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Mechanical Drying of Paddy Using BAU-str Dryer for Reducing Drying Losses in Bangladesh

MA Alam
Bangladesh Rice Research Institute, Gazipur, Bangladesh

CK Saha
Department of Farm Power and Machinery, Bangladesh Agricultural University, Mymensingh 2202, Bangladesh

MM Alam
Department of Farm Power and Machinery, Bangladesh Agricultural University, Mymensingh 2202, Bangladesh

Abstract/ Executive Summary:

Mechanical intervention in each stage of post-harvest operation of paddy is time demand due to increased cost of labour as well as shifting of labour from agriculture to non-agriculture sector. Mitigation of food demand of rapidly increasing population is becoming a major future challenge in agriculture sector. Drying of paddy is important for maintaining quality and long term storage of paddy. Among the drying methods, traditional sun drying is the most common practice in Bangladesh. Normally, farmers use yard in wet season (Boro & Aus) and field in dry season (Aman) to dry paddy. In this case, appropriate paddy drying technology could play a vital role to strengthen food security by reducing drying loss. Therefore, a study was conducted to investigate the drying loss of paddy both in traditional sun drying and mechanized drying method (BAU-STR dryer) at selected areas of Bangladesh. Popular and mega rice varieties cv. BRRI dhan28 and BRRI dhan49 were used as drying materials to evaluate the performance of BAU-STR dryer with different dryer capacity i.e. 300, 400, 500 and 600 kg of paddy per batch. Drying losses of BAU-STR dryer were examined during Boro and Aman season of 2015 and 2016 whereas drying losses under open sun drying method was measured during Aman season 2017 in the selected areas of Tangail, Mymensingh, Netrokona and Jessore districts of Bangladesh. The results showed that the average drying loss of paddy in BAU-STR dryer was found 0.48% and 0.36% during Boro and Aman seasons, respectively at 2015 and 2016 while sun drying loss at farmer’s field level was found 3.95, 3.24, 2.98 2.41 and 3.04% in Tangail, Mymensingh (Phulpur), Mymensingh (BAU), Netrokona and Jessore districts, respectively. The low cost BAU-STR dryer would be an alternative and effective drying technology to save 1.4 MMT of paddy by reducing 2.7% losses of national production (51.87 MMT) for combating hunger and improving food security in Bangladesh.

Keywords: Drying loss; BAU-STR dryer; Paddy, Food security; Rice

Location: Farm Power and Machinery Department, Bangladesh Agricultural University, Mymensingh, Bangladesh

Start Date: 00-00-2015

End Date: 00-00-2017

Program Area: Postharvest and Agro-processing

Commodity: Rice

Objectives:

To investigate drying loss of paddy in traditional sun drying method at farm level and compared with mechanized drying method using BAU- STR dryer.

Methodology:

