Qi Niu

Catalytic pyrolysis of microalgae and derived fractions into biofuels and added-value chemical compounds

As the third-generation source of biofuels, microalgae have a growing potential in energy supply having advantages such as high photosynthesic efficiency and high growth rate compared to terrestrials crops and lignocellulosic biomass. Microalgae mainly contain three components, i.e. carbohydrates (12-25 wt%), proteins (30-55%) and lipids (15-30%). Fast pyrolysis of microalgae is a thermochemical conversion method that can process the feedstock into a liquid, char and gases.

(1) There are many factors that can affect the composition and stability of pyrolysis liquids, the content and species of inorganic elements is one of them. The inorganic composition of microalgae can not only reduce the yields in organic phase of pyrolysis liquids, but also alter the heating value and viscosity in a negative way. This study evaluates the effect of Nannochloropsis gaditana (marine microalgae) and Scenedesmus almeriensis (fresh) pretreated in different ways on the composition of pyrolysis products by applying micro-pyrolysis (Py-GC/MS).

(2) The ‘traditional’ way of microalgae use is oil extraction which is then transesterified for production of biodiesel. The residues, i.e. defatted microalgae have been considered as waste biomass. The bio-oil produced from this waste microalgae have some advantages such as high heating value and high hydrogen content compared to bio-oils from lignocellulosic biomass, but there are still some unsatisfactory issues like high oxygen and nitrogen contents which result in acidic, unstable bio-oils and NOx pollution when these bio-oils are burned. Thus it is necessary to resort to upgrading processed in which a catalyst is used to realize deoxygenation and denitrogenation.