Moisture reduction technologies for freshly harvested cereals

Code No: TMS010 Price: 500 Category: Foods & Agriculture: Optimum use of Soil

Moisture reduction technologies for freshly harvested cereals
The primary objective of this report has been to present the following aspects of moisture reduction techniques for freshly harvested cereals and akin products:

Need for moisture reduction in freshly harvested cereals.
Techno-economic requirements of actual users.
Survey of published options.
Techno-economic performance of pilot plants established and actual user’s reaction on acceptance.
Probable option, their techno-economic analysis, and actual user’s reaction
Preferred type of fuels and their availability.
Evaluation of promising option and its critical analysis.
Problem areas which require further investigations;
Action considered necessary for promotion and induction of promising technology.

2. Methodology

The report is based on published information presented in journals, paper, monographs and reports on the subject. The draft was discussed with leading experts in the field. The present (final) report incorporates their suggestions.

3. Need for Improved Drying Methods

Traditional methods of drying infields, courtyards and on rods by direct exposure to sunshine, practiced in India from times immemorial, are no more appropriate. These methods were adequate with the traditional methods of production of food grains, when the inputs and yields per hectare were low. With the introduction of higher yielding varieties, use of fertilizers, pesticides and irrigation facilities, there has been an extraordinary increase in inputs and yields. The problem of harvesting, threshing and drying has increased, because of increased amounts of crop that have to be handled per unit area. The most importance factor which affects post harvesting losses is rain during or immediately after harvesting. Analysis of published precipitation data during or immediately after harvesting of paddy, wheat, jowar, maize and bajra for states of India reveal the probability of rain during harvesting as:

Paddy	28.4, 15.2 and 11.7 percent, respectively, for Tamil Nadu, Uttar Pradesh, and Andhra Pradesh.
Wheat	16.7., 9.7 and 7.1 percent, respectively for Uttar Pradesh, Bihar and Madhya Pradesh.
Jowar	24.7, 13.9, 12.3, 9.7 and 9.7 percent, respectively, for Tamil. Nadu, Karnataka, Andhra Pradesh, Madhya Pradesh and Maharashtra.
Maize	63.2, 59.0, 41.6 and 30.6 percent, respectively, for Himachal Pradesh, Karnataka, Jammu & Kashmir and Uttar Pradesh.
Bajra	18.2 and 6.2 percent, respectively, for Andhra Pradehs and Maharashtra.

Results of analysis of published precipitation data and average crop production in the respective states show that the percentage of food crops which are prone to higher post harvesting losses are:

Crop	% of Total Country’s Production
Paddy	36.44
Wheat	51.64
Jowar	92.83
Maize	60.30
Bajra	10.41

The only option available to minimize this loss is installation of, and/or making available, suitable drying systems at the village or at appropriate levels within easy approachable distance.

Under normal weather conditions, farmers have little incentive to dry their produce. Whenever the crops are damaged due to adverse weather conditions, during of immediately after harvest, the government generally advices the procurement agencies to accept even adversely affected cereals, to mitigate the hardships faced by the farmer.

4. Optimal Location for Dryers

A detailed analysis of production, market arrival and procurement by government agencies shows that, except in the states of Haryana and Punjab, the major part of production of cereals is retained at the farm all over the country. All Indian figures of percentage retained at farms are:

Cereal	Production	Retained at farm	Brought to Market for Disposal	Procured by State Agencies
Rice	100	68.8	31.2	14.7
Wheat	100	74.3	25.7	22.8
Jowar	100	87.5	12.5	0.5

Scrutiny of above data shows that, to minimize post harvest losses, drying facility for the produce has to be made available at the farm or village level.

