Feasibility Analysis of Rice Husk Pelletizing

Rice, as one of the three most important grain crops in the world, has been increasingly applied as raw materials to produce either molded or un-molded fuels. Or rather, it’s the byproduct in source mill (rice husk, also called rice hull or rice chaff) and residue left behind during harvesting (rice straw) that really come into play. This article briefly introduces the feasibility of rice husk pellets manufacturing from both internal and external aspects.

Subjective/Internal Factor
Rice husk is the byproduct in rice mill. Tested by thousands of manufacturers, the process of turn it into rice husk pellets is quite feasible. On one hand, its self attribute features make it an option when taking the raw material requirements for pelletizing machine as a benchmark. On the other hand, it’s easy to be obtained due to wide distribution and short growth period.
1. Self Attribute Features
The following chart shows some parameters of rice husk

1.1 Moisture: Not all raw materials are suitable to be fed into pellet mill. It has certain requirements for several elements, such as moisture, size, etc. Although the lignin content of different feedstock differs greatly, the appropriate water content for processing rice husk pellets and others is basically consistent, ranging from about 6% to17%. Obviously, the 8.84% shown above is definitely among this scope, making drying process unnecessary and saving the expense on this procedure including dryer, electricity and man power.
1.2. Volatile matter: Volatile matter refers to the gaseous outcome produced during the splitting decomposition of organic materials in fuels, or the weight loss of fuels after being heated under isolated air and other rated conditions. The content of volatile matter has great influence on fuels’ combusting characteristics. Generally speaking, the higher it is, the easier fuels are to combust. From the chart we can see that content in rice husk is 57.95%, contributing to its superior burning features and feasibility for further rice hull processing.
1.3. Ash: As the residues of fuels after their complete combustion under certain temperature, ash is a kind of useless substances, so the less of it, the better. Enhancement of ash content can not only lower the caloric value of fuels but also taking some heat while being discharged. When it comes to this factor, three advantages of rice husk pelletizing are included. First, with the relatively low ash content of 15.24%, rice chaff can be processed successfully and smoothly because neither clogging of machine nor slagging of materials should be worried about. Second, low residues are equal to little discharging work, which will save some cost, time and labor as well as speed up the whole manufacturing process. Third, small amount of ash causes less environmental pollution, reducing such problems as wastes piling and soil deterioration.
1.4. Length: The length of rice chaff ranges from 5mm to 10mm or 2.5mm to 5mm (differs according to different categories) which absolutely accords with pelletizer’s requirement for raw materials size, within about 6mm. Thus, in the process of rice husk pelletizing, the chipper and crusher used to cut feedstock into chips and grind it into smaller powder are no more needed.
1.5. Heat value: Although its heat value (about 3800Kcal/kg) is not as high as that of some wood wastes, such as pine sawdust and maple chips, rice husk is still a promising alternative for pellet fuel processing. As is known, alliance between giants helps all of them obtain double results by doing half the work. After playing the role of feedstock, rice husk can get the density 6.3 times higher than before, which can improve the heat value and other heating features of final rice husk pellets.
1.6. Sulfur: The combustion of fuels with sulfur in may lead to serious consequences. On one hand, boilers or furnaces they serve may be corroded, shortening their lifetime and causing abnormal operation. On the other hand, the volatilization of produced gas may result in severe atmospheric problems led by acid rain. Using rice chaff as raw materials, neither of these will become a threat because sulfur is contained neither in it and nor the finished rice chaff pellets.

2. Wide Distribution
Mainly distributing in southern China, Taiwan, Japan, Korean Peninsula, Southeast Asia, South Asia, Mediterranean Coast, Southeastern U.S., Central America, Oceania and Africa, rice covers an area of about 155 million hectares, among which East Asia occupies the largest proportion (33%), followed by South Asia and Southeast Asia who account for 31% and 33% respectively. From the figure we can see rice is cultivated in almost every district except Antarctica, making the feedstock for rice husk pelletizing cheap and facile..

3. Short Growth Period
Rice grows very fast, one year for the longest and 3-4 months for the shortest. That is to say, the whole period from sprouting, blooming and bearing can be completed only in about 130-140 days. Besides, 5-6 days is enough for the buds and first leaf to come out, so triple cropping per year can be realized for some rice species. The distribution of rice is so wide and growth period is so short that its byproducts can be obtained from almost every corner of the world in large quantity, which further proves the point that rice husk pellets are feasible to be produced.

Objective/External Factor
1. Government Support
According to the prediction of international renewable energy organization, the reserves of underground petroleum, natural gas and coal are only enough to be utilized for about 60 years. Therefore, the R&D of biomass energy technology has become one of the universally hottest topics, attracting more and more attention from governments and scientists all over the world. Many countries have made relative plans about it, such as the “sunshine project”of Japan, “green energy engineering”of India and “energy farmland”of USA. Thanks to the support of related institutions, the application of many biomass energy including rice husk pellets has reached commercialization level. For example, their application scopes in USA, Sweden and Austria occupies 4%, 16% and 10% of the total primary energy consumption in their own countries.
2. Considerable Profits
The following gives P&L analysis of rice hull processing, from which we can see considerable profit margins exist in it.
2.1 Cost
A.Purchasing price of raw materials: 15USD/ton
B.Processing cost: 22kw*0.2USD/kw=4.4USD/ton
C.Labor cost: 5*7.5USD/person/day=30USD/day ÷ 10 tons=3USD/ton (Assume the daily output is 10 tons.)
Total cost: 15+4.4+3=22.4USD/ton
(1)Market price of final rice chaff pellets: 55USD/ton
(2)Profit
A.Profit of one ton: 55-22.4=32.6USD
B.Daily profit: 32.6*10 tons/day=326USD
C.Monthly profit: 326*25 days=8150USD
(Assume the pellet mill operates for 25 days per month.)
D.Yearly profit: 8150*10=81500USD
(Assume the labors work for 10 months per year.)

As a kind of renewable resources, biomass used to be burnt directly when used as energy substance. However, the effective availability is very low because of its inferior combustion features. So how to transform such precious materials into convenient and clean energy has attracted more and more interest. Nowadays, the considerable economic and social benefits of biomass pellets production have received acceptance from both manufacturers and farmers. Among various kinds of applicable feedstock, rice husk accounts for an essential place. Please refer to the above information for the feasibility of rice husk pelletizing.