Biochar can help agriculture meet its climate targets – but getting it onto farmland remains a challenge

Biochar is widely recognised as a promising climate mitigation measure because it can store carbon in a stable form, thereby contributing to long-term CO₂ storage. At the same time, several stakeholders point to potential benefits for soil, nutrients, aquatic environments and the circular use of residual biomass.

However, the precautionary principle applied in environmental permitting currently limits the possibilities for routine application of biochar to agricultural land. At the same time, the planned Danish government funding tender has been postponed. According to the ministry, an executive order and accompanying guidance for regulating the use of biochar are still needed and are expected in 2027. The funding scheme has therefore been postponed while barriers to the potential scaling up of pyrolysis technology are addressed.

Meanwhile, Aarhus University and the University of Copenhagen have launched new long-term field trials to generate more knowledge about the effects of biochar under Danish conditions.
Although biochar has demonstrated potential for carbon storage, wider adoption still requires more knowledge, clear regulatory frameworks and practical experience.

The debate about biochar is therefore not only about whether the technology works. It is also about where its use makes sense – and what needs to be in place before it can be applied on a larger scale.

Not all biochar is the same

One of the key points in the debate is that biochar cannot be treated as a single, uniform product.

Tobias Pape Thomsen, Associate Professor and Research Group Leader at Roskilde University, describes biochar as a broad category of materials with different properties. These properties depend on several factors, including the type of biomass used, the pyrolysis process, post-treatment and the intended application.

It therefore makes little sense to ask whether biochar is generally good or bad. What matters is the type of biochar, its intended purpose and the conditions under which it is used.

According to Tobias Pape Thomsen, the current focus in Denmark is primarily on carbon storage. When biomass undergoes pyrolysis, some of its carbon is converted into a more stable form. This means that the carbon is not rapidly released as CO₂, even when the biochar is used in soil, water or materials.

He considers carbon storage to be one of the most well-documented effects of biochar.

“The carbon storage effect is not particularly dependent on context. Most of the other positive effects, however, are,” says Tobias Pape Thomsen.

In some circumstances, biochar can improve the soil’s ability to retain water and nutrients, improve the structure of sandy soils and reduce nutrient leaching. However, these effects depend on soil type, climate, cropping system, the properties of the biochar and how it is applied.

Many Danish soils are already fertile, so biochar may not provide the same soil-improving effects as it would on more depleted soils. However, less fertile soils also exist in parts of Denmark, where the application of biochar could potentially be beneficial.

A climate mitigation tool for agriculture

Erik Jørgensen, Senior Adviser at the Danish Agriculture & Food Council, sees significant potential for biochar as a climate mitigation measure in Danish agriculture.

The organisation highlights biochar as one of the few measures available to agriculture that can contribute to permanent carbon removal and storage. This makes the technology particularly interesting in a sector where some emissions are difficult to eliminate entirely.

According to the Danish Agriculture & Food Council, reducing emissions alone will not be sufficient to meet climate targets. Solutions that can remove CO₂ from the atmosphere are also needed. Biochar could play a role in this, provided the technology is used responsibly and its effects can be documented.

As part of the Agreement on a Green Denmark, DKK 10.2 billion was allocated to support carbon storage through biochar on agricultural land between 2027 and 2045. However, the planned funding tender has been postponed, and DKK 192 million has been reallocated from the biochar support reserve to compensation related to the new nitrogen regulations.

Erik Jørgensen also highlights the potential of pyrolysis to contribute to more circular management of agricultural residual biomass. This could, for example, be relevant for digestate from biogas plants and other residual streams, where nutrients and carbon could be utilised in new ways.

However, this potential will not be realised automatically. The Danish Agriculture & Food Council emphasises the need to ensure biochar quality, provide analyses and traceability for individual batches, and offer farmers an economic incentive to participate. Individual farmers do not necessarily benefit directly from the climate gains, making financial viability a decisive factor if biochar is to be adopted more widely.

Nutrients could become part of the value

Biochar is not only being discussed as a climate technology. It could also play a role in managing nutrients such as phosphorus and nitrogen.

Tobias Pape Thomsen points out that pyrolysis can help concentrate phosphorus in biochar. This could create opportunities to redistribute phosphorus from areas with a surplus to areas where it is needed. Using nutrients where there is a demand for them could improve fertiliser-use efficiency and reduce the risk of leaching.

However, Tobias Pape Thomsen emphasises that no general conclusions can be drawn about phosphorus in biochar. Its availability to plants depends on factors including the biomass used, the pyrolysis process, post-treatment, cropping system and climate.

The Danish Agriculture & Food Council shares this perspective. Depending on how readily available the phosphorus in biochar is to plants, the technology could become a tool for redistributing phosphorus between regions. At the same time, pyrolysis of materials such as slurry-derived fibre residues could potentially help reduce nitrogen surpluses in catchment areas draining into vulnerable aquatic environments.

Authorities must assess environmental risks – not climate ambitions

For biochar to be applied to agricultural land, it is not enough for the technology to be considered promising from a climate or agricultural policy perspective. Its specific application must also meet environmental approval requirements.

According to Ann Ammitzbo, Acting Technical Director at Skive Municipality, the municipality can provide guidance to applicants and has knowledge of pyrolysis technology. However, when an application concerns the spreading of biochar on agricultural land, the municipality acts as the competent authority under Section 19 of the Danish Environmental Protection Act.

