CO2-liquefaction - Krieg & Fischer Ingenieure GmbH

Biogenic CO2 from biogas upgrading

With the increased use of biogas in the form of biomethane, carbon dioxide can now be effectively harnessed as a by-product of biogas upgrading. The combination of feeding the upgraded methane into the gas grid and using the by-product CO₂ makes it possible to operate biogas plants with virtually no emissions and no losses. In this way, a major contribution can be made to reducing greenhouse gas emissions in the fuel and energy sectors. It also creates local synergies with CO₂-consuming industries.

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The carbon dioxide stream from biogas plant can be valorized in different sectors. CO₂ is traditionally used in various industries, such as food and beverages (for cooling and carbonization), agriculture, fire suppression, medicine and so on. Most of the commonly used production technologies rely on fossil fuels. Biogas plants are source of biogenic (biomass based) CO₂ and are part of the natural short carbon cycle, which starts with extraction of atmospheric CO₂ through photosynthesis. As companies seek to reduce their carbon footprint and demonstrate their commitment to sustainability, the demand for biogenic CO₂ is rising, as well as new applications in production of fuels, chemicals and building materials.

The process of CO₂-liquefaction itself is well established, most prominently in the brewing sector. The use of liquefaction in the biogas sector is relatively new, because the technology uses of electricity and fossil CO₂ was very cheap until 2022.

For the plants with biogas to biomethane upgrading, the process includes the collection of gaseous CO₂ from biogas, its purification and liquefication. A synergy effect with the upgrading is that methane in the raw CO₂ stream can be brought back to the upgrading plant resulting in a methane yield of almost 100%.

When engineering this system for biogas plant, multiple recirculations and interfaces have to be considered and coordinated to prevent accumulation of undesired components, make the most of the synergistic effects and reduce the emissions to a minimum.

If you consider switching or expanding your CHP biogas plant with biomethane production or already have upgrading system, we will be happy to help you effectively utilize your CO₂stream.

In the recent assignment for Krieg & Fischer engineering team, CO₂ liquefication will be implemented alongside installing a biogas upgrading system for two already existing biogas plants owned by LSW Energie GmbH, energy distribution network operator in North Germany.

Bioerdgas Isenhagen (Germany): 2023/24

The latest project by Krieg & Fischer Ingenieure shows the installation of a CO₂ liquefaction plant in combination with a biogas upgrading plant for two existing biogas plants of LSW Energie GmbH.

The project Bioerdgas Isenhagen will replace the existing biogas processing plant and involves the installation of a biogas to biomethane upgrading and CO₂ liquefaction plant producing food-grade quality CO₂. 1,400 Nm³/h of biogas will be sourced from two existing plants that use renewable raw materials and manure and from a nearby wastewater treatment plant (200 Nm³/h of biogas from potato processing waste). These three biogas flows will be integrated into the processing plant to produce 750 Nm³/h of biomethane, which will be fed into the local natural gas network.

The separated CO₂ will be liquefied, stored temporarily on site, and sold. Production of liquefied CO₂ will be about 1,1 t/h. It is also planned to implement a Dry-Ice production of 1.000 t/a. The proximity allows otherwise emitted Off-Gas to be reliquefied in the liquefaction plant.

The plant complies with all relevant regulations, including EU regulations, DIN standards, safety rules for biogas plants, operational safety regulations, and WHG and DVGW regulation.

Krieg & Fischer engineering team carries out the integration of the biogas upgrading and CO₂ liquefaction with the pre-existing biogas plants, determining suitable biogas extraction points, purification and function of the gas system, as well as using waste heat and coordinating between multiple heat and electricity consumers. CO₂ liquefication consumes quite a bit of electricity (0,21 kWh/kg liquid CO₂) and at the same time produces heat that comes from the compressor. So, part of the biogas is used at the existing CHPs that will supply the plants on site with electricity.

Waste heat from the biogas upgrading and CO₂-liquefaction plant's compressors will be used to heat the digesters. The remaining heat needed for the digesters will be supplied from CHPs. Excess CHP heat is used for heating in the nearby villages.

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