Abstract
Valorization of crude biogas to value-added products is the key step toward techno-economic biogas business. Besides, the increasing world population puts heavy pressure on food supply and will double protein demand in the coming decades. In this context, we propose a bioinorganic electrosynthesis process for the integration of biogas upgrading and edible single-cell protein production, which could be an alternative solution to address these challenges. With a biogas inflow of 70%CH4/30%CO2 at 50 mL·d−1 and an applied voltage of 3.0 V, the protein concentration of 472.04 ± 22.05 mg·L−1 was achieved with the “CO2-to-CH4” bioconversion efficiency of 92.97 ± 5.61%. Higher CO2 content in the biogas resulted in a comparatively lower protein concentration. The system was tested resilient to the toxic H2S in biogas (up to 5000 ppm). It was possible to improve the protein yield three times by scaling up the fermenter from 100 mL to 1 L, with a “CH4-to-SCP” fermentation efficiency of 70.67 ± 2.37%. The methanotrophic biomass produced in the system was found rich in protein with a total amino acids mass-content of over 62.8%. The outcomes of this study will offer a new solution for sustainable protein production, biogas upgrading and valorization, which are perfectly in line with the United Nations Sustainable Development Goals.
Highlights
Biogas, produced by Anaerobic digestion (AD) of organic materials, has a long tradition of being utilized as a sustainable energy alternative against conventional fossil fuels [1,2]
We propose a bioinorganic electrosynthesis process for the integration of biogas upgrading and edible single-cell protein production, which could be an alternative solution to address these challenges
We propose a Bioinorganic electrosynthesis (BIES) system to realize the engagement of upstream biogas upgrading and downstream Single-cell protein (SCP) production
Summary
Biogas, produced by Anaerobic digestion (AD) of organic materials, has a long tradition of being utilized as a sustainable energy alternative against conventional fossil fuels [1,2]. To enhance the usability of biogas for multiple applications (e.g., to the natural gas grid), cleaning and upgrading of crude biogas to remove or reduce the component of CO2 (30 ~ 40%) and H2S (500 ~ 5000 ppm) are neces sary. This step is currently still energy-intensive and costly [5,6,7]. Considering that it is an inevitable trend that the government gradually reduces or cancels the financial support for biogas plants, the profitability of future biogas business is challenged by high initial capital costs and market barriers such as inadequate institutional framework and infrastructure [9,10,11]. Alternative technology for cost-effective biogas upgrading and value-added product production is urgently needed
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