Hydrothermal carbonization of lipid extracted algae for hydrochar production and feasibility of using hydrochar as a solid fuel

In this study, hydrothermal carbonization was conducted to convert lipid extracted algae (Chlorella vulgaris) from the algal biodiesel process to produce hydrochar, while evaluating its feasibility for use as a solid fuel. Hydrothermal carbonization was conducted at a relatively low temperature range, owing to the energy consumption during the process. Based on the results, the properties of lipid extracted algae as a solid fuel improved during hydrothermal carbonization, being comparable to the low-ranked coals. The hydrochars thus produced showed stable combustion characteristics at high temperature. Moreover, the sulfur and ash content in the lipid extracted algae decreased through devolatilization during hydrothermal carbonization, allowing the hydrochar (low sulfur and ash content) to be considered as a clean energy source. Thus, a sustainable integration process, combining the hydrochar production from lipid extracted algae with the algal biodiesel process, seems to be feasible for solid fuel production and disposal of waste.