2013 Annual Report
1) To optimize production of oil and high protein meal from heterotrophic oleaginous algae and fungi that use papaya, sweet potato and sweet sorghum as a carbon source. 2) To identify and test agricultural and other wastes for potential use as feedstock in farm scale anaerobic digesters to produce energy, fertilizer and value added components.
The proposed research falls under our broad “zero waste” approach to simultaneously make agriculture in Hawaii more profitable and address food and energy security issues. While the available feedstock sources may be useful and plentiful, cost-effective technologies need to be deployed to produce biofuels. In this proposal, we will focus on the development of biodiesel or derivatives, and not alcohol. Using a systematic approach, a range of potential feedstocks will be analyzed to determine the qualitative and quantitative components (such as sugars, oils, cellulose content) that could be converted to biofuels. One specific approach that the investigators plan to focus on will be the use of heterotrophic algae for converting waste material from food crops to biodiesel. We have made significant progress in using papaya as a feedstock for algae and we will optimize growth conditions of the algae for increasing the fatty acid production and analyze the economics of the process. We are currently trying to determine how to go from robust algae growth, as indicated by an increase in biomass and the presence of replicating cells, to limited cell replication and increased lipid production. We will also look at the potential for sweet potato and sweet sorghum as feedstock using a similar approach as we used for papaya.
Since Hawaii Island has a vast array of agricultural and nonagricultural plants that could be used in our 'zero waste' concept, additional conversion approaches will also be utilized for crops that are not amenable to heterotrophic algae. Anaerobic digesters are ideal for utilizing these waste streams because the output of this process results in production of energy, fertilizer, and value added products. Our ultimate goal is to adapt the process so it is scalable for Hawaii farm systems. We will focus on identifying feedstocks and on optimizing conditions for selected microbes to efficiently digest feedstock combinations under anaerobic conditions. Some of the possible feedstocks available are wastes from papaya, sweet potato, guava and other fruits (lychee, longan, mango, etc.), and albizia (Falcatatia moluccana), a fast growing invasive legume tree/weed that has infested an estimated 100,000 acres in East Hawaii Island. Two anaerobic digesters are slated to be constructed on Hawaii Island, one in Waimea the other in Hilo. Thus, our research could have an immediate impact.
This agreement supports collaborative research between USDA, ARS, the Pacific Basin Agricultural Research Center (PBARC) and the University of Hawaii at Hilo College of Agriculture, Forestry and Natural Resource Management, with the goal of identifying potential feedstock for anaerobic digesters to generate alternative sources of energy in Hawaii.
Albizia, Falcatatia moluccana, is an invasive, weedy tree that is one of the fastest growing trees in the world. This tree has quickly spread throughout the Big Island and the rest of the state. Using high-resolution satellite imagery, we have been able to distinguish the population of albizia in the Hilo and Puna regions of the Big Island native forests and other vegetation, determine how much the albizia population has grown over time and estimate the potential biomass that might be available as a feedstock for anaerobic digestion. Different methods have been compared to distinguish albizia from other vegetation and this technique will be used to determine the impact of albizia on the rest of the Big Island and all other major islands in the state of Hawaii.
In addition to albizia, other agricultural wastes such as sweet potato, papaya and taro have been sent to Ohio State University (UH) to determine the methane (energy) potential for each crop. UH and PBARC personnel were involved in collecting and reducing the material to be sent for analysis. A hammer mill from the UH is on loan at PBARC to assist in size reduction of each feedstock. In addition, we are using a fungus to breakdown the albizia wood chips into a more digestible composition for anaerobic or algae fermentation. Once this analysis is complete, we will start small scale experiments to determine feedstock mixtures required for methane production and investigate other feedstock or methods to optimize methane potential. Liquid waste from this small scale anaerobic digestion will be used for small scale fertigation or hydroponics experiments and solid waste will be evaluated as a soil amendment.