Can Cotton Stalks Become Biochar? How Farmers Could Turn Crop Waste Into a Soil Input

Cotton stalks left after harvest can become a disposal problem for farmers. ICAR-Central Institute for Research on Cotton Technology is studying whether these residues can be converted into biochar and used as a soil input instead of being discarded or burned.

On September 18, ICAR-CIRCOT held a strategic discussion on cotton-stalk biochar and its possible use in agriculture. Researchers discussed enriching biochar with banana pseudostem sap and phosphate-solubilising bacteria, along with the possibility of developing carbon-credit opportunities for farmers.

Biochar is a carbon-rich material produced by heating plant biomass under limited oxygen. Unlike ordinary burning, controlled production aims to retain much of the carbon in a stable form that can later be incorporated into soil.

Farm residues such as cotton stalks can provide the raw material. The process needs suitable equipment and controlled conditions because simply burning stalks in an open field does not produce the same material or provide the same potential soil benefits.

Biochar is different from compost. Compost results from biological decomposition of organic materials, while biochar comes from thermal conversion. The two can also be used together because biochar can hold nutrients and water while compost supplies decomposed organic matter and nutrients.

Why is ICAR studying cotton-stalk biochar?

Cotton stalks contain significant amounts of plant biomass after harvesting. Finding productive uses for this residue could give farmers another option besides disposal or burning.

ICAR-CIRCOT’s September discussion focused on converting cotton stalks into biochar and examining how the material could be improved for agricultural use. Researchers also discussed enriching biochar with banana pseudostem sap and phosphate-solubilising bacteria.

The research is not simply about producing charcoal-like material. The goal is to understand whether biochar can become a useful soil amendment and whether farmers can gain value from converting agricultural residues into a stable carbon-rich product.

Research has associated biochar with changes in soil properties such as water retention, nutrient availability, pH and soil organic carbon. The effect depends on the raw material, production temperature, soil type, application rate and other farm conditions.

Farmers should not expect the same result from every biochar product. Biochar made from different crop residues can have different chemical and physical characteristics, which is why recommendations should be based on tested material and local soil conditions.

Biochar can also provide a habitat for microorganisms because of its porous structure. When combined with suitable organic inputs, it may support soil processes, although the results depend on how and where the material is applied.

Can farmers enrich biochar?

Researchers at ICAR-CIRCOT are examining enrichment using banana pseudostem sap and phosphate-solubilising bacteria. The idea is to add biological or nutrient-related value to biochar rather than applying untreated material alone.

Phosphate-solubilising bacteria can help make certain forms of soil phosphorus more available to plants. Their performance depends on soil conditions, bacterial survival and the crop environment. This approach is still part of research and development. Farmers should not copy a laboratory or research formulation without guidance on dosage, preparation, quality and application method.

Biochar has attracted attention because much of the carbon in the original biomass can remain in a more stable form after controlled conversion. Researchers are studying whether this carbon storage can be linked to carbon-credit systems.  ICAR-CIRCOT’s September discussion specifically included farmer carbon credits as part of the conversation around cotton-stalk biochar.

A farmer should not assume that producing biochar automatically generates a tradable carbon credit. Carbon-credit projects require recognised methods, measurement, reporting and verification, along with an eligible project structure.

Producing biochar requires controlled heating with limited oxygen. Commercial equipment can provide more consistent conditions than open burning and can help reduce smoke and uncontrolled emissions. The equipment required depends on the quantity of residue available. A small farmer may not need individual ownership if a cooperative, Farmer Producer Organisation or service provider can process residues for several farms.

Farmers should also consider transporting bulky cotton stalks. If residues need to travel long distances before processing, transport costs can reduce the value of the final product.

Can small farmers use biochar?

Small farmers can potentially use biochar, but the economics depend on access to biomass, processing equipment and application requirements. A farmer producing only a small amount of cotton residue may find shared processing more practical.

Farmers should first establish what soil problem they want to address. If the goal is improving soil organic carbon, water retention or nutrient management, soil testing can help determine whether biochar fits the existing farm strategy.

Poorly produced biochar can contain undesirable compounds or have chemical properties unsuitable for a particular soil. Excessive application can also alter soil conditions, especially where the material has high pH. Farmers should therefore use tested biochar and follow crop-specific recommendations. They should not apply ash or ordinary charcoal assuming that it will provide the same benefits as agricultural biochar.

Quality also matters when biochar is enriched with nutrients or microorganisms. Farmers need information about the material’s composition, production method and recommended application rate before using it on crops.

Can biochar replace fertiliser?

No. Biochar should not automatically be treated as a replacement for fertilisers or other nutrient sources. Its main role depends on its properties and the soil where it is applied.

Enriched biochar may supply or help retain certain nutrients, but farmers still need to manage nitrogen, phosphorus, potassium and other nutrients according to crop requirements and soil-test results.

Combining biochar with compost or other organic materials may be more useful in some systems than applying biochar alone. The correct approach depends on soil type, crop and available organic inputs.

Farmers should avoid treating every cotton stalk as waste. Residues can be incorporated, composted, used for suitable livestock or industrial purposes, or processed into other products where local systems exist.

For biochar specifically, farmers should first look for tested local options rather than setting fire to residues. ICAR-CIRCOT’s current work shows that cotton stalks are being studied as a potential source of soil amendments and carbon value.

The practical question is not simply whether cotton stalks can become biochar. Farmers also need to know how much residue they have, what processing will cost, how the resulting material will be tested and whether their soil needs it.