Drying loss of BAU-STR dryer was examined during Boro and Aman season of 2015 and 2016 at the workshop of the Farm Power and Machinery Department, Bangladesh Agricultural University, Mymensingh, Bangladesh whereas drying loss under open sun drying method was measured during Aman season 2017 in the selected areas of Tangail, Mymensingh, Netrokona and Jessore districts of Bangladesh. Freshly harvested paddy varieties BRRI dhan28 and BRRI dhan49 were collected from the Bangladesh Agricultural University farm in the Boro and Aman season respectively to evaluate the BAU- STR dryer with the different drying capacity of 300, 400, 500 and 600 kg per batch of paddy and three replications. Description of the dryer: The BAU-STR dryer consists of a perforated inner bin and a perforated outer bin with annular space for rice grains, a biomass stove, a hot air conveyance pipe and a blower to provide the heated air. A pictorial view, schematic view and experimental set up of BAU-STR dryer. The inner and outer bins are made of stainless steel wire (8 meshes). The diameter of inner bin is fixed (40 cm) while the diameter of the outer bin is adjustable to hold desired volume of rice. Heated air is forced from the inner bin through grains and perforated walls of the outer bin with bottom and top closed to dry the grains inside the annular space. An axial flow blower is used to suck the hot air from the biomass stove a through steel pipe and also the blower forces the air radially through the grains in the annular space between the perforated bins. A diesel generator is used as alternative source of power for running the blower in absence of electricity supply from the national grid. Locally available rice husk briquette is used as a fuel in a portable locally made stove. Experimental procedure for BAU-STR dryer: The BAU-STR dryer was installed in the workshop of the Department of Farm Power and Machinery, Bangladesh Agricultural University. Fresh harvested paddy was collected from BAU farm. The collected samples were cleaned, weighed and recorded initial moisture content. Initial moisture content and weights were adjusted at 14% moisture content (wet basis) to calculate drying loss of paddy. The dryer was loaded with desired volume of paddy and drying operation continued till the desired moisture content of 12% (w.b.) was achieved. Final weights and moisture content were also measured and adjusted at 14% moisture content (wet basis) to calculate drying loss of paddy. Initial and final moisture content of paddy were determined in two ways: manually using digital moisture meter and an electric oven (105 °C for 24 hrs). Two electrical balances (Model- ES-HA precision balance scale) were used to weight paddy. The drying air temperature was measured using nine K- type thermocouples which were attached to a data logger (Model-FLUKE 2635A Hydra series Data bucket). The data logger was connected with a computer to record and store temperature reading at one minute interval during drying operation. The ambient air temperature and relative humidity were measured by using a data logger (Model-TRH 1000, temperature accuracy: ±0.2°C and RH ±4%). Moisture content was measured at the five locations in side of the grain bin named M_m1, M_m2, M_m3, M_t and M_b, respectively. A digital moisture meter was used to measure moisture content of paddy (Model-RiceterL, accuracy: ± 0.2% 105^oC, measurement range 11-30% for paddy rice) after collection of sample with the help of steel made sample collector. Data were collected in every half an hour interval during drying operation.

Experimental procedure for field drying: The experimental procedure to determine field drying loss was followed as mentioned by Jose et al. (1985). Existing farmer’s practices in post-harvest operation were taken in consideration to investigate field drying loss which includes harvesting time, harvesting process and drying practice of paddy. For this purpose, 50 m² (5m X 10m) test area were marked randomly by staking the corner poles in the field. The test area was select about 1 m distance from the levee to avoid manmade shattering loss because of passing people. Harvesting loss was measured by marking 1 m along the length of test area from the 5 m side to cover an area of 5 m² (1m X 5m). All the grains lying on the field were picked up carefully from the selected 5 m² area after harvesting paddy by sickle. Collected paddy were cleaned and weighted. Moisture content was also measured at the same time. Weights are adjusted at 14% moisture content to calculate harvesting loss. Another 10 m² (2m X 5m) areas were selected randomly from the remaining 45 m² field to determine field drying loss. Harvested stalks with grains were spread over the test area for field drying as practiced by the farmers. Farmers collect paddy after 5 to 7 days sun drying. Fallen paddy was picked carefully from the test area which represent harvesting and field drying loss. Collected paddy were cleaned, weighted and adjusted weight at 14% moisture content. Harvesting loss was subtracted from total loss to determine field drying loss. The remaining 35 m² area were also harvested following same practice to determine the grain yield.

Source of Information: Progressive Agriculture, Vol. 30, Suppl. 1: 42-50, 2019

Article Link (Online Journal): DOI: https://doi.org/10.3329/pa.v30i0.41556

Funding Source:

Budget:

Total Budget (Tk.) :

Achievement/Findings:

Bangladesh government has been increasingly interested in policy issues concerning national food security and has enforced programs for its improvement to reduce drying loss as well as post- harvest loss of paddy. Drying loss of paddy in BAU- STR dryer was found between 0.31 to 0.59% with an average 0.43% at laboratory level whereas it was found between 0.34 to 0.45% with an average 0.39% at farmer’s field level. On the other hand, drying loss of paddy in open sun drying method at farmer’s field was ranged from 2.41 to 3.95% with an average 3.1%. Therefore, mechanical intervention reduces drying loss of paddy significantly. The low cost BAU-STR dryer would be an alternative effective drying technology to save 1.4 MMT of paddy by reducing 2.7% losses of national production (51.87 MMT) to combat hunger and improve food security in Bangladesh. The knowledge of post-harvest losses of rice are useful to policy makers for intervention in national production, loss reduction process, existing storage structure and import rice towards attaining food security for the growing people of Bangladesh. In addition, the government should take initiative to introduce appropriate mechanical drying technology like BAU- STR dryer through government subsidy to the farmers and small traders for reducing post-harvest losses.

Knowledge Management: Journal