Palm kernel shell (PKS) is a valuable resource derived from the palm oil industry. This by-product, once considered waste, is now widely utilized across various sectors. Its importance stems from its unique properties, which lend themselves to a range of applications, especially in energy production. As industries seek more sustainable materials, PKS has emerged as a significant commodity.
Understanding Palm Kernel Shell
Palm kernel shell originates from the processing of oil palm fruits. After the fleshy outer part of the fruit is processed for palm oil, the hard inner nut remains. This nut is then cracked to extract the palm kernel, which is used to produce palm kernel oil. The remaining hard, dark, and irregularly shaped outer part is the palm kernel shell, a fibrous biomass residue. It is an abundant by-product, particularly in major palm oil-producing regions like Southeast Asia and West Africa.
Unique Properties
Palm kernel shell possesses several characteristics that make it a valuable material. It exhibits a high calorific value, typically 4,000 to 4,500 Kcal/kg, which makes it an efficient source of bioenergy. This high energy content is partly due to residual palm oil within the shells. PKS also features a low ash content, generally less than 3% by weight, and a low moisture content, often between 10% and 15% when air-dried.
These properties contribute to its efficiency as a fuel. Low ash content means minimal residue after combustion, and low moisture content allows for more effective burning. The material also has an appreciable bulk density, ranging from 600 to 750 kg/m³ when dry, making it relatively easy to handle and transport. Its durability and fibrous nature further enhance its utility across various applications.
Primary Applications
Palm kernel shell is primarily used as a biofuel, serving as a renewable energy source for industrial boilers and power generation. Its high calorific value and low ash content make it an attractive alternative to fossil fuels, and it is often co-fired with coal to reduce carbon emissions. Many biomass power plants use PKS to generate electricity, reducing reliance on non-renewable energy sources.
Beyond energy, PKS is a raw material for producing activated carbon due to its high carbon content and porous structure. The carbonization process heats the shells in a controlled environment, yielding a highly porous product. This activated carbon is then used in water purification and air filtration systems.
PKS is also utilized in the construction industry as a lightweight aggregate in concrete or a component in road construction. Its lower density, about 60% lighter than traditional coarse aggregates, can reduce concrete weight, with densities ranging from 1600 to 1900 kg/m³. Additionally, it can be used in filtration processes or as a mulching material in agriculture to help retain soil moisture and regulate temperature.
Sustainability and Economic Value
Palm kernel shell is a renewable biomass resource that contributes to sustainability by reducing reliance on fossil fuels. Its utilization helps manage agricultural waste from the palm oil industry, preventing open burning or decomposition that could release methane, a potent greenhouse gas. When combusted under controlled conditions, PKS emits less carbon dioxide compared to coal, and is considered carbon-neutral as it releases only the CO₂ absorbed during the palm tree’s growth.
The growing demand for PKS in global markets has elevated its economic value. It provides an additional revenue stream for palm oil producers, especially in countries like Indonesia and Malaysia, which are major exporters. The market price for palm kernel shells typically ranges between $90 and $130 per metric ton, with demand continuing to rise, particularly in Asian and European markets. This commodity supports biomass energy markets and creates employment opportunities in collection, processing, and transportation within local economies.