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Energy Balance of Biogas Production from Microalgae: Effect of Harvesting Method, Multiple Raceways, Scale of Plant and Combined Heat and Power Generation

by John J. Milledge and Sonia Heaven

J. Mar. Sci. Eng. 2017, 5(1), 9; https://doi.org/10.3390/jmse5010009 - 25 Jan 2017

Cited by 24 | Viewed by 7930

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 [...] Read more.

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. Full article

(This article belongs to the Special Issue Algal Biofuels)

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252 KiB

Open AccessReview

UK Macro-Algae Biofuels: A Strategic Management Review and Future Research Agenda

by Per Gegg and Victoria Wells

J. Mar. Sci. Eng. 2017, 5(3), 32; https://doi.org/10.3390/jmse5030032 - 31 Jul 2017

Cited by 20 | Viewed by 6248

Abstract

Macro-algae is increasingly gaining attention as a potential feedstock for biofuels and as a potential alternative fuel for aviation. Technological aspects are showing promise, and being examined more widely. This paper uses a strategic management perspective to complete an initial macro-environmental scan of [...] Read more.

Macro-algae is increasingly gaining attention as a potential feedstock for biofuels and as a potential alternative fuel for aviation. Technological aspects are showing promise, and being examined more widely. This paper uses a strategic management perspective to complete an initial macro-environmental scan of the potential opportunities and threats to a seaweed biofuels industry. This is in response to calls to look beyond technological aspects, and highlights the importance of social acceptance. It is clear that very little is known about the potential economic, social, environmental and political/legal issues that might arise in the development of this industry. While we can look at the development of other, more established renewable technologies and seaweed industries away from the UK to highlight potential issues this does not give us a clear picture. Further research is needed to ensure that a proactive approach is used to research and inform stakeholders who will affect the further technological development and commercialization of the industry. Full article

(This article belongs to the Special Issue Algal Biofuels)

289 KiB

Open AccessReview

Golden Tides: Problem or Golden Opportunity? The Valorisation of Sargassum from Beach Inundations

by John J. Milledge and Patricia J. Harvey

J. Mar. Sci. Eng. 2016, 4(3), 60; https://doi.org/10.3390/jmse4030060 - 13 Sep 2016

Cited by 134 | Viewed by 16307

Abstract

In recent years there have been massive inundations of pelagic Sargassum, known as golden tides, on the beaches of the Caribbean, Gulf of Mexico, and West Africa, causing considerable damage to the local economy and environment. Commercial exploration of this biomass for [...] Read more.

In recent years there have been massive inundations of pelagic Sargassum, known as golden tides, on the beaches of the Caribbean, Gulf of Mexico, and West Africa, causing considerable damage to the local economy and environment. Commercial exploration of this biomass for food, fuel, and pharmaceutical products could fund clean-up and offset the economic impact of these golden tides. This paper reviews the potential uses and obstacles for exploitation of pelagic Sargassum. Although Sargassum has considerable potential as a source of biochemicals, feed, food, fertiliser, and fuel, variable and undefined composition together with the possible presence of marine pollutants may make golden tides unsuitable for food, nutraceuticals, and pharmaceuticals and limit their use in feed and fertilisers. Discontinuous and unreliable supply of Sargassum also presents considerable challenges. Low-cost methods of preservation such as solar drying and ensiling may address the problem of discontinuity. The use of processes that can handle a variety of biological and waste feedstocks in addition to Sargassum is a solution to unreliable supply, and anaerobic digestion for the production of biogas is one such process. More research is needed to characterise golden tides and identify and develop commercial products and processes. Full article

(This article belongs to the Special Issue Algal Biofuels)

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