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Biochar for Anaerobic Digestion, Landfill Gas Filtration, PAS100 Compost Odours

Tony Callaghan 24/01/2022

Biochar for Anaerobic Digestion, Landfill Gas Filtration, PAS100 Compost Odours

(Image: "example AD site", courtesy of Malaby Biogas, Wiltshire)

Biochar improves methane output in anaerobic digestion (AD)

There are an increasing number of research papers indicating that activated carbon can be used to increase the conversion efficiency of methane made in an AD reactor - anywhere from 5-20%. 



Application of biochar as an additive to enhance biomethane potential in anaerobic digestion

Many activated carbons are derived from fossil fuels and using them in AD would negate the "sustainability" of the carbon LCA (Life Cycle Analysis). Activated carbons are also expensive and needed in high tonnage. In the first instance, they can be uneconomic. However, we believe our biochar can deliver a positive benefit.  

Biochar (by definition and certification) is carbon made from sustainable resources. If the biochar is eventually added to soil, it is an approved IPCC carbon-negative technology. Technically biochar works and performs the same DIET task (see ref. papers) as activated carbon.  There is work to do around scaling output, but biochar manufacturers are confident that biochar will give lower-cost, higher-benefit over activated carbon.  We now have trials underway with a leading AD Biogas company.

You can find high quality biochar for sale from our online store!


A complete circular economy story

  • Biochar is not consumed during the process - it is carried away into the digestate. Subject to strict EA testing protocols (PAS100, PAS110), the digestate can be applied to farmland as a soil improver. When added to the soil, it not only improves soil fertility, it also creates a carbon sink to offset climate change.
  • We are keen to collaborate with industry users to bring back spent biochar and process it in our patent-pending SF60 super compost process.

Biochar for the removal of siloxanes from syngas

Activated carbon is sometimes used to 'polish' (or 'scrub') sulphur and other volatiles such as siloxane from SynGas prior to combustion in CHP engines. (This reduces fouling of the CHP engines. Development work is needed to prove biochar can replace activated carbon for this application. Please call if interested in working with us.

Biochar as a biofilter to remove odours from PAS100 composting, methane and VOCs from landfill gas

Carbon can be used to filter odours from landfill gas and composting. However, the tonnage required and the price per tonne make this uneconomic, so the current default option is to use wood chip as a biofilter.  Using new production methods and sustainable raw materials biochar is set to become a viable option. If you are interested in testing the concept, please call to discuss it.

How/Why Biochar biofilters outperform wood chip or compost biofilters

  • It is possible to do both chemical and biological filtration in one filter
  • The same biofilter media can be used for many years – saving a huge amount of money, reducing waste and its negative environmental impact
  • Spent biochar filter media can be used to make a 'super compostsoil improver. Biochar inoculated in compost helps improve soil health and plant growth. The carbon is also locked (sequestered) into the soil - offsetting your carbon footprint and helping to mitigate climate change. 
  • Removes organic molecules by adsorption onto the pore surface. As organic molecules are removed the water is clarified. (Many organic molecules have a yellow colour tinge)
  • Biochar filters act as a living space for nitrifying bacteria. The aerobic (oxygen requiring) nitrifying bacteria convert toxic ammonia into the less toxic nitrate/nitrite molecules. 
  • Biochar filters do not degrade. Wood chip is cheap and plentiful but over time it degrades and the filters block with fine particles and microbial biofilms. At this point, they need replacing.
  • Biochar supports microbes that break down methane. Wood chip does not support methanotrophic bacteria (i.e. bacteria that break down methane).

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