Figure 2.

Schematic representation showing the elements of a complete GHG accounting system. For a full accounting of the GHG consequences of any biomass energy production system, it is essential to quantify: (a) emissions from production, harvesting, processing and transport, when these come from fossil fuels and not from harvested material; (b) emissions (persistent carbon debt) associated with the initial conversion from original vegetation to biomass crop. The carbon losses may occur over many years or decades as coarse woody debris and soil organic matter decompose. Harvested materials converted to long‐lived products should appear as offsets reducing the impacts of materials from the ecosystem; (c) rotational sources (cyclical carbon debt) and sinks (cyclical carbon repayment) that reflect changes in the site carbon balance with harvests over time. On a large landscape, these may be partly or completely smoothed; and (d) any foregone sink that would have operated in the absence of the initial clearing. Finally, fossil emissions offsets are an important component of the overall budget. Biogenic fluxes are shown in blue. Fossil fluxes are shown in red