Forest Fire Emissions Calculator

Fire emission estimates follow a four-term product: burned area, fuel load available on that area, the combustion factor describing what fraction of that fuel actually burns, and a species-specific emission factor giving grams of each gas released per kilogram of dry matter consumed. Combustion completeness is the term practitioners most often get wrong. A surface fire in closed tropical forest may consume only 20 to 40 percent of the standing fuel because live crowns and large boles do not burn, whereas grassland and savanna fires routinely reach 85 to 90 percent, and slash piles left to cure before ignition burn higher still. Emission factors reflect combustion chemistry: efficient flaming produces mostly carbon dioxide, while smouldering combustion in duff, logs, and peat produces disproportionate methane and carbon monoxide. Widely used forest values are near 1,600 g of CO2, 6.8 g of methane, and 0.2 g of nitrous oxide per kilogram burned. Methane and nitrous oxide are placed on a common footing using 100-year global warming potentials of 28 and 265 respectively. The crucial accounting caveat concerns carbon dioxide. Where forest regrows after fire, the CO2 released is reabsorbed over the recovery cycle, so national inventories on land remaining forest report only the non-CO2 gases from fire and treat the CO2 as part of a closed loop. Carbon dioxide counts as a genuine net emission where fire drives permanent conversion to other land uses, or where combustion consumes soil carbon that will not be rebuilt, as in drained tropical peatlands.

Biomass burning was largely absent from global atmospheric budgets until Wolfgang Seiler and Paul Crutzen published their assessment in the journal Climatic Change in 1980. They estimated gross and net carbon fluxes between the biosphere and atmosphere from burning worldwide and, in doing so, set out the multiplicative structure of area, biomass density, burning efficiency, and emission factor that essentially every subsequent inventory has used. Crutzen, who received the Nobel Prize in Chemistry in 1995 for work on stratospheric ozone, went on to argue that savanna and deforestation fires were a leading global source of carbon monoxide, methane, nitrogen oxides, and photochemical ozone precursors in the tropics. The emission factors themselves came from aircraft and tower measurements through the 1990s, including campaigns over southern Africa and the Brazilian Amazon that sampled fresh smoke plumes directly. Meinrat Andreae and Pierre Merlet synthesised this material into the reference compilation published in Global Biogeochemical Cycles in 2001, tabulating factors by fuel type for dozens of species; Andreae issued a substantially revised update in Atmospheric Chemistry and Physics in 2019. Burned area, historically the weakest input, was transformed by satellite mapping once MODIS began operating in 2000, and the Global Fire Emissions Database assembled by Guido van der Werf and colleagues combined satellite burned area with a biogeochemical model to produce consistent global emission time series. The IPCC adopted the same equation form in its 2006 national inventory guidelines.