flat bed drying including survey results on the drying costs of various drying methods practiced in mekong delta ''''

FLAT BED DRYING INCLUDING SURVEY RESULTS ON THE DRYING COSTS OF VARIOUS DRYING METHODS PRACTICED IN MEKONG DELTA " SECTION FLAT BED DRYING INCLUDING SURVEY RESULTS ON THE DRYING COSTS OF VARIOUS DRYING METHODS PRACTICED IN MEKONG DELTA 93 CARD Project FLAT-BED DRYER Sub-Component 2006/2007 Report Reporting period: from 15 May 2006 to 28 Feb 2007 Compiled by: Phan Hieu Hien, Ph.D with contributions from staff of the NLU Center for Agricultural Energy and Machinery: Le Quang Vinh, Tran Thi Thanh Thuy, Tran Van Tuan, Nguyen Thanh Nghi March 2007 94 CONTENTS CARD PROJECT, FLAT-BED DRYER SUB-COMPONENT 2006 REPORT 96 INTRODUCTION 96 INSTALLATION OF THE 8-TON FLAT-BED DRYER 96 EXPERIMENTS WITH THE 8-TON DRYER UNDER ACTUAL PRODUCTION CONDITIONS 98 3.1 Objectives .98 3.2 Materials and methods 98 3.3 Results and discussion: .98 3.3.1 3.3.2 July 2006 experiments .98 March 2007 experiments 98 FABRICATION OF A LAB (MINI) DRYER FOR EXPERIMENTING UNDER CONTROLLED CONDITIONS .99 4.1 4.2 Materials and methods 99 4.3 Objective 99 Results and discussion (1-to dryer) 104 THE PRRA SURVEY ON THE USE OF FLAT-BED DRYER AND THE COST OF VARIOUS DRYING METHODS IN THE MEKONG DELTA .110 5.1 Background 110 5.2 Objectives .110 5.3 Method 110 5.4 Result and discussion 110 5.4.1 Background data 110 5.4.2 Post-harvest and drying status .112 5.4.3 Conclusions 114 EXTENSION MATERIALS FOR TRAINING COURSES, BASED ON THE OUTCOME OF THE SURVEY AND EXPERIMENTS 115 CONCLUSIONS AND FURTHER PROPOSALS 116 EVALUATION OF FARMERS’ PRACTICE .117 8.1 Value losses due to field drying and sun drying 117 REFERENCES 118 10 APPENDIX 119 10.1 Appendix : Paddy milling quality analysis (procedure by IRRI) 119 95 CARD Project, FLAT-BED DRYER Sub-Component 2006 Report (from 15 May 2006 to 28 February 2007) INTRODUCTION The sub-component of CARD Project 026/VIE-05 on the flat-bed dryer study, as specified in the contract, consists of the following activities: • Select the site and supervise the installation of an 8-ton flat-bed dryer for experiments • Conduct experiments with the 8-ton dryer under actual production conditions • Build a lab (mini) dryer and other needed tool for experimenting under controlled conditions • Conduct experiments to determine the optimum drying conditions for the flat-bed dryer (with or without air reversal) using the lab mini-dryer at the Nong-Lam University or a nearby location • Conduct a Participatory Rapid Rural Appraisal (PRRA) survey on the use of flat-bed dryer in the Mekong Delta • Write extension materials for future training courses, based on the outcome of the survey and experiments The above activities can be clustered into groups: - The 8-ton dryer - The 1-ton dryer - Survey, training, and extension This is the final report of the above-mentioned activities, covering the period from 15 May 2006 to 28 Feb 2007 It is compiled from earlier Progress Reports, and updated with most recent data and findings, thus conclusions from this report supercede the earlier reports for any discrepancies INSTALLATION OF THE 8-TON FLAT-BED DRYER Together with the Project Leader, Dr Truong Vinh, we selected the site for installing the 8-ton flat-bed dryer; the site was Tan-Phat-A Cooperative, located in Tan-Hiep District, Kien Giang Province At first, we intended to contract from a local dryer builder for a typical dryer in the region, adding features needed for the experiment, but no contractor was willing to meet the needs they considered too time-consuming with these added features in a miscellaneous contract for their business So, the research team decided to build an 8-ton air-reversible dryer which is a SRA-8 design from NLU with slight modifications The installation of the dryer was completed in mid-July 2006 (Fig.1 & 2), just in time for the wet-season harvest and for experimental purposes 96 Figure 1: The 8-ton dryer at Tan-Phat-A Cooperative, Kien Giang Figure 2: The 8-ton dryer with the air for downward direction 97 EXPERIMENTS WITH THE 8-TON DRYER UNDER ACTUAL PRODUCTION CONDITIONS 3.1 Objectives To determine the performance of the dryer under actual production conditions, for different drying regimes 3.2 Materials and methods The experiments were conducted in July 2006 Tan-Phat-A Cooperative, Tan-Hiep District, Kien-Giang Province Eight experiments were done, with factors under study • Air reversal at levels: a) YES , and • Drying temperature at levels: a) Constant at 43 oC ; and b) At 50 oC for the first hour, and afterwards