Paper Title: Carbon Storage due to Disposal of Biogenic Materials in U.S. Landfills

This paper reviews the methodology used to quantify carbon storage in landfills for the Inventory of U.S. Greenhouse Gas Emissions and Sinks. Though the Intergovernmental Panel on Climate Change (IPCC) does not provide specific guidance on quantifying this carbon sink, the IPCC Guidelines recommend that countries be comprehensive in their coverage of greenhouse gas emissions and sinks. The US has developed separate methods for quantifying storage attributable to harvested wood products (HWP), and yard trimmings and food scraps. Net changes in carbon stored in HWP (including solid wood products and paper) in use and in dumps or landfills is estimated by tracking the disposition of HWP produced, imported, and exported beginning in 1910 and continuing up to the present using the WOODCARB model. WOODCARB uses assumptions on the fate of carbon in landfill environments to track annual carbon accumulation and emissions. For yard trimmings and food scraps, storage factors are used to estimate the proportion of annual disposal that will persist in the landfill environment. Landfill carbon storage due to wood products, yard trimmings, and food scraps was about 165 Tg CO2 Eq in 2002, comprising 24 percent of estimated carbon sequestration in U.S. forests and other carbon pools. To put this in perspective, if the annual carbon storage in the U.S. landfill pool were considered a separate category in the U.S. national greenhouse gas inventory, it would rank 5 th out of the 47 categories of sources and sinks investigated, behind only fossil fuel combustion, forest carbon storage, agricultural soil emissions, and landfill methane, and ahead of such sources as natural gas systems, coal mining, and all of the "high-GWP" sources combined.