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Post Harvest Management

Post Harvest Management
29
Jul

‘Hand Operated Winnower’ Improved Rice Quality and Income


Mr. Dwan Khream is a small farmer of the Ri-Bhoi district in Meghalaya. Among other vegetable crops, he mainly grows rice on his 1.5 acre of land which falls under 50 per cent plain and 50 per cent sloppy categories- a prominent feature of the ‘hill farming’ in the NEH region. Despite good yield from paddy, Dwan did not make profit by selling it at nearby market as impurities mixed with rice due to traditional winnowing method had reduced the price of the paddy. Then, on advice of scientists, he used “Hand Operated Winnower” which made winnowing easier and resulted in better income.

Traditional winnowing

Total 5-6 labours are required to start traditional paddy cleaning where rice crop is beaten by two or three persons on wooden logs. After collecting the rice in big baskets, these are raised above the head by a person standing on a self-made bamboo-frames platform to clean husk and impurities from rice. Sometimes, the person has to stand long on the bamboo-platform to wait for a gust of wind. Under such threshing operation, the standing person has to balance himself against the flow of wind. Since the method of paddy cleaning is wind dependent, arrival of monsoon, or untimely rains, also got spoil the rice crop permanently. Other than this, many farmers use dao (chopper), spade, hoes, sickles, country plough, bamboo made leveller, and transporting baskets for different farm jobs. Following the age-old threshing technique, rice quality deteriorated, resulting into poor market price of the same crop.

Hand operated winnower
Agriculture Engineering Division of ICAR-RC-NEH Region, Barapani demonstrated ‘Hand operated winnower’ to few farmers in Meghalaya, so that they could clean paddy crop timely maintaining. Practically, the Hand Operated Winnower is a machine that uses fan blades, chain and sprocket arrangement to enable fan operations faster with little effort. Weighing around 29 kg, the Hand Operated Winnower is provided with a fan guard to prevent any accident

Extra Income Generation
Dwan purchased the machine at Rs 3,000 from the ICAR institute. He re-threshed his paddy and noticed the difference. This time, he got better quality rice follwed by better market price thereafter. Seeing the difference of rice threshing comparing the old ones, a few of his close friends came to him and used the machine. They were satisfied with the quality of rice. After a short while, on hearing the news that Hand Operated Winnower increased incom, a large group of fellow rice farmers swarmed around him.

Mr. Dwan decided to rent the winnower out to fellow farmers at Rs. 100 per user in the local area which brought him Rs. 3,000-5,000 in one-year duration from 2011 – 2012.
“If small and marginal farmers go for it, rice crop alone can give them extra money, and a suitable job also,” said Dwan to fellow farmers during a recent training programme at ICAR-Barapani. There is considerable scope for this technology, since rice covers about 3.5 million hectare (10% of the total rice growing area of the country) in NEH Region. On an average, output of the winnower, taken by the local farmers, was recorded to be as 2.5-3.5 q/h.

File Courtesy: 
NAIP Mass Media Project, DKMA, with input from ICAR-RC-NEH, Barapani and Agriculture Engineering Division, ICAR
26
Aug

Reporting

Calculate the following data to characterize the performance of the dryer: 

1. Average and standard deviation of the moisture content before and after drying.  

2. Total weight loss of paddy

3. Drying rate (%/h)

4. Increase in broken grain (i.e. percentage of broken grains before drying minus percentage of broken grains after drying)

5. Increase in cracked grain (i.e. percentage of cracked grains before drying minus percentage of cracked grains after drying)

6. Electric power consumption/Fuel consumption

File Courtesy: 
http://www.riceindia.net/RKBank/Training_Manual_Paddy_Drying.pdf
26
Aug

Drying test

1.Paddy of a known source should be selected with grain moisture content that is typical for grain harvested in the area. 

2. The paddy should be cleaned to remove very few impurities (straws, etc).

2. Before loading the materials, mix the paddy and take at least 10 samples of the paddy of 10g each to determine variance in moisture content. 

