics1000-2000 ppmSource: Falzon 1998 p.2Figure 1: Methanogenesis Production Factors in Landfill SitesSource: Adapted from Falzon 1997. p.2.According to the Department of the Environment (1997, p.7), 1 million tonnes ofmixed solid waste will produce about 4 million cubic metres of landfill gas in the firstyear after closure. Assuming that the gas contained 50 percent methane, the gas wouldbe sufficient to produce 4,958 megawatt hours (mWh) of electricity. If sold at 7 centsper kWh the electricity would recover $347,060 for that year.Adelaide metropolitan landfill sitesSince the first settlement of Adelaide, landfill has been the main method of domesticand industrial waste disposal. Councils established numerous landfill sites within theirboundaries, but as urban sprawl absorbed available land, waste disposal has becomeconcentrated in a few major sites located in peripheral areas surrounding Adelaide(Figure 2).Figure 2: Landfill sites around Adelaide used for producing power

NLEGEND1. Wingfield I &22. Highbury3. Tea Tree Gully• Source: SAWMC 1993The concentrated stockpiling of waste in a few large landfill sites rather than many ofsmall sites has several advantages including:• Total land area committed to, or affected by landfill is reduced.• Risk of groundwater pollution and landfill gas migration reduced.• Management and operational processes more efficient, thus reducing costs.Most of the major landfill sites around Adelaide are either privately owned or jointlyoperated by the councils within the region, but within each Council boundary arenumerous disused landfill sites. Landfill gas production peaks within a year of siteclosure then gradually diminishes for 30 to 50 years in a typical environment (Falzon1997, p.2). The respective councils are responsible for monitoring and managementfor the active life of these sites, however Falzon (1998, p.1) suggests that landfill gasrecovery in itself is not sufficient to ensure landfill gas control. In many cases,appropriate legislation is required before correct procedures are implemented.Public Health and SafetyHealth risks, including bacterial infection and toxicity associated with the handlingand disposal of waste are recognised hazards, and precautions are taken to minimisethese risks. Because of the widely varying nature of the contents of landfill sites theconstituents of landfill gases vary widely. In an interview on the 14 September 1998,the service manager of Energy Developments, Mr. J. McCann, stated that more than900 different chemical compounds have been identified from samples taken from theWingfield site. Although there is no evidence to indicate that landfill gas is harmful to

public health it is reasonable to expect that people frequently exposed to landfill sitesare at risk from bacterial or toxic emissions.The primary components of landfill gas are methane and carbon dioxide, which areboth odourless gases. Carbon dioxide is a health hazard by affecting humanrespiration in concentrations greater than 1.5 percent, and methane is an asphyxiant.Probably the most indicative characteristic of landfill gas is the unpleasant odourcaused by small amounts of hydrogen sulphide and mercaptans present.The threat to public safety resulting from landfill gas explosions is of more concernthan the health risks. There have been over 50 cases of death or serious injuryreported overseas resulting from explosions caused by landfill gas Sixteen peoplewere killed in one incident at a landfill site near Istanbul in Turkey, as a direct resultof the emission of landfill gas (Falzon 1998, p.1). The dangers are not confined to thesite area, as the gas can migrate extensively through soil substrates. Gas migrationwas responsible for a fatal explosion near Masserano, Italy in December 1995. Theexplosion occurred at a water well 100 metres from the border of the landfill site(Jarre, Mezzalama &Luridiana 1997, p.497). The fact that methane becomesexplosive at relatively low concentration levels increases the risk potential. It isflammable when 5 to 15 percent of methane is mixed with air.Soil and Air PollutionCarbon dioxide and methane are recognised as major contributors to global warming.One tonne of methane has the global warming effect as 24.5 tonnes of carbon dioxide.According to Falzon (1997, p.3) methane from landfill accounts for 13.5 percent ofAustralia's total emissions, with an estimated 710 000 tonnes of methane beingreleased into the atmosphere annually. With current technology, it is feasible torecover up to 90 percent of the methane from landfill, significantly reducingatmospheric pollution.Soil degradation from poorly managed landfill sites results in vegetation being killedoff as gas percolates through the soil substrates to the surface. Methane displacesoxygen in the soil, starving the plant roots, causing established vegetation to die.Methane also prevents revegetation of landfill sites until the methane has dispersedfrom the soil (Haylock 1996 p.9). Dispersion may take more than 70 years in semiaridclimates.Landfill Gas Management PracticesThe recovery of landfill gas alone does not constitute proper control. Landfill sitemanagement requires an initial comprehensive survey followed by constantmonitoring in conjunction with any extraction or ventilation system employed. Theestablishment of a formalised Environment Protection Policy for landfill is currentlybeing prepared by the Environmental Protection Authority, to comply with therequirements of 1S014001(International) code of management (Rodenberg 1997, p.7).The economic viability of landfill site gas extraction depends on the production rate,the quality (methane content) of recoverable gas and expected active life of a site. Atpresent, flaring or gas lighting is the more practical option for most smaller or older

