Environmental and Energy Assessment of Small Scale Ethanol Fuel Production

Rio Grande do Sul (RS) State edaphoclimatic conditions are suitable only to produce ethanol in small scale. However, small scale ethanol production (SSEP) was not proven to be feasible because of its lower process efficiency compared to large scale, and its environmental impacts were not assessed. The objective of this study is to evaluate SSEP through life cycle assessment (LCA) and energy efficiency analysis (EEA), showing potential scenarios of improvement in SSEP efficiency. Eco-Indicator 99 and CML 2 Baseline 2000 were the assessment methods, and the results demonstrated that nitrogen- and phosphorus-rich fertilizers, along with herbicides and limestone, were responsible for the highest environmental impacts in the agricultural sector, while the use of equipment and electricity had the highest impacts in the industrial sector. In the overall analysis, the industrial sector showed the highest environmental impacts. The SSEP global warming potential is 0.128 kg CO2eq/MJ(ethanol), almost 20 times higher than in large scale ethanol production, demonstrating the negative impact of lower SSEP efficiency. The EEA results were given in terms of net energy balance (NEB) and net energy ratio (NER) considering four scenarios (Cases 1 to 4). The agricultural sector showed high NER (19.59), while the industrial stage showed an NER of 0.20 and 2.08 for the baseline scenario (Case 1) and for the improved scenario (Case 4), respectively. The overall process showed a NER of 0.69 for Case 1, in which the bagasse was not considered as coproduct. When bagasse energy was taken into account, the NER rose to 4.82 (Case 4), showing the importance of coproducts in the process energy efficiency. The higher environmental impact of the industrial stage is an incentive to develop and use more efficient technologies in SSEP.