Discarded Nut Shells Transformed into Eco-Friendly Ship Fuel

Newswise — A research team led by Dr. Choi, Young-chan from the Clean Air Research Laboratory at the Korea Institute of Energy Research (KIER) has successfully converted cashew nut shells, discarded during cashew nut food product manufacturing, into an eco-friendly biofuel.

Biofuel is a type of fuel produced from biomass, which consists of organic materials from plants and animals. Compared to fossil fuels, it emits less carbon dioxide during combustion, making it a prominent eco-friendly energy source.

However, producing biofuel from biomass in Korea is very challenging. Due to the limited availability of single types of biomass domestically, the cost of collecting various biomass sources makes it less economical compared to fossil fuels. Therefore, the research team focused on cashew nut shells, a material readily available overseas, which contains about 40% high-calorie oil components.

The mechanical pressing process of producing biofuel from cashew nut shells has been commercialized in Southeast Asian countries like Vietnam, but the production yield is only 20% of the raw material, and the quality of the oil produced is relatively low. Additionally, converting it into bio-heavy oil requires chemical processes involving catalysts such as sulfuric acid and alcohols, which can lead to environmental pollution.
*Bio-Heavy Oil: A type of bio-fuel that is a heavy fuel suitable for industrial boilers, power plants, and ship fuel. It provides energy comparable to conventional heavy oil but with lower greenhouse gas emissions, making it a promising eco-friendly fuel.

To address the limitations of traditional mechanical pressing processes, the research team developed a core technology that produces high-quality bio-heavy oil through a medium-temperature pyrolysis method. This technology reduces bio-oil production time to one-third of conventional processes and more than doubles the production yield.
^{*Production Time: With the developed technology, the continuous process takes approximately 1 hour. In contrast, conventional technology requires about 3 hours due to additional non-continuous processes, including separation, heat treatment, and esterification.
*Production Yield: The developed technology achieves a yield of 40% relative to the raw material, compared to 20% with conventional technology.}

The conventional mechanical pressing process requires significant cost and time, as it involves pressing the raw material, separating it into solid and liquid phases, and then undergoing heat treatment and chemical reactions. In contrast, the newly developed technology produces bio-oil through a single pyrolysis process after raw material input, eliminating the need for complex procedures.

Unlike traditional processes, which require manual handling at each step, the new technology enables full automation of bio-oil production, cutting operating costs by half. Additionally, pyrolysis gases that are not condensed during the process can be recirculated as a heat source, enhancing overall efficiency.

The research team validated the bio-oil production performance by operating a pyrolysis facility with a daily capacity of one ton. The results showed a bio-heavy oil production yield of 40%, more than double that of the conventional pressing process. Additionally, the sulfur content of the produced bio-heavy oil was 90 ppm, meeting the sulfur oxide emission standards set by the International Maritime Organization (IMO), proving its potential as a ship fuel. In addition, the by-product, bio-char, with its high carbon content, can be used as a fuel to replace coal as fossil fuel in power plants or steel mills.

Dr. Choi, Young-chan, the project leader, stated, “The eco-friendly bio-fuel production process we developed allows for the large-scale production of bio-heavy oil and bio-char and features a simple manufacturing process, making it highly feasible for commercialization in Southeast Asia. We plan to begin pilot-scale facility research in 2025 and advance into the full commercialization phase.”

Meanwhile, the developed technology was supported by the Korea Institute of Energy Research’s project funding.