Global methane emissions from landfills: New methodology and annual estimates 1980-1996

Significant interannual variations in the growth rate of atmospheric CH4 justify the development of an improved methodology for landfill emissions, the largest anthropogenic source in many developed countries. A major problem is that reliable solid waste data often do not exist, especially for developing countries where emissions are increasing. Here we develop and apply a new proxy method to reconstruct historical estimates for annual CH4 emissions for the period 1980-1996. Using composited solid waste data from 1975-1995, we developed linear regressions for waste generation per capita based on energy consumption per capita, a surrogate which reflects population and affluence, the major determinants of solid waste generation rates. Using total population (developed countries) or urban population (developing countries), annual landfill CH4 emissions were estimated using a modified Intergovernmental Panel on Climate Change (IPCC) methodology. Methane recovery was modeled by fitting historic data to time-dependent linear relationships. Two scenarios for global emissions using the surrogate were compared to two scenarios using an IPCC standard methodology. Results from all four scenarios range from 16 to 57 Tg CH4 yr(-1,) a similar range as previous estimates. We support the use of the lower energy surrogate scenario (A) with annual emissions of 16-20 Tg CH4 yr(-1), both positive and negative annual variations, and commercial recovery > 15% by 1996. The surrogate provides a reasonable methodology for a large number of countries where data do not exist, a consistent methodology for both developed and developing countries, and a procedure which facilitates annual updates using readily available data.