constant at 43 oC In reality, due to the furnace configuration, the temperature rarely exceeded 50 oC, and was about 48 oC at most b) NO Each treatment was replicated twice However, due to severe difficulty in securing batches of the same quantity or initial moisture content, the experiments were not strictly factorial The arrangement of factor levels is for systematic observation only Due to different views on milling analysis, data on head rice recovery were discarded Thus in March 2007, another set of experiment was replicated, with focus on comparing the crack and head rice recovery of different drying modes, namely with and without air reversal Sun drying on the cement drying yard with a 7-cm paddy layer, as popularly practiced by local farmers, was replicated as control treatment The crack analysis was done at the VINACONTROL, an accredited agency in charge of certifying the rice quality for export Each treatment was analyzed by samples, each consisting of 30 grains taken at random; each paddy grain was hand-husked and examined under the magnifying glass for fissure The head rice recovery analysis was done at the Rice Quality Laboratory of the NLU Chemical Technology Department, following procedures adopted by International Rice Research Institute (see Appendix) and the University of Queensland 3.3 Results and discussion: 3.3.1 July 2006 experiments The experiment results are summarized in Table Figures and show the moisture reduction curves Remarks: - The effect of air reversal is very apparent in reducing the final moisture differential When operated correctly, this differential is less than % with air reversal, but at least 5% without air reversal More MC differential means more rice cracking during milling This explains why dryers installed since 2003 have been more and more of the reversible principle - Air reversal also decreased the drying time - The drying temperature is stable and can be kept within ± oC 3.3.2 March 2007 experiments Results are in Table All above observations hold with these new experiments Data on the crack of rice upon milling show that: 98 a) Mechanical drying, whether with or without air reversal, is superior to sun drying in terms of less crack percentage or more head rice recovery About 3- % less cracking, and about % more head rice recovery are main data obtained from this set of experiments b) Mechanical drying with air reversal resulted in less Final MC differential (2.2 %) compared to without air reversal (4.6 %) c) The increase in crack percentage between mechanical drying with and without air differed by only %; while judged by the head rice recovery, the difference was only 0.4 %, or almost no difference (Table 2) This was not expected in line with the above data on Final MC differential Thus more experiments should be conducted in the future to confirm the trend FABRICATION OF A LAB (MINI) DRYER FOR EXPERIMENTING UNDER CONTROLLED CONDITIONS 4.1 Objective To determine the performance of the 1-ton dryer under controlled conditions 4.2 Materials and methods A lab mini-dryer of maximum capacity of ton was designed and fabricated for experimenting under controlled conditions (Fig.5) (a) (b) Figure 5: The 1-to dryer: Airflow upward; (b) Downward reverse airflow 99 Table 1: Summary of drying batches (July 2006 ) 2523-7 25-7 Date /2006 26/7 30-7 24-7 27-7 23-7 29-7 Batch Number Temperature, oC 43 43 43 43 48 x43 48 x43 48 x43 48 x43 Air reversal Yes Yes No No Yes Yes No No Drying time, h+xx/100 10.42 6.00 10.50 8.75 10.00 3.58 5.75 11.67 Air reversal time, minute 10 15 - - 15 10 - - - - 60 - - - Ave - Break-down time, minute Initial MC, % 27.4 19.3 21.5 24.5 25.6 20.7 25.6 26.0 Final MC: Bottom, Max: 9.1 13.9 11.7 13.2 13.4 14.1 8.1 12.8 Final MC: Bottom, Min: 5.9 12.1 11.2 11.2 12.2 13.1 6.1 10.6 Final MC: Bottom, Ave,%: 8.2 13.4 11.6 12.0 12.7 13.6 7.6 11.3 Final MC: Top, Max: 15.5 14.9 23.1 22.7 17.3 15.2 13.0 22.6 Final MC: Top, Min: 15.2 13.3 15.2 15.5 15.8 14.4 12.2 17.8 Final MC: Top, Ave, %: 15.3 14.2 18.9 19.1 16.5 14.8 12.5 20.4 7.1 0.8 7.3 7.1 3.8 1.2 4.9 9.1 10.13 9.72 10.23 9.62 10.23 9.78 9.78 9.71 0.28 0.22 0.16 0.17 0.16 0.22 0.15 0.20 5.31 5.10 5.37 5.05 5.37 5.13 5.13 5.10 5.19 42.8 42.5 43.3 41.4 42.2 44.8 42.2 44.3 42.9 2.0 2.8 2.4 2.8 3.6 2.8 3.6 3.2 2.9 16.2 16.25 12.41 12.14 12.0 11.83 12.0 12.20 13.1 Bulk density:Before, kg/m 521 505 529 495 529 525 522 523 519 After drying, kg/m3 480 484 465 493 498 515 477 503 489 Paddy : BEFORE, kg 8338 7246 8185 7860 8805 8724 5307 9438 AFTER drying, kg 6946 6564 - 7368 7462 7706 4599 8307 Grain depth: BEFORE, m 0.508 0.456 