Theoretical assessment of biomethane production from algal residues after biodiesel production

摘要

Energy shortage, global warming, and climate changes call for the creation andrnbreakthroughs of renewable and sustainable energy technologies, and thus biofuelsrnfrom microalgae have been the object of ever-increasing interest. Microalgalrnbiodiesel production presents as one of the promising options for biofuel production,rnsince most microalgal species contain rich lipids. However, large amounts ofrnresidues are left behind after microalgal biodiesel production. In an effort tornimprove the potential economics of microalgal biofuels, it is essential to make fullrnuse of microalgal post-extracts. This Focus Article determines the theoretical yieldsrnof microalgal biodiesel and biomethane together with the relevant calorific valuesrnduring the continuous production. Based on the investigated species, the microalgalrnbiodiesel and biomethane yields widely range from 6 to 134 g/kg-VS and fromrn0.24 to 0.63 L/g-VS, respectively, while the total calorific values experience thernrange of between 6.88 and 18.80 MJ/kg-VS. Microalgal biodiesel production is notrnalways required before anaerobic digestion, especially for those microalgal speciesrnwith low lipid contents. Net energy ratio and cost-effectiveness analysis arernhighlighted in order to evaluate the viability of the biorefinery process. Wellfundedrnresearch and development programs can help develop technologies andrnpolicies, thus driving the industry toward prosperity.