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Carbon dioxide CO2

Apsley Farms supplies high-grade, sustainably produced carbon dioxide that is indispensably used within the UK food industry.

  • Putting the ‘fizz’ into soft drinks and beers
  • Increasing shelf life for food products
  • Keeping food fresh in transport

To find out more about the sustainability of the process, please visit our sustainability page.

The CO2 production process

Carbon dioxide is naturally produced as part of our low energy, sustainable biogas production processes. As a result, our CO2 has a fraction of the carbon footprint of traditional manufacture.

Anaerobic digestion is the process driving our plant. This is where bacteria break down organic plant matter, without the presence of oxygen inside our biodigesters.

As a result of consistent feeding of crop matter biogas is constantly produced.

It is then separated into various constituents by using sophisticated carbon membranes. Carbon dioxide is one such constituent, and we capture this by-product for use predominantly in the food industry.

Our biodigesters harness anaerobic digestion to sustainably produce four useful products: biogas, carbon dioxide, mulch and liquid plant food.

What’s in our gas?

The composition of the raw gas produced by our biodigesters is:

Compounds Biogas Natural gas Unit
Methane 50 – 60 mol %
Carbon dioxide 40 – 50 ≤ 2 mol %
Hydrogen sulfide ≤ 200 ≤ 5 mg/m3 (STP)
Ammonia ≤ 50 0.5 mg/m3 (STP)
Oxygen ≤ 2 ≤ 0.5 mol %
Nitrogen ≤ 8 ≤ 5 mol %
Water 37 at 1 bar ≤ 8 at 40 bar °C
Combustion heat 6.7 – 8.4 10.7-12.8 kWh/m3(STP)
Wobbe index 6.9 – 9.5 13.3 – 15.7 kWh/m3(STP)

Due to the fact that biogas is a mixture of CO2, methane, water, and other impurities, we must separate and clean the gas to achieve a product with a concentration of over 97% methane to ensure it produces the highest possible calorific value.

Dutch manufacturer DMT has developed a membrane system that does just that, separating the carbon dioxide from the methane. Because the CO2 and CH4 molecules are different sizes, the membrane system acts like a sieve, allowing them to be separated.

This separation system has massive advantages compared to traditional methods of removing CO2. Its low cost, high energy efficiency, easy operation, modular construction and flexibility all add up to a more efficient and sustainable approach.

  • The CO2 from the membrane is 98.7% pure – pretty good, but not a high enough standard for the food industry. We start the cleaning process by compressing the gas up to 17 bars. For comparison, pressure inside the tyres of passenger cars is typically 2 – 2.2 bar.
  • The CO2 is ‘dried’, turned into liquid, re-boiled and turned back into liquid again. Each process helps to remove further impurities. moving gases that can be condensed into liquid.
  • Liquid CO2 at -43 degrees centigrade is passed into our storage tanks, with a total capacity of 150 m3.
  • The final stage is to check the quality of the CO2 once certified, the CO2 is collected and distributed.

Our CO2 output

All of the energy needed for the manufacture of CO2 is supplied by our own biodigestion process. This means that we are unaffected by fluctuations in energy prices and were able to keep supplying the UK during the commercial CO2 shortages in 2021.

Currently, our daily production is around 32 tons of CO2. With a purity of 99.99%, this is suitable for any use within the food industry.

To enquire about our commercial CO2, or discuss any aspect of our process, please get in touch.