0.491 0.504 0.528 0.528 0.323 0.573 AFTER drying, m 0.459 0.431 - 0.474 0.475 0.475 0.306 0.524 416.4 206.4 220.9 282.2 371.5 138.9 160.5 373.0 39.95 34.40 21.04 36.41 37.16 38.80 27.92 31.96 18.0 17.0 16.6 12.0 17.00 6.0 9.50 17.0 1.73 2.83 1.58 1.55 1.70 1.68 1.65 1.46 Final MC differential, % Air SUPERFICIAL Velocity Average , m /minute ± Std Dev., m /minute AIR FLOW, m3/s Av Drying temp, oC ± Std.Dev, oC Temp Increase, oC Husk consumption: Total, kg kg/ hour Diesel consump :Total, Lit Lit/ hour 9.90 33.45 1.77 100 Table 2: SUMMARY results of March 2007 experiments: Comparison of drying batches Batch (46+43 oC, with air reversal) Batch (46 x43 oC, WITHOUT air reversal) (46 x43 = 46 oC in first 1,5 hours, &43 oC in remaining time) Place Tan Phat A Cooperative, Ken Giang Province Date: March 2007 Batch Number Batch Batch Air reversal Yes Drying temperature (oC) ± StDev No 43.3 ± 3.1 43.0 START date-time 08-03-07 10:30 10-03-07 11:30 END date-time 08-03-07 16:30 10-03-07 17:30 6.00 ± 2.9 6.00 Drying time, h+xx/100 Air reversal time, minute 15 Laborer for air reversal Initial MC, % (Ave ± StDev) 23.86 Final MC % (Ave ± StDev) ± 0.71 14.94 20.41 ± 0.45 16.07 Top layer 13.92 0.31 18.23 0.75 Middle layer 16.16 1.05 16.38 0.7 Bottom layer 14.75 0.63 13.59 0.47 MC differential Top-Bottom, % MC differential Middle-Top , % 0.83 4.64 2.24 AIRFLOW (20 points) Airflow, m3/s 5.88 Superf vel (Ave ±StDev), m/min 11.20 5.70 ± 0.30 10.85 Rice husk consumption: kg /batch 171.2 215.2 Rice husk consumption: kg / hr 28.5 35.9 Diesel consumption, liter /h 1.70 1.75 Initial Paddy mass, kg 9276 ± 0.37 9197 Initial Paddy Layer (Ave±StDev), mm 517.8 15.6 507.8 7.5 Crack BEFORE drying, % 12.00 Differ 21.00 Differ Crack AFTER drying, % 13.75 1.75 23.75 2.75 Crack, Sun drying on Cement yard, 7-cm layer, % 17.80 5.80 26.80 5.80 Head Rice Recovery, % Head Rice %, BEFORE drying 62.72 Differ 59.12 Differ Head Rice %, AFTER drying 59.39 -3.33 56.21 -2.91 Head Rice %, Sun drying 55.58 -7.14 52.12 -7.00 Difference (Sun & Mechanical) % -3.81 -4.09 101 Table 3: Summary of drying batches Nong-Lam University Center for Agr Energy & Machinery No Drying conditions Date TESTS: drying paddy with SRA-1 dryer (CARD Project) Place : Le- Minh BRVT Rice Mill drying batches Batch 50+43o C with Air Batch Batch 50+43oC Without Air Reversal 43oC Without Air Reversal Batch 43oC with Air Batch Batch 43oC with Air Reversal 43oC Without Air Reversal Reversal Reversal 09-16/ Dec.2006 Pers: : TTT Thuy, NV Quy Batch 50+43 oC with Air Batch Note 50+43oC Without Air Reversal Reversal Date 10 /12 /06 11 /12 /06 1112/12/06 12 /12 /06 1314/12/06 14/12/06 15/12/06 16/12/06 10 11 12 13 14 Paddy MC Before drying (%) Paddy MC After drying (%) Ave Final MC, Top layer Ave Final MC, Bottom layer Final MC Differential = Top - Bottom Layer thickness before drying (m) Layer thickness after drying (m) Fresh /Dried before air reversal - Top Layer Fresh /Dried after drying - Top Layer Fresh / Dry Ratio before air reversal - Bottom L Fresh / Dry Ratio after drying - Bottom Layer Coal consumption (kg) Coal consumption (kg / hr) 24.71 13.43 18.84 12.82 0.364 0.321 1.11 1.22 1.36 1.39 22 1.93 0.243 0.230 24.35 12.62 13.9 11.8 2.1 0.248 0.208 1.11 10 2.50 1.26 18 2.25 25.97 12.49 12.8 11.0 1.8 0.405 0.361 1.19 1.29 1.41 1.45 17 1.55 21.83 12.64 13.3 11.1 2.2 0.249 0.220 1.18 27.70 13.53 13.6 11.7 1.9 0.379 0.350 1.10 1.25 1.34 1.36 20 1.74 27.35 13.35 13.6 11.4 2.2 0.261 0.230 1.07 21.10 13.65 12.9 11.2 1.7 0.246 0.219 1.14 1.20 1.23 1.25 0.84 1.23 1.38 1.23 1.13 1.20 0.00 Table (continued) 105 No 18 19 20 21 22 23 24 25 26 27 28 29 30 Drying conditions Air SUPERFICIAL Velocity, Ave (m/minute) Batch Batch 50+43 50+43oC o Without C Air with Reversal Air Reversa l 11.46 0.42 Batch 43 oC Without Air Reversal Batch 43 oC with Air Reversa l Air SUPERFICIAL Velocity, Std.Dev., m/minute) Air Flow, m3 / s 0.76 > 0.80 Air flow rate (m3 /s / ton) > 1.39 1.32 Mass of Paddy Before Drying (kg) 893 572 576 606 Mass of Paddy After Drying(kg) 665 474 420 434 Mass Reduction, Actual (kg) 228 98 155 172 Mass Reduction, from MC calc.