Techno-economic analysis of milking of Botryococcus braunii for renewable hydrocarbon production

Abstract

Microalgal biofuel has the potential to address two major global issues; 1) fulfill the rising energy demand of the world and 2) mitigate the increasing global warming by CO2 sequestration. Botryococcus braunii is a unique alga producing high hydrocarbon contents which can be hydrocracked into high quality fuel. However, there is a lack of interest on the use of B. braunii for biofuel production due to its slow growth rate, an influencing parameter in determining the economics of conventional algal fuel production process. Non-destructive extraction (milking) of B. braunii hydrocarbons is a process which enables the alga to reproduce the hydrocarbons reducing the requirement of fast growth of this alga for biofuel production. This study targets to establish a techno-economics of B. braunii milking to analyze its potential for the renewable hydrocarbon production. The minimum sales price (MSP) to achieve a 10% rate of return was estimated to be US$3.20 L−1 of B. braunii hydrocarbons for the base case scenario. The extraction efficiency and the hydrocarbon contents were found to be the major economy drivers of the process as a result of the additional sensitivity analysis performed to identify the most economic influencing parameters. The MSP has the potential of significant reduction (down to US$1.45 L−1) if a B. braunii with higher hydrocarbon contents is identified as long as the selected strain is suitable for milking and the higher non-destructive extraction efficiency is achieved. A resource assessment comparison was also made to evaluate the significance of the repetitive extraction versus the single extraction. The milking has the clear advantage over the conventional single extraction regarding resource consumption and the cost of the process.