Abstract
The increasing demand for biofuels has encouraged the researchers and policy makers worldwide to find sustainable biofuel production systems in accordance with the regional conditions and needs. The sustainability of a biofuel production system includes energy and greenhouse gas (GHG) saving along with environmental and social acceptability. Life cycle assessment (LCA) is an internationally recognized tool for determining the sustainability of biofuels. LCA includes goal and scope, life cycle inventory, life cycle impact assessment, and interpretation as major steps. LCA results vary significantly, if there are any variations in performing these steps. For instance, biofuel producing feedstocks have different environmental values that lead to different GHG emission savings and energy balances. Similarly, land-use and land-use changes may overestimate biofuel sustainability. This study aims to examine various biofuel production systems for their GHG savings and energy balances, relative to conventional fossil fuels with an ambition to address the challenges and to offer future directions for LCA based biofuel studies. Environmental and social acceptability of biofuel production is the key factor in developing biofuel support policies. Higher GHG emission saving and energy balance of biofuel can be achieved, if biomass yield is high, and ecologically sustainable biomass or non-food biomass is converted into biofuel and used efficiently.
Highlights
This study aims to examine various biofuel production systems for their greenhouse gas (GHG) savings and energy balances, relative to conventional fossil fuels with an ambition to address the challenges and to offer future directions for Life cycle assessment (LCA) based biofuel studies
The environmental performance of biofuels based on their GHG savings and energy balances depend on a wide range of factors such as feedstock types, conversion technologies, issues related to land-use and land-use changes along with substituted products like electricity, transportation fuel, and animal feed (Menichetti and Otto, 2009)
A wide range of results in terms of net energy balances and net GHG emission savings has been obtained from various biofuel production systems and their biomass sources
Summary
Biofuels are often classified as first, second, and third generation biofuels (Table 1). Third-generation biofuels use algae and microbes as fuel source materials (Singh et al, 2012). Following is the detail of GHG savings and energy balances of most prominent biofuel systems, relative to conventional fossil fuels. Ethanol: Wheat, Beet, Straw, Wood waste, Sugar cane Methanol: Wood waste, Farmed wood Diesel: Rapeseed, Sunflower. Palm oil Maize, Sugar cane, Soybean, Palm oil, Waste material Maize, Switchgrass Maize, Wheat, Cellulose Imported soy oil (40%)/ domestic Sunflower oil (10%)/ imported Palm (25%)/domestic and imported rapeseed (25%). Wheat straw Sugarcane, Maize Wheat, Barley Sugar cane Biogas: Woody biomass, Beet, Lignocellulose, Rapeseed Wheat, Sunflower, Rapeseed 1 WtT : Well to Tank 2 WtW: Well to Wheel 3 TtW: Tank to Wheel
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