Bio-Oil from Microwave-assisted Pyrolysis of Microalgae (Chlorella sp)

Pyrolysis is a thermochemical process for conversion of biomass to biofuels. The biomass is usually heated at high temperatures in the absence of air. Depending on operating conditions, the products are either a gaseous fuel, a liquid mixture of hydrocarbons, a solid fuel, or combinations of the three. In many biomass pyrolysis processes, liquid biofuels are often the target. In microwave-assisted pyrolysis, heating is supplied by microwave technology, and this is reported to have the following advantages: "Uniform internal heating of large biomass particles, ease of control, and less ash in the bio-oil (due to elimination of fluidization/agitation)."

Although many studies have been made on the pyrolysis of many types of lignocellulosic biomass for liquid biofuels, little has been done so far on microalgae. Scientists from the University of Minnesota (United States, Nanchang University (China) and Fuzhou University (China) investigated the production of "bio-oil" from the microwave-assisted pyrolysis of the microalgae, Chlorella sp. With a microwave power of 750 watts, they were able to obtain a maximum bio-oil yield of 28.6%.

Based on certain physic-chemical properties, the microalgal bio-oil exhibited better quality compared to lignocellulosic bio-oil. About 22.18% of the oil were identified as "aliphatic hydrocarbons, aromatic hydrocarbons, phenols, long chain fatty acids and nitrogenated compounds, among which aliphatic and aromatic hydrocarbons. The full results are published in the journal, Bioresource Technology (URL above).