Greenhouse gas balance and algae-based biodiesel

Abstract

This chapter discusses the use of life cycle assessment (LCA) in relation to algal biofuels by first of all describing life cycle assessment (LCA) as a process that considers the whole process chain from biomass production to the biodiesel combustion. The chapter continues with an example in which the methods of life cycle assessment are used to analyse the potential greenhouse gas emissions and energy balance of biodiesel production from microalgae. The design chosen in this study focuses on commercial scale, plastic-bag reactors and the biofixation of CO2 from a nearby power station to assist in the growth of the algae. Eight different scenarios involving photobioreactors are examined that involve two methods for harvesting the algae (mechanical harvesting and chemical harvesting by flocculant); two methods for oil extraction (solvent extraction and high pressure extraction), and also two end-uses for the algal cake that remains after oil extraction (animal feed and production of energy through methane combustion after anaerobic digestion). The scenario results are compared with previous scenarios of biodiesel from microalgae grown in ponds, and also with diesel and canola biodiesel production.