(kg) 116 39 77 52 Ratio Reduction: Actual/ MC Calc 2.0 2.5 2.0 3.3 Drying time (hr) 11.42 4.00 8.00 10.67 Time of Air Reversal, after (hr) 7.00 7.00 Bulk Density WET, kg / m3 613 588 581 616 Bulk Density DRIED , kg / m 695 621 692 692 Note Batch &2 for Lots of immature, tune-up green grains Batch & 3: from same input paddy Batch Batch 43 oC with Air Reversal 43 oC Without Air Reversal Batch 50+43 o C with Air Batch Note 50+43 oC Without Air Reversal Reversal > 0.79 > 0.80 > 0.99 > 1.43 803 560 851 586 556 381 620 486 247 179 231 100 132 90 131 62 1.9 2.0 1.8 1.6 11.50 6.50 11.00 7.20 9.00 9.00 530 535 525 588 573 608 590 666 Good grain, little impurities - Very wet paddy, forced aeration for 1.5 hr to obtain desired initial MC - Lots of immature grains & impurities -Batch 5, 6& 7: from same input paddy 106 BATCH ( 43 oC, Without air reversal) BATCH ( 43 oC, with Air reversal) Batch ( 43 oC, Without Air Reversal ) B a tc h (43 o C , with Air R e ve rs a l ) 28 28 T1 24 T3 24 T1 26 T2 26 22 22 T4 20 T5 T2 T3 T4 20 T5 18 D1 D2 16 D2 D3 14 D4 12 D1 18 16 14 12 D5 10 D4 D5 10 10 D3 11 12 10 11 12 Drying tim e , hr D rying t im e , hr Batch (43 oC, Without Air Reversal ) Batch (43 oC, with Air Reversal ) Batch (43 o C, Witho ut Air Revers al ) Batch (43 oC, with Air Reversal ) 28 28 24 22 20 18 16 14 12 10 T1 26 Moisture content, % T1 T2 T3 T4 T5 D1 D2 D3 D4 D5 26 T2 24 T3 22 T4 20 T5 18 D1 D2 16 D3 14 D4 12 D5 10 10 11 12 Drying time , hr Figure : 10 11 12 Drying time, hr Moisture reduction curves at 43 oC drying temperature 107 Batch (50 oC + 43 oC, WITHOUT Air Reversal Batch (50 oC + 43 oC, with Air Reversal ) Batch (50 oC + 43 oC, WITHOUT Air Reversal Batch (50 oC + 43 oC, with Air Reversal ) 28 28 T1 26 T1 24 T2 24 T2 22 T3 20 T4 18 T5 16 D1 14 D2 12 D3 10 D4 Drying time, hr Figure : 10 11 12 D5 Moisture content, % Moisture content, % 26 22 T3 20 T4 18 T5 16 D1 14 D2 12 D3 D4 10 10 11 12 D5 Drying time, hr Moisture reduction curves at 50 oC + 43 oC drying temperature 108 The following remarks could be pointed out: - The effect of air reversal was very apparent in reducing the final moisture differential (FMD) Without air reversal this FMD was larger than % point With air reversal, it was less than % point; even that the grain quantity dried was much more than the former case - For this lab dryer, air reversal did not decrease the drying time, because for the same airflow, with less grain on the floor, the specific airflow rate (per ton) was higher in the case air was not reversed - The drying temperature is stable and can be kept within ± oC The above remarks not offer much new findings; yet the tests give specific and handy data for preparing training materials on rice drying, as part of the Project activities The problem of non-uniformity of the input materials for testing is reflected with data on the bulk density of the input (wet) as well as the output (dried) paddy (Fig 9) SRA-1, Ba-Ria VT, Dec.2006 (DRIED paddy) Bulk density, kg /m3 640 620 600 kg/ m3 580 Regression 560 540 520 18 20 22 24 26 Bulk density, kg /m3 SRA-1, Ba-Ria VT, Dec.2006 (Wet paddy) 28 700 650 600 550 500 12.0 12.5 13.0 13.5 14.0 Moisture content, % wb Moisture content, % wb (b) (a) Figure 9: Bulk density of the wet (a) and dried paddy (b) used in the tests The learning experience from the tests have been: A balanced set of experimental data for drying treatments of even ton each is difficult to obtain under actual field conditions Perhaps, a quantity of around 20 kg each is more appropriate Even so, cold storage room is needed for conditioning the grain for one-week-long testing Miscellaneous equipment such as cleaner is also needed All these rigorous procedures would give pure academic results, which in fact not reflect the realities, as the graph on the bulk density showed Thus in the future, an alternative -that several drying researchers followed - would be modeling of the drying process This hopefully can cope with diversities in material conditions as well as ambient conditions Another constraint was the laboratory milling equipment for milling analysis (for head rice recovery) could not be standardized for proper operation at the time Page 109 THE PRRA SURVEY ON THE USE OF FLAT-BED DRYER AND THE COST OF VARIOUS DRYING METHODS IN THE MEKONG DELTA By the terms of the contract, two other activities were conducted: The survey using the Participatory Rapid Rural Appraisal (PRRA) method on the use of flat-bed dryer in the Mekong Delta and the cost of drying; and the writing of extension materials for future training courses, based on the outcome of the survey and experiments 5.1 Background The flat-bed dryer has been with the rice agriculture in the Mekong Delta of Viet Nam since early 1980’s Its development over the past 25 years and its current status need to be examined in the context of the CARD Project 026/VIE-05 with focus on the cracking of paddy grains in the area Thus a survey using the PRRA method on the use of flat-bed dryer in selected Provinces of the Mekong Delta was conducted 5.2 Objectives - To confirm the role of