5. Affordable Cost of Drying & Feasibility of Using Existing Facilities (Diesel Pump Set & Utility Power) for Crop Drying

Under normal conditions, a saving of 2 to 3 percent can be achieve, that too only during the kharif season, by the installation of a dryer. The maximum affordable cost of drying, with an optimistic saving of 10 percent due to introduction of drying, is estimated to be around Rs. 0.15 per kg. based on an average procurement price of Rs. 150/100 kgs of cereals. As on date, around 88 percent of Indian villages are electrified. A very high percentage of Indian villages have more than one diesel pump. Thus, it will be ideal if these could be used for drying freshly harvested cereals. It is technically feasible to dry freshly harvested cereals using either utility power and /or diesel pump sets. A detailed study on the use of utility power and/or diesel pump sets for drying revealed that the direct cost of drying freshly harvested cereals using utility power (@ of Rs. 0.30/KWh) and diesel pump (@ Rs. 4 per liter of diesel) is estimated to be Rs. 0.28 and Rs. 0.50 per kg, respectively. This is more than the maximum affordable drying costs even at an optimistic saving of 10 percent. More over, as there is shortage of both electricity ad diesel, it may mot be possible to use either of them for drying, logically.

6. Duration for which Dryer is Required

Actual users required a dryer during, and immediately after, harvesting (a period which is normally restricted to only 15 to 20 days). Even during this period, dryers are not required to be operated at the raised capacity. As on date, no farmer, not even the state farm organizations, is using any drying system to dry freshly harvested cereals, primarily because returns accruing from the use of drying systems have not yet been found to be commensurate with the investment required.

7. Optimal Dryer Capacity & Affordable Capital Cost of Drying Systems

A detailed analysis of various categories of holding reveal that the dryer capacity required, and affordable capital costs of dryers, for each category of holdings are as under:

Category of Holding	Av. Yield in Kg./Holding per Crop	Optimum Dryer Capacity Reqd. Kg./Day	Affordable capital Cost of Dryer in Rs.
Marginal	223	30-50	125
Small	840	50-10	400
Semi-Medium	1662	100-200	600
Medium	3490	300-400	1400
Large	10,105	500-1000	7580

8. Spatial Distribution of Cereal Procurement & Probability of Precipitation During Harvesting

An analysis of spatial distribution of cereal procurement and probability of adverse weather conditions shows that the majority of rice and wheat is procured from areas which have very low probability of adverse weather conditions. Only the areas from where Jowar is procured have a higher probability of adverse weather conditions. However, since the quantity o jowar procure is very small, requirement for dryers by procurement agencies for drying of freshly harvested cereals is negligible. As on date, no procurement agency is drying any freshly harvested grains using driers. Although Food Corporation of India has installed around sixty driers to dry freshly harvested cereals, they have rarely been used for the purpose.

9. Published Options

Realizing the importance of drying freshly harvested cereals, extensive development work was initiated in India and abroad. This resulted in establishment of:

120 nos. of small scale solar dryers;
80 nos. of community/ commercial solar dryers; and
10 nos. of agricultural waste, furnace/dryer

Around the world, the results of which were published, in around 40 countries. The contribution of India in this regard has been significant. The number od dryers established in the country are:

26 nos. of small scale solar dryers;
12 nos. of community/commercial scale solar dryers;
8 nos. of agricultural waste furnaces/ dryers.

Analysis of the results of the above studies revealed:

i) Development work and pilot plant studies have resulted in the perfection of technology of drying of cereals and akin products.

ii) Actual user is satisfied with the technical performance of dryer.

iii) However, none of the system so far developed have found actual users acceptance. This can be primarily ascribed to: higher capital cost and /or high cost of drying, which is basically due to limited period of usage of the dryer (normally only 15 to 20 days in a year).

“Published options” inability to satisfy the requirements of actual users can be ascribed due to:

a) Drying requirement of actual user is for a limited time period of operation, of around a maximum of 30 to 50 days only in a year.

b) Major losses during post-harvesting occur only during adverse weather conditions, which do not occur every year in most part of the country.

c) Under the prevailing environment, little incentive is available to the farmer to dry the cereals under normal weather conditions.

d) Extra cost incurred on drying is not commensurate with returns.

e) Drying equipment, till date, is not classified as an agricultural implement/equipment. Thus the capital investment required for establishment of dryers, is not available on softer terms.

