Hydrothermal Conversion of Microalgae to Biofuels

Algae represent a potential third generation biofuel. Biofuels that use terrestrial grown crops compete with food crops for land and resources. We have a finite amount of arable land in the US, so we can never supplant gasoline with the current fuel crops. Algal biofuels have the potential to replace all of the petroleum in the US without competing for arable land or fresh water. Cultivated microalgae can grow 5 times as much biomass as corn, and produce 10 times the oil of oil palm in a year in the same area. Future research could push these numbers up by another factor of 5 and 10 respectively.

Current schemes for producing algal biofuel involve large amounts of energy and solvents to recover the oil from the algal biomass. The algae are very dilute in water, and must be de-watered significantly in these processes. However, hydrothermal processing is well-suited to very wet biomass. Hydrothermal processes can be used to convert a wide range of biomass into fuels. The special features of high-pressure, high-temperature water allow for chemical reactions that could not occur under other conditions. In this research, algae are subjected to hydrothermal conditions in a batch reactor system in the Tester Lab. The products are analyzed to discover the fate of the different portions of the algal biomass. Model compounds are also reacted in hydrothermal environment to improve the process understanding in hydrothermal systems.