Methane and nitrous oxide are the two gases that are included in emissions estimates from the Agriculture sector. Emissions declined during the early 1990s due to a large reduction in emissions of PFCs from aluminium smelting as a result of technological changes. Production of aluminium has been increasing during this period and between 1997 and 1998 emissions increased as increasing production exceeded reductions due to improved processes. However, from 1998 to 1999, despite increased production, emissions of PFCs declined due to a proportionately larger fall in emission factors. Production of cement clinker and lime increased from 1998 to 1999 with a consequent increase in emissions.
Most emissions are from solid waste disposal .
Forestry and Other land management Forestry , including commercial forestry, is both a source of and sink for CO 2 . As a result of a lack of data, estimates of this sink have remained unchanged since 1990. Land clearing Land clearing is accounted separately from other sectors due to the high level of uncertainty associated with the estimates and major improvements to methodology and sources of data. Developments over the next couple of years are expected to lead to a more robust approach to estimating emissions in this sector that will be applied to estimates for all years. Emissions from land clearing are the result of burning cleared vegetation, decay of unburnt vegetation, and emissions from soil disturbed in the process of clearing.