Recovered CO₂ Supply Technology Comparison — Exhaust-Gas Catalytic Post-Treatment vs Upgrade-Linked Purification

Two CO₂ Supply Pathways

Biogas from the anaerobic digestion of organic feedstock can yield CO₂ at two different points, depending on where it is recovered.

Route 1 separates and purifies CO₂ during the biogas upgrading (biomethane) stage and supplies high-purity CO₂. Route 2 diverts only the amount needed from the exhaust gas after gas-engine power generation, treats it with a catalyst, and uses it on-site.

• Route 1 (separation at the upgrading stage) — organic feedstock → anaerobic digestion → biogas → desulfurization & drying → membrane/absorption/adsorption → CO₂ purification & compression → supply to AlphaFarm (high-purity)
• Route 2 (utilization from exhaust gas after power generation) — gas-engine power generation → exhaust-gas split → oxidation catalyst (CO·HC·NO reduction) → cooling & condensate removal → supply to AlphaFarm (on-site CO₂)

Method 1. Upgrade-Linked CO₂ Purification

Linked to the process that purifies biogas into biomethane, this method purifies and compresses the separated CO₂. It secures relatively high purity on a stable basis, suiting medium-to-large projects and potential external sales.

• Advantages — relatively higher CO₂ purity, stable and continuous supply, suitable for larger facilities and potential external sales, can be combined with a biomethane business
• Limitations — more complex system and higher capex, power consumption from separation and compression, lower utilization efficiency at small scale, requires operation and maintenance expertise
• Recommended scale — Core 5 and above, or medium-to-large projects considering external CO₂ sales

Method 2. Exhaust-Gas Catalytic Post-Treatment

Adding only downstream equipment to existing power generation, this method treats part of the exhaust gas with a catalyst and uses only what the farm needs. Its low initial capex and operating burden suit small on-site consumption PoCs.

• Advantages — only downstream equipment added to existing generation, no separation/compression/liquefaction required, relatively lower initial capex, lower operating and maintenance cost, only the amount needed by the farm is diverted, suitable for short-term PoC deployment
• Limitations — CO₂ at lower concentration mixed with air, concentration varies with engine load and operating hours, requires safety management for CO, NOₓ, formaldehyde, etc., supply stops when the generator stops, not suitable for precise control
• Recommended scale — small on-site consumption PoCs such as Core 2

Economic Comparison (Relative Index)

With exhaust-gas catalytic post-treatment set to 1.0, these are conceptual relative indices comparing both methods for the same annual CO₂ supply quantity. The upgrade-linked purification method shows higher capex and opex because it adds separation, compression, and purification equipment.

※ These are conceptual relative indices. Actual values vary with generator and exhaust-gas characteristics, existing downstream equipment, piping distance, and whether compression or storage are included, so they are estimated separately for each site.

• CAPEX index per 1 ton CO₂ supplied — exhaust-gas post-treatment 1.0 vs upgrade-linked purification ≈ 6.0 (~6× difference)
• OPEX index per 1 ton CO₂ supplied — exhaust-gas post-treatment 1.0 vs upgrade-linked purification ≈ 4.0 (~4× difference)
• CO₂ quality (purity) — exhaust-gas post-treatment: on-site farm supply level / upgrade-linked purification: relatively higher purity
• System complexity — exhaust-gas post-treatment: low / upgrade-linked purification: high
• External sales potential — exhaust-gas post-treatment: limited / upgrade-linked purification: can be considered
• Recommended scale — exhaust-gas post-treatment: Core 2 PoC / upgrade-linked purification: Core 5 and above

Phased Application Strategy

We recommend a two-phase approach that first confirms field applicability and economics, then scales up.

• Phase 1 · Core 2 PoC — prioritize the exhaust-gas catalytic post-treatment route, verifying field applicability and economic feasibility with lower capex and opex.
• Phase 2 · Core 5 and above — review the upgrade-linked CO₂ purification route, together with farm scale-up and external CO₂ commercialization.
• Final goal — supply the CO₂ required by AlphaFarm safely and economically on a continuous basis