Biodiesel production from microalgae, edible and non-edible oils.

摘要

The current fossil fuel-based economy is not sustainable because of environmental impacts, economic dependence, and energy security issues. Thus, it is important to find an alternative energy source that is renewable, sustainable, and environmentally benign which pushes the attention in areas such as biomass, hydrogen, fuel cells and solar cells to the forefront. Carbon neutral renewable liquid fuels are needed to replace the petroleum-derived transport fuels. Among all the renewable biofuels sources today, biodiesel from renewable feed-stocks including edible, non-edible oils and microalgae seems more promising as an alternative sustainable fuel as it is biodegradable, non-toxic and environmental friendly.;The direct conversion of algal biomass to biodiesel using the supercritical methanol and the microwave-assisted transesterification techniques were investigated. Wet algal biomass was used as feedstock in the supercritical methanol process and dry algal biomass for the microwave-assisted transesterification. Experimental runs were designed using a response surface methodology and the process parameters such as wet/dry algae to methanol ratio, reaction temperature, reaction time and catalyst concentrations were optimized for both processes. It was observed that both conversion techniques have the potential to provide energy-efficient routes for biodiesel production from algal biomass.;Alkali transesterification process was used to produce biodiesel (alkyl ester) from low free fatty acid (FFA) canola and corn vegetable oils. This process yields about 80-95 % (vol %) for canola and 85-96 % (vol %) for corn using potassium hydroxide (KOH) as a catalyst. The fuel properties of biodiesel produced were compared with ASTM standards for biodiesel and regular petroleum diesel. The conversion of waste cooking oil to methyl esters was carried out using ferric sulfate and sulfuric acid catalysts and the supercritical methanol one-step process. A two-step transesterification process using ferric sulfate and sulfuric acid catalysts was used to remove the high free fatty acid contents in the waste cooking oil (WCO).;The optimization of the transesterification of camelina sativa oil using different heterogeneous metal oxide catalysts, i.e., BaO, SrO, MgO, and CaO, was evaluated. The relative order of the effectiveness of the catalysts was BaO > SrO > CaO > MgO. Transesterification of camelina oil using supercritical methanol with hexane as a cosolvent and subcritical methanol along with potassium hydroxide as a cosolvent/catalyst was investigated to study the methyl ester conversion process. Catalytic conversion of Camelina Sativa oil to biodiesel through both conventional heating and microwave radiation was investigated. Three different types of catalysts: homogeneous catalysts (NaOH and KOH), heterogeneous metal oxide catalysts (BaO and SrO), and sol-gel derived catalysts (BaCl2/AA and SrCl2/ AA) were evaluated for their efficacy in biodiesel production. It was estimated that the microwave-heating method consumes less than 10% of the energy to achieve the same yield as the conventional heating method.;A comparison of the energy consumption for the single step extraction and transesterification for algal biomass by the supercritical methanol (SCM) process and microwave (MW) was evaluated. Energy requirements for supercritical methanol process are much larger than the microwave assisted method. Considering availability of dry algal biomass, supercritical methanol (SCM) process for wet algae needs more energy than microwave irradiation process for dry algae.