In this role, the municipality must assess whether the application can be carried out safely with regard to soil, groundwater, nature and the environment. Among other things, the municipality requires information about the feedstock, the type of pyrolysis process and the content of pollutants in the final product, documented through analyses carried out by accredited laboratories.

“When the municipality processes an application to spread biochar on agricultural land, we can only assess relevant factors within the environmental field. We cannot take a potential climate benefit into account in that assessment,” says Ann Ammitzbo.

Ann Ammitzbo also points out that, in practice, the Danish Environmental Protection Agency’s advisory statement and the precautionary principle mean that permits under Section 19 are currently not being issued for routine application. In her assessment, the municipality does not have a sufficient basis for granting permits beyond small-scale experimental application rates.

This creates challenges for the development of biochar in Denmark. On the one hand, biochar has been identified as an important part of the solution for agriculture. On the other hand, the authorities cannot allow potential climate benefits to outweigh environmental uncertainties when assessing individual applications.

The precautionary principle sets the framework

Tobias Pape Thomsen believes that the Ministry of Environment could hardly have avoided adopting a precautionary approach while uncertainties remain that need further investigation. However, he argues that the precautionary principle could have been implemented differently.

In his view, a temporary and restrictive framework could have been introduced, with clear limit values, low application rates and specific requirements while further knowledge was being developed. Instead, he finds the current guidance so vague and cautious that it has effectively brought the application of biochar in Denmark to a halt.

This dilemma is also highlighted by Professor Lars Elsgaard from Aarhus University, who leads the new long-term field trials, Danish Biochar LTE, investigating the agronomic and environmental effects of biochar in Danish agricultural soils.

“It is, of course, understandable that the precautionary principle is applied when there is uncertainty about groundwater. But at the same time, we need to be able to generate the knowledge required to move forward,” says Lars Elsgaard.

He has personally experienced having to spend considerable time obtaining municipal permits to initiate field trials designed specifically to provide the authorities with a better understanding of the effects of biochar.

The Danish Agriculture & Food Council is also calling for clearer legislation, pointing out that the lack of unambiguous guidance poses challenges for farmers, researchers and local authorities alike. The organisation is calling for clear limit values and regulatory frameworks that protect the environment while making it possible to use biochar in practice.

For municipalities, the situation is different. There is still no specific executive order governing how municipalities should regulate biochar. This may lead to differences in practice between municipalities. Meanwhile, the planned funding tender has been postponed. According to the ministry, a new executive order and accompanying guidance are expected to be ready in 2027.

New long-term field trials will provide further knowledge

In the new research project Danish Biochar LTE, researchers from Aarhus University and the University of Copenhagen will monitor biochar under Danish agricultural conditions over an extended period.

The project was launched at Aarhus University’s experimental station in Askov in 2026. Since then, experimental fields with different types of biochar have been established at four locations across Denmark, covering both sandy and more clay-rich soil types.

According to Professor Lars Elsgaard, the trials will investigate carbon storage and greenhouse gas emissions, plant growth and crop yields, the leaching of nutrients and environmental contaminants, and the effects on soil microbiology and fauna.

The project is funded by the Danish Agency for Green Land Use and Aquatic Environment under the Ministry of Green Transition and is currently scheduled to run until 2028, with the possibility of an extension until 2033.

The trials could therefore contribute valuable knowledge in an area where both authorities and researchers are calling for a stronger evidence base for assessing the use of biochar.

From potential to practice

However, more research and documentation will not be sufficient on their own.

According to Tobias Pape Thomsen, practical knowledge is also lacking. Researchers can investigate mechanisms and effects, but if biochar is to create value in agriculture, its application must be developed as part of everyday farming practice.

This requires farmers, advisers, researchers and authorities to have opportunities to test different approaches and learn under realistic conditions.

Opportunities with clear conditions

Biochar could play an important role as a climate mitigation measure in agriculture because the technology can store carbon and thereby help address emissions that are difficult to eliminate through other means.

In addition, biochar could contribute to the management of residual biomass, phosphorus, nitrogen and soil. However, these opportunities depend on how the biochar is produced, as well as where and how it is used.

An executive order and accompanying guidance specifically addressing biochar are still lacking and are expected to be ready in 2027. Until then, the current guidance makes it difficult for municipalities to approve routine application of biochar to agricultural land. As a result, the way in which the precautionary principle is implemented in practice becomes a barrier to development rather than a framework that enables it.

Biochar is expected to contribute to climate targets, but moving from climate potential to widespread adoption requires clear regulations that both protect the environment and allow the technology to be developed and tested in practice.

Fact box: What is biochar?

Biochar is a solid, carbon-rich material that remains when biomass is processed through pyrolysis.

Pyrolysis is a thermal treatment process in which biomass is heated to high temperatures in the presence of little or no oxygen. The biomass can include materials such as straw, digestate from biogas production, fibre fractions or sewage sludge.

During the process, the biomass is converted into different products, including gas, oil and biochar. Some of the carbon contained in the biomass is retained in the biochar in a more stable form. It is primarily this stable carbon fraction that makes biochar interesting as a potential method for long-term carbon storage.

Biochar may also have other potential applications, including soil improvement, nutrient management, filtration and materials. However, its effects depend on the biomass from which it is produced, the production process and where it is used.

Programme Manual Online

Choose