Environmental and energy analysis of biodiesel production in Rio Grande do Sul, Brazil

Abstract

Brazil’s mandatory blending of 5.0 % biodiesel with diesel calls for an assessment of the environmental impacts of the biodiesel production process chain. Life-cycle Assessment (LCA) and energy efficiency analysis methodologies were used to assess biodiesel production from soybeans in Rio Grande do Sul state, Brazil. The study used a “Cradle to Gate” boundary and two levels in the energy analysis. The main results of the LCA were given in terms of environmental impact categories and indicated that phosphorus-rich fertilizers along with herbicides were responsible for major environmental impacts in the agricultural sector, whereas diesel accounted for greater damage in the soybean oil extraction sector. The influence of material flows in the refining of soybean oil varied according to the impact. The highest impacts were obtained using firewood to generate steam and phosphoric acid using sodium hydroxide for oil neutralization. Sodium methoxide and methanol more significantly influenced the transesterification step. Diesel affects all of the industrial sectors, mainly in relation to respiratory organics, the ozone layer, and fossil fuels, contributing no less than 50 % of the impact. Comparing the individual process sectors, the agricultural sector had the highest environmental impact. In terms of energy gain, biodiesel production presented a net energy gain of 3.08 units of useful energy when glycerin and soy meal are considered. Without these co-products, the process was very close to be unfavorable (1.04).