10. Suitability of Other Types of Dryers

A study on the suitability of other types of dryers, presently being used for processing other food products, for drying freshly harvested cereals revealed that most of the dryers namely:

- Moving tray dryers used in tea industry.
- Tunnel dryers used in confectionary industry.
- Infra red dryers used in baking painted product etc.

are used not only for removal of moisture or solvent, but also effect some organoleptic changes in the product. The product after drying, cannot be changed to its original form by rewetting after being processed by these dryers. Thus, neither of the above types of dryers can be used for drying freshly harvest cereals, as rewetting characteristics of dried products an essential in case of freshly harvested cereals.

11. Basic Requirements of Promising Options

For any option to be promising, it must satisfy the following basic conditions:

a) It must allow use of major plant and equipment of the option for some of the activities essential for farming community, such as:
- Pumping of water for irrigation and/or drainage;
- Harvesting operation, like threshing, winnowing, etc;
- Preparation of fodder;
- Generation of motive power required by the farming community for various applications, including proceeding of produce, and/or production of higher value added products or improving its quality/marketability;
- Generation of electrical power to improve the quality of life, and/or improve their earning capacities.

Increased utilization of major investments on the option will reduce the cost of drying significantly.

b) It must allow the actual user to obtain major plant and equipment of the option, on softer terms and /or obtain subsidy on its procurement and installment.

c) It must use locally available fuel, ideally surplus agricultural residues.

d) It should provide 100 percent (notional) reliability in carrying out drying operations even under adverse weather conditions.

e) The farmer should be able to re-install it at an alternative site, should the need arise, without major investments.

12. Availability of Surplus Crop Residues & Agro By-products

A detailed study on the production, consumption and surplus of available crop residues and agro by-products on All India basis, was carried out by National Productivity Council. The study revealed:

i) Sufficient surplus crop residue and agro industrial by-products are available in all states for usage as fuel for any promising option.

ii) Surplus crop residue available at the village farm are:
- Paddy straw in all states
- Sugarcane trash in Andhra Pradesh, Gujarat and Karnataka only.

iii) Surplus agro- industry by-products available are:
- Rice husk (sometime also called paddy husk) in all states.
- Groundnut shell, in Andhra, Gujarat, Orissa and Uttar Paradesh. Uttar
- Cotton Gin waste, in Gujarat and Orissa.
- Saw dust in Himachal and Maharashtra.

Thus, the fuels which the promising option should use, in order of preference, are:

- Paddy straw; and/or
- Rice husk.

Usage of paddy straw is likely to be preferred as the same is available at the farm/village and, hence, cost of transportation will be expected to the minimal.

13. Routes Available for Usage of Paddy Straw or Rice Husk in Promising Option

Three routes are available to use paddy straw and/or rice husk to provide operable energy for the probable options. These are:

Biogas,
Gasification,
Combustion

14. Biogas Route

Basic constituent of both paddy straw and rice husk is cellulose. Technology for bio-degradation of cellulose to produce gas has not yet been established, although considerable efforts are afoot in this direction.

15. Gassification Route

As on date, gasification of loose biomas is not possible. Normal methods used for gasification of biomas are:

i) Fluidized bed gasification. This method of gasification is not easily amenable for small size units.
ii) Briquetting and gasification in drawn draft gassifier. This method is amenable for small sizes. For a gassifier using this technology, a briquetting machine has an important bearing on the overall economics, as the cost of the briquetting machine is substantial.

Analysis of thermogram of rice husk shows that, it is not easily amenable to gasification. Thermogram of rice straw is not readily available, it is likely to be similar to that of rice husk. Gaccifier drying system has the following limitations:

Capital cost is likely to be higher.
Use of diluted exhaust gas of internal combustion engine for drying may affect the quality of dried product.
Even under most optimal conditions, diesel will be required, at least to start the engine.

16. Combustion Route

Energy required by