A Novel Prediction Method and Techno-economic Analysis for Sustainable Biofuel Production from Native Polyculture Microalgae in Japan and Indonesia

概要

Native polyculture microalgae is a robust community and provide stable productivity compared to the monoculture system. Therefore, native polyculture microalgae is appropriate as a biofuel feedstock for large-scale and sustainable production. There are some challenges regarding biofuel production from native polyculture microalgae. Some of them are limited research data, uncertainly on process production, and feasibility production on the industrial scale. Despite promising on large- scale manufacture, this culture is a novel application for commercial biofuel production. Therefore, it is essential to figure out that native polyculture microalgae is a feasible biofuel feedstock for industrial scale.

　This dissertation is aims to investigate the aspects of biofuel production from native polyculture microalgae on developing models for technological strategy, investment planning, and approach to accomplish the goals regarding sustainable biofuel production in Japan and Indonesia. This study consist of three primary research works: novel prediction method to forecast productivity using polyculture growth model, algae- based biorefinery schemes in Japan and Indonesia, and techno-economic analysis for production of biocrude oil. The following are the major findings of the research.

　The first research provides a polyculture growth model for forecasting annual biomass productivity and biocrude oil yield in the semi-continuous open raceway system. The model simulation and validation have satisfactory results based on root mean square error (RMSE) values of 0.12 and 0.08, respectively. The critical points regarding the polyculture growth model are polyculture species determination, polyculture factor, and initial concentration. This model can be applied to other native polyculture and can be simulated to increase biomass productivity based on the initial concentration, cultivation area, and cultivation depth.

　The second research proposes algae-based biorefinery schemes from native polyculture microalgae in Japan and Indonesia that can be applied for industrial practitioners. The algae-based biorefinery scheme was developed to produce different kinds of high-value biofuels and by-products using industrial waste/effluent as low-cost nutrient resources and water recycling. The biorefinery is designed to fit the characteristics of native polyculture microalgae in Japan and Indonesia.

　The third research provides techno-economic analysis of native polyculture microalgae in Indonesia and Japan that can be used as preliminary data for feasibility study of biofuel feedstock production from native polyculture microalgae on commercial scale. The results show that the biocrude oil price for Indonesia in the optimistic scenario with the utilization of excess energy from palm oil mill is 2 USD/liter. This price is equal to the biocrude oil price from the monoculture system. For Japan case, the biocrude oil price in the optimistic scenario with utilization of wastewater treatment plant is 5.47 USD/liter. The sensitive factors regarding the production of biocrude oil from native polyculture microalgae are biomass productivity, operational cost, and equipment cost especially for centrifuge and hydrothermal liquefaction.

　This study supports an improved understanding of biofuel feedstock production using native polyculture microalgae and offers a conceptual basis for sustainable biofuel production from native microalgae biomass to increase primary energy supply. Sustainable biofuel production from microalgae biomass can be achieved by applying native polyculture as biomass culture, utilizing industrial waste/effluent as a low-cost nutrient and excess energy as a power source, and finding appropriate technology and optimum condition, particularly for dewatering and HTL process, on large-scale and continuous system. For future perspectives, a new strategy and breakthrough technology should be investigated to make feasible algal biofuels from native polyculture microalgae for commercial scale. Research that combines science, engineering and economic perspective with consideration regarding environmental issues and sustainable development is required. Finding appropriate and economical process technology in dewatering and oil extraction and selling valuable by-products is one of the challenges to reduce high fuel costs.