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Crop Biotech Update

Use of Papaya-Loving Algae to Produce Biodiesel for Hawaii

August 2, 2017

In Hilo, Hawaii, Agricultural Research Service (ARS) Plant Pathologist Lisa Keith is leading an effort to produce biodiesel using the green algae Auxenochlorella protothecoides (formerly Chlorella protothecoides).

She used the pulp of discarded papayas, those deemed too blemished, malformed, or damaged, to be sold for market as food for the algae. Keith and her colleagues grew the algae in "bioreactors" and fed them "papaya smoothie". In the process, the algae end up storing 60% of their cellular weight in lipids. These lipids provide material for making biodiesel.

Remains from the oil-extraction process, called "algal meal," can offer Hawaiian farmers a low-cost source of feed for fish or livestock. The algae's fondness for papaya also could offer a way for growers to regain some losses due to discarded fruits.

The project was supported by the state government of Hawaii, which hopes to ease the state's reliance on imports of petroleum-based oil.