In recent years, research interest in biochar has gained significant attention in mainstream discourse. The sustainable alternative to synthetic fertilisers offers triple benefits: enhanced soil health, improved livelihoods, and climate protection.
By 2050, global crop yields are projected to decline by 10 percent due to harmful agricultural practices, land degradation, and climate crisis. The widespread degradation of soils has resulted in reduced carbon storage, thereby diminishing soil fertility. Between 2009 and 2018, an estimated 70 million tons of organic carbon were lost from the mineral soils of croplands in the EU and UK. Farmers worldwide are experiencing this development and often resort to harmful agricultural practices to boost yields, including increased reliance on climate-damaging synthetic fertilisers. But there is an alternative. Biochar is a portmanteau derived from the words biomass and charcoal; it is a solid, porous, black, carbon-rich material with a charcoal-like appearance.
The use of biochar in soils is often described as a solution that can kill two birds with one stone. First, it naturally reduces greenhouse gas concentrations, such as carbon dioxide (CO2), which would otherwise be released during the decomposition of biomass waste. Second, it enhances soil fertility without the need for synthetic fertilisers. The application of biochar could remove 0.4 to 2.6 gigatons of CO2 annually. A gigaton of CO2 is equivalent to the emissions of approximately 250 million gasoline-powered vehicles.
Biochar was initially identified as a component of the so-called Terra Preta soils found in and around the Amazon Basin, which are anthropogenic, nutrient-rich soils characterised by their high organic carbon content, derived from additions of charcoal, organic matter, and nutrients by ancient indigenous populations. In 2018, biochar was referenced for the first time in the Intergovernmental Panel on Climate Change (IPCC) Special Report, highlighting its role as an effective, science-backed solution for carbon dioxide removal.
Biochar is produced by heating unutilised or unproductive biomass and organic residues – both plant- and animal-based, such as rice husks, sugarcane bagasse, or livestock manure, at high temperatures in oxygen-limited environments through the pyrolysis process. Recalcitrant carbon, which is relatively resistant to microbial degradation, can persist in the soil for centuries to millennia, retaining approximately 50 percent of the original carbon content from the residual biomass. Biochar enhances soil carbon accumulation and reduces its susceptibility to releasing greenhouse gases back into the atmosphere, compared to other uncharred organic amendments such as manure, compost, or tree leaves, which decompose rapidly.
The effectiveness of biochar in improving soil quality depends on factors such as the type of biomass used as feedstock, the application method and rate, as well as the processing conditions. Not all types of biochar are suitable for carbon dioxide removal, as different feedstocks result in varying rates of carbon sequestration. For example, residual wood exhibits a higher carbon sequestration potential compared to chicken manure. Some biochar pyrolysis equipment may retain less than 40 percent of original carbon.
As a soil amendment, biochar accelerates the rehabilitation of soils, which are both farmers’ most valuable asset and a finite resource. In Ghana, thousands of farmers are experimenting with biochar to improve soil health and nurture their seedlings. Integrating biochar into farming systems enhances water and nutrient retention, while protecting biodiversity by stimulating beneficial soil organisms.
The Soil Atlas 2024 presents data and facts about the importance and condition of land, soils and arable land. In numerous graphics and text contributions, it provides a current insight into the condition of and threats to the soils on which we live.
In general, biochar helps tackle climate change stressors such as drought and water stress, benefiting both plants and microbes. Biochar can hold up to six times its weight in water. This is possible due to its porous structure and large surface area, which allow the soil to function like a sponge.
Roughly 40 percent of soils globally are high in acidity; a problem linked to intensive farming and the overuse of synthetic fertilisers. Since biochar is mostly alkaline, it can neutralise soil acidity. Several research trials and studies have demonstrated a reduction in methane (CH4) and nitrous oxide (N2O) emissions following biochar application – two hard-to-abate greenhouse gases that are estimated to be 25 times and 300 times stronger than CO2.
The average fertiliser application rate in Sub-Saharan Africa is approximately seven times lower than the global average. Increasing the use of artificial fertilisers will not resolve the continent's food security challenges or compensate for the depletion of soil organic carbon stocks. Instead, biochar offers a viable alternative to artificial fertilisers. Its effectiveness can be enhanced by incorporating beneficial microorganisms, fungi, and compost to increase nutrient bioavailability, thereby reducing the need for artificial fertilisers.
By 2060, global biomass production is predicted to increase at least two times. Biochar fosters a circular economy and a sustainable recycling pathway as it adds value to unutilised or unproductive on- and off-farm biomass waste trapped with CO2 by diverting it from landfills, reducing greenhouse gas emissions when buried in soil. Deforestation is not necessary to produce biochar, nor is there a need for land competition to grow virgin biomass. Studies and trials have identified a wide range of suitable feedstocks that can be converted into biochar, including cereal residues, deadwood from well-managed forests, rice husks, cane bagasse, storm debris, livestock manure, sargassum seaweed, and wood chips. In South Africa, certain invasive tree species are used as feedstock for biochar.
It is crucial to consider biochar as a soil enhancer in a holistic manner, from sustainable sourcing to carbon sequestration, in order to achieve positive ecosystem benefits. There are numerous exemplary projects that demonstrate the potential significance of biochar in the future. In Denmark, for example, the government has introduced a national biochar strategy, demonstrating its commitment to maintaining and regenerating soils while achieving climate-neutral targets. Accelerating soil rejuvenation and enhancing ecosystem functionality requires the application and selection of appropriate biochar formulations tailored to address environmental and soil challenges in agricultural fields.