Carbon emissions from biodiesel engines in Brazil compared to other fuels

Coronado et al. (2009) examined the greenhouse gas (GHG) emissions from engines running on biodiesel, from both soybean and frying oil, as compared to the GHG emissions from gasoline, diesel, and anhydrous ethanol engines in Brazil.  The latter three are currently the predominantly used fuels in the Brazilian transportation market.  Pure biodiesel and mixtures of biodiesel and conventional diesel were considered.— Jenny Ward 
Coronado, Christian Rodriguez, Andrade de Carvalho, João, Silveira, José Luz. 2009. Biodiesel CO2 emissions: A comparison with the main fuels in the Brazilian market. Fuel Processing Technology. 90, 204–211

 The authors used data from the Brazilian Association of Automotive Vehicle Manufacturers (ANFAVEA) and the Brazilian Department of Transit (DENATRAN) to develop an idea of the transportation system in the nation.  Then, the CO2 emissions for each fuel were reported in tons of CO2 per m3 of fuel.  The emissions for various blends of biodiesel, and biodiesel from various sources were also compared.  Using the vehicle data from the last five years, the tons of CO2 per year for Brazil were calculated.  Finally, Coronado et al. projected the GHG emissions for pure diesel, 20% biodiesel (B20), and 100% biodiesel (B100) vehicles in Brazil for the next fifteen years.
Ethanol fuel emitted the least amount of carbon (1.511 ton CO2 per m3 fuel), followed by gasoline (2.316 ton CO2 per m3 fuel), soybean-derived biodiesel (2.480 ton CO2 per m3 fuel), and frying oil-derived biodiesel (2.492 ton CO2 per m3 fuel), and diesel fuel was the worst contributor of GHG (2.683 ton CO2 per m3 fuel).  Although by just considering vehicle emissions biofuels seem to have higher carbon footprints, the authors explain that biomass-derived fuels reduce the net atmospheric carbon content because, unlike fossil fuels, they rapidly recycle carbon from the atmosphere into fuel.  The photosynthetic biomass takes CO2 from the atmosphere, then the combustion of biofuels emits CO2 back into the air.  The rapid turnaround is much more carbon efficient than burning fossil fuels, which releases carbon that took millions of years to sequester from the atmosphere.
Coronado and colleagues also display how as the percentage of biofuels in diesel/biodiesel blends increases, the CO2 emissions caused by using these fuels decreases.  They predict that by phasing out diesel and other main fuels, and phasing in biodiesel use in Brazil’s vehicular fleet, the nation will improve its environmental and economic state.

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