J. Mar. Sci. Eng. 2017, 5(1), 9; doi:10.3390/jmse5010009
Energy Balance of Biogas Production from Microalgae: Effect of Harvesting Method, Multiple Raceways, Scale of Plant and Combined Heat and Power Generation
1
Engineering and the Environment, University of Southampton, Southampton SO17 1BJ, UK
2
Science and Engineering, University of Greenwich, Chatham Maritime, Kent ME4 4T, UK
*
Author to whom correspondence should be addressed.
Academic Editor: Magnus Wahlberg
Received: 9 September 2016 / Revised: 30 December 2016 / Accepted: 18 January 2017 / Published: 25 January 2017
(This article belongs to the Special Issue Algal Biofuels)
Abstract
A previously-developed mechanistic energy balance model for production of biogas from the anaerobic digestion of microalgal biomass grown in open raceway systems was used to consider the energetic viability of a number of scenarios, and to explore some of the most critical parameters affecting net energy production. The output demonstrated that no single harvesting method of those considered (centrifugation, settlement or flocculation) produced an energy output sufficiently greater than operational energy inputs to make microalgal biogas production energetically viable. Combinations of harvesting methods could produce energy outputs 2.3–3.4 times greater than the operational energy inputs. Electrical energy to power pumps, mixers and harvesting systems was 5–8 times greater than the heating energy requirement. If the energy to power the plant is generated locally in a combined heat and power unit, a considerable amount of “low grade” heat will be available that is not required by the process, and for the system to show a net operational energy return this must be exploited. It is concluded that the production of microalgal biogas may be energetically viable, but it is dependent on the effective use of the heat generated by the combustion of biogas in combined heat and power units to show an operational energy return. View Full-TextKeywords:
microalgae; algae; bioenergy; biogas; anaerobic digestion; energy balance
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Milledge, J.J.; Heaven, S. Energy Balance of Biogas Production from Microalgae: Effect of Harvesting Method, Multiple Raceways, Scale of Plant and Combined Heat and Power Generation. J. Mar. Sci. Eng. 2017, 5, 9.
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