Production method and application scope of straw pellet

Under the background of carbon neutral development strategy, straw pellet, as a typical solution for high-value utilization of agricultural waste, have become an important topic in the field of renewable energy. Based on engineering practice data, this paper systematically explains the preparation process, equipment selection and application scenarios of straw pellets, and provides standardized technical references for practitioners.

What are straw pellet?

Straw pellet are a product that converts agricultural waste into standardized biomass fuel through mechanical processing. The product is made from the straw of crops such as rice, wheat, and corn, and is made through processes such as crushing, drying, and high-pressure compression.

The finished product is cylindrical, with specifications of 6-10 mm in diameter and 20-50 mm in length. Its physical properties are as follows: the bulk density reaches 1.1-1.4 g/cm3, and the calorific value is stable in the range of 3500-4500 kcal/kg. Tests and verifications have confirmed that this process increases the combustion efficiency of straw fuel by more than 300% compared with the original straw.

Why make straw pellet?

Environmental value

It has been calculated that straw pellet fuel has significant energy substitution and environmental benefits. In terms of calorific value equivalent, 1 ton of straw pellets fuel can effectively replace 0.8 tons of standard coal; in terms of carbon emissions, its entire life cycle can achieve a reduction effect of about 1.5 tons of carbon dioxide equivalent.

Economic benefits

The price of processed pellets is 2-3 times higher than that of original straw. A farm in Northeast China has increased its annual income by more than 120,000 yuan after using a straw pellets machine

Storage advantages

The process reduces the volume to 1/6 of the raw material, prevents moisture and mildew, and allows operators to stack the product in the open air.

Policy support

my country’s “Renewable Energy Law” provides tax incentives for biomass energy projects

How to make straw pellet? (Core process)

‌Raw material pretreatment‌

‌Crushing‌

Select dry, mildew-free corn, wheat and other straws, and crush them to a particle size of 3-5mm through a hammer mill to improve molding efficiency and reduce equipment wear.

‌Impurity removal‌

Use a vibrating screen to remove hard impurities such as gravel and metal to avoid equipment failure in subsequent links.

‌Tempering‌ (optional)

If the moisture content of the raw material is lower than 12%, operators need to spray atomized water mist to temper it to 15%–18% in order to ensure the density of the particles.

‌Pellet forming‌

‌Ring die granulation‌

The pretreated raw material is transported to the ring die pellet machine and extruded through the die hole at a pressure of 10-15MPa. The die hole diameter is 6-8mm, the speed is 150-200r/min, and the production capacity is about 1-2t/h.

‌Cooling‌

The newly formed particles reach a temperature of 80–90℃, and operators use a countercurrent cooler to cool them to room temperature ±5℃ to prevent mildew.

‌Post-processing‌

‌Screening and packaging‌

The powder is removed by a vibrating grading screen. Operators package the finished particles in ton bags or 25kg woven bags, maintaining a moisture content of ≤12% and a density of 1.1–1.3 g/cm³.

Note

A newly purchased straw pellets machine needs a 20-hour run-in period. It is recommended to add 5% edible oil to lubricate the mold for the first use.

Multiple applications of straw pellet

Fuel field

Replace coal for boilers (1 ton of pellets = 0.6 tons of coal)

Special fuel for household heating stoves (thermal efficiency of 85%)

Agricultural use

Make organic fertilizer carriers (porosity of 35%)

Livestock bedding (water absorption rate is twice that of sawdust)

Industrial raw materials

Artificial board adhesives

Biogas engineering auxiliary materials

Conclusion

At present, Shandong, Henan and other places have built more than 300 straw pellet machine production lines, processing more than 2 million tons of straw annually. As the “dual carbon” goal advances, analysts estimate that the market size of straw pellets in my country will exceed 5 billion yuan in 2026.