Improving Lifecycle Assessments of Biofuel Systems

We apply systems thinking to the background, complexity and weaknesses of liquid biofuel lifecycle assessments and propose a new way of approaching the problem. The history of corn-based ethanol in North America is illustrative of the problematic interdependencies that can arise when decisions about liquid biofuel are made without comprehensive systems analysis [17]. At the direction of Congress [25], the EPA has proposed new standards for renewable fuels to be based on lifecycle assessment (LCA) methodology [6]. At the same time, the European Commission explicitly dictates the use of LCA for biofuel in their Renewable Energy Sources Directive [8]. Likewise, the United Nations Environment Program (UNEP) has directed that biofuel assessment be made based on LCA [1]. Recent lifecycle assessments of complex biofuel systems follow standard methodology such as EPA guidelines and ISO14040 standards, yet there are wide variations in the results. Studies conducted on the same liquid biofuel system reveal diverse and even conflicting results, some showing a net greenhouse gas (GHG) reduction, while others show a net increase for the same biofuel system [16], [18]. The results from these studies, therefore, cannot be considered viable for quantitative system impact comparisons. [While there are solid and gaseous biofuels, this paper focuses on liquid biofuel for simplicity and because of a strong economic need for liquid transportation fuels. The conclusions would apply to all three modes of biofuel.] We present an overview of the complexity of different liquid biofuel system processes and relate this complexity to the principal deficiencies in current biofuel LCA methodology: inconsistencies in LCA system boundaries, system boundaries that exclude relevant sub-processes, elements and environmental factors, a lack of standardized units and the reliance of commonly used LCA tools on industry average data without regard for relevant impact. We conclude that improved methodologies of determining system boundaries based on a comprehensive system impact assessment are necessary to adequately assess biofuels and their environmental effect. We propose work on a new approach based on an integrated hybrid assessment with unitized impact metrics (Renewable System Impact Rating - RSIR). This work will also lead to viable system impact optimization, permitting engineers and farmers to maximize the net energy balance of a biofuel system, while minimizing negative impacts on the environment and on world food supplies.