BECCS and storage of biogenic CO₂ from biomethane plants: the road to negative emissions

BECCS (Bioenergy with Carbon Capture and Storage) is the combination of energy use of biomass with the capture and permanent storage of CO₂. Because the carbon in biomass comes from the atmosphere, storing it permanently leads to the removal of CO₂ from circulation, i.e. to net negative emissions. A biomethane plant is particularly well suited to BECCS: the CO₂ is already separated there during biogas upgrading, and in amine and cryogenic technologies it is of high purity, so it only needs cleaning, compression or liquefaction and transport to the storage site. Transport and storage infrastructure in Europe is only now being built, so practical application depends on local possibilities.

The BECCS chain for a biomethane plant

1. Capture: the CO₂ stream from upgrading (amine scrubber, cryogenics; in other technologies it requires additional treatment).
2. Cleaning and drying: removal of methane, hydrogen sulphide and water, so as to meet the transport and storage specification.
3. Compression or liquefaction: to transport pressure (pipeline) or to liquid CO₂ (tankers, ships).
4. Transport: road or rail tankers to a terminal, ships to offshore storage sites or pipelines.
5. Geological storage: injection into deep formations (saline aquifers or depleted fields).
6. Monitoring and verification: measurements, reporting, certification.

Worked example (illustrative)

A plant with 500 m³/h of biogas (45% CO₂, 8,000 hours of operation a year, CO₂ density about 1.98 kg/m³) produces about 3560 t of CO₂ a year. If the CO₂ is stored, and emissions associated with capture and transport (liquefaction energy about 0.1–0.15 MWh/t, transport) are, for example, 0.05 tCO₂ per tonne under an assumed energy mix, net removal is about 3380 t CO₂ a year. At an assumed cost of the full chain (liquefaction, transport, storage) of 150 EUR/t, the annual cost is about 534 thousand EUR. If 200 EUR/t were obtained for the 3380 t of CO₂ removed (about 676 thousand EUR), the surplus would be about 140 thousand EUR a year. The values are hypothetical; actual costs depend on distance and the availability of a storage site, and the market for removal certificates is only now taking shape.

Legal framework and certification

Regulation (EU) 2024/3012 establishes an EU framework for the voluntary certification of carbon removals, including permanent removals (e.g. BECCS and DACCS), agricultural practices that increase carbon storage in soil, and storage in products. The framework sets out quality criteria (among others quantification, additionality, long-term storage, sustainability) and requires verification by independent bodies. The directive on the geological storage of CO₂ sets requirements for storage sites. Projects are being developed in Europe, such as the Norwegian CO₂ transport and storage system, but availability for small sources is limited.

Advantages of biomethane plants

• high purity and concentration of the CO₂ stream,
• compression infrastructure already in place in many configurations,
• documented biogenic origin (sustainability certificate),
• the possibility of combining an energy product (biomethane) with CO₂ removal.

Challenges

1. No local storage site or terminal; transport over long distances increases costs.
2. Scale: a single plant produces thousands of tonnes of CO₂, which is a small amount for CCS projects requiring hundreds of thousands of tonnes; collective logistics is necessary.
3. Costs of liquefaction and buffer storage.
4. Uncertainty over the market for removal certificates and prices.
5. Accounting rules: avoiding double counting (CO₂ as a feedstock for e-fuels or as a removal).

Choosing between CCU and CCS

Using CO₂ in products with a short life cycle (beverages, e-fuels) does not remove it from the atmosphere permanently. Geological storage provides permanent removal. The choice is determined by price, the local market and regulations. In some cases both approaches can be combined: part of the CO₂ sold to the food industry and the surplus stored.

Collective CO₂ logistics

For small sources it is practical to collect CO₂ from many plants at one point: local pipeline networks, rail tankers or a transhipment terminal in a port. Such a model lowers the unit cost, but requires coordination and a common quality specification. It is good if biomethane producers already design their plants today so that a liquefaction and storage system can be added in the future, reserving space and connection capacity.

Summary

BECCS for biomethane plants is technically possible and logical, but requires infrastructure and a market. For investors it is an additional option worth considering in the project concept, especially when a CO₂ transport network is being developed in the region.