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

Table 63-28: AD Process Emissions
Parameter Parameter
Assumption
Assumption
Dry matter content of food waste 30%
Organic matter content of VS 93%
Carbon content of VS 45%
VS content of organic matter 45%
VS loss during digestion 70%
Methane content of biogas 60%
Electricity requirement 10% of biogas energy
Heat requirement 125 kWh / t
Fugitive emissions (% carbon converted to CH4) 1%
Notes
The energy requirement is assumed to be supplied by the plant itself (i.e. as parasitic load).
No additional emissions are therefore associated with the use of this energy, but the biogas
used in this way is assumed to be unavailable for further utilisation. The energy utilisation
figures are based on data supplied by plant operating in the UK and Germany.
Sources: Greenfinch (2005) Mass and Energy Balance: Ryegrass and Pig Slurry Biogas Plant,
Produced for DTI, September 2005; University of Glamorgan, The Wales Centre of Excellence for
Anaerobic Digestion and the Sustainable Environment Research Centre (2007) Ludlow (Greenfinch)
Trial Scale Kitchen Waste Treatment Plant; H. Bachmaier, M Effenberger and A Gronauer (2008)
Agricultural Biogas Production: What About the Climate Balance?, 17 th Annual Convention of
Fachverband Biogas e.V, 15 th -17 th January 2008, Nuremberg; Eunomia (2007) Managing Biowastes
from Households in the UK: Applying Life-cycle Thinking in the Framework of Cost-benefit Analysis,
Appendices to the Main Report, Report for WRAP, May 2007
Assumptions used to model the on-site utilisation of biogas in a gas engine are
presented in Table 63-29. These assumptions have been developed from data
provided by German plant operators.
Table 63-29: Emissions from the Use of Biogas in a Gas Engine
Parameter Parameter
Assumption
Assumption
Gross electrical efficiency of gas engine 40%
Fugitive emissions (gas engine slip) 2%
Notes
Net electrical efficiency is 30% taking into account parasitic load figures provided in Table
63-28. The net electricity generation total is assumed to be 286 kWh per tonne of waste to
the facility.
Sources: H. Bachmaier, M Effenberger and A Gronauer (2008) Agricultural Biogas Production: What
About the Climate Balance? 17 th Annual Convention of Fachverband Biogas e.V, 15 th -17 th January
2008, Nuremberg; F. Scholwin (2008) The State of Treatment of Biogas for Feeding in the Natural Gas
Network in Germany, 17 th Annual Convention of Fachverband Biogas e.V, 15 th -17 th January 2008,
Nuremberg
1026
29/09/09