flat-bed dryers in reducing post-harvest losses and in preserving rice quality - To identify operating factors of the flat-bed dryer which contribute to the reduction of rice crack - To identify problems with the flat-bed dryer that the CARD Project could possibly help 5.3 Method The survey used the PRRA method, through interviewing different people class, from farmers to rice millers to governmental officials… But it also relied heavily on both available data gathered in the past 10 years by various agencies, and on personal experience of the people involved with the dryer at NLU over the past 20 years Four Provinces were selected, namely Can-Tho City, Kien-Giang, Long-An, and Tien-Giang The first three Provinces have sites which had been selected by the CARD Project for all related experiments, demonstrations, and extension activities The fourth Province is adjacent to Long-An, and also planned as site for rice milling survey, so facts and data on the dryer would be relevant Note: Can-Tho = Can-Tho City, which used to be part of Can-Tho Province, and is about half of the latter in terms of rice land 5.4 Result and discussion 5.4.1 Background data The Provinces under study have similar data in terms of climate and other agricultural features All have the average monthly temperature of 27- 28 oC, with the average maximum of 29 oC in April and minimum of 25 oC in January But the temperature difference between daytime and night time is more pronounced, say between 25 and 36 oC in hot months, or 23 and 33 oC in cooler months Page 110 The rainy season in the region occurs from May to October, the remaining months are dry season (no Spring, Summer …Winter like in Northern Provinces) The annual rainfall is 400 mm in Long-An, and higher in Can-Tho and Kien-Giang (1 600 and 1800 mm respectively) The average annual relative humidity is 80- 82 % This just says that is typical tropical humid climate, and not specific enough about its significance in post-harvest Figure 10 presents average variation of a typical day of March (dry season) and of August (rainy season) in Can-Tho, which is very similar to that of other places in the Mekong Delta Whether in rainy or dry season, the relative humidity during the night time (21h00 PM to 7h00 AM) is very high, over 90% This is totally different with Australia, where the RH is below 70 % even in night time The implication is the moisture re-absorption of the grain during storage 100 90 80 70 60 50 40 30 20 10 42 40 38 36 34 32 30 28 26 24 22 12 15 18 21 Rel.Humidity, % Temperature, oC Temperature and Rel.Humidity, CAN-THO (average 1988- 1992) 24 Tim e of the day (12= noon ; 24 = m idnight) oC-March oC-August %RH-March %RH-August Figure 10 Weather data of a typical day in March and August, at Can-Tho Province (average 1988- 1992) Specific data pertaining to each Province are shown in Table Table 4: Selected data of the Provinces under survey Can-Tho Population (2005), million Kien-Giang Long-An Tien-Giang 1.14 1.65 1.41 1.70 of which % in agriculture/ rural area Rice Yearly PLANTED area, Rice production, 50 76 83 85 231 000 million ton 596 000 430 000 252 000 1.23 2.90 1.93 1.31 of which % harvested in rainy months 47 ≈350 Number of flat-bed dryers % of wet-season paddy dried by machines ≈15 (10- 20) 48 1100 35 580 24 # 60 300 22 ## 12 Source: General Statistics Office, Ha-Noi, Viet Nam, http://www.gso.gov.vn/ (2005) Danida ASPS Report (2004) # Mr Con, Office of Long An Rural Development (2006) Page 111 ## Mr Viet, Post-harvest Advisor at Tien-Giang Province(2006) 5.4.2 Post-harvest and drying status a) The number of flat-bed dryers in the Provinces is listed in Table Long-An and TienGiang are more backward in terms of dryer development b) The flat-bed dryer was first installed in these Provinces in the early 1990’s These were “first-generation” conventional flat-bed dryer with central air inlet to the plenum chamber, using flat-grate rice husk furnace with precipitation chamber (Fig.11) Later, “second-generation” flat-bed dryer with side-duct plenum (Fig.12) and improved rice husk was installed between 1995 and 1997 in these Provinces Last, the “thirdgeneration” reversible dryer (the principle is shown in Fig.13), with its advantage of saving labor and land space, was introduced first at Long-An in 2000, and at Tien-Giang and Kien-Giang in 2002 There are now about 400 reversible dryers in the Mekong Delta, among which 30 units are from original design and installed by NLU, which include about 15 units in the Provinces under study c) The percentage of mechanically dried paddy is not evenly