sites, or those emitting low-grade gas such as those at Garden Island and thePatawalonga South Golf Course. Landfill Management Services is an Australiancompany specialising in the development and application of this, and other forms oflandfill gas control technology in Adelaide and interstate.The commercial use of landfill gas began in Adelaide in 1982, when the Falzon BrickCompany extracted gas from the nearby Highbury landfill site to supplement the fuelused for kiln firing bricks (Falzon 1997, p.4). Since then further developments inlandfill gas use include purification of gas adopting membrane technology to producehigh quality gas. This project, undertaken by Boral Gas operated from 1984 to l989,but in a telephone conversation with Boral Gas representative Mr. T. Hockley on 14September 1998, I was informed that this became uneconomic due to the decliningquality of available landfill gas at the time.The most significant commercial use of landfill gas currently being undertaken ispower generation. There are only 4 of the fourteen major landfill depots servicingAdelaide from which gas is being extracted to supply 5 power generation sites asdescribed in Table 2.Table 2: LFG Power generation sites in Adelaide.LocationWingfield (1)Wingfield (2)Tea Tree GullyPedler CreekHighburyNominal Output4 MW2 MW3 MW3 MW2 MWSource: EDL 1997The sites currently operating are owned and operated by Energy DevelopmentsLimited, which is an Australian company focusing on power generation from landfillgas. The application system is based on the use of a series of l megawatt generatormodules that can be parallel connected, and relocated to other sites, dependant on theavailable gas supply rate.Plate 1: Modular power Generator site at Wingfield.

Source: Energy Developments, 1998Landfill gas is drawn from the clay capped landfill sites via a series of interconnectedbores and, after filtration and drying, is fed directly to the diesel generators. Dieselengines have been converted to run on landfill gas with a methane content as low as30 percent. The power generated is fed directly into the state power grid under a buybackagreement with the Electricity Trust of South Australia (ETSA).BenefitsThe benefits of using landfill gas for power generation are:• Exhaust emissions are environmentally less damaging than vented gas.• Economic gain from utilisation of an environmentally damaging by-product.• Positive extraction of gas prevents soil infiltration, preserving vegetation.• Clean, visually and audibly unobtrusive sites.As new technology improves the efficiency of gas extraction methods and powergeneration from landfill gas, more sites are likely to be developed for this, or othercommercial purposes.Solutions for the futureLandfill gas utilisation is an emerging industry in Australia. Technologicaladvancements overseas, particularly in Western Europe and the United States aredeveloping not only alternative applications for landfill gas, but more effective waysof converting waste to energy. Converting landfill gas to methanol, utilisation in fuelcells and enhanced methane production by using waste digesters are someapplications being developed overseas. Australia should take advantage of availabletechnology, as well becoming more involved internationally in research anddevelopment.

ConclusionThe indications from the research conducted for this report show that availablelandfill gas from existing resources is grossly under utilised in Adelaide. This islargely due to lack of commitment by local and state governments to providelegislative or financial incentives. Apart from kerbside recycling there have been fewchanges in waste management practices for many years. Public opposition based onenvironmental concerns inhibit the establishment of new landfill sites and gasutilisation schemes. Most people accept the necessity for landfill sites, as long as theyare not in their own backyard. One such example was the rejection of a proposedlandfill site at Highbury due to community action (Leue 1997, p.6).Initiatives such as separating all waste prior to disposal can produce a higher methaneconcentration, making landfill gas more commercially viable. Increasing wastedisposal charges would help offset the cost of sorting, and reduce the total volume ofmaterial discarded as material reuse becomes more economical. The technology isavailable, and in many instances has been implemented for controlling and exploitinglandfill gas. What is needed are more stringent and definitive regulations that wouldpromote further investment in this area. Greater awareness of the problems associatedwith the ever increasing amount of landfill, and a proactive approach by the wasteindustry to effectively manage landfill sites can result in positive action in the future.ReferencesCampbell, M.1997, 'Adelaide's Waste Solutions for the Future 1 Environment SA,vol.6, no.1, p.19.Department of Environment, 1997, Waste: Methane capture and use quick reftrenceguide, Environment Protection Group, Canberra.Falzon, J. 1997, 'Landfill gas: an Australian perspective ' , Proceedings from the sixthInternational Landfill Symposium held 1997, Sardinia.Falzon, J. ~998, 'Landfill gas Developments ' , Proceedings from the fourth NationalHazardous & Solid Waste Convention held April 1998, Brisbane.Haylock, L. 1996, 1 Landfill Gas: from liability to asset', Environment SA, vol.5, no.3,p.9.Jarre, P., Mezzalama, R. & Luridiana, A. 1997, Lessons to be learned from a FatalGas Explosion, pp.497-506.Leue, C., 1997, 'Waste of a Community', Environment SA, vol.6, no.1, p.6.Modular Landfill Gas Power Generation System. Pamphlet, Energy DevelopmentsLtd., South Yarra, Victoria.NGGIC (National Greenhouse Gas Inventory Council) 1996, 1988 to 1994 Summaryand Analysis of Trends, AGPS, Canberra.

Rodenberg, R. 1997, 'Waste Management - 21st Century Solutions', Environment SA,vol.6, no.1, p.7. South Australian Waste Management Commission, 1992/93, AnnualReport, Government Printing Office, Adelaide.GEOView Home | GEOS Home | Editorial Information | Notes to Contributors |Submission Form | ContentsSchool of Geography, Population and Environmental ManagementFlinders University, Adelaide, Australia