Improving gaseous biofuel yield from seaweed through a cascading circular bioenergy system integrating anaerobic digestion and pyrolysis

Chen Deng, Richen Lin, Xihui Kang, Benteng Wu, O’Shea, Richard and Jerry D. Murphy

Renewable and Sustainable Energy Reviews, 2020, vol. 128, issue C

Abstract: Advanced biofuels include biomass sources free from land use such as seaweed. Seaweed biomethane may contribute significantly to a climate-neutral transport future; however, seaweed has limited biodegradability via anaerobic digestion (AD). To address this issue, the authors proposed a cascading circular bioenergy system incorporating pyrolysis (Py) for production of biochar, syngas and bio-oil, with the primary use of biochar in AD to promote biomethane production through direct interspecies electron transfer. The feasibility of the proposed AD-Py system was demonstrated by integrating a seaweed-based AD and a residue-based Py system to enhance advanced biofuels production. The AD results showed biochar achieved comparable performances to high-cost graphene in terms of enhancing biomethane production from seaweed. When digesting Laminaria digitata (common kelp), optimal biochar addition at 1/4 (biochar mass: volatile solid of seaweed) increased biomethane yield by 17% and peak production rate by 29% with accelerated volatile fatty acids conversion during AD. When digesting Saccharina latissima (sugar kelp), biomethane yield increased by 16% with optimal biochar addition. A mass and energy balance analysis indicated that processing 1.000 t of Laminaria digitata in AD, combustion of syngas and surplus biochar (in excess of biochar added in AD) from Py of 1.254 t forest residue and 0.078 t dried digestate could fulfil all the heat demand for the integrated AD-Py system. The process integration increased biomethane yield by 17% and bio-oil yield by 10%. Furthermore, a 26% decrease in digestate mass flow could be achieved, thereby reducing the demand for agricultural land for digestate application.

Keywords: Biomethane; Anaerobic digestion; Seaweed; Biochar; Pyrolysis; Cascading circular bioenergy system (search for similar items in EconPapers)
Date: 2020
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Citations: View citations in EconPapers (15)

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DOI: 10.1016/j.rser.2020.109895

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