For decades, modern agriculture has relied on chemical fertilizers. While effective, their overuse has led to a host of environmental problems, including soil infertility, water pollution (eutrophication), and increased soil acidity. Scientists are urgently searching for sustainable alternatives that can heal the soil while still feeding a growing population. A new review by Ujjwal Pokharel and colleagues, published in the journal Bioengineering, synthesizes a massive body of recent research on one of the most promising solutions: biochar.

You can think of biochar as a rigid, carbon-rich sponge. Its microscopic pores and vast surface area make it fantastic at holding onto water, nutrients, and microbes, which is why it has been used to improve soil fertility for thousands of years. But the new review focuses on “engineered biochar”—a next-generation version that has been physically or chemically modified to perform specific jobs.

One of its most impressive jobs is environmental cleanup. The review highlights stunning figures: engineered biochar has shown the ability to remove 99.3% of mercury and 99.2% of the rare earth material europium from soil. It’s not just exotic materials; it’s also highly effective at trapping common and toxic heavy metals, demonstrating an 85% removal of chromium (Cr VI), 73% of cadmium , and a 4-fold increase in copper removal. It also works on organic pollutants. By modifying biochar with chitosan (a material from shrimp shells), researchers increased its adsorption of the herbicide imazapyr by 78%. Other modifications, like simple steam activation, enabled biochar to reduce stubborn industrial pollutants (PAHs) by 57%.

This cleanup potential is critical, but for farmers, the ultimate question is: does it grow more food? The review answers with a resounding yes. Data from numerous studies show that biochar application alone can lead to a significant 43.3% increase in crop yield. This is a huge gain, but it’s not even the most exciting finding.

The real magic happens when biochar is mixed with compost. While biochar provides the “house” (structure, water retention, and carbon), compost provides the “food” (rich, readily available nutrients). The review highlights a study where this “super-mix” was applied, resulting in a staggering 155% increase in biomass yield. This combination far outperforms either material on its own, creating a synergistic effect that dramatically improves soil health and productivity.

Beyond these headline numbers, biochar works in other, more subtle ways. It improves the soil’s physical structure, decreasing bulk density (making it less compacted) and increasing porosity. This allows roots to penetrate more easily and ensures a better flow of water and air. It can also help neutralize soil pHpH is a measure of how acidic or alkaline a substance is. A pH of 7 is neutral, while lower pH values indicate acidity and higher values indicate alkalinity. Biochars are normally alkaline and can influence soil pH, often increasing it, which can be beneficial More, making it a valuable tool for reclaiming soils that have become too acidic.

Of course, the research also points to real-world hurdles. Biochar is often a light, dusty, and hard-to-transport material. The review notes the importance of “post-processing”—techniques like granulating or pelletizing the biochar to make it stable, dense, and easy to apply with standard farm equipment. This step is key to taking biochar from the lab to the field.

The takeaway is clear: biochar is a powerful tool for building a more sustainable agricultural future. By engineering it for specific tasks or simply mixing it with compost, we can use this ancient technology to clean up industrial-age pollution and dramatically boost food production, all while sequestering carbon back into the earth.

Source:Pokharel, U., Neelgund, G., Ray, R. L., Balan, V., & Kumar, S. (2025). Biochar for Soil AmendmentA soil amendment is any material added to the soil to enhance its physical or chemical properties, improving its suitability for plant growth. Biochar is considered a soil amendment as it can improve soil structure, water retention, nutrient availability, and microbial activity.   More: Applications, Benefits, and Environmental Impacts. Bioengineering, 12(x). (Note: Full publication details like issue/page are based on the provided draft).