Page Banner

United States Department of Agriculture

Agricultural Research Service

Research Project: Characterization of Potential Feedstocks of Hawaii Island and Development of Effective Technology for a "Zero-Waste" Biofuels Approach

Location: Tropical Plant Genetic Resources and Disease Research

2012 Annual Report

1a. Objectives (from AD-416):
A program has been established which focuses on the development of an effective agriculture system based on the concept of ‘zero waste’. The project consists of interrelated components on agriculture production and value added research, development of biofuels from regional feedstock, and enhancement of the communities in Hamakua through the deployment of the ‘zero waste’ concept. The objectives of this proposal are: Objective 1- To continue to investigate 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. Objective 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.

1b. Approach (from AD-416):
Hamakua and other parts of Hawaii Island produce a range of feedstocks that could be potential sources for biofuel production. Many of them are food crops, such as papaya and sweet potato, for which the waste stream (as culled fruits, parts of the plant) could be an inexpensive and excellent source for production of biofuel. Others may be trees or plants which could be used for biofuel production, while still others may be grown to produce an inexpensive source of feedstock (such as sweet sorghum on very marginal land) that would be used specifically for biofuel. All of these crops could ensure a sustainable, available and efficient supply of biomass which will serve as the beginning point for all conversion technologies. 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. Anerobic 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.

3. Progress Report:
The goal of this project focuses on the development of an effective agriculture system based on the concept of ‘zero waste’ which contributes to objectives 1 and 2 of the in-house project 5320-21610-001-00D which this project was originally established under (expired in FY2011). Significant progress was made towards producing economical levels of algae oil and meal by growing the algae Chlorella protothecoides on papaya as a carbon source under heterotrophic conditions. C. protothecoides strain #3 that was adapted to feed on papaya and use ammonium sulfate as a nitrogen source was received from Biotork at the end of August 2011. We enhanced growth and created an axenic (pure) culture in September 2011 and growth experiments in papaya media began in October 2011. In January 2012 the first oil was processed from this strain, obtaining a maximum of about 10% oil/dry weight. Over the next several months, the algae growth rate and amount of oil produced was improved significantly. Growing condition variables analyzed included starting inoculum concentration, carbon:nitrogen ratio, temperature, pH, aeration, papaya (juice, puree) and length of experiment. Methods for growth determination (plate counts, haemocytometer) and oil production (using Sudan black staining with microscopy) were optimized. Oil processing methods using bead milling and hexane extraction were improved; we are currently consistently collecting 50% oil/dry weight and have begun to achieve levels close to 70% oil/dry weight. Current yields include >15 ml oil/1 lb papaya (not including seeds) and ca, 20 g algae meal which can be used for feeds, etc. The next step is to ramp up to significantly larger volumes. More funding was approved in April 2012. New initiatives will include the identification of feedstocks that are suitable for anaerobic digesters. Equipments are on order and personnel are being hired. The first target is to test whether Albizia (Falcataria Mollucana), a wide spread weed tree in Hawaii, might be useful as a source for anaerobic digesters.

4. Accomplishments

Last Modified: 06/24/2017
Footer Content Back to Top of Page