Pellets are fuels made from compressed organic matter or biomass. Wood pellets can be made from any one of five general categories of biomass: industrial waste and co-products, food waste, agricultural residues, energy crops, and virgin lumber. Wood pellets are the most common type of pellet fuel and are generally made from compacted sawdust and related industrial wastes from the milling of lumber, manufacture of wood products and furniture, and construction. According to the International Energy Agency Task 40, wood pellet production has more than doubled between 2006 and 2010 to over 14 million tons. In a 2012 report, the Biomass Energy Resource Center says that it expects wood pellet production in North America to double again in the next five years. Philippines, one of the world’s coconut-producing countries, how to make use of its advantages to produce wood pellets with international competitiveness. This article will delve into the possibility of coconut for the production of wood pellets.
1. Wood Pellets Formation Mechanism
The proximate chemical composition of wood is Cellulose, Hemi-Cellulose, and Lignin. Cellulose is the major component of plant cell wall, the higher its content, the more the plant cell wall tissue. Hemi-Cellulose in plant cell walls serves to cellulose and lignin through effect. Lignin can enhance the mechanical strength of the plant itself, plant binder fibers.
At the beginning of compression, the solid particles are arranged loosely, and the packed structure began to change. Under pressure, the mutual position of the particles occurs constantly changes during operation, as the air between the particles of the raw material is extruded. Larger lignocellulosic particles under tremendous pressure molding began to break, while plastic flow, due to the engagement between the raw material particles to each other becomes very tight. In the direction perpendicular to the main stress on the continuous extension of the raw material, particles continue to fill the voids. The high pressure of the pressure roller causes the temperature of the wood to increase greatly, and the lignin plasticizes slightly forming a natural “glue” that holds the pellet together as it cools.
2. The Possibility of Making Use of Coconut Timber to Make Wood Pellet
Coconut (Cocos nucifera L.), we all know, is the proud owner of the distinction “Tree of Life.” The tree provides mankind with food, shelter, furniture, novelty items, fuelwood, household implements, and important industrial products.
In the Philippines, the decade of the 80s saw lumber from coconut becoming a popular alternative to lumber from traditional wood species. This was brought about mainly by the ban on logging in Philippine forests. Compared with conventional lumber, coconut wood is more available and affordable. But coconut timber can be used to make wood pellets or not, let us see the several aspects.
First, coconut timber can burn. According to the study of T.K.Dhamodaran and R.Gnanaharan, the Average calorific value of coconut stem wood in air-dry conditions was found to be about 16.3 MJ/kg and it compares fairly with that of hardwoods. According to the study of FAO, coconut trunk and other sawmill residues are readily usable for charcoal making and for the production of energy. Coconut wood is similar to other woods in its characteristics as fuel, although the range of densities within the stem leads to variation in the energy potential.
Secondly, coconut timber can be pressed into shape. By wood pellets formation mechanism, if something contains Lignin, it could be pressing molding. The study found the proximate chemical composition of coconut wood are the following: holo-cellulose (66.7%); lignin (25.1%) and pentosans (22.9%). Wheat straw contain holocellulose(68%) and lignin(17%). Rice husk contain holocellulose(58%) and lignin(12%). The cellulose content of coconut timber in the middle of straw and rice husk. The lignin content of coconut is higher than wheat straw and rice husk. Through the above analysis, can be introduced, coconut timber is more easily pressed into shape than wheat straw and rice husk. According to the study of T.K.Dhamodaran and R.Gnanaharan, a highly positive correlation (r=0.96) was obtained between density and calorific value per unit volume. According to the message of FAO, a technology for briquetting coconut trunk charcoal has already been developed. A briquette plant in the Philippines produces ovoid-type briquettes of 1.5 oz size at 500 lb/hr. The briquettes have good crushing strength and burning properties. Sorghum grain is an effective binder for charcoal briquettes of coconut trunk.
3. Production of Coconut Pellet
There are already patents of use coconut make pellets. The U.S. Pat. No. 4,933,314, Marumo, et al. (1990) which describe making CMS from spherical phenol resin powder mixed with a binder and pelletized and heated to carbonize the pellets. In making the CMS, various materials such as finely divided cellulose, coconut shell, coal, tar, pitch, or other resins can be added in small amounts to improve workability, e.g. in pellet molding. The US 6863027 B1, Tilak Silva (2003) which describes the method of making pellets of coconut coir pith used as a cat litter.
For pellet production, a flat die pellet machine is suitable for small-scale production, and a ring die pellet mill is for large-scale production. There is also a coconut pellet for sale. Supreme Carbon Indonesia produces wood pellets with all natural materials, made of sawdust and wood shaves from tropical woods or coconut and palm kernel shells, free from recycled materials like particle board, and treated or painted wood. Combustion efficiency is more than 90%.
Through the above analysis can be drawn, we found that the use of coconut: (including coconut timber, coconut shell, coconut fiber, and other coconut waste) to make wood pellets is very mature in theory and technology. The Philippines is the largest producer of coconut, and the coconut processing industry is relatively mature, with its waste to produce wood pellets, there is a very good economic and social benefits.