BioTork develops microorganism to convert papaya waste to fuel

By Erin Voegele | January 05, 2012

A developmental research project being completed in collaboration with Florida-based BioTork LLC, Hawaii-based Rivertop Solutions LLC and the USDA Pacific Basin Agricultural Research Center has successfully demonstrated a method to turn Hawaiian papaya waste into renewable oil that can then be converted into biofuels.

According to BioTork Chief Scientific Officer Tom Lyons, Hawaii’s unique economy and infrastructure offers several challenges. As much as 90 percent of the state’s fuel is imported, at relatively high cost, which causes energy challenges. In addition, livestock producers and fisheries within the state are in need of locally sourced feed materials. The state also has significant challenges in the arena of waste disposal. A solution made available through BioTork’s unique technology can address all three of these issues by diverting waste biomass from landfills and using that material to produce oil for conversion into fuel, as well as a feed product suitable for use by Hawaii’s livestock producers and fisheries.

The process being developed by the group currently addresses Hawaii’s papaya waste, but could be tailored to deal with other types of agricultural wastes in the future. Hawaii produces a lot of papaya, Lyons said. In a down year in a down economy, he estimates that as much as 50 percent of the state’s papaya harvest is disposed of by packing houses because of imperfections in the fruit that make them unsalable to the market. In fact, Lyons estimates that more than 15 million pounds of the fruit is currently disposed of each year.

The developmental research project BioTork is participating in seeks to convert that waste papaya into microbial biomass that is rich in oil. According to Lyons, the oil can be converted into biofuels, with the remaining biomass serving as feed.

BioTork has developed a new technology that allows microorganisms to be cultured continuously, in essence allowing for accelerated breeding. “We start with naturally occurring microorganisms,” Lyons said. In the case of the papaya waste project, the process features two different types of microorganisms; and algae strain and a single-celled yeast-like mushroom.

“The process we use is essentially evolutionary optimization,” Lyons explained. “[These microorganisms] are kept growing in a constant state of active growth. Over time they adapt to the conditions where they are growing—in this case, adapting to grow on puréed papaya. Over time they will learn to eat more of [the material] that is in the papaya faster because the use of evolutionary optimization forces the fittest, fastest progeny to take over. In essence, what we are doing is accelerated breeding.”

BioTork’s contribution to the developmental research project stems primarily from its ability to complete this type of evolutionary optimization on microorganisms. In turn, PBARC is scaling up the process. To date, the organization has evaluated the technology on a 15-liter scale. According to Lyons, there are near-term plans to scale that production level up to the 100-liter and 500-liter scales. A pilot project of 2,000 liters is also in the works.

To complete the conversion, puréed papaya is introduced into a standard fermentation tank, where it is suspended in a growth media. The algae and mushroom cells are cultured in the fermentation tank where they feed on the material, converting it into oil. The resulting oil can then be pressed out of the cells and converted into fuel. According to Lyons, the microorganisms his company has developed for the project have already achieved an oil yield of approximately 30 percent of the dry weight of the cells.

Lyons adds that the group is interested in developing similar microorganism mixes to deal with other agricultural waste materials in Hawaii. The consortium is also currently working to form partnerships with end-users of fuel within the state. This includes the U.S. Department of Defense and the U.S. Navy, which is Hawaii’s single largest fuel user.