While China grapples with the environmental impact of discarded durian shells, millions of tons of these "billion-dollar fruit" shells are also being thrown away in Vietnam. However, these discarded shells have the potential to be transformed into biochar, reducing emissions and producing high-value wood vinegar.

Durian, a fruit that has taken Asia by storm, drives China to spend up to $6.7 billion annually on imports. In Vietnam and Thailand, this "king of fruits" has brought prosperity to many farmers, turning them into millionaires.

However, only 30-35% of a durian's weight is edible, leaving 65-70% as waste in the form of shells and seeds, which are often discarded.

Thai expert Sakda Sinives explains that organic waste from durian shells contributes to greenhouse gas emissions. He notes that the anaerobic decomposition of organic waste in landfills produces significant amounts of methane (CH4), while aerobic decomposition releases carbon dioxide (CO2). Additionally, nitrogen oxides (N2O) are generated from the breakdown of nitrogen in the waste.

Moreover, the decomposition of organic waste, such as durian shells, emits unpleasant odors that can harm health, pollute water sources, and degrade the environment.

While specific figures on greenhouse gas emissions from decomposing durian shells are not provided, Sakda Sinives highlights that this is a pressing issue China is currently trying to address.

In Vietnam, the area of durian cultivation is rapidly expanding, now covering 151,000 hectares. Currently, about 60% of this area is in production, yielding 1.5 million tons of fruit. Besides the quantity exported to China, most durians are consumed domestically, leading to a substantial amount of durian shells being discarded annually.

To mitigate environmental pollution, research has shown that durian shells can be converted into biochar.

Biochar is produced through the pyrolysis of organic materials in an oxygen-limited environment. It has the potential to improve soil properties by enhancing moisture retention, cation exchange capacity, and organic carbon levels. Additionally, biochar can reduce nutrient leaching, neutralize soil acidity, and ultimately increase crop yields.

Biochar also effectively removes pollutants such as heavy metals, dyes, pesticides, and organic waste from water. Moreover, it plays a crucial role in reducing greenhouse gas emissions by serving as a natural carbon sink, capable of storing CO2 in the soil.

In a study conducted by researchers My Phuong Do, Thanh Tuyen Phan, and Xuan Loc Nguyen from the Faculty of Environment and Natural Resources at Can Tho University, durian shells from production facilities in several Mekong Delta provinces were converted into biochar through pyrolysis at 500°C in an inert nitrogen environment.

The study analyzed the physicochemical properties of the biochar, including moisture content, pH, electrical conductivity, cation exchange capacity, and carbon content. The findings suggest that durian shells can be effectively converted into biochar, with potential applications in improving acidic or degraded soils. However, the practical application of durian shell biochar in soil remediation needs further evaluation.

In late 2023, a report from Khanh Hoa highlighted a business that successfully produced biochar and wood vinegar from durian shells.

Nguyen Van Xuan, Director of Resa Energy Corporation, shared that while researching waste treatment methods, he noticed that farmers often discarded durian shells after harvesting the edible fruit. These shells decompose slowly in nature, causing environmental pollution.

Inspired by this, Xuan developed a method to convert durian shells into biochar, thereby utilizing this agricultural by-product to increase farmers' income while protecting the environment.

Xuan designed a temporary setup consisting of a pyrolysis furnace to process fresh durian shells (50-100 kg) and a condensation chamber. All the energy needed for this process is supplied by solar power.

After testing, the pyrolysis furnace produced various products. At temperatures between 150-190°C, wood vinegar is produced, followed by combustible gases that are burned off to yield biochar. Each batch of pyrolysis yields 25 liters of wood vinegar and 15-20 kg of biochar.

Xuan explains that wood vinegar has multiple uses, including deodorizing livestock pens, acting as a pesticide, and killing insects. On the market, 1 liter of wood vinegar sells for 100,000-150,000 VND.

Biochar, besides being a soil amendment, can be ground, mixed with additives, compressed into briquettes, and dried to create smokeless, high-energy charcoal that doesn't pollute the environment. This biochar is priced between 14,000-15,000 VND per kilogram.

Xuan believes that this process will contribute to the development of green agriculture, circular farming, and environmental cleanliness. His company is willing to share the model and guide those interested in producing biochar from agricultural by-products, including durian shells.

Tam An