Jet Fuel from Domestic Wastewater Treatment Using Microalgae: A Review

Domestic wastewater can contain numerous toxic substances making it a public health hazard. Recycling wastewater with the possibility of reuse can be considered as a viable option. Various ways of remediation are being used to solve the issue of water pollution. The current review analyses the possibility to use microalgae for wastewater treatment followed by the conversion of biomass into aviation fuel. It is well known that conventional wastewater treatment plants are energy demanding and pollutant removal processes are not always cost-effective. Furthermore, sludge management is another issue that requires a sustainable solution to reduce its environmental footprint. Algae biotechnology can be an option that can be used to overcome these challenges. Microalgae species such as Nannochloropsis, Euglena, Oscillatoria, Chlamydomonas, Scenedesmus, Chlorella, Nitzschia, Navicula and Stigeoclonium have the ability to accumulate contaminants/pollutants, therefore reducing the pollutant/contaminant load from wastewater. Removal efficiency can reach up to more than 90% for organic substances, nitrates, phosphates and heavy metals. Microalgae species supply also oxygen to aerobic microorganisms. This can reduce the costs related to oxygen supply in a conventional plant. Once clean effluent is generated, algae biomass is harvested and used for bio-jet fuel production. The biomass is processed to produce crude bio-oil which has similar physical properties compared to the petrochemical crude oil. Algae bio-oil can be processed via transesterification, thermal cracking or pyrolysis and fractionation including reforming and upgrading processes to produce renewable jet fuel. This fuel is expected to have the same physico-chemical properties compared to conventional jet fuel. It is environmentally friendly due to its low carbon footprint. However, the major challenge with algae-based fuels is the low lipid content for many species and the costly biomass harvesting process.