HZI selected for CO2 liquefaction project

With a capacity of 90,000 tonnes per year, Granville Ecopark is the largest anaerobic digestion (AD) plant of its type in Northern Ireland, recycling food waste into biogas to produce renewable electricity and high-quality fertilizer.

Utilize biogenic carbon dioxide

In addition, part of the biogas is upgraded to biomethane aka renewable natural gas (RNG). Now the by-product carbon dioxide (CO₂) produced in the separation process process is also to be harnessed.

To enable this to happen, HZI, an expert in biogas and CO₂utilization, is building a liquefaction technology with a capacity of more than 1,000 kg of CO₂per hour, including precleaning.

After completion of the detailed engineering, the plant will be manufactured and delivered to Northern Ireland from HZI’s German production site in Zeven by the end of August 2024.

After approximately eight weeks of construction and connection work on site and trial operation, the plant is to be handed over to the client in the middle of the fourth quarter of 2024.

Meeting specific market requirements

Traditionally the CO₂separated from the methane (CH₄) in the biogas upgrading process has been released into the environment.

However, given ongoing global decarbonization efforts and the fact that CO₂is needed in so many different areas of application, increasing attention is being paid to this by-product of biomethane production.

Besides enabling us to meet our high CO₂purity standards, HZI has the experience as a system supplier to offer a convincing overall package meeting our needs in terms of the technical design of the plant, explained David McKee, CTO of Bio Capital.

HZI has designed the plant in such a way that the warm CO₂off-gas from the amine scrubbing upgrading process is first cooled down via a heat exchanger at the entrance to the liquefaction plant.

The subsequent liquefaction does not need an ammonia-based coolant that otherwise would entail special requirements from a licensing perspective in the UK.

The CO₂in the off-gas stream is purified by trickling pure, liquid carbon dioxide (LCO₂) in a separation column in the opposite direction to the CO₂off-gas from the upgrading plant, explained Dr Benoît Boulinguiez, Managing Director of HZI BioMethan, the German HZI subsidiary that developed the plant and is manufacturing it in its facilities near Hamburg.

Once it is up and running, the system will provide the cleaning solution itself in a closed circuit. While pure LCO₂is used initially, during regular operation part of the LCO₂produced will be returned to the process as a cleaning solution.

According to HZI, projects like Bio Capital are gaining importance because, like alternatives to fossil fuels, solutions providing renewable CO₂are becoming more and more important in numerous areas of application, enhancing circularity, decarbonization, and supply security.