One of the most significant chapters of this work took David to Tamil Nadu in southern India, where he initiated a biochar research project with the rural development organisation SCAD (Social Change and Development). The project explored how locally available agricultural and organic wastes could be transformed into biochar and returned to the land, creating a resource from materials that might otherwise have been discarded or burned.

Importantly, the work wasn't simply about demonstrating that biochar could improve soil. David was interested in whether biochar systems could make practical, economic and social sense for the communities using them.

A particularly inspiring part of this work involved the Anila biomass gasifier stove, developed by Professor U. N. Ravikumar. The stove could use biomass to provide heat for everyday cooking while simultaneously converting some of that material into charcoal suitable for use as biochar. The Anila design works by pyrolysing biomass around a central combustion chamber, with the gases produced contributing to the cooking flame while char remains behind.

The potential was especially important for women. Traditional cooking over smoky biomass fires can expose women and families to harmful indoor air pollution. Cleaner-burning stove technologies offered a way of reducing that exposure while still using readily available local fuels.

But the Anila stove offered something more: cooking itself could produce a useful resource.

Instead of biomass simply disappearing as smoke and ash, the charcoal left behind could potentially be used as biochar on the family's own land, helping to improve depleted soils, or become a product that could be sold to generate additional income. David's early project calculations explored the possibility of substantial char production if the technology were adopted across the women's self-help groups involved with SCAD.

It was a beautifully circular idea: local residues provided fuel; the fuel cooked food; cooking produced biochar; and the biochar could help build soil or create economic value.

Just as importantly, the experience reinforced something that has remained central to David's approach ever since: a technology cannot simply be imposed because it looks good on paper. It has to work for the people using it. Education, demonstration, listening and adaptation are therefore every bit as important as the technology itself.

David's interest in biochar as a tool for addressing several problems at once also took his work to Namibia, where the landscape presents a very different challenge.

Large areas of Namibian savanna have been affected by bush encroachment, where dense woody vegetation reduces available grazing and alters the functioning of the wider ecosystem. Today, biochar initiatives in Namibia continue to explore converting this problematic bush biomass into a useful resource—creating biochar that can contribute to healthier soils, carbon storage and rural economic opportunities while supporting restoration of savanna landscapes.

For David, Namibia provided another example of the principle that had driven his work in India: what appears to be a problem can sometimes become part of the solution.

Unwanted woody biomass can become biochar. Biochar can become a resource for soil. And, when production happens locally, that resource can potentially create livelihoods and economic opportunities as well.

Running through all of David's work is a deep commitment to education and knowledge-sharing.

Whether working with rural communities overseas, collaborating with researchers, demonstrating biochar production or simply explaining what happens inside a kiln, his interest has always been in taking biochar out of the realm of theory and showing what it can actually do in the real world.

David also co-authored The Biochar Debate, published in 2009, which explored biochar's potential for carbon storage, restoring degraded land and improving agricultural soils at a time when the subject was still relatively unfamiliar outside specialist circles.

That same philosophy continues at Sweethill Biochar today. What began with questions about soil fertility and rural livelihoods thousands of miles away has ultimately come home to Devon, where David's decades of experience inform the biochar we produce, the way we manage our woodland and our commitment to helping more people understand the possibilities contained in this deceptively simple material.

For David, biochar has never really been about charcoal alone. It's about soil, climate, landscapes and people—and finding practical ways in which looking after one can help look after them all.