Palm kernel shells (or PKS) are the shell fractions left after the nut has been removed after crushing in the palm oil mill. Palm kernel shells are a fibrous material and can be easily handled in bulk directly from the product line to the end use. Large and small shell fractions are mixed with dust-like fractions and small fibres.

Moisture content in kernel shells is low compared to other biomass residues with different sources suggesting values between 11% and 13%. Palm kernel shells contain residues of Palm Oil, which accounts for its slightly higher heating value than average lignocellulosic biomass. Compared to other residues from the industry, palm kernel shells are a good quality biomass fuel with uniform size distribution, easy handling, easy crushing, and limited biological activity due to low moisture content.

Press fibre and kernel shell generated by the palm oil mills are traditionally used as solid fuels for steam boilers. The steam generated is used to run turbines for electricity production. These two solid fuels alone are able to generate more than enough energy to meet the energy demands of a palm oil mill.

Most palm oil mills in the region are self-sufficient in terms of energy by making use of kernel shells and mesocarp fibers in cogeneration. The demand for palm kernel shells has increased considerably in Malaysia, Indonesia and Thailand resulting in price close to that of coal. Nowadays, cement industries are using palm kernel shells to replace coal mainly because of CDM benefits.

PKS has also emerged as a hot biomass commodity in the Asia-Pacific region, especially in South Korea and Japan, where PKS is being used to power huge biomass power plants. PKS is also getting traction in Europe as an attractive alternative fuel.

The problems associated with the burning of these solid fuels are the emissions of dark smoke and the carry-over of partially carbonized fibrous particulates due to incomplete combustion of the fuels can be tackled by commercially-proven technologies in the form of high-pressure boilers.

Dual-fired boilers capable of burning either diesel oil or natural gas are the most suitable for burning palm Oil waste since they could also facilitate the use of POME-derived biogas as a supplementary fuel. However, there is a great scope for introduction of high-efficiency CHP systems in the industry which will result in substantial supply of excess power to the public grid.

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