Life cycle and technoeconomic analysis of microalgae-based biofuels

Abstract

Microalgae are an appealing feedstock for production of biofuels due to their high productivity compared to terrestrial plant-based feedstocks, and their relative tolerance of low quality land and water. Despite these potential benefits, there are technological, environmental and economic challenges that must be overcome to enable commercialization of any microalgae-to-biofuels process. Due to the relative immaturity of the field, assessments of the environmental performance, scalability and economic performance of microalgae-based biofuels are highly uncertain, data poor, and incomparable across technologies. This dissertation seeks to study these aspects of microalgae-based biofuels so as to provide models of increased utility for technical design, investment planning, and achieving policy-level objectives. This work is divided in three primary research efforts. First, this research develops an integrated life cycle assessment of the microalgae to biofuels process using a detailed engineering model derived from a pilot-scale photobioreactor system. The life cycle assessment quantifies and compares energy consumption, greenhouse gas emissions, and scalability of the biofuel life cycle. Second, this work defines the water footprint for a photobioreactor-based biofuel production system with geographical and temporal resolution. The water footprint (WF) of microalgae biofuel is comprehensively assessed using a combined process and economic input-output lifecycle analysis method, using blue, green and lifecycle WF metrics, four different fuel conversion pathways, and 10 continental US locations with high productivity yields. Finally, a technoeconomic analysis of the baseline enclosed photobioreactor microalgae to biofuels system is performed with stochastic economic risk assessment. This section provides a range of probabilities of economic success based on the sensitivity of the microalgae-to-biofuel process to the variable economic variables and scenarios. Based on the results of these integrated assessments of microalgae biofuels, this study communicates an improved understanding of the economic and environmental performance of microalgae biofuels and their characteristics compared to petroleum and biofeedstock-based biofuels.