Life cycle assessment of seaweed biomethane, generated from seaweed sourced from integrated multi-trophic aquaculture in temperate oceanic climates. (15th June 2017)

• Record Type: Journal Article
• Authors: Czyrnek-Delêtre, Magdalena M.; Rocca, Stefania; Agostini, Alessandro; Giuntoli, Jacopo; Murphy, Jerry D.
• Is Part Of: Applied energy. Volume 196(2017)
• Page Start: 34
• Page End: 50
• Publication Date: 2017-06-15
• Subjects: Seaweed -- Biomethane -- Anaerobic digestion -- Life cycle assessment (LCA) -- Wastewater -- Integrated multi-trophic aquaculture (IMTA); Power (Mechanics) -- Periodicals; Energy conservation -- Periodicals; Energy conversion -- Periodicals; 621.042
• DOI: 10.1016/j.apenergy.2017.03.129
• Languages: English
• ISSNs: 0306-2619

Abstract

Highlights: Seaweed composition is the key factor in decreasing environmental impacts. Digestate handling and storage is a large contributor to impacts. Proper management of digestate offsets carbon emissions by 3–7 g CO2 eq/MJ. Seaweed farming represents 53% of impacts in production of seaweed biomethane. Seaweed biomethane can deliver over 60% carbon savings as compared to fossil fuel. Abstract: Biomethane produced from seaweed is a third generation renewable gaseous fuel. The advantage of seaweed for biofuel is that it does not compete directly or indirectly for land with food, feed or fibre production. Furthermore, the integration of seaweed and salmon farming can increase the yield of seaweed per hectare, while reducing the eutrophication from fish farming. So far, full comprehensive life cycle assessment (LCA) studies of seaweed biofuel are scarce in the literature; current studies focus mainly on microalgal biofuels. The focus of this study is an assessment of the sustainability of seaweed biomethane, with seaweed sourced from an integrated seaweed and salmon farm in a north Atlantic island, namely Ireland. With this goal in mind, an attributional LCA principle was applied to analyse a seaweed biofuel system. The environmental impact categories assessed are: climate change, acidification, and marine, terrestrial and freshwater eutrophication. The seaweed Laminaria digitata is digested to produce biogas upgraded to natural gas standard, before being used as a transport biofuel. The baseline scenario shows high emissions in all impact categories. An optimal seaweed biomethane system can achieve 70% savings in GHG emissions as compared to gasoline with high yields per hectare, optimum seaweed composition and proper digestate management. Seaweed harvested in August proved to have higher methane yield. August seaweed biomethane delivers 22% lower impacts than biomethane from seaweed harvested in October. Seaweed characteristics are more significant for improvement of biomethane sustainability than an increase in seaweed yield per unit area.