Abstract
In the near future, renewable energy sources will replace fossil energy. To allow full carbon utilization of renewable biomass, we have demonstrated a possible integration between a biogas reactor, an electrolysis unit, and a catalytic methanation reactor. Stringent removal of all sulfur contaminants in raw biogas is required to enable this integration. We demonstrate how existing bulk sulfur removal solutions, like a biotrickling filter loaded with Acidithiobacillus thiooxidans and impregnated activated carbon, are unable to meet this requirement. Only the main sulfur contaminant hydrogen sulfide (H2S) can effectively be removed. Contaminants carbon disulfide (CS2), dimethyl sulfide (DMS), and carbonyl sulfide (COS) will leak through the carbon filter, long before hydrogen sulfide can be detected. Utilization of surplus oxygen from the combined system is proven problem free and allows sulfur removal without introducing contaminants. Provided that a recommended sulfur guard is included, the proposed design is ready for full-scale implementation.
Highlights
Production of energy from biomass is one of the technologies enabling a fossil-free future
The H2S removal capability of both the biotrickling filter (BTF) and carbon filter was unaffected when air injection was replaced by pure O2
This result shows how these existing technologies offer efficient bulk sulfur removal and how integration with an electrolyzer removes the current issue with nitrogen contamination
Summary
Production of energy from biomass is one of the technologies enabling a fossil-free future. Highlights - Pure oxygen available from the electrolysis of the combined power-tomethane system removes nitrogen contamination. - The proposed treatment removes biogas contaminants to a level enabling direct methanation. Production of biogas is used as an efficient way to handle waste streams from agricultural production facilities, and biogas reactors at wastewater treatment plants are being installed to reduce the overall energy requirement. The produced biogas is carbon neutral, and the main component in the biogas, methane (~55–70%), is moved from producer to consumer/storage via the existing natural gas grid. Export of methane to the grid will require the main byproduct in biogas, CO2 (~30–45%), to be removed on-site [3]. Available biomass is a restricted resource, and replacing natural gas in this way will not be possible. Gas consumption is at a high level in multiple sectors: industrial, district heating, and transport [4]
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