distributed within each Province For example, Kien-Giang with an average of 24%, yet in many villages, only % of the paddy harvested in the wet-season is mechanically dried d) The percentage of mechanically dried paddy might not proportional to the number of dryers, but also depends on the weather That is why in Can-Tho, different sources quote different percentage, from 10 to 20 % e) Mechanical drying not only reduces post-harvest losses, but also preserves grain quality This fact is widely recognized now by farmers, rice millers, governmental officials, which is a different view compared to about 10 years ago f) Despite the above salient advantage, the majority still practice sun drying For example, in Can-Tho, while the installed drying capacity can meet 25 % of the harvest, yet only 15 % is dried by machine One source even says that 90 % are sun drying, consisting of 40% on earthen yard, 40 % on cement yard, and 10 % on roadside g) The reason lies with the drying cost, while the quality factor does not account much under the present agricultural production and trading system Our data gathered from Long-An resulted in Table Table 5: Drying cost under different settings (the details of the raw data will be provided later) Mode VNdong /kg US$ /ton SRA-4 (reversible, 4-ton/batch) dryer, with rice husk furnace 98 6.1 SRA-8 (reversible, 8-ton/batch) dryer, with rice husk furnace 79 4.9 80 5.0 SDG-4 (reversible, 4-ton/batch) dryer, COAL furnace 130 8.1 Sun drying, in the dry-season harvest 70 4.4 Sun drying, in the wet-season, normal (moderate) weather 140 8.8 Sun drying, in the wet-season, ADVERSE weather 210 13.1 SDG-4 (reversible, 4-ton/batch) dryer, rice husk furnace Note: Page 112 # #1: SDG-4 = A “lower-cost” reversible ton/batch dryer, made by a local manufacturer in Dong-Thap Province This dryer uses the fan design transferred by NLU, but with a devised drying bin which reduces material costs, while still ensuring airflow uniformity through a “distributed center tube” from the fan outlet (Fig 14) From Table 5, the following remarks can be made: • In the dry season, the mechanical drying cost of the SRA-4 dryer (98 VND/ kg) is still higher than the manual sun drying cost • In the wet season, the mechanical drying cost is lower than sun drying cost Thus a charged drying fee of % of paddy value, or about 130 VND/kg, would enable the dryer owner to recover the investment after 2- years, depending on the investment • From the farmer’s (paddy owners) standpoint, they would not spend more than sun drying in the normal weather, and surely the paid fee is cheaper than sun drying in the worst, adverse weather This has not yet taken into account the cost of paddy deterioration, as reflected in the sale price drop of 10- 20 %, or 270- 540 VND/ kg • SRA-8 dryer, with rice husk furnace, and SDG-4 dryer with rice husk furnace are alternatives to further reduce the drying cost • However, the SDG-4 dryer with coal furnace is not recommended, since the drying cost is so high that makes the operation unprofitable for the dryer owner to recover the investment • The drying cost does not include yet the transportation cost charged to the grain owner, which is 10- 12 VNdong /kg or US$0.6- 0.7 or about 10 % of the proper drying cost Figure 11: Conventional FBD with central air inlet to the plenum chamber Drying Air UP Figure 12: Conventional FBD with side-duct plenum Drying Air UP 0.3m Grain Drying Air DOWN Grain 0.6m Grain CONVENTIONAL SHG FLAT-BED DRYER Floor: 50 sq.m / ton REVERSIBLE SRA DRYER Floor: 25 sq.m / ton Figure 13: Principle of reversible-air dryer Page 113 Figure 14: SDG-4 (reversible, 4-ton/batch) dryer, shown with the coal furnace, and the solar collector (a new development at NLU in early 2007) 5.4.3 Conclusions The above facts and analysis point to a single major problem in drying at the four Provinces under study, which is: The unbalanced between drying cost and drying benefits While the drying cost is real and quantified, the drying benefits might not be so Better-quality rice due to mechanical drying may not be bought by traders with a price higher enough to compensate for the drying cost Possible reasons are: - The output grain was not good due to improper dryer operation - Even with proper dryer operation, the output grain was not really good, because farmers only brought paddy to the dryer as a last recourse when paddy was about to deteriorate after days of rain - The good-quality dried rice was mixed with the bad sun-dried rice, for convenience in transporting in a same boat-load - The quality of the mechanically-dried