Agriculture contributes to more than 20% of greenhouse gas emissions in the global atmosphere. The use of chemical fertilizers and anthropogenic activities has no doubt increased the crop yield on a short-term basis, but these pose a great threat to sustainability in agriculture. Repeated use of chemicals (mainly those containing nitrogen) results in deterioration of the soil environment and the residual inorganic matter emits into the atmosphere, contaminating the global climate. Biochar is a carbonaceous compound formed by the pyrolysis of biomass such as agricultural feedstock, and greenhouse compounds, in the absence of oxygen. Researchers across the world have found that employing biochar in soil can help in achieving sustainability in agriculture. There are several characteristics that makes biochar a good fit for agricultural soil.

biochar can improve the agricultural sustainability by improving air and soil quality
Causes and solution of air and soil quality deterioration. Created by Hemashree Kakar for SoilSphere.

Sustain the soil nutrients for decades, thus reducing the nutrient leaching

The complex aromatic and graphitic nature of biochar attributes to its high resistant capacity to environmental stresses and this allows it to remain inland for more than 5000 years. As a result, biochar acts a source to reverse the massive exploitation of land and atmosphere that is currently being done for the last many decades.

High sorption capacity allows the soil to retain water and organic content

The carbon-rich biochar has high sorption capacity and can sorb several toxic elements like arsenic, nitrous compounds, mercury, cadmium, nickel, lead, zinc, etc. when used with fertilizer. It also improves crop yield, growth, and quality. Research studies have proved that amending biochar in the soil can enhance soil organic carbon, water-retaining capacity, encourage microbial activities, increase soil base saturation and improve nutrient use efficiency.

Improve soil fertility

Pyrolysis of organic matter in the absence of oxygen removes several contaminants including pathogens and heavy metals. Biochar obtained after pyrolysis varies according to the temperature attained during the process. The aromatic compound thus obtained has a porous structure with high soil water retaining capacity, cation exchange capacity, and surface sorption capacity. Soil fertility is defined based on the cation exchange capacity it has. Biochar improves the carbon sequestration capacity of soil which further increases cation exchange capacity, thus enhancing soil fertility.

Improve soil carbon sequestration and reduce agricultural emissions from soil

Furthermore, biochar has a high surface area with low surface charge density which allows it to retain the soil minerals and minimizes the draining of nutrients and minerals. Scientists and researchers from around the globe, after studying Amazonian fertile soil concluded the efficacy of biochar in contributing to soil-ecosystem sustainability, soil-carbon sequestration, and eradicating global atmospheric contaminants.

Scientists have concluded that a gram of Biochar can have a surface area that is equivalent to the surface area of two tennis courts.

Oregon Department of Forestry: Biochar is an evolved charcoal made from woody biomass. Current uses include soil amendment, storm water filtration, and environmental remediation. The biochar industry in Oregon is small but growing.

Reduces the soil’s acidic content

Biochar also improves the pH value of soil and thus making it less acidic. It reduces the presence of toxic elements like Aluminum in the soil and increases the content of essential elements like Potassium, Magnesium, Calcium, and Phosphorous by retaining them in the soil. The increase in soil pH by the biochar pyrolyzed at a high temperature is greater than the biochar pyrolyzed at a lower temperature.

However, the above-mentioned effect is the opposite in the case of yield obtained after the application of biochar in soil. To reach equilibrium among these two factors, an optimized temperature (500°C) is chosen for the pyrolysis of biochar. Further, researchers are exploring ways to produce biochar for specific purposes like producing biochar at a moderate temperature for application in less acidic soil, biochar rich in a specific nutrient to fulfill the deficiency of that nutrient in the soil, application of biochar with inorganic fertilizers to inhibit leaching losses, etc.

biochar in achieving sustainability in agriculture
Role of biochar in environmental sustainability and improved health. Created by Hemashree Kakar for SoilSphere

Helps improve the seed germination rate

Using biochar under certain parameters and specificities it is found to increase seed germination rate in the soil. Most biochar are alkaline with pH values ranging from 8-to 13. Many of these possess good acid-neutralizing capacity which is attributed to the presence of certain nutrients (Phosphorous, Molybdenum) and lack of others (iron, zinc, and boron).

While the wide characteristics of biochar can help achieve sustainability in agriculture, many studies, however, have addressed challenges occurring in integrating biochar into agriculture. With an increase in global climate change and deteriorating soil quality, it is the need of the hour to look into the improvement and advancement of technology and shape it in a way to bring the offsets on the track. The capacity of biochar, however, is not just limited to carbon sequestration and there are many unexplored areas where biochar employment can result in improvement in global climatic conditions.