3. In addition, sample of 500g of wet paddy is taken for laboratory analysis. If possible, take the entire weight of the paddy before loading.  

File Courtesy: 
http://www.riceindia.net/RKBank/Training_Manual_Paddy_Drying.pdf
26
Aug

Evaluation of grain dryers

1. After purchase or instalment of a grain dryer it is important to evaluate its performance.  

2. This is usually done by conducting a drying test. 

3. Drying tests are important because actual performance data are often different from rated performance that is provided by the manufacturer. 

File Courtesy: 
http://www.riceindia.net/RKBank/Training_Manual_Paddy_Drying.pdf
26
Aug

Troubleshooting

1. A drying system can only maintain quality but it cannot improve the quality of paddy. 

2. When a dryer produces poor quality paddy it is therefore important to compare the paddy from the dryer with a reference sample from the same batch that was dried under controlled conditions, e.g. in an air-conditioned room, or in the shade by spreading a thin layer and frequently mixing.

3. Otherwise it is difficult to tell whether the low quality is caused by quality reduction that occurred before drying, e.g. during field drying, or in the drying system.

File Courtesy: 
http://www.knowledgebank.irri.org/rkb/index.php/examples-ofdryers/troubleshooting
26
Aug

Conclusions for Economic Feasibility Studies

Considering the issues in the last two sections the following recommendations for economic analyses of mechanical drying can be made: 

1. Investing in a dryer for saving the crop. 

2. The problem is that in this case the fixed cost component of the drying cost (depreciation) per batch is very high because the dryer is only used in emergency, meaning a few times a year.

3. A dryer used only in emergency cannot be used economically.

File Courtesy: 
http://www.riceindia.net/RKBank/Training_Manual_Paddy_Drying.pdf
26
Aug

Cost of drying

1. Case studies in Asian countries indicate that mechanical dryers with cost higher than 5% of the paddy value cannot be introduced successfully.

2. There is no point in listing cost numbers for different drying systems here since drying cost depends on many site specific factors and a “business plan” including a cost-benefit calculation is needed for each individual drying system considering the conditions of the locality.

File Courtesy: 
http://www.riceindia.net/RKBank/Training_Manual_Paddy_Drying.pdf
26
Aug

Weight loss in drying

1.During the drying process water is removed from the grains .

2. That means that after drying, paddy weight is lost and the dried paddy is to be sold since in most markets paddy is traded on a weight basis.

3. In markets, where paddy is still traded on a volume basis there is a similar effect since paddy shrinks in volume during drying also. 

File Courtesy: 
http://www.riceindia.net/RKBank/Training_Manual_Paddy_Drying.pdf
26
Aug

Potential Economic Benefits from Drying

Depending on the prevailing frame conditions and the postharvest system the use of mechanical dryers might provide the following economic benefits                    

Economic benefit Pre-condition constraints:

1. Increased market value of the (higher quality) paddy 

2. Existing and significant price differentiation for different quality levels must compensate for drying cost plus weight reduction occurring during drying

File Courtesy: 
http://www.riceindia.net/RKBank/Training_Manual_Paddy_Drying.pdf
26
Aug

Economic aspects of drying

1. The use of mechanical drying systems offers so many advantages over sun drying like maintenance of paddy quality, safe drying during rain and at night, increased capacity, easy control of drying parameters and the potential for saving on labour cost. 

2. Reasons for failure of introduction of numerous drying systems have been attributed. 

3. The constraints can be grouped under headers related to technology, know-how, post-production system, management and economics.

File Courtesy: 
http://www.riceindia.net/RKBank/Training_Manual_Paddy_Drying.pdf
26
Aug

Two stage drying

The requirements for quick drying immediately after harvest to moisture content that is safe for temporary storage, the two-stage drying system or combination drying system was developed.

1. A typical first stage dryer takes advantage of the fact that surface moisture can be removed rapidly from very wet paddy without causing any damage to the grains by using very high temperature for a short period of time. 

File Courtesy: 
http://www.riceindia.net/RKBank/Training_Manual_Paddy_Drying.pdf
26
Aug

Centralized drying

1. Economics of scale in drying can often only be reached through centralized dryers in a strategic location where enough paddy can be collected to be dried in a machine with sufficient capacity. 

