Algae feed on rejected papaya to create biodiesel
Scientists at the US Pacific Basin Agricultural Research Center in Hawaii have developed a biodiesel using a green algae known as Auxenochlorella protothecoides. Bioreactors are filled with malformed papayas, which the algae then feed on, absorbing the organic sugars from the fruit. The algae are capable of storing 60% of their cellular weight in lipids, which provide the material for developing biodiesel. The diesel is considered an environmentally and economically effective way of dealing with the one-third of Hawaii’s papaya crop that is thrown away each year.
In Hawaii, Agricultural Research Service (ARS) researchers are leading an effort to produce biodiesel using a type of green algae known as Auxenochlorella protothecoides (formerly Chlorella protothecoides) tied with the pulp of discarded papayas, namely, those deemed too blemished, malformed, or damaged to be sold for market.

The system devised by researchers calls for growing the algae in giant bioreactors where, hidden from sunlight, the algae are fed what might be likened to a papaya smoothie.

Keith’s team thinks their remains from the oil-extraction process, called “algal meal,” can offer Hawaiian farmers a low-cost source of feed for fish or livestock, cutting importation costs. The algae’s fondness for papaya also could offer a way for growers to recoup some of the losses on about one-third of Hawaii’s $11-million papaya crop discarded because of defects.