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From Bonfires to Biochar


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April 3, 2024

Composting is one of the few really positive things nearly all of us can do to positively benefit our environment and even play a small part in sequestering carbon. Even keen gardeners can find it a challenge to deal with especially woody material. All too often this kind of material is simply burnt on a bonfire. However, the high water content generally in bonfires produces masses of choking smoke and particulates extremely harmful to health. A bonfire could produce up to 30 times more particle pollution than a wood burning stove. 

"Burning at home, particularly with traditional house coal or wet wood, is a major source of the pollutant PM2.5 – tiny particles which can enter the bloodstream and lodge in lungs and other organs. PM2.5 has been identified by the World Health Organisation as the most serious air pollutant for human health." Government website

Your local community composting site is one solution where these materials can be shredded and composted or used as a mulch.  

Other solutions are available too. If you have somewhere you can dry out your woody material, it can then be burnt in a controlled way to make charcoal which can then be made into bio-char. 

The topic of biochar has been increasingly discussed in recent years, particularly among passionate gardeners and growers who note the positive effects of biochar as a soil additive According to the Royal Horticultural Society, its benefits include 'neutralising acidity, providing improved water and nutrient retention (especially in sandy soils) and improved drainage and aeration', plus acting as a growth medium for helpful soil microbes. 

Biochar is produced by slowly heating organic material with very little oxygen supply, a technique that can be carried at very small scales or at industrial levels in the modern day. It has been in use more than two thousand years, the ancient Amazonians who we created 'terra preta' a rich black soil using this method to build stable soil in the thin rainforest soils and those soils are still sequestering carbon till today. The form of burning that creates biochar actually keeps much of the carbon stored in the organic matter, sequestering carbon that would have otherwise generated 3.6 tons of carbon dioxide.

SusSH Compost Mentor Ben Bryant said: ‘Biochar has massive potential for remediating impoverished soils and bringing carbon back home into the soil where it belongs i.e. carbon sequestration. Changing the culture from bonfires to biochar would have a big impact in fighting climate change, reducing pollution and rebuilding healthy fertile soils.  By reintroducing and supporting microbiology (inc. mycorrhizal fungi & bacteria) into soils and giving organisms more structure to inhabit, in the form of biochar, we can help maintain and grow life teaming in the soil microbiome.

‘Healthy soil is a foundation for life, and biochar application along with compost could be a real game changer in adding value to community composting projects. The SusSH compost pilot projects now being delivered aim to support and help composting groups in the South Hams to explore options for biochar production and usage on different scales.’

By Ben Bryant

Want to learn how to develop a community composting site or convert a brown bin for composting?

'Dr Compost' Nicky Scott and Compost Expert Ben Bryant will be offering a deep dive for all those interested in developing a community composting site on a two-day masterclass this Spring (27th and 28th April). For more information click here.

SusSH mentors and compost experts Ben Bryant and Stuart Saunders will be demonstrating the best methods for repurposing redundant brown bins into wormeries, rainwater butts and compost bins on a two-day masterclass this Spring (4th May & 8th June). For more information click here.

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