2. Centralized drying can be done by farmers’ cooperatives or small contract operators at village level, at local rice mills or at collection points in the trading system. 

File Courtesy: 
http://www.riceindia.net/RKBank/Training_Manual_Paddy_Drying.pdf
26
Aug

De-centralized On-farm drying

1.Ideally the paddy needs to be dried on farm level immediately after harvest, which is mostly done through sun-drying.

2. For the production of better quality rice and the prevention of the weather risk farm level dryers can offer solutions, if the following criteria are taken care of: 

File Courtesy: 
http://www.riceindia.net/RKBank/Training_Manual_Paddy_Drying.pdf
26
Aug

Drying strategies

1.  Paddy should be dried as quickly as possible but other considerations regarding the rice postproduction system and economic criteria have to be taken into account when developing a drying strategy. 

2. Options include de-centralized on-farm drying, centralized drying at collection points and two-stage drying also referred to as combination drying.

File Courtesy: 
http://www.riceindia.net/RKBank/Training_Manual_Paddy_Drying.pdf
26
Aug

Dust collection system

1. Grain handling will create dust, making 

working around a grain drying hazardous.

2.  Efficient dust collection systems should be installed around the dryer to remove dust in and around the dryer.  

3. The conventional system for dust collection of grain is the cyclone.  

4. As with other accessories, fan and cyclone need to be properly sized depending on the dryer specifications.

File Courtesy: 
http://www.riceindia.net/RKBank/Training_Manual_Paddy_Drying.pdf
26
Aug

Conveyors and Elevators

1. Using conveyors and elevators for horizontal

and vertical transport of grains to load, circulate or discharge grains will improve the efficiency of the drying operation and reduce labour cost. 

2. Elevators should be properly sized so that they match the capacity of the dryer.

3. A properly designed bucket elevator for a re-circulating batch dryer can easily reach capacities of 10 t/h.

 

File Courtesy: 
http://www.riceindia.net/RKBank/Training_Manual_Paddy_Drying.pdf
26
Aug

Moisture meter

1. Keeping track of grain moisture content during

drying is crucial to properly dry grain; that is, to avoid over drying or incomplete drying.

2. Over drying leads to monetary loss when selling the grain and reduced milling yields due to cracking of the brittle dry grains.

3. Incomplete drying causes qualitative and quantitative losses due to fungal growth, insect activity and respiration.

File Courtesy: 
http://www.riceindia.net/RKBank/Training_Manual_Paddy_Drying.pdf
26
Aug

Paddy Pre-cleaner

1. Paddy Pre-cleaner: Fines in rice create dust

during the loading and drying process and reduce airflow through the rice grain.

2.  Pre-cleaners are indispensable in many drying systems. 

3. Pre-cleaners usually consist of a scalper that lets through the grain but retains straw and a smaller second screen that removes small stones and other impurities.

4. An air aspirator will suck out dust and light empty grains.

File Courtesy: 
http://www.riceindia.net/RKBank/Training_Manual_Paddy_Drying.pdf
26
Aug

Safety considerations for Solar drying

For safe operation of the burner, the dryer needs to be equipped with: 

1. A flame control to turn off fuel supply in case of ignition failure (automatic burners in re-circulating batch dryers).

2. In gravity-fed pot-type burners a safety device that turns off fuel supply when there is a power failure that shuts of the fan.

3. High temperature limits switch or temperature control to prevent overheating.

4. Proper electrical wiring of all electric components.

File Courtesy: 
http://www.knowledgebank.irri.org/rkb/index.php/safety
26
Aug

Solar Drying

The use of solar energy as a heat source (solar drying, solar assisted drying) has been evaluated intensively by many projects and institutions. While some solutions were proven to be technically feasible none was successfully commercialized for paddy drying because of the following reasons: 

File Courtesy: 
http://www.riceindia.net/RKBank/Training_Manual_Paddy_Drying.pdf
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