In true Tarantino style, I am leaving the ‘backyard biochar’ series as a perfect 10-parter (a reference for the film buffs). I am not sure what this new series will be and, hopefully, it will be as well received as its predecessor, but alas it is time to move on!

In today’s blog, I want to nerd out on some maths; and I promise to keep it interesting, as I will be illustrating some of biochar’s key numbers in the context of the UK climate landscape. I hope that this article may act as a useful reference point for anyone doubting, or perhaps not fully visualising, biochar’s impact potential – focusing on its carbon sequestration capabilities, which I am aware is only a fraction of the image.

The calculations below are deliberately simple, but they give a sense of what could be possible. They’re based on three assumptions: biocharBiochar is a carbon-rich material created from biomass decomposition in low-oxygen conditions. It has important applications in environmental remediation, soil improvement, agriculture, carbon sequestration, energy storage, and sustainable materials, promoting efficiency and reducing waste in various contexts while addressing climate change challenges. More contains 80% carbon by mass; 70% of that carbon remains stable for at least 100 years; and each tonne of carbon is equivalent to 3.67 tonnes of CO₂. Land area figures come from Defra’s statistics on the UK’s utilised agricultural area.

One Tonne Per Acre Across All Agricultural Land

If we applied just one tonne of biochar per acre across all of the UK’s agricultural soils – around 41.5 million acres – that would equate to roughly 85.3 million tonnes of CO₂ held in long-term stable form. That is comparable to the emissions produced from both the energy sector and residential emissions combined. To put that in context, UK households collectively emitted about 63 MtCO₂ from heating in 2022 (ONS, 2023). In other words, this one scenario could more than offset domestic heating emissions across the country.

Five Tonnes Per Hectare on Arable Land

Looking at arable land specifically, applying five tonnes per hectare (a rate often trialled in field studies) across all 4.1 million hectares would deliver around 42.1 MtCO₂ in stable sequestration. That’s comparable to the UK’s entire manufacturing sector emissions in 2022 (BEIS, 2023). For arable soils, which often benefit most from improved structure and nutrient retention, the dual case for biochar is compelling.

Two Tonnes Per Hectare on Permanent Grassland

Permanent grasslands cover 9.73 million hectares in Britain. If two tonnes of biochar were applied per hectare, the result would be about 40 MtCO₂ stored away. That’s roughly equal to a third the UK’s transport sector emissions in 2022 (DESNEZ, 2024). For livestock-heavy regions like the South East, where grassland dominates, this pathway could be especially powerful if linked to manure management where biochar enhances the nutrient application value and has been said to reduce smell. 

One Tonne Per Hectare Nationwide

A lighter, nationwide approach also has potential. If one tonne of biochar per hectare were applied across the UK’s 16.8 million hectares of farmland, the outcome would be around 34.5 MtCO₂ locked away. That equates near perfectly to the UK’s aviation sector emissions in 2023 at 34.4 MtCO₂ (DfT, 2024). Even modest rates, applied widely, stack up quickly at the national scale.

Twenty Tonnes Per Hectare on 1% of Farmland

Finally, consider a more intensive but focused deployment. If 20 tonnes per hectare were applied on just 1% of UK farmland (around 168,000 hectares), the result would be nearly 6.9 MtCO₂. That’s comparable to all UK cement sector emissions in – 6.5 MtCO₂ – 2022 (Li and Unluer, 2025). Concentrating effort like this in priority areas could be logistically simpler than blanket coverage.

What These Numbers Tell Us

Of course, these figures are theoretical. They don’t account for messy realities – wet feedstocks, inconsistent burner performance, waste regulations, or the economics of producing char at scale. But they help ground the conversation in real comparisons.

It’s also worth remembering that carbon isn’t the whole story. Biochar’s sustainability benefits also come from its role in circular systems: diverting waste streams, improving soils, supporting forestry, or enhancing composting. The sequestration figures make headlines, but they sit alongside a host of other ecosystem services that are harder to quantify.

Still, seeing that just one tonne per acre nationwide could offset heating emissions, or that a focused programme on 1% of farmland could rival cement’s footprint, makes it clear that biochar deserves a stronger place in the UK’s climate and land-use strategy. With unmanaged woodlands, diseased ashAsh is the non-combustible inorganic residue that remains after organic matter, like wood or biomass, is completely burned. It consists mainly of minerals and is different from biochar, which is produced through incomplete combustion.   Ash Ash is the residue that remains after the complete More, and garden waste already piling up across the UK, the raw material is here. The question is whether we can design systems that match these numbers with practical, economic, and legal realities.

For me, running the calculations reinforces a simple truth: the scale of biochar’s promise depends entirely on how we choose to use it. From an allotment plot to national agriculture, the carbon maths stacks up in ways that few other land-based interventions can. The challenge is not in the numbers – it’s in the will, the networks, and the practicalities to make them real. 

One thing to notice about all of these comparisons is that they rely on someone putting it in the ground. Whether it is farmers, landowners or gardeners; there is a clear need for buy-in and thus communication. Any approach to biochar decarbonisation needs to be co-authored with those getting the physical task done, otherwise the policy / theory / objective dies in the office.