Credit: © ISTOCKPHOTO / JILLKYLE

Current estimates of the carbon emissions reductions that can be achieved from renewable biomass systems may be inaccurate, a study suggests.

In tallying the greenhouse contribution of certain biomass fuels, Thea Whitman and Johannes Lehmann of Cornell University in Ithaca, New York, noticed that current practice, which treats such fuels as carbon-neutral, result in incorrect measurements. That's because when biomass is burned, some carbon is returned to the atmosphere in the form of methane and carbon monoxide — greenhouse gases more powerful than carbon dioxide. If biomass burns particularly inefficiently, as it does in cook stoves, some of the fuel's carbon can be emitted in those forms and their climate impact must be accounted for. Whitman and Lehmann re-analysed data from a recent study where participants replaced their old biomass-fuelled cook stoves with cleaner-burning versions1 and found that the study overestimated the greenhouse gas reductions achieved by the cleaner stoves by about 30 per cent.

An emissions-tracking scheme that accurately accounts for all carbon-bearing greenhouse gases would help boost confidence in programmes designed to reduce emissions, the researchers contend.