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Benefits of biofuels overestimated – study

The environmental benefits of using biofuels tend to be overestimated due to some omissions in calculations of the fuel's greenhouse gas emissions, a scientific paper claims.

The study led by University of Edinburgh Professor Keith Smith refers to biofuel production's Life Cycle Analysis, a technique which measures and compiles all factors relating to the production, usage and disposal of a fuel or product.

According to the study, the model omits the carbon dioxide emissions of vehicles that use ethanol and biodiesel, a measure which, according to the study, cannot be easily justified. Biofuel proponents say these should be ignored because plants grown for biofuel absorb and therefore offset the same amount of carbon emitted by refining and combusting the fuel.

But the study says it would not necessarily result in additional carbon absorption, as it would double count the absorbed carbon once bioenergy crops are already used for production. They add that greenhouse gas reductions would only result if there would be additional plant growth, or if additional useable biomass would be generated from waste material.

The overestimation is magnified by the underestimation of nitrogen emissions from fertilizer application.

"Emissions of nitrous oxide from the soil make a large contribution to the global warming associated with crop production because each kilogram of nitrous oxide emitted to the atmosphere has about the same effect as 300 kg of carbon dioxide," said Dr. Smith.

He adds that the observed increase in atmospheric nitrogen shows that the Life Cycle Analysis only reports half of actual emissions from the gas.

Dr. Smith suggests using waste material or focusing on relatively wet but highly degraded land as the best opportunity for making beneficial biofuels. The degraded land would store more greenhouse gas and reduce its emissions. In addition, this method would not compete with crop production for food, textiles and others uses.

The paper is published in GCB Bioenergy. – EcoSeed Staff

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