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Peanut Shell Pellets and Briquettes Treasure Hunting in Peanut Wastes

By Jack Huang    Mar 02, 2015
Peanut shell waste? No. it could be peanut shell pellets and briquettes treasure produced by a pellet or briquette machine. How to dig your own peanut fuel treasure from the waste? It’s better to conduct a survey on peanut now.

Peanut and Peanut shell

Peanuts, also known as groundnuts, earthnuts, ground-peas, manila-nut, jar-nut, are pea-like fruit from Arachis hypogaea plant. There are various types of peanuts available around the world distinguished by branching habit and branch length. Even though there are numerous varieties of peanuts, there are two main growth forms , the bunch and runner.


Peanuts are planted in the warm climates of Asia, Africa, Australia, and North America. In 2012, China was the largest cultivation country of peanut, with its peanut production of 16.7 million metric tons , accounting for 42% of global production, followed by India, 5.0 million metric tons, 12%, both of which account for more than half of the world’s production. Other major peanut growing countries are United States, Nigeria, Burma, Indonesia, and Argentina, etc. The world total peanut production was 40.1 million metric tons in 2012, which showed the potential to grow in the future. The large amount of peanut production left abundant peanut wastes, such as, peanut shell or hull, and peanut fibers, which is now considered as a potential fuel source.

Value of Peanut Shell

After harvesting and de-hulling, the peanut shell or hull are separated from nut, accounting for approximately 20% of the dried peanut pod by weight, which means a substantial amount of shell residual biomass left after processing. Peanut shells or hulls are used as cattle feed, poultry litter and garden mulch and now they are seen as potential fuel source.

Peanut Shell Components Analysis

Although the composition of peanut shells or hulls may vary with its types, the main chemical compositions of peanut shells are not changed largely by the varieties. The main compositions of peanut shells or hulls are cellulose 37.0%, lignin 28.8%, protein 8.2%, , carbohydrate 2.5%. The compositions of peanut shells make peanut a treasure in disguise, which can be used for fuel and for feed production.

Chemical components of peanut shell
Characteristics Cellulose Hemicelluloses Carbohydrate Proteins Calcium Phosphorous Crude ash Minerals
Peanut shell 65.5-79.3% 10.1 % 10.6-21.2% 4.8-7.5% 0.24-0.27% 0.08-0.09% 1.9-4.6% 4.3%

Peanut Shell Pellet Fuel

peanut hull pellets made by peanut shell pellet mills

In order to make the best of peanut hull and develop a new energy source, peanut shell or hull can be compressed into fuel pellets with a peanut shell or hull pellet mill. There are two types peanut shell pellet mills, the flat die sort and the ring die sort. The former is usually used for small scale pellet production, favored by household users, and farmers, and small business pellet producers while the latter is used for large scale pellet produced, used by medium and large scale pellet producers for large scale boilers and power generations.

After pelletizing, the moisture content of the peanut hull will be lowered significantly and the bulk density will be increased from 151 kg/m(3) to more than 600 kg/m(3). What needs to mention is the peanut pellet density and bulk density are largely affected by moisture content attained by the pellets during exposure to the low or high humidity environment.

Advantages of peanut shell pellets fuel

Peanut shells or hulls used as fuel directly may cause transportation difficulty because of the large volume and low combustion rate. Pelletizing of peanut shell or hull will largely improve their storage and logistics, and the peanut shell pellets has the following advantages:

  • Densified peanut shell or hull pellets can be ignited quickly, and have a good combustion performance, high burning efficiency, and produce less ash.
  • Peanut shell or hull are easy to get, which will lower the production cost of peanut shell pellet, providing a big profit margins.
  • Peanut pellet fuel is a green biomass energy will lower emission and is environment-friendly.
  • Peanut shell or hull pellets can be used widely either in civil heating and daily energy supplying or in industry boilers for power generation due to high burning rate and easy to storage.

Peanut shell briquette fuel

Peanut shells or hulls briquettes is also a biomass densified fuel made by briquette presses. The briquette machine is designed to press the biomass residues, such as, peanut shell, and any other crop straw or husks into densified briquettes, which will be burned in furnace, large boiler and power station to produce heat and power.

peanut shell briquttes

Peanut shell briquettes machines

Peanut shell briquettes machine is the key to produce high quality peanut shell briquettes. No matter it is the piston briquette press, the screw briquetting press or the hydraulic briquetting press, the most common seen briquette machines in the market, most of the briquettes machines influence the quality of peanut shell or hull briquettes by their physical parameters in briquetting process, such as pressing temperatures, compacting pressure, and moisture content.

  • The pressing temperature impacts the soften and excretion of lignin which will work as a natural binder to join the fibers of the feed stocks to form solid high density briquettes.
  • The compacting pressure influences the briquettes strength in direct proportion within the compacting limit of the feed stock.
  • Moisture content is mainly affected by the feed stock moisture and properties. The optimal moisture content in around 10-18 %.
stamping briquttesf machine and peanut shell briquttes

Advantages of Peanut Shell Briquettes

The densified briquettes has the following advantages:

Firstly, the high quality peanut shell briquettes have smooth surface, and homogenous compacted cross-section, which means the burning of the peanut shell will be more clean, and it will be more convenient to transport and store the fuel.

Secondly, the moisture content should be around 5%, which ensures good combustions.

And the last and the most, the unit calorific value of briquette will be largely improved. Heat value or calorific value is the decisive factor for evaluating the quality of the briquette fuel. Calorific value of briquettes largely determines the burning of briquettes. Higher the calorific value is, the easier and better they will be burned. As an alternate fuel, the heat value of briquettes made by the biomass briquetting machines range from 4.48 to 5.95 KJ/G, depending on the composition, according to a study conducted by Boise State University. Even compare with coal fuel, biomass briquettes is not inferior because they have their own advantages and features. The calorific value of briquettes are largely determined by its constitutional elements and the element analysis of peanut shell or husk are shown in the following table for your reference.

Elemental Analysis of Peanut Shell
Element C H N O Ca Fe Mg Mn Na K
Percentage% 45.5% 6. 7% 0.9% 33.9% 0.28% 0.00l% 0.009% 0.002% 0.004% 0.024%

Naturally, there are other factors that influence the quality of the wood briquettes and other methods to evaluate but if the wood briquettes have smooth surface, high heat value and good combustion rate, they are high quality briquettes.