Biochar explained: all you need to know about biochar

A 350x magnified bagasse biochar showing its highly porous nature (Source: ResearchGate)

Biochar is more than just a buzzword in environmental circles - it’s a game-changing material that holds promise for tackling some of the most pressing challenges of our time. At its core, biochar is a form of carbon-rich charcoal created by heating organic materials like wood, crop residues, or agricultural waste in a process called pyrolysis. Unlike traditional charcoal, biochar isn’t primarily used as a fuel but as a tool for improving soil health, reducing greenhouse gas emissions, and storing carbon for centuries.

Let’s explore how biochar works, why it matters for the UK’s net zero goals, and how we feel it has the potential for breathing new life into sustainable farming, industry, and beyond.

The concept of biochar isn’t new. Thousands of years ago, Indigenous communities in the Amazon rainforest enriched their nutrient-poor soils with charcoal and organic waste, creating "Terra Preta" (Portuguese for "black earth"). These soils remain highly fertile even today, with research highlighting biochar’s remarkable ability to enhance soil health and retain nutrients. This ancient practice laid the groundwork for modern biochar technology, blending centuries-old wisdom with cutting-edge sustainability science.

Why Biochar Matters Today

In the face of escalating climate challenges and environmental degradation, biochar has emerged as a versatile solution for a number of global challenges. Its benefits extend beyond just improving soil fertility - biochar plays a crucial role in carbon sequestration, the process of capturing carbon dioxide from the atmosphere storing it away. 

Moreover, biochar’s ability to retain water and nutrients makes it a vital resource for sustainable farming, especially in regions prone to drought or soil erosion. By improving soil health, biochar has been shown to supports higher crop yields and more resilient agricultural systems, aligning with global efforts to ensure food security and reduce reliance on chemical fertilisers.

In the UK, biochar is gaining traction as a critical tool for achieving net zero targets and promoting sustainable farming practices. Research indicates that biochar could sequester between 8% and 49% of the UK's agricultural-related emissions, offering a significant contribution to the nation's climate goals.

How is Biochar made?

At the heart of biochar production is the process of pyrolysis, where organic materials are transformed into a carbon-rich product under controlled conditions. Pyrolysis is the thermal decomposition of organic matter in the absence of oxygen. Here’s how it works:

• Feedstock Preparation: Locally sourced biomass (e.g., wood logs, crop waste) is processed  and dried.

• Heating: The material is heated to 350–700°C in an oxygen-free chamber, preventing combustion. The exact temperature, heating rate, and duration significantly influence the properties of the resulting biochar, including its porosity, surface area, and nutrient content. The rough rule of thumb is the higher the temperature and longer the residency time, the more durable the carbon will be in your biochar.

• Transformation: This controlled heating process prevents combustion, instead breaking down biomass into three primary products - biochar, bio-oil & pyrolytic gas. 

How Biochar Captures Carbon

Most people don’t realise that carbon removal happens before biochar is made. It occurs when biomass - whether a tree, plant, or other vegetation - photosynthesises and captures carbon in its trunk, stem, or leaves. Turning that biomass into biochar prevents the stored carbon from re-entering the atmosphere, locking it away in a stable, long-term form.

When biomass decomposes naturally, carbon dioxide (CO₂) and methane (CH₄) are released into the atmosphere. However, through pyrolysis, this carbon is converted into biochar, which resists decomposition and remains in the soil for hundreds to thousands of years. This process not only prevents the release of greenhouse gases but also creates a durable form of carbon storage.

Studies suggest that biochar can store about 50% of the carbon present in the original biomass. Depending on the feedstock and pyrolysis conditions, a tonne of biochar can sequester roughly 2.5 to 3 tonnes of CO₂ equivalent. This capacity to "lock away" carbon makes biochar a valuable addition to carbon removal portfolios.

While biochar's carbon removal properties  get a lot of the headlines, the physical biochar offers additional environmental benefits that support broader sustainability goals:

Other Applications of Biochar

1. Agriculture and Soil Health

One of the most prominent applications of biochar is as a soil amendment. Its porous structure and high surface area allow it to retain water, nutrients, and beneficial microbes, transforming soil health and boosting agricultural productivity.

2. Water Filtration and Pollution Control

Biochar’s adsorption capabilities make it an excellent material for water purification and pollution mitigation. Its ability to trap contaminants stems from its microporous structure and chemical properties.

3. Livestock and Animal Husbandry

Biochar is increasingly being used in animal agriculture to improve health, reduce emissions, and enhance waste management.

4. Construction and Green Building

In the construction industry, biochar is gaining attention as a sustainable material that can reduce the carbon footprint of buildings.

5. Renewable Energy Production

During the pyrolysis process, biochar is produced alongside bio-oil and syngas, which can be harnessed for renewable energy. While biochar serves as a long-term carbon sink, the by-products provide immediate energy benefits.

6. Landscaping and Urban Applications

Biochar is increasingly being adopted in urban environments to improve green spaces, manage stormwater, and support sustainable landscaping.

7. Carbon Offset Programmes

Biochar plays a growing role in carbon offset initiatives. By sequestering carbon in a stable form, biochar production and application can generate verified carbon credits for businesses and organisations aiming to neutralise their emissions.

Conclusion

From its production through pyrolysis to its various applications, biochar has potential across multiple industries. It can contribute to climate efforts while also supporting resource efficiency and circular economy principles. The challenge we face is in understanding where best it can be deployed and in which form. 

We feel Cornwall’s rugged landscape, the fact that 70% of its land is farmed,  and innovative spirit make it the perfect home for biochar innovation. At Restord, we’re making biochar and exploring its real-world impact with UK farmers, businesses, and councils. Follow our journey on Grounded: A Climate Startup Journey, our award-winning podcast. Listen on Apple Podcasts and Spotify.