Rice plants growing in biochar-amended soil, symbolizing mercury remediation and sustainable agriculture.

Can Biochar Save Our Rice? How This Ancient Secret Could Combat Soil Pollution

Jordan Keane in Climate & Environment August 2025 • 4 min read.

"Discover how biochar, a sustainable soil amendment, is revolutionizing rice farming by tackling mercury contamination and boosting crop yields."

For centuries, rice has been a staple food for billions, especially across Asia. Yet, in regions plagued by industrial activities, rice paddies often bear a hidden burden: mercury contamination. This silent threat accumulates in the soil, finding its way into the rice grains we consume, posing serious health risks.

But what if there was a simple, sustainable solution rooted in ancient practices? Enter biochar, a charcoal-like substance created by burning organic matter in a low-oxygen environment. For generations, indigenous communities have recognized biochar's ability to enrich soils. Now, modern science is uncovering its potential to combat soil pollution, specifically mercury contamination in rice paddies.

Recent research from China highlights biochar's remarkable ability to immobilize mercury in contaminated soils, preventing its uptake by rice plants. This discovery could revolutionize rice farming in polluted areas, offering a pathway to safer, more sustainable food production. Let's delve into the fascinating science behind biochar and its potential to transform our approach to agriculture and environmental remediation.

Biochar: An Ancient Solution to a Modern Problem

Rice plants growing in biochar-amended soil, symbolizing mercury remediation and sustainable agriculture.

Biochar isn't a new invention. It's been used for centuries by indigenous people in the Amazon basin to create incredibly fertile soils known as "Terra Preta," or dark earth. This process involves burning organic waste, like rice husks and wheat straw, in a controlled environment with minimal oxygen, resulting in a highly porous and carbon-rich material.

When added to soil, biochar acts like a sponge, improving water retention, aeration, and nutrient availability. But its benefits extend far beyond simply improving soil quality. Biochar has the unique ability to bind to heavy metals, like mercury, preventing them from being absorbed by plants. This is particularly crucial in rice paddies, where mercury contamination can be a significant concern.

Reduced Mercury Uptake: Biochar significantly reduces the amount of mercury absorbed by rice plants, leading to safer grain for consumption.
Improved Soil Health: It enhances water retention, aeration, and nutrient availability, creating a healthier environment for rice to thrive.
Sustainable Waste Management: Biochar production utilizes agricultural waste, turning a potential environmental problem into a valuable resource.
Cost-Effective Solution: Biochar production can be relatively inexpensive, making it an accessible option for farmers in developing countries.

In a recent study, researchers tested the effectiveness of two types of biochar – rice shell biochar (RSB) and wheat straw biochar (WSB) – in mercury-contaminated rice paddies. They found that both types of biochar significantly reduced mercury levels in rice grains, with RSB proving particularly effective. This is because RSB seems to promote sulfate levels in the pore water of the soil, which can then be reduced to sulfide. This sulfide can combine with mercury, forming mercury sulfides that are much less likely to be absorbed by the rice plants.

A Greener Future for Rice Farming

The research on biochar's impact on mercury contamination in rice paddies offers a beacon of hope for a more sustainable future. By harnessing the power of this ancient soil amendment, we can transform polluted lands into productive fields, ensuring safer food and healthier communities. As we face increasing environmental challenges, biochar stands out as a testament to the potential of nature-based solutions, offering a path towards a greener, more resilient world.

About this Article -

This article was crafted using a human-AI hybrid and collaborative approach. AI assisted our team with initial drafting, research insights, identifying key questions, and image generation. Our human editors guided topic selection, defined the angle, structured the content, ensured factual accuracy and relevance, refined the tone, and conducted thorough editing to deliver helpful, high-quality information.See our About page for more information.

This article is based on research published under:

DOI-LINK: 10.1016/j.ecoenv.2018.11.111, Alternate LINK

Title: A Pilot Study On Using Biochars As Sustainable Amendments To Inhibit Rice Uptake Of Hg From A Historically Polluted Soil In A Karst Region Of China

Subject: Health, Toxicology and Mutagenesis

Journal: Ecotoxicology and Environmental Safety

Publisher: Elsevier BV

Authors: Ying Xing, Jianxu Wang, Jicheng Xia, Zhenmei Liu, Yonghang Zhang, Ying Du, Wanli Wei

Published: 2019-04-01

Everything You Need To Know

What is biochar, and how does it help in rice farming?

Biochar is a charcoal-like substance created by burning organic matter, such as rice husks and wheat straw, in a low-oxygen environment. In rice farming, biochar helps by reducing mercury uptake in rice plants, improving soil health by enhancing water retention, aeration, and nutrient availability. Moreover, it offers a sustainable waste management solution by utilizing agricultural waste and providing a cost-effective option for farmers.

How does biochar combat mercury contamination in rice paddies?

Biochar combats mercury contamination by binding to heavy metals like mercury, preventing their absorption by rice plants. Recent studies show that biochar, especially rice shell biochar (RSB), promotes sulfate levels in the soil's pore water, which reduces to sulfide. This sulfide then combines with mercury, forming mercury sulfides that rice plants are less likely to absorb. Thus, biochar acts as a barrier, making the rice grains safer for consumption.

What are the benefits of using rice shell biochar (RSB) versus wheat straw biochar (WSB) in contaminated rice paddies?

Both rice shell biochar (RSB) and wheat straw biochar (WSB) significantly reduce mercury levels in rice grains. However, RSB has shown to be particularly effective because it promotes sulfate levels in the soil's pore water, which can then be reduced to sulfide. This sulfide reacts with mercury to form mercury sulfides, making the heavy metal less available for uptake by the rice plants. This process makes RSB a potentially more effective solution in reducing mercury contamination.

Where does the use of biochar originate, and how is it made?

The use of biochar originates from indigenous communities in the Amazon basin who used it centuries ago to create incredibly fertile soils known as "Terra Preta" or dark earth. It is made by burning organic waste like rice husks and wheat straw in a controlled environment with minimal oxygen. This process produces a highly porous, carbon-rich material with the ability to improve soil quality and bind to heavy metals.

In what ways does the application of biochar contribute to sustainable agriculture and environmental remediation?

The application of biochar contributes to sustainable agriculture and environmental remediation in several ways. First, it transforms polluted lands into productive fields by reducing mercury uptake in rice, ensuring safer food production. Secondly, it enhances soil health by improving water retention, aeration, and nutrient availability. Furthermore, biochar utilizes agricultural waste, turning a potential environmental problem into a valuable resource. It's a cost-effective solution, making it accessible for farmers in developing countries and offering a pathway to a greener, more resilient world.