Rice is a primary food source for billions of people, yet its cultivation often leads to environmental challenges like soil acidity and high greenhouse gas emissions. A systematic review published in the International Journal of Environmental Sciences by S.A. Hashim and colleagues examines how specialized charcoal materials, known as biocharBiochar is a carbon-rich material created from biomass decomposition in low-oxygen conditions. It has important applications in environmental remediation, soil improvement, agriculture, carbon sequestration, energy storage, and sustainable materials, promoting efficiency and reducing waste in various contexts while addressing climate change challenges. More and hydrochar, can make rice farming more sustainable. These materials are created from organic waste through different heating processes. The review analyzes findings from 41 international studies to determine how these amendments affect crop growth, soil health, and the environment. By recycling animal waste and plant residues into these stable carbon forms, farmers may be able to improve their harvests while protecting the planet.

The research shows that biochar made from animal waste, such as poultry litter, is particularly effective at boosting rice production. In various experiments, applying these materials helped increase the amount of grain harvested, sometimes reaching levels between 9 and 13 tons per hectare. This improvement happens because the biochar helps the soil hold onto nutrients more effectively and reduces the acidity that often plagues long-term rice fields. Furthermore, using biochar allows farmers to reduce their reliance on chemical nitrogen fertilizers by about 25 percent without losing any of their crop yield. This is a significant finding for reducing costs and preventing chemical runoff into local water supplies.

Hydrochar, a different version produced using pressurized water and lower heat, offers unique benefits for managing nitrogen. While its effects on yield can vary more than traditional biochar, modest amounts of hydrochar can improve how efficiently rice plants use nitrogen. In some cases, it allowed for a 40 percent reduction in nitrogen fertilizer without a drop in production. However, the study warns that using too much hydrochar can actually hinder plant growth due to certain organic compounds released during the process. When used at the correct, lower doses, it becomes a powerful tool for keeping nutrients in the soil where the plants can reach them.

The environmental impacts of these amendments are equally promising, especially regarding climate change. Rice paddies are well-known sources of methane, a potent greenhouse gas. The review found that biochar consistently helps reduce these emissions and also cuts down on ammonia gas losses. Modified versions of hydrochar were particularly successful at mitigating both methane and nitrous oxide emissions. Additionally, biochar proved useful in “cleaning” the soil by reducing the amount of toxic heavy metals, like arsenic and cadmium, that rice plants absorb. This means the resulting rice is not only more plentiful but also safer for human consumption.

Ultimately, the success of these materials depends on using the right amount and choosing the right type for specific soil conditions. While animal-waste biochar provides very reliable gains in yield and soil quality, hydrochar is an excellent specialized tool for nitrogen management and emission control when carefully applied. The researchers emphasize that these carbon-rich additions transform agricultural waste into a valuable resource. As rice farming faces the dual pressure of feeding a growing population and reducing its environmental footprint, these innovative charcoal amendments offer a scientifically backed path toward a more sustainable and productive future for global agriculture.

Source: Hashim, S. A., Kasim, S., Naharudin, N. S., & Jais, F. M. (2026). Advancing sustainable rice production with hydrochar and animal-waste biochar of agronomic, soil, and environmental impacts: A systematic review. International Journal of Environmental Sciences, 12(1), 9–28.