Abstract:
Aquatic micro-algae grown on a commercial scale have the potential to substitute first generation bio-fuels and even fossil fuels in the future due to their fast growth rates, high lipid contents and the fact that they do not compete with food production. The process of growing algae on a commercial scale does however require substantial amounts of water. At the same time, the coal seam gas industry disposes of considerable amounts of wastewater through the energy intensive process of reverse osmosis. In this thesis, the multiple benefits of using coal seam gas wastewater as a growing media for large-scale algae production were investigated. The investigation was based on a case study related to the Queensland Gas Company (QGC) in Dalby, Queensland. The objectives of the study were to assess the environmental impacts of producing biodiesel through transesterification, methane through anaerobic digestion and biochar, bio-oil and methane through pyrolysis from algae. Several algal strains were also investigated to determine suitability for the parameters in the proposed case study. A proposal for the design of an algae plant was presented based on local weather data and inflow data obtained from the QGC. The findings indicate that the alga strain D. salina could be a viable option in the production of methane through anaerobic digestion, while Amphora offers potential as a viable solution for biodiesel production. Design of the conceptual plant demonstrates that in order to accommodate expected flows, a surface area of 26.5 km2 is needed until 2029, with intermittent downsizings thereafter. Of this area, 67.1% would be allocated for productive racecourses, while the remainder is required for media evaporation from a buffer storage or evaporation ponds. By coupling coal seam gas wastewater with algae production, substantial environmental benefits could be achieved as the results show that net emissions of CO2 equivalents can be significantly reduced if bio-fuel production is pursued. At the same time, feasibility studies show that a net profit could be achieved. It should however be noted that the data used in this dissertation is based on theoretical growth rates and theoretical lipid yields, hence further research is mandatory before commencing a project on a commercial scale.
