This book details the attractive features of algae as a sustainable third-generation feedstock for biorefineries. The commonly explored algal biofuels technologies such as pyrolysis, fermentation, transesterification, gasification, and briquetting/pelleting are assessed in a biorefinery concept and discussed based on resource utilization and sustainability considering biorefinery concepts. Process improvement options for sustainable algal biorefineries are also discussed in this book. Finally, the thermo-environmental sustainabilities of algal biorefineries using exergy and life cycle assessment (LCA) tools are reviewed and assessed based on literature data.