On-farm biochar production has moved a step closer to a commercial product after UK clean-technology company CapChar installed an integrated biochar, heat-recovery and carbon-measurement system on a livestock farm near Petersfield in Hampshire. The 80-hectare farm in the South Downs National Park rears dairy replacements and runs an 80-cow suckler herd.

Biochar is a charcoal-like residue of 75–80% carbon made by pyrolysis — heating organic material to 300–700C with little oxygen. On the Hampshire farm locally sourced woodchip goes in; the biochar will be used as an under-layer in cattle bedding to cut ammonia and improve foot health, then spread with the manure on grassland to raise organic matter and water-holding capacity.

Pyrolysis also throws off a lot of heat, but only while the kiln runs, which rarely matches when a farm needs it. CapChar's answer is a patent-pending thermal battery that stores the recovered energy for release on demand; here it will dry woodchip and logs for the solid-fuel market, with other uses under study. Co-founder Adam Samuel said the biggest lesson from an earlier Cornish project with developer Restord was that using the pyrolysis energy well is fundamental to a viable business.

The company is adding digital measurement, reporting and verification so each installation can quantify durable carbon removal. About four tonnes of woodchip yield a tonne of biochar, roughly 2–2.5 t of CO2 equivalent, and CapChar estimates some 74% of that carbon stays in the ground for more than a century; the Hampshire project is expected to remove close to 250 t CO2e, subject to final production data and life-cycle assessment. CapChar has also written a Biochar Carbon Code for verifying UK removals.

With carbon-credit adviser Carbon350, whose founder Catherine Daley describes the aim as a distributed British model of local biomass, local heat, local soil health and high-integrity credits, the firm wants small modular kilns close to both the woody residues and the users of the heat, avoiding the cost and emissions of hauling bulky biomass to central plants. Biochar's porous structure can shelter soil microbes and improve nutrient-use efficiency, though the agronomic benefit depends on feedstock, process, soil and rate.

Source: Farmers Weekly