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

the Swedish ORWARE model for controlled anaerobic processes). 1211 Emissions of
methane from landfill are allocated to specific years over a 150 year period. The
degradation factors within the model have been validated to some extent through
assessing the implied methane emissions from the materials and cross-checking
against work undertaken in the United States and by the UK Environment Agency. 1212
The constituent carbon fractions degrade at different speeds as a result of variations
in their chemical and physical structure. Our model uses three degradation speeds to
represent the varying speeds at which carbon degrades within the landfill. 1213 The
simplified grouping of carbon fractions used within the model is shown in Table 63-4.
Table 63-4: Simplification of Carbon Fractions for Landfill
Speed Speed of of Decay Decay
Carbon Carbon Fraction(s)
Fraction(s)
Fast Sugars
Medium Fats, Proteins, Cellulose
Slow Lignin and some Cellulose 1
Notes
1. Some cellulose is bound within the lignin and is therefore similarly resistant to
degradation
Source: Dalemo M (1996) The Modelling of an Anaerobic Digestion Plant and a Sewage Plant in the
ORWARE Simulation Model, Rapport 213, Swedish University of Agricultural Sciences, Uppsala 1996
To take account of the time profile of these emissions over the 150 year period, the
damage costs for landfill emissions are discounted using a declining long-term
discount rate as recommended in the UK Treasury’s Green Book. 1214 Table 63-5
shows the rates at which damage costs are discounted for the relevant time periods
1211 M. Dalemo (1997) The ORWARE Simulation Model - Anaerobic Digestion and Sewage Plant Submodels;
Licentiate thesis, Swedish University of Agricultural Sciences, SLU, Uppsala; Dalemo M (1999)
Environmental Systems Analysis of Organic Waste Management; The ORWARE Model and the Sewage
Plant and Anaerobic Digestion Submodels, Ph D Thesis, Swedish University of Agricultural Sciences,
Uppsala.
1212 M. Barlaz (1997) Biodegradative Analysis of Municipal Solid Waste in Laboratory-scale Landfills,
EPA 600/R-97-071, Washington, DC: USEPA; R. Gregory and A. Revans (2000) Part One, in
Environment Agency (2000) Life Cycle Inventory Development for Waste Management Operations:
Landfill, Project Record P1/392/3, Bristol: Environment Agency
1213 The same approach is taken in modelling other anaerobic processes, including landfill (see, for
example, LQM (2003) Methane Emissions from Landfill Sites in the UK, Report for Defra, January
2003). The method is not usually applied to aerobic processes, though some work of a similar nature
has been undertaken for degradation of organic matter in soil (including the work by DU).
1214 HM Treasury (UK) The Green Book: Appraisal and Evaluation in Central Government, Treasury
Guidance, http://www.hm-treasury.gov.uk/d/green_book_complete.pdf .
989
International Review of Waste Policy: Annexes