An Integrated BioGas-Solar Dehydration System: Increasing Sustainability through Value-Added Agriculture

Mandates for biofuels have resulted in the significant increase of biodiesel production in rural communities. Hawaii's Jatropha biodiesel production will produce nearly 650-700 kg of residues, consisting of Jatropha seedcake and fruit hulls for every metric ton of seeds harvested for oil production. In addition, the biodiesel conversion process will produce another 30-50 kg of crude glycerin, as a co-product for every metric ton of oilseed processed. In Hawaii, nearly 270 million gallons of petroleum diesel is consumed annually. As the local production of just one million gallons of Jatropha biodiesel will result in more than 20 metric tons of processed residuals each day. This substantial production of biofuels leaves a tremendous amount of low-value residues needing to be properly disposed of, on an island setting that is environmentally fragile. Thus, the onsite anaerobic digestion (AD) of these organic residues, into a methane gas, will not only generate energy - through the use of a combined heat and power (CHP) micro turbine - but will also resolve the issues of wastes disposal. The system will supply enough power and heat to efficiently operate a biodiesel production facility, as well as an adjacent solar dehydration plant, with all of its surplus power, sold to the utility grid. This integrated biogas-solar dehydration system is a natural progression, as Hawaii lays abundant in solar radiation, throughout the year. The project will build a scalable pilot system producing up to 50kW of electricity. Thermal recovery is integrated through the CHP for drying food and co-products. Design benefits will facilitate rural replication, to where the AD system will utilize a broad range of locally-available low-value residues and waste materials that relies on a simple technology, which can be developed and supported locally, while being designed to minimize operational costs. The plan is to set-up and utilizes an integrated biogas facility that will fully utilize and appropriately capitalize on all the synergies provided by a biogas plant. The system biologically converts organic waste and residues into energy-rich biogas that also provides nutrient-rich digested solids that is utilized as an organic fertilizer. Thus, local food production, processing and preservation are realized benefits from this biogas facility's electrical and thermal generation. Hence, food and energy security can now be achieved for our geographically isolated rural communities. Therefore, commercialization plans will focus on the main Hawaiian Islands, first. And thereafter, pursue the market potential that exists throughout the American Pacific Protectorates of Micronesia and American Samoa. Wherever imports of nutrients, food and energy have outpaced rural production, there is a similar biogas development opportunity that exists. While incentives are substantial for renewable energy projects and realizing the financial benefits of tax credits, environmental credits and loan programs can be complex. Hawaii's generous feed-in-tariff will ultimately provide the needed financial support for smaller projects that cannot benefit from the economies of scale principal.