Field trial of in-store paddy drying and storage

Aim of this paper is to investigate the field trial of in-store paddy drying and storage. Both paddy quality and economics were taken into consideration. Ambient air flow rate of 0.57 cubic m/min-cubic m of paddy was blown through the paddy bulk with 105 ton capacity. The experimental results revealed that moisture reduction at deeper depth from surface was faster than that at lower depth from surface. Moisture content of paddy was reduced from 17 percent wet-basis to 11.6 percent wet-basis within 9 weeks and then paddy bulk was continually stored within 19 weeks. Paddy qualities in terms of whiteness and head yield were still maintained as compared to reference sample. Electricity consumption during drying stage was 14 kW-h/ton of paddy (US$ 0.84/ton of paddy). For storage, electricity consumption for ventilation, 2 h each time in a week, was 1.31 kW-h/ton of paddy (US$ 0.08/ton of paddy). The economics analysis by present worth method showed that in the case of in-store drying with only additional investment in air ducts, payback periods were 1.5 years and 1.6 years for discount rates of 10 percent and 15 percent respectively (for once a year of paddy drying). However, for twice a year of paddy drying, payback periods reduced to be 0.6 year and 0.7 year at discount rates as mentioned before. Moreover, both income and project life were sensitive to net present worth. From comparison between the investment cost of in-store paddy drying and that of sun drying on a concrete pad during term of 20 year project life, it was found that payback periods for the in-store paddy drying were 6 and 7.5 years for discount rates of 10 percent and 15 percent respectively but there were no payback periods for the sun drying. Income, cost and discount rate for in-store paddy drying were very sensitive to net present worth while only cost in sun drying was significant to net present worth.