BECCS from biogas production

BECCS from biogas production Global CO₂ emissions amount to about 40 Gtonnes/year and they need to be rapidly reduced if we are to meet adopted climate targets. To achieve this, a variety of measures is needed, such as more electrification, reduced use of fossil energy, more renewable energy, energy efficiency improvements and CCS (Carbon Capture and Storage). However, this will not be enough, but will also require so-called negative emissions, which means that CO₂ is removed from the atmosphere through, for example, increased afforestation, increased carbon storage in soil (e.g. biochar), or by capturing and storing CO₂ of biogenic origin in geological formations, also known as bio-CCS or BECCS. At global level, the need for negative emissions is estimated to be in the order of several billion tonnes of CO₂ per year if it shall be possible to reach the 1.5-degree target and net zero emissions by 2050. At national level, Sweden’s target is to achieve net zero emissions by 2045 and from then on to be climate positive. This means that territorial emissions from the 1990 level must be reduced by at least 85% by 2045 and that the remaining 15 % will be eliminated by means of so-called supplementary measures including bio-CCS as an important measure. The need for bio-CCS is significant and the actors who can deliver biogenic CO₂ at the right quality and at low cost will have good business opportunities in an expected future global marketplace for negative emissions. With this project, we have investigated the opportunities CO₂ from biogas production has to contribute to bio-CCS in Sweden. At biogas plants that produce vehicle gas, there is already equipment to separate CO₂ from biogas, so-called upgrading technologies. By modifying and extending this technology, pure liquid CO₂ can be generated. The CO₂ is then transported to terminals in Swedish ports while waiting for transport by ship to the place for permanent storage. The project has studied gas purification and liquefaction based on the four most common upgrading techniques: water scrubber, PSA (pressure swing adsorption), membrane separation and amine scrubber. The residual gas (the CO₂-rich gas leaving the upgrading equipment) differs between different upgrading technologies, which affects the need for subsequent purification steps. Results from modelling and simulation have led to two proposed technology chains. For amine scrubbers, a simple process of compression, drying and liquefaction is sufficient to achieve the CCS specification of the liquid CO₂. PSA, membranes and water scrubbers require more advanced gas purification including a two-phase separation and recirculation of gases with low dew point, such as O₂ and CH4. The recirculated gas is recycled to the inlet of the upgrading process, leading to the double benefit of increased amount of valuable CH₄ product and further reduction of greenhouse gas emissions to the atmosphere. A side effect is that the need for conventional residual gas management is eliminated. Cost calculations have been carried out for biogas plants with a production capacity of 20, 50 and 120 GWh/year. With an availability of 95% and a CO₂ content of 39% in raw biogas (gas before upgrading), this equates to a CO₂ production of 2,400, 5,900 and 14,200 tons/year, respectively. A starting point for the study has been that systems for large-scale bio-CCS/CCS will be established and that this will lead to the construction of several CO₂ terminals in Swedish ports. Furthermore, it is assumed that these terminals allow third-party access where a supplementary volume of biogenic CO₂ from biogas plants can constitute a portion of the total managed amount. Around each terminal, clusters of biogas plants are estimated to emerge, which each can deliver approximately 20,000–100,000 tons CO₂ per year. The distribution from biogas plants to port terminals may be done by truck transport where the loading capacity amounts to 34 tons of CO₂. After the terminal, CO₂ is transported by ship to the place for permanent storage. The cost of producing liquid CO₂ from biogas depends on local conditions such as CO₂ flow, O₂ content, upgrading technology, new or existing plant, transport distance to terminal, etc. In order to determine what the cost will be for each individual biogas plant, it is necessary to adapt the calculations to local conditions. Through the project, generic calculations have been carried out which show that large biogas plants have good opportunities to produce liquid CO₂ at competitive costs, but also that there is a strong scaling effect. For example, the cost is about SEK 200–300/tonne CO₂ for new plants with 120 GWh in annual biogas production. With investment support, the cost drops to about SEK 150–200/tonne. For new plants in the intermediate segment (50 GWh/year), the cost is slightly higher, SEK 300–450/tonne (without capital grants) and SEK 190–275/tonne (with capital grants). For smaller plants (20 GWh/year), the cost rises significantly, especially for water scrubbers. The transport cost up to the terminal is affected by the distance and amount of CO₂ handled. For example, the cost of truck transport from larger biogas plants is about SEK 200/tonne at 100 km one-way to terminal. The total cost of bio-CCS from biogas including terminal handling, ship transport and final storage is affected by many parameters and there are uncertainties in cost estimates along the entire chain. In a calculation example for a biogas plant with membrane upgrading, 100 km of truck transport one way to terminal in Gothenburg and transport and final storage according to Northern Light's concept, the total cost was estimated at SEK 830–1020/tonne CO₂ for larger biogas plants (120 GWh/year). When the bio-CCS from biogas is introduced, negative emissions arise from two sources, firstly from the final storage itself, which is the main part, and secondly by reducing CH₄ emissions from the upgrading plants, which is a smaller, but not negligible part. The total CO₂ efficiency of the value chain is determined by energy consumption, transport distance, selected storage solution and CH₄ slip before the introduction of bio-CCS. Emissions from truck transport are small in this context. In total, CO₂ efficiency in many cases amounts to close to 100%, i.e. net emissions in the value chain up to final storage are close to zero. For plants that initially had relatively high CH₄ emissions from the upgrading unit, the climate benefit is even greater, with CO₂ efficiency throughout the chain being well over 100%. A driving hypothesis in the project has been that CO₂ from biogas can be the CO₂ stream in society that is one of the lowest-hanging fruits and that the value chain is well placed to be more cost-effective than other concepts for bio-CCS. Based on the results of the project, we can conclude that the hypothesis is likely to hold. The cost up to the terminal will in many cases likely be lower compared to capture and liquefaction from large point sources. With efficient technology and distribution solutions, biogas producers should be able to contribute to bio-CCS to a fairly large extent, up to about 10% of Sweden's need for negative emissions. For biogas operators, this would mean a broadening of the business where CO₂ is seen as a valuable product which complements the revenues from the production of biomethane. Bio-CCS från biogasanläggninga