Techno-Economic Analysis of Biogas Production from Microalgae through Anaerobic Digestion

Abstract

Microalgae are a promising feedstock for bioenergy due to higher productivity, flexible growing conditions, and high lipid/polysaccharide content compared to terrestrial biomass. Microalgae can be converted to biogas through anaerobic digestion (AD). AD is a mature technology with a high energy return on energy invested. Microalgae AD can bypass energy intensive dewatering operations that are associated with liquid fuel production from algae. A techno-economic assessment of the commercial feasibility of algae-based biogas production was conducted using Cyanothece BG0011 biomass as an example. BG0011 is a naturally occurring, saline cyanobacterium isolated from Florida Keys. It fixes atmospheric nitrogen and produces exopolysaccharide (EPS). Maximum cell density and EPS concentration of 2.7 and 2.1 g afdw 1 /L (for total algae biomass concentration of 4.8 g afdw/L) were obtained by air sparging. For an areal cell and EPS productivity of 12.4 and 9.6 g afdw/m2/day, respectively, the biomethane production cost was 14.8 $/MMBtu using covered anaerobic lagoon and high-pressure water scrubbing for biogas purification. Electricity production from biogas costs 13 cents/kwh. If areal productivity was increased by 33% from the same system, by sparging air enriched with 1% CO2, then biomethane cost was reduced to 12.16 $/MMBtu and electricity cost to 11 cents/kwh.

Socio-Economic and Environmental Impacts of Biomass Valorisation: A Strategic Drive for Sustainable Bioeconomy

“…Biogas (biomethane, biohydrogen, and biohytane): Taking lignocellulosic biomass as a source to produce biofuels, anaerobic digestion is the cheapest, most stable, and well-established technique that recovers a higher amount of energy from the source [125][126][127]. Digestion of cellulose and hemicellulose (i.e., lignocellulosic biomass) underpins that anaerobic microbes can synthesise methane-rich biogas [128,129]. Lignin also reduces the substrate availability to the enzymes of anaerobic microbes, decreasing the productivity of methane [130].…”

The Enhancement of Energy Efficiency in a Wastewater Treatment Plant through Sustainable Biogas Use: Case Study from Poland

“…It is a mixture containing methane (CH 4 ) and carbon dioxide (CO 2 ) that is generated in the anaerobic digestion process (AD) [9,10]. Biogas may be easily used as fuel to generate heat or electricity at WWTPs [11,12]. It should also be noted that the treatment and disposal of sewage sludge is related with a significant financial and energy expenditure for WWTPs.…”

Isolation of Industrial Important Bioactive Compounds from Microalgae

“…Microalgae can be converted to biogas through anaerobic digestion which is a biochemical process that mineralizes organic material through the action of microorganisms in the absence of oxygen [ 210 ]. Biogas is mainly made up of a mixture of methane, CH 4 (50–70%), CO 2 (30–45%) and traces of other gases such as hydrogen, H 2 (<2%) and hydrogen sulphide, H 2 S (<3.5%).…”