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SUBLIME Energie unveils on-farm biogas liquefaction technology

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Energy Global,

Emerging from the Energy Environment Processes Center (CEEP) at the prestigious engineering school Mines Paris-PSL, deeptech startup SUBLIME Energie is revolutionising biogas valorisation with a unique technology: biogas liquefaction. By efficiently transporting and pooling biogas produced by multiple farms, this technology reduces initial investments and operating costs. Therefore, it opens access to untapped biomass resources, increases the resilience of farms and territories, and provides a decarbonisation pathway for the agricultural and transport sectors. SUBLIME Energie democratises biogas production for isolated or small farms and creates local supply chains for biomethane and bio-carbon dioxide (CO2).

SUBLIME Energie unveils on-farm biogas liquefaction technology

Over 80% of biomass is held by farmers, yet biogas sector development is hindered by the limited profitability of traditional technologies and the mismatch between potential biogas production sites and their consumption locations. Co-generation, the oldest method, has limited profitability due to low engine efficiency. Biomethane injection into gas networks, on the other hand, involves costly purification and connection steps requiring high flow rates. This excludes small or remote farms which represent an estimated additional potential of nearly 26 TWh of renewable energy by 2050. SUBLIME Energie addresses these challenges by offering a third biogas valorisation pathway suitable for low flow rates, making these positive-impact units profitable.

SUBLIME Energie's technology is based on an innovative biogas liquefaction process directly on the farm. By introducing a carrier agent into the biogas, the company overcomes technical constraints related to mixture crystallisation. This process is protected by the company's first patent. The second patent covers the centralised purification phase, where the three substances are separated before mutual valorisation.

SUBLIME Energie has reached a crucial phase of its technological maturation. After a successful proof of concept (POC) in 2020, the company worked on the engineering, manufacturing, and commissioning of its first demonstrator at CEEP. This demonstrator aims to mitigate the two main technological barriers: biogas liquefaction at a representative flow rate and the separation of purified methane and CO2 for separate valorisation as bio-LNG and bio-CO2. Technical results are promising, achieving liquefaction of a ternary mixture with a predefined final composition corresponding to biogas with 50% methane (CH4) and 50% CO2. This composition was verified through gas chromatography measurements, with a 2% deviation due to measurement uncertainty. The solid CO2 formation temperature appears experimentally lower than the theoretical model, with a deviation of about 4°C, co-firming the model's conservativeness regarding freezing.

Following the necessary technical validations, SUBLIME Energie is designing a second demonstrator to be installed at the Gazéa methanisation site in Côtes-d'Armor, France’s Bretagne region, in 2025. The first commercial series installation is planned for the end of 2026, pooling production from about ten methanisers.

By capturing CH4 – a greenhouse gas 80 times more potent than CO2 over 20 years – from livestock effluents, SUBLIME Energie helps decarbonise the agricultural sector, which is responsible for 25% of global greenhouse gas emissions. The methane is transformed into bio-GNV, a mature fuel for heavy-duty mobility, reducing GHG emissions by 85% over the fuel's lifecycle compared to diesel. This substitution could prevent 270 000 t of CO2 annually by 2030, thanks to the SUBLIME Energie solution. The fuel offers up to 1500 km range for trucks and is suitable for agricultural machinery, especially tractors, enabling a full day's work. Simultaneously, the captured bio-CO2 replaces fossil CO2 in industries such as agriculture, food, and cryogenics, with long-term prospects for geological storage.

This approach is part of a circular economy, with systematic recycling and reuse of carrier agents.

Additionally, the digestate produced alongside biogas can replace up to 95% of fossil fertilizers, whose production is notably GHG-intensive.

SUBLIME Energie's innovation provides farmers with additional income while reducing the initial investment and barriers to entry for methanisation. It also reduces fossil fertilizer costs through the production of digestate. The democratisation of on-farm biogas production also means that farms can be brought up to standard, enhances their attractiveness for future generations, and creates local, non-relocatable jobs. This model strengthens the resilience of farms in remote areas, bringing new dynamics, new jobs and territorial independence thanks to local production and citizen participation. For example, the start-up plans to create 15 non-relocatable jobs per project, i.e. 360 jobs by 2030.

Bruno Adhemar, President and Co-Founder of SUBLIME Energie, said: “With a unique technology, SUBLIME Energie offers a solution to democratise profitable on-farm biogas production. This virtuous model valorises untapped biomass, decarbonising farms that are far from the grid or small in size. Our field-adapted approach takes into account appropriate investments for farmers through equipment pooling and local job creation without significant additional workload. By physically and locally valorising all productions, we offer a comprehensive and sustainable solution for the future of agriculture, addressing current social and environmental crises.”



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Energy Global's Spring 2024 issue

The Spring 2024 issue of Energy Global starts with a guest comment from Field on how battery storage sites can serve as a viable solution to curtailed energy, before moving on to a regional report from Théodore Reed-Martin, Editorial Assistant, Energy Global, looking at the state of renewables in Europe. This issue also hosts an array of technical articles on electrical infrastructure, turbine and blade monitoring, battery storage technology, coatings, and more.

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