Lifecycle assessment of fuel ethanol from sugarcane in Brazil

Abstract

Background, aim, and scope This paper presents the lifecycle assessment (LCA) of fuel ethanol, as 100% of the vehicle fuel, from sugarcane in Brazil. The functional unit is 10,000 km run in an urban area by a car with a 1,600-cm 3 engine running on fuel hydrated ethanol, and the resulting reference flow is 1,000 kg of ethanol. The product system includes agricultural and industrial activities, distribution, cogeneration of electricity and steam, ethanol use during car driving, and industrial by-products recycling to irrigate sugarcane fields. The use of sugarcane by the ethanol agribusiness is one of the foremost financial resources for the economy of the Brazilian rural area, which occupies extensive areas and provides farreaching potentials for renewable fuel production. But, there are environmental impacts during the fuel ethanol lifecycle, which this paper intents to analyze, including addressing the main activities responsible for such impacts and indicating some suggestions to minimize the impacts. Materials and methodsThis study is classified as an applied quantitative research, and the technical procedure to achieve the exploratory goal is based on bibliographic revision, documental research, primary data collection, and study cases at sugarcane farms and fuel ethanol industries in the northeast of São Paulo State, Brazil. The methodological structure for this LCA study is in agreement with the International Standardization Organization, and the method used is the Environmental Design of Industrial Products. The lifecycle impact assessment (LCIA) covers the following emission-related impact categories: global warming, ozone formation, acidification, nutrient enrichment, ecotoxicity, and human toxicity. Results and discussion The results of the fuel ethanol LCI demonstrate that even though alcohol is considered a renewable fuel because it comes from biomass (sugarcane), it uses a high quantity and diversity of nonrenewable resources over its lifecycle. The input of renewable resources is also high mainly because of the water consumption in the industrial phases, due to the sugarcane washing process. During the lifecycle of alcohol, there is a surplus of electric energy due to the cogeneration activity. Another focus point is the quantity of emissions to the atmosphere and the diversity of the substances emitted. Harvesting is the unit process that contributes most to global warming. For photochemical ozone formation, harvesting is also the activity with the strongest contributions due to the burning in harvesting and the emissions from using diesel fuel. The acidification impact potential is mostly due to the NOx emitted by the combustion of ethanol during use, on account of the sulfuric acid use in the industrial process and because of the NOx emitted by the burning in harvesting. The main consequence of the intensive use of fertilizers to the field is the high nutrient enrichment impact potential associated with this activity.

Water Use in Sugar and Ethanol Industry in the State of São Paulo (Southeast Brazil)

“…Moreover, sugarcane is an energetically favorable feedstock and the avoided emissions of green house gases associated with its production and use has been estimated to be approximately 2100 kg CO 2 -eq·m −3 ethanol [9]. Even when estimates of energy balance for sugarcane ethanol are obtained through life cycle analysis, where the energy balance is expressed in terms of energy input:output, the results are usually more positive than negative, as shown in different studies 1:0.5 [10], 1:1.5 [11], 1:1.8 [12]; 1:3.7 [13] up to 1:9.3 [9]. However, unless some of the key environmental impacts which result from widely used agricultural practices and industrial processes for the production of sugarcane ethanol are addressed [8], the advantages of this alternative biofuel may not be as enticing in an economic market that is progressively more environmentally friendly.…”

Active crop sensor to detect variability of nitrogen supply and biomass on sugarcane fields

“…In the sugarcane production system, especially in humid areas, nitrogen (N) availability in the soil is the most important factor limiting plant growth, development and yield, but N is also the second impact factor on the fuel ethanol lifecycle (Ometto et al 2009). Although biological N fixation seems to play a role in the N nutrition of sugarcane crops, it seems premature to use inoculants of N 2 -fixing bacteria since the main contributors to the observed biological N fixation are not well known (Boddey et al 2003).…”

Thermodynamic and Environmental Analysis of Scaling up Cogeneration Units Driven by Sugarcane Biomass to Enhance Power Exports

“…The LCI built up for the agricultural stage considered data obtained from [37,[54][55][56][57][58][59][60][61][62][63].…”