Using macroalgae as biofuel: current opportunities and challenges

The rising global demand for energy and the decreasing stocks of fossil fuels, combined with environmental problems associated with greenhouse gas emissions, are driving research and development for alternative and renewable sources of energy. Algae have been gaining increasing attention as a potential source of bio-renewable energy because they grow rapidly, and farming them does not, generally, compete for agricultural land use. Previous studies of algal biofuels have focused on microalgae because of their fast growth rate and high lipid content. Here we analyze the multiple merits of biofuel production using macroalgae, with particular reference to their chemical composition, biomass and biofuel productivity, and cost-effectiveness. Compared to microalgae, macroalgae have lower growth rates and energy productivity but higher cost-effectiveness. A biomass productivity of over 73.5 t dry mass ha(-1) year(-1) with a methane yield of 285 m(3) t(-1) dry mass would make electricity production from macroalgae profitable, and this might be achieved using fast-growing macroalgae, such as Ulva. Taking into account the remediation of eutrophication and CO2, exploring macroalgae for a renewable bioenergy is of importance and feasible.