Hedgemead biochar with caption 7

Biochar: snake oil or elixir for climate change?

Can biochar be used to make soil more productive, increase yield and mitigate climate change through carbon sequestration and reduced fertiliser use?

Transition Bath and Bath Organic Group have this year been involved in a nationwide research experiment with Coventry and Oxford Universities to investigate whether the ancient Amazonian agricultural practice of using biochar has benefits in our modern world.


Terra Preta soils exist in the Amazon and were developed as part of a pattern of agriculture in the Amazon basin between 450BC and 950AD. Charcoal, bone and manure was mixed in with what was originally poor infertile soil to make it rich and fertile. Land immediately surrounding settlements benefited from the disposal of residues from food preparation, broken clay pots and fires. An essential component of this soil enrichment was biochar.

Biochar is created the pyrolysis – the burning of biomass in a low oxygen environment. It can be made by creating a ‘smouldering’ fire in a closed container.

The experiment

The research taking place in Bath is to assess whether biochar has an effect in normal garden and allotment sites. Transition Bath’s garden at Hedgemead Park, Bath Organic Growers plot at Victoria Park and the private gardens of 3 Transition Bath volunteers are all being used for the experiment. Each garden site has a ‘treated’ plot and an untreated control plot. Gardeners are making regular assessments of germination rates and plant growth, and later will be weighing and measuring the yield from each plot.

The production, science and benefits of biochar

A bi-product of agricultural waste used in biomass power plants, the production of biochar not only generates energy but the resulting fertilised soil retains carbon for many hundreds if not thousands of years providing a form of carbon sequestration. Methane and nitrogen dioxide emissions, powerful greenhouse gases are reduced compared with alternative disposal mechanisms and use of fossil fuel based fertilisers is reduced.

If biochar proves to have a positive effect on soil fertility and yields, then it opens the possibility of sequestering carbon in the soil, reducing fossil fuel production, producing low carbon energy and having beneficial effects on food production.


As the first year of the experiment has not been completed we have no results from the experiment, apart the observation that biochar enrichment does not seem to deter slugs! We will of course keep you updated with any results when they become available.


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