Microalgal liquid, solid, and gaseous biofuels: Cultivation and production strategies for biofuel accumulation

igh demands for fuel energy worldwide and environmental concerns have increased the interest in renewable energy sources. Thus, microalgae emerge as a promising raw material to produce liquid, solid, and gaseous biofuels. Depending on the strain, these microorganisms can accumulate high amounts of carbohydrates and lipids, interesting for bioethanol and biodiesel production. Furthermore, the integral biomass can be applied to gaseous and solid biofuel production without previous biomolecules extraction or fractionation. This versatile feedstock can fix atmospheric CO2 besides being cultivated in nonarable land and using wastewater as a nutrient source, contributing to the environment. Another advantage is the possibility to apply the biorefinery concept, obtaining simultaneously high valuable biomolecules, while produce biofuels. Therefore, this chapter provides insights into several microalgae already used as a substrate to produce promising biofuels, as well as the main processes and methodologies employed recently. Besides, the challenges and future trends to microalgae use for biofuel purposes are addressed.