The palm oil industry is currently expanding rapidly and oil palm plantations yield large amount of poorly utilised waste biomass. Being one of the waste by-products, palm empty fruit bunch, known as palm EFB, its utilization becomes an important subject. Most of the palm EFB are processed into biomass pellet fuels, but the high ash content of the palm EFB pellets is a problem that needs to be solved.
Ash composition of palm EFB is mainly alkali metals such as sodium (Na), potassium (K), magnesium (Mg), phosphorus (P) and calcium (Ca), by either the thermochemical or biochemical process.

The Ash Composition of Oil Palm EFB Waste:

Major Element (ppm)
Ca	Fe	Mg	Na	K	P	Si
14300	2900	1900	3300	86100	10600	19500

 
During the harvest season of oil palm, EFB is generally stored in open air, the ash is possibly exist due to its contact with soil as well as transportation process.


High ash content affects the quality of palm efb pellet, making it difficult to be widely accepted by biomass fuel market. Fortunately, most of the ash in palm EFB can be washed by water. It was found that a given level of ash reduction will correspond to a particular level of alkali metal reduction with water washing, as removal of alkali and earth alkali metals dominates the overall reduction in ash content.
Water washing pre-treatment on palm EFB is one of the effective methods to reduce alkali metal content in the palm EFB to improve its quality before further process steps to make biomass palm EFB pellets.
The fundamental formation of potassium and sodium in ash influences the quality of organic yield since ash is a proxy indicator of potassium and sodium, they can be removed effectively by simple water washing pre-treatment since one of the properties of potassium and sodium is that they are water soluble. And experimental results showed that about 71% of potassium and 96% of sodium can be removed through this procedure.


By varying some palm EFB washing parameters such as the residence time, and the amount of water, we can study the effectiveness of washing with water. Generally the ash content of the unwashed palm EFB was around 5.2-5.5 moisture free (mf) wt%. According to the experimental result, basically total ash was reduced by about 24.9–70.3% in the palm EFB with an average ash content of 2.48 mf wt% achieved. The longer the residence time, the larger amount of washing water, the less ash remain in the palm EFB. The maximum yield that can be achieved by washing palm EFB is 72 mf wt% with an ash content of 1 mf wt%.

As one of the countries with the largest imported biomass pellet fuel amount in the world, Japan is also a major importer of palm EFB pellets. It has higher standards for imported palm EFB pellet than other countries, among them the potassium content in the ash is reqiured not exceed 2000 ppm. Therefore, in order to reduce the potassium content in the ash, to obtain higher quality palm efb pellets, and to occupy a wider international market, water washing pre-treatment of palm EFB before pelletizing is extremely important for palm EFB pellet manufacturers.

For more information about palm EFB water washing pre-treatment technology, please contact info@simecpellet.com.