Upstream and downstream processing of microalgal biogas: Emissions, energy and economic performances under carbon taxation

George Victor Brigagão, Igor Lapenda Wiesberg, Juliana Leite Pinto, Ofélia de Queiroz Fernandes Araújo and José Luiz de Medeiros

Renewable and Sustainable Energy Reviews, 2019, vol. 112, issue C, 508-520

Abstract: The study evaluates alternative and innovative arrangements for processing a microalgae biomass by anaerobic digestion to produce biogas. Cell wall limits bio-accessibility of microalgal intracellular compounds, demanding pretreatment to improve methane yield. Two pretreatments are evaluated at 75 °C using residual heat: thermal (1 bar) and thermomechanical (20 bar),which increased biogas production in 40% and 159%, respectively. Thermomechanical pretreatment is coupled to the following downstream processing cases: (i) biomethane; (ii) bioelectricity; (iii) biomethane with enhanced oil recovery; (iv) bioelectricity with enhanced oil recovery and (v) pressurized anaerobic digestion (6 bar) for biomethane with enhanced oil recovery. Processes are compared in three dimensions: energy, economic and carbon footprint. Such a framework including upstream and downstream processes, besides comparison of atmospheric and pressurized anaerobic digestion, with in-depth economic analysis, configures the main novelties of this work. Resource utilization efficiency metrics point advantage of pressurized anaerobic digestion case, while indicate biomethane production as less efficient than bioelectricity. When carbon dioxide post-combustion capture and enhanced oil recovery are applied to abate bioelectricity emissions, bioelectricity loses competitiveness to biomethane due to high energy penalties. Sensitivity of Net Present Value to varying carbon taxation (increasing costs), Capture & Trade mechanism and enhanced oil recovery (adding revenues) show superior resilience of biomethane with enhanced oil recovery. In base scenario conditions, where 30US$/GJ electricity is applied, maximum biomass costs to economic feasibility for cases (i) to (v) are 50, 21, 100, 5 and 83US$/t (dry-basis), respectively. Priced at 50US$/GJ, the bioelectricity production frontier to feasibility starts at biomass costs ≈150US$/t.

Keywords: Biogas; Microalga pretreatment; Biomethane; Bioelectricity; CO2 capture; Anaerobic digestion (search for similar items in EconPapers)
Date: 2019
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Citations: View citations in EconPapers (5)

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DOI: 10.1016/j.rser.2019.06.009

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