Production of jet fuel from microalgae biomass cultivated in saline domestic wastewater.

Abstract

Jet fuel from crude petroleum oil is known as the most efficient energy carrier for the aviation sector. Environmental concerns and economic pressure drive major industries to adapt to current global revolution towards alternative, sustainable, and clean fuels. In this study conversion of algae biomass to jet fuel is presented as a novel technology of low carbon footprint and a cost-effective jet fuel. In this current study, it is reported that there is a possibility of substantially converting microalgae oil into aviation fuel by adapting and applying the same processes used for the conversion of fossil crude petroleum oil into conventional jet fuel. The drawback, however, remains the low oil output from used species of microalgae and the general operating costs which are still at developmental stages. A part from the introduction and the literature review making respectively chapter 1 and chapter 2, this study, therefore, has focused on the magnification of lipid production and the simplification of the conversion processes in chapter 3. Microalgae cells were physiologically stressed by totally depriving them of all growth nutrients for three days aiming to modify their genetic physiology which in turn will favour the yield of lipid and bio-oil. An elaborate experiment was established from algae biomass cultivation to jet fuel production. The experiment involved biomass cultivation, harvesting and bio-oil extraction using a solvent mixture made of methanol and chloroform. Thermal cracking without catalyst or pyrolysis of crude bio-oil were undertaken to break down the carbon chains in order to complete the fractionation. ASTM methods and standards related to aviation fuels were used to generate the relevant data. The conceptual design with a simplified conversion process undertaken in chapter 4 was established based on the experiment completed in chapter 3. It suggested to cultivate the species in domestic wastewater ponds or use the seawater/saline water because the used species was comfortable in saline or marine environment. Parameters such as density, kinematic viscosity, flash point, freezing point, total sulfur, net heat of combustion and distillation were evaluated during the experiment in chapters 3 and 4. It was found that the majority of parameters analysed regarding the algae-based jet fuel from the laboratory was complying to ASTM standards. However, it will require additional processes such as upgrading and reforming to enhance the quality of jet fuel and improve the level of some parameters such as density and freezing point which were not rigorously complying with ASTM standards. Also, the improvement involves the use of the same additives used for conventional jet fuels for flow ability and freezing at higher altitudes. The scaling up of the production process is still a challenge due to operating costs. In this regard, blending algae-based jet fuel and the conventional jet fuel in 50/50, 80/20 and 20/80 ratios was carried out and evaluated in Chapter 5 and Chapter 6 as an alternative approach for sustainability.