This entails a dual effort: on one hand, implementing technologies capable of capturing CO₂ with a quality high enough for it to be reused as a substitute for fossil CO₂. The expected uses of CO₂ involve industries such as food and beverage (hence the importance of CO₂ quality) or the production of Synthetic Gas through methanation processes. On the other hand, it is crucial to develop energy-efficient technologies so as not to affect the carbon intensity level.

The demo plant currently under development for CS3 applies a Cryogenic Upgrading (or Cryoupgrading) process to the Biogas. This process is conducted in an integrated cryogenic unit, which enables the separation of CO₂ from the Biogas to obtain a pure CO₂ stream with food-grade quality. The resulting Biomethane, with a CO₂ concentration of less than 1%, is then cooled, liquefied, and polished. 

The biogas stream (>100Nm3/h) received at the inlet of the demo plant is processed and converted into two streams: one of liquid bio-methane and the second of liquid CO₂.

Liquid CO₂ and liquid biomethane are valuable and highly versatile resources with a wide range of industrial and energy applications. As previously mentioned, liquid CO₂ is used in the food and beverage industry, as a coolant or freezing agent, and as a chemical reagent in industrial processes. In agriculture, it optimizes plant growth in greenhouses through the carbonation of irrigation water. On the other hand, liquid biomethane is a sustainable energy source with multiple practical applications. For example, it can be used as a fuel for vehicles, contributing to emissions reduction in the environment. 

Another significant application is for self-consumption. The produced biomethane can indeed become a fuel used for agricultural vehicles and tractors, thus opening up a scenario of circular economy. 

• The CS3 takes place at a dairy farm (approx. 1500 cows) in West Flanders, Belgium, characterized by a local nutrient surplus due to agro-residues. Flanders is one of the Nitrate Vulnerable Zones in Europe so the application of manure/digestate is limited to 170 kg N/ ha. In frame of the CS3, the farmer will try and meet hygienization requirements of the By-product Regulation (EC) 1069/2009 (by means of post thermophilic anaerobic digestion) that would allow export across the border and application of Belgian digestate on a French arable land in need of such fertilisers. Some part of the digestate, together with liquid CO₂, will be used to grow microalgae as an alternative protein source for animal feed which can potentially reduce soybean imports. 
• So far, the energy profile of the dairy farm has been calculated and lab-and pilot-scale anaerobic digestion experiments have been carried. Feedstock optimization was done via biomethane potential tests to determine the most suitable co-feedstock to cow manure which the farmer could supply if necessary. Pilot-scale anaerobic digesters were operated mimicking the farm-scale digester set-up to determine and solve any potential operational problems in advance. The digestate samples were collected and analyzed according to the parameters given in the Regulation (EU) 2019/1009 to assess its safe and efficient use as bio-based fertilizer.

Currently, the construction of the biogas plant is already underway, outside the scope of SEMPRE-BIO but essential for generating the required biogas input to the demo plant. The demo plant is currently under construction at CRYOinox while testing is being conducted with a dedicated test bench. The start-up of the demo plant is expected in April 2024.