Biologically produced carbon dioxide (CO鈧�) is expected to increase as demand grows for renewable, locally produced energy. A central question is becoming more prominent as biomethane production expands and becomes more visible: what should be done with the CO鈧� generated in the process?
鈥淯nlike fossil carbon dioxide, this has a biological origin. It should therefore not be seen only as an emission, but as a potential resource in the transition to a circular economy. Carbon dioxide is already used today, for example in the food industry and as a refrigerant,鈥� says Stephanie Cordova, a doctoral student in Industrial Environmental Technology.
From by-product to resource
Biogas is formed when organic material breaks down without oxygen. To be used as a vehicle fuel, it is upgraded to biomethane, which in everyday language is also often called biogas. In that process, the carbon dioxide is separated out. It accounts for around 30 to 50 per cent of the gas.
Ulrik Svedin
Biomethane can replace fossil natural gas and is produced locally from waste and residues. In Link枚ping, the municipal energy company Tekniska verken has already begun producing food-grade carbon dioxide as a by-product of the biomethane process.
Several possible areas of use
Stephanie Cordova鈥檚 study shows that several applications appear particularly promising. One is methanation, which means that carbon dioxide reacts with hydrogen to form more methane. This can increase production without requiring more raw material.
鈥淭he climate benefits are considerable, but the technology requires access to large amounts of fossil-free electricity for hydrogen production.鈥�
Another option is liquid carbon dioxide, which can be used in cooling applications, for example in refrigerated transport. There it can replace fossil carbon dioxide and provide direct climate gains. At the same time, the market is limited and purity requirements are high.
Can be useful
鈥淚n the short term, food-grade carbon dioxide is needed to avoid contamination, which increases the costs of purification and monitoring.鈥�
Carbon dioxide can also be useful in greenhouses for horticultural applications.
鈥淐arbon dioxide can stimulate plant growth and thereby contribute to more efficient food production.鈥�
Mineralisation is another option, where the carbon dioxide is bound into solid materials.
鈥淭his enables long-term storage and can create new materials, but the technology is still under development.鈥�
In the longer term, biogenic carbon dioxide could also become an important feedstock for fuels and chemicals.
鈥淪ociety will continue to need carbon-based products. The focus should therefore be on replacing fossil carbon with renewable alternatives,鈥� says Stephanie Cordova.
Challenges and opportunities
Using carbon dioxide can in many cases reduce climate impact compared with releasing it directly. At the same time, the results need to be considered from a broader systems perspective.
鈥淔actors such as access to electricity, transport solutions and local markets influence the outcome.鈥�
Despite its potential, biogenic carbon dioxide is still used only to a limited extent. It requires investment and profitability is uncertain. Demand is not unlimited, and the infrastructure for transport and storage can be difficult to establish.
鈥淎 key challenge is economic uncertainty. There are also infrastructural barriers and uncertainty in political decisions on energy solutions, which makes it difficult for biogas actors to invest.鈥�
At the same time, there are strong drivers for change. Interest in biogenic carbon dioxide and carbon-based renewable fuels is growing, driven by both climate targets and new business models.
鈥淲hich option is most suitable depends on local conditions. This means that future systems are likely to combine several different solutions,鈥� says Stephanie Cordova.