grain was not yet appreciated enough by the market A few percentage point more of head rice recovery might not command a paddy price superior enough to compensate for the drying cost - Even in case the mechanically-dried grain obtained higher price, its effects did not benefit the farmer growing rice, because the rice miller got practically all advantages from the head rice recovery Farmers own paddy, while rice millers and traders own white rice! Thus the drying problem in 2007 differs from that of 1997: It is no longer (or much less in scope) of quantity post-harvest losses, it is more on quality post-harvest losses Thus this CARD project is timely because it addresses this issue It will take sometime before the farmers and traders will realise that the quality is as important as quantity and the price of the paddy will also be determined by both factors This is also a matter of policy from the relevant institutions to encourage the adoption of these practices through financial measures, although the policy affecting the whole rice system is complicated and not easy to alter in a few months But as far as the CARD Project is concerned, an integrated system from paddy supply to drying to milling, which involves farmers, should be Page 114 established as demonstration sites in all the Provinces in Mekong Delta after successful implementation of current project in three cooperatives in three provinces EXTENSION MATERIALS FOR TRAINING COURSES, BASED ON THE OUTCOME OF THE SURVEY AND EXPERIMENTS Based on the outcome of the survey and experiments (Section 3, 4, and 5) a hand-out for training has been prepared in Vietnamese, which includes the following topics: - Development of flat-bed dryers in the Mekong Delta in the past 25 years and problems solved by mechanical dryers - The issue of the rice grain crack and the consequent post-harvest losses - Ways to avoid rice cracking with mechanical drying - Current research from CARD Project relating to rice crack - Preliminary results with the eight-ton-per-batch SRA-8 dryer (version 2006) - Economic calculation for the SRA-8 dryer at Tan-Phat A Cooperative The hand-out was used for a training course held at Tan-Phat-A Cooperative in 25 and 26 February 2007, with about 50 participants including farmers, rice millers, and governmental extension staff (Fig.15) Figure 15: Training course on drying at Tan-Phat-A Cooperative, February 2007 Page 115 CONCLUSIONS AND FURTHER PROPOSALS In the first year of the Project (actually within 10 months), the sub-component on the flat-bed dryer has completed a number of activities: - Installation and testing of an 8-ton reversible dryer in Kien-Giang Province - Installation of two 4-ton dryers for the Go-Gon Cooperative (instead of one 8-ton dryer) One dryer equipped with the solar collector has already been installed by the time this report is being submitted This new collector was developed at Nong-Lam University in 2006 for macaroni, and also tested on the STR-1 with promising result (Fig.16) The other ton dryer is being installed - Installation of one 8-ton reversible dryer at Tan-Thoi Cooperative, Can-Tho City, which is another selected by the CARD Project for experimentation and demonstration - Fabrication of the 1-ton mini-dryer for basic testing at Ba-Ria Vung-Tau near Nong-Lam University - Rapid survey on the current status on the use of flat-bed dryers in Provinces - Writing of the hand-out for use as training materials, based on the outcome of the survey and experiments During the coming second year of the Project, the following activities for the flat-bed dryer Sub-Component is being implemented: To conduct more test and analyze the rice cracks in the dry and the wet season harvest, at various actual dryers in the production It is time now to be applied at production scale, especially during the dry season harvest Paddy crack in the dry-season harvest is even more severe, as people rely more on the pavement natural sun drying to save the cost of fuel for drying To study on ways to integrate the dryer in the whole chain of rice post-harvest, so that the benefit and paddy drying reflect back to increase farmers’ income by their active participation, as analyzed in Section 5.4.3 and 5.4.4 Figure 16: Solar collector tested with STR-1 dryer in Moc Hoa (Long An), 2006 Page 116 EVALUATION OF FARMERS’ PRACTICE 8.1 Value losses due to field drying and sun drying Currently, most of the farmers apply a half time field drying (1-2 days) followed by half time sun drying (1-2 days) We undertook experimental work in the farmer’s field to compare sun drying with mechanical drying (Binh, 2007).