International Review of Waste Management Policy - Department of ...

plant is still relatively limited. 1273 The air quality limits imposed upon AD facilities are
typically less onerous than those for waste incinerators; thus there is a lack of
incentive to incur the further expense that the installation of this additional
equipment requires.
Table 63-31 outlines the emissions from the combustion of biogas using a gas
engine. The table uses data from the previously cited Reference Document along with
information supplied through emissions tests at an Australian MBT plant operated by
Global Renewables Ltd (GRL). The latter may overstate emissions, being derived from
mixed waste sources.
Table 63-31: Emissions from the Combustion of Biogas
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Emissions Emissions from from from biogas biogas combusti combustion combusti on (g / tonne
of of of waste waste to to process)
process)
CO 200
Dust 20
NOx 250
Hydrocarbons 40
SO2 20
Notes
Emissions are calculated assuming 3,960 m 3 exhaust gas is produced per hour from each of
two gas engines, using data provided by GRL from their Eastern Creek MBT facility in Australia
(that facility treats 70,000 tonnes of waste per year in the AD part of the plant).
Sources: European Commission (2006) Integrated Pollution Prevention and Control: Reference
Document on Best Available Techniques for the Waste Treatment Industries, August 2006; EML Air
PTY (2008) Test Report Prepared for Eastern Creek Operations, report for Global Renewables Ltd, April
2008; AEA (2007) Mechanical Biological Treatment: Case Study 2: Eastern Creek UR 3R Sydney,
Report to IEA Bioenergy Task 36, April 2007
However, as was previously indicated in Table 63-29 the plant is assumed to
generate 286 kWh of electricity per tonne of waste to the facility, and emissions to air
are assumed to be offset as a result of this energy production. The avoided air
emissions resulting from electricity generation are presented in Table 63-32,
calculated using emissions data supplied by Ecoinvent for European CCGT plant. The
data suggests that there is a marginal air quality benefit associated with generating
electricity using AD in comparison to generation at larger scale CCGT plant. As gas
turbine efficiencies increase, the resultant higher firing temperatures lead to greater
NOx formation. Thus measures taken to reduce NOx formation will be less effective at
the larger and more efficient CCGT plant. 1274 Levels of other emissions will depend on
1273 It is understood, however, that authorities in The Netherlands wanted to impose this as standard
for all AD facilities.
1274 European Commission (2006) Integrated Pollution Prevention and Control: Reference Document
on Best Available Techniques for Large Combustion Plants, July 2006