Open sun drying generally means spreading grain on the ground in a yard or leaving cut grain in the field. In some cases, grain is spread on a tarp or mat, which can reduce losses. Open sun drying is the least resource-and-cost-intensive method of drying and is suitable for small batches. However, weather conditions can sharply limit the effectiveness and safety of open sun drying.
Capacity: limited by space
Drying time: depends on weather conditions, 2 to 5 days
Crops: any
Fuel: sun
Portable? not applicable
Performance considerations: grain needs to be shifted periodically to improve drying.
The solar bubble dryer uses solar energy for heating and electric energy for forcing air through the grains. It is a tunnel-type dryer, designed as an alternative to open field drying. Grain is placed in the bubble and a fan circulates the warm, dry air through the tunnel to dry the grain.
Capacity: 500 or 1,000 kg
Drying time: Reducing moisture by .5 percent every hour for rice or corn in good conditions. With optimal conditions, a crop can be brought from 22 to 14 percent moisture in 6 to 8 hours, according to the manufacturer.
Crops: tested for rice and maize
Fuel: solar or electric options available
Portable? yes, can be rolled up and transported easily
Ease of construction: professional
Product available for purchase? Yes, from GrainPro
Performance considerations: grain should be mixed regularly for optimum drying.
An instructional setup video is available from GrainPro.
FAQ from the International Rice Research Institute (IRRI)
Circular bin dryers ventilate the grain outwards from a center column. They are compact, save floor space, and can be expanded or contracted to accommodate different batch sizes. Based on the Vietnamese SRR dryer design, modifications by ADMI partner Bangladesh Agricultural University include a mesh cage, improved blower, and an option for LP gas as a heat source.
Capacity: 500 kg and up, bin can be expanded to more than 500 kg
Drying time: 500 kg of paddy dried from 24.75% to 8.5% moisture content in 7.5 hours. Time can depend on air temperature and blower speed.
Crops: rice, maize
Fuel: Electricity needed for blower, heat generated by burning rice briquettes or LP gas
Portable? yes, can be disassembled and transported
Ease of construction: some technical expertise required
Performance considerations: grain should be mixed regularly for optimum drying
Detailed instructions and specifications from Bangladesh Agricultural University
This classic simple flatbed dryer was developed in Vietnam. It can be constructed in 4-ton (SGH4) or 8-ton (SGH8) configurations.
Capacity: 4 (SGH4) or 8 tons (SGH8) per batch depending on configuration
Crops: paddy, maize
Drying time: reduce moisture by about 1.5% per hour; 4 ton batch of paddy dried from 25% to 15% in 9-11 hours
Fuel: generator or electricity connection for fan and additional biomass furnace for heat
Performance considerations: grain needs to be mixed by hand; cover over the dryer allows use in more weather conditions.
Portable? no
Ease of construction: no technical expertise required
Technical specifications and further information available from IRRI
The reversible air dryer adds a cover to a standard flatbed dryer and an air channel to allow the operator to force air from the top down or from the bottom up. By reversing the airflow, these dryers reduce the moisture differential between the topmost and bottommost layers of grain, thereby increasing the consistency in drying.
Capacity: 500 kg up to 12 tons
Drying time: reduce moisture by about 1.15% per hour; an 8-ton batch of paddy can be dried from 24% to 12.5% moisture content in 9-11 hours.
Crops: paddy, whole coffee, coffee bean, pulped coffee, peanuts
Fuel: generator or electricity connection for fan and additional biomass furnace for heat
Portable? no
Performance considerations: Due to reverse flow drying, grain does not need to be mixed.
Read more about flat-bed dryers from the IRRI Knowledge Bank.
The Easydry M500 dryer is a small collapsible flatbed dryer designed to be portable, unlike the conventional flatbed. In addition to portability, it differs from the conventional flatbed dryer by using a heat exchanger after the blower, so that clean air is blown through the grains to be dried.
Capacity: 500 or 1,000 kg
Drying time: for 500 kg, the dryer can reduce moisture by about 1.6% per hour; a batch of maize can be dried from 17% to 13% moisture content in 2.5 hours.
Crops: paddy, whole coffee, coffee bean, pulped coffee, peanuts
Fuel: generator or electricity connection for fan and additional biomass furnace for heat
Portable? yes
Performance considerations: Grain needs to be mixed frequently.
Ease of construction: technical expertise required
Download the EasyDry user manual from ACDI-VOCA
The Flatbed Wagon Dryer is a completely self-contained mobile flatbed dryer, which is commercially available. This dryer can be shipped into a standard 20-foot shipping container anywhere in the world. It is designed for precision drying and contains a thermo-humidistat, which regulates the heater to bring the product to the desired moisture content.
Capacity: 215 bushels and 315 bushels
Drying time: reduce moisture by about 1.67% per hour; the 215 bushel dryer takes about 3 hours per 5% moisture reduction.
Crops: maize, but steel mesh can be customized to accommodate finer grains including flaxseed, rice, and wheat
Fuel: electricity
Portable? yes
Ease of construction: professional production required
Performance considerations: No grain mixing necessary. Difficult to use in poor electricity supply situations. Sides are 9 feet high, which could make loading difficult.
Learn more about the drying wagon, including a demo video