* When full time sun drying was applied in the winter-spring crop, the following data (Table 6) was obtained for different varieties Table 6: HRY (%) of different drying methods for some varieties of winter-spring crop Variety Sun drying Difference between Shade drying Mechanical (control) drying (flat-bed (plastic, Ts = mechanical and sun 42-48oC) dryer) drying (SD%) OM1490 49.12a 49.62a 47.45b 2.17 OM2517 a 49.05 a b 3.80 50.67 a b 6.03 51.31 a b 3.08 Jasmine Sticky rice 48.67 a 50.36 a 50.56 45.25 44.64 48.23 Note: the values with the same supper script letter in a row are not significantly different (P > 0.05) Ts is the surface temperature of the grain layer The results presented in Table 15 suggests that flat-bed drying is as good as control sample (in shade drying, SD) whereas, sun drying on plastic net as current practice of the farmers reduced the HRY significantly (SD = 2.17 – 6.03%) For the OM2718 and AG24 varieties, average losses of HRY 3.77% can be used In order to calculate the HRY losses of the farmer who applied both field drying (FD) and sun drying (SD), the following equation was introduced: Losses of HRY = FD% f + SD% s Where, f and m are the days of field and sun drying; FD = 8% is the losses of HRY due to field drying (as reported by Cuong, 2003) and SD% is the losses of HRY due to sun drying The fractions f and s are assumed to be the constants in the following Table 16 depending on the actual drying situation: Table 7: Loss factors f and s for combination of field and sun drying currently practiced by farmers Actual drying method f s note Full time sun drying 3-4 days Full time field drying 3-4 days Half time field drying and sun drying 0.5 0.5 1-2 days field drying and 1-2 days sun drying Page 117 Table 8: Losses of HRY in equivalent to losses of paddy (kg/100kg yield) for different varieties in the MRD due to current practices of field and sun drying of the farmers Variety OM1490 OM2718 Jasmine AG24 Losses (%) 7.32 8.97 10.45 7.87 On average, losses due to field and sun drying are around 8.7% This loss is for winter-spring season The losses in the wet season (Summer-Autumn crop, July/August) are expected to be much higher due to changeable weather of rain and storm Data collection from farmers will continue this year in wet season *Binh, Ngo (2007) Study the effect of sun drying and mechanical drying on the milling rice quality of different varieties Study Report under CARD 026/05VIE project REFERENCES Ministry of Agriculture-Rural Development, and Danida ASPS 2004 Study on the current status and need assessment for post-harvest equipment in the Mekong Delta (Compiled from Reports and 12 Provinces) Internal Report (in Vietnamese) Phan Hieu Hien 1987 Grain dryer for the summer-autumn crop in Southern Vietnam Journal of Agricultural Science and Technology, No 6-1987, Ministry of Agriculture, Ha-Noi Phan Hieu Hien 1998 Grain dryers and rice quality in the Mekong Delta of Viet Nam: Development process and perspective (In Vietnamese) Paper presented at the 15th Science and Technology Conference of the Mekong Delta , Ca Mau City 24 & 25 –9 –1998 Phan Hieu Hien 2000 Research and Extension on Rice Dryers in Vietnam: a Sketch of 20Year Evolution Paper presented at the Seminar on “Rice research and development in Vietnam for the 21st century; and aspects of Vietnam-India cooperation”, at the Mekong Delta Rice Research Institute, Can-Tho City, 18 & 19 September 2000 Phan Hieu Hien, Nguyen Hung Tam, Nguyen Van Xuan 2003 The reversible air dryer SRA: One step to increase the mechanization of post-harvest operations Proceedings of the International Conference on Crop Harvesting and Processing, 9-11 February 2003 (Louisville, Kentucky USA) ASAE Publication Number 701P1103e Post-harvest Project of Can-Tho Province 1998 Report on the survey of paddy dryer and drying in Can-Tho Province Page 118 10 APPENDIX 10.1 Appendix : Paddy milling quality analysis (procedure by IRRI) Page 119 ...SECTION FLAT BED DRYING INCLUDING SURVEY RESULTS ON THE DRYING COSTS OF VARIOUS DRYING METHODS PRACTICED IN MEKONG DELTA 93 CARD Project FLAT- BED DRYER Sub-Component 2006/2007 Report Reporting... context of the CARD Project 026/VIE-05 with focus on the cracking of paddy grains in the area Thus a survey using the PRRA method on the use of flat- bed dryer in selected Provinces of the Mekong. .. flat- bed dryer in the Mekong Delta and the cost of drying; and the writing of extension materials for future training courses, based on the outcome of the survey and experiments 5.1 Background The