The narrow window of energy application for oil extraction by arc discharge

Oil production by microalgae is investigated as a possible solution to sustain the petroleum shortage. Some microalgae such as Botryococcus braunii have the advantage of being able to produce a high amount of hydrocarbon without requiring arable lands to grow on. Also, hydrocarbons extracted from B. braunii are suitable for the cosmetic industry, as they are long-chain hydrocarbons similar to squalene. As such, B. braunii oil might generate a high profit. However, harvesting hydrocarbon from microalgae cultures is difficult. Here we show an innovative way of collecting hydrocarbon from algae culture using high voltage electric discharges (HVED). Botryococcus braunii form a matrix full of hydrocarbons allowing many cells to stick together as microcolonies. When the energy applied is too high, hydrocarbons are destroyed; and when the energy is to low, algae culture stays unchanged. But when energy applied is just sufficient (near 625 J mL−1), cells leave colonies and sink to the bottom of the samples, while hydrocarbons remain unaffected and float to the surface of the samples. Such a phenomenon allows us to harvest the matrices of colonies which are empty of cells, suitable as a biomass for biofuel production.