The Pilot‑SBG project, carried out at the German Biomass Research Centre (DBFZ) in Leipzig, investigates small‑scale liquefaction of renewable methane (biomethane) for transport and storage. The pilot plant, with a maximum capacity of 15 t d⁻¹, serves as a testbed for five liquefaction technologies: the Mixed Refrigerant Cycle (MRC), Gas Expansion Cycle (GEC), open Linde Cycle (LC), Stirling Refrigeration (SR), and Cryogenic Liquid Vaporisation (CLV). The study compares technical performance, economic cost, and greenhouse‑gas (GHG) emissions for each approach.
Technical results show that liquefaction costs across the technologies range from 0.20 € kg⁻¹ to 0.33 € kg⁻¹. The MRC delivers the lowest cost and the highest energy efficiency, achieving a specific energy consumption of roughly 5–10 % of the methane heating value. However, it requires complex equipment and high capital investment. The GEC, while simpler and safer due to the use of inert nitrogen as refrigerant, exhibits lower efficiency and higher energy demand, leading to higher costs. The open LC is attractive for its low complexity and absence of external refrigerants, but the compression step demands significant energy, reducing overall efficiency. SR offers a robust, self‑contained system with easy operation, yet its small capacity limits scalability. CLV is the most straightforward and capital‑light option, needing only minimal equipment and inert gas, but it is constrained by the need for on‑site liquid nitrogen and offers the lowest throughput.
GHG emissions from the liquefaction step vary between 0.1 g CO₂‑eq MJ⁻¹ and 12.4 g CO₂‑eq MJ⁻¹, depending largely on the source of electricity and the specific cycle used. The MRC, when powered by renewable electricity, can achieve emissions as low as 0.1 g CO₂‑eq MJ⁻¹, whereas the GEC and LC can reach up to 12.4 g CO₂‑eq MJ⁻¹ when using conventional grid power. The study also highlights that the overall life‑cycle emissions of biomethane liquefaction are dominated by upstream processes such as feedstock collection and biogas upgrading; therefore, site‑specific conditions strongly influence the environmental performance.
The project’s first phase, completed in 2023, produced a comprehensive techno‑economic and environmental assessment, culminating in a focus paper on market analysis and GHG quotas. The pilot plant’s design and operation were documented in a series of figures and tables, illustrating the process flow, cost breakdowns, and emission factors. The results feed into a broader concept for commercial deployment, where decentralized liquefaction units could be integrated into existing biogas plants to enhance the marketability of renewable methane.
Collaboration in Pilot‑SBG is led by DBFZ, which provides the research infrastructure and project management. Partners include academic institutions specializing in thermodynamics and process engineering, as well as industry stakeholders offering expertise in refrigeration technology and environmental assessment. The project is funded by DBFZ under a national research program aimed at advancing renewable energy technologies. The timeline spans from initial feasibility studies in 2022 to pilot plant construction and testing in 2023, with subsequent phases planned to scale the technology to commercial operations. This integrated effort seeks to establish a viable pathway for small‑scale, low‑emission liquefaction of biomethane, thereby expanding the use of renewable gases in the European energy system.