Assessment of a Dry and a Wet Route for the Production of Bio-Fuels from Microalgae: Energy Balance Analysis ASSESSMENT OF A DRY AND A WET ROUTE FOR THE PRODUCTION OF BIO-FUELS FROM MICROALGAE: ENERGY BALANCE ANALYSISHow the Technology WorksMicroalgae release various high value by-products of metabolism that are useful in production of renewable energy when cultured on a large scale, especially due to its ability to develop completely closed algae to bio-fuel cycle. Microalgae are converted into energy both bio-chemically and thermo-chemically, which produce bio-diesel and ethanol, and gas and oil respectively (Xu et al, 2011). Recently, microalgae have been used to produce renewable energy through two techniques. the wet route and the dry route. Both routes have diesel production as their main target and, because it is in liquid form, it can be mixed with fossil diesel and applied in the transport industry. In the dry extraction route, Microalgae is cultured in the presence of makeup nutrients, water, carbon dioxide, and sunlight before undergoing the processes of flocculation, centrifugation, mechanical dehydration, thermal drying, and cell disruption, leading up to dry extraction (Xu et al, 2011). Oil cake and lipids are produced at the dry extraction stage, in which the oil cake undergoes pyrolysis to form pyrolysis oil and biogas, as well as char that is shunted back into the pyrolysis stage (Xu et al, 2011). Lipids, on the other hand, are treated with methanol for trans-esterification to occur, producing glycerol and bio-diesel. In the process, water and carbon dioxide are also recycled from the mechanical dehydration stage. In the wet process, the microalgae are cultured in similar conditions to the dry process, after which they are flocculated, centrifuged, and mechanically dehydrated, leading up to wet extraction. The products here are lipids and residues, of which the former is hydro-treated to form green diesel. The residues undergo supercritical gasification to produce hydrogen gas that is used in the hydro-treatment phase (Xu et al, 2011). In addition, supercritical gasification also produces water, carbon dioxide, and other gas products, of which the former two by-products are recycled in the microalgae culture.How It Was Applied To Solve A Particular Problem For a long time, there has been a need for less energy-intensive models of bio-fuel production from microalgae, particularly by reducing energy consumed during dewatering (Xu et al, 2011). Thus, because the two routes discussed above do not consume significant energy in the dewatering process, they have been used in making the process of renewable energy production from microalgae more efficient. The ability of both routes to produce more efficiently bio-diesel was tested by comparing the energy balance of the wet and dry routes. It was found that both the dry and wet route achieved large positive energy balances, while their energy output per unit area was higher than that achieved by sugar crops and vegetable oil crops. In addition, the wet phase only consumed 12% of the energy required for dewatering in the dry route since it skipped the thermal drying process, while extraction of oil using the wet route used 2.8 times more energy than the dry route (Xu et al, 2011). Therefore, there is a comparable total energy output for both routes, especially taking into consideration the cumulative effects from culture cultivation to conversion (Xu et al, 2011). However, the process of drying that is applied in the dry route consumes a significant energy amount, which is also true for the process of oil extraction in the wet route. The energy balance can be improved through the application of more efficient extraction and drying process for the wet and dry routes respectively, while coupling the process with waste energy in the form of heat from a power plant in the vicinity can also significantly improve the energy balance. From the results of this study, it can be concluded that the dry route offers a more efficient model of energy production compared to other conventional bio-diesel production methods in the short term due to its higher fossil energy ratio (Xu et al, 2011). However, the wet route holds more promise in the long term due to its production of higher value bio-fuels.ReferenceXu, L., Wim, B. D. W., Withag, J. A., Brem, G., amp. Kersten, S. (2011). Assessment of a dry and a wet route for the production of bio-fuels from microalgae: energy balance analysis. Bioresource Technology, 102, 8, 5113-22.
Assessment of a dry and a wet route for the production of biofuels from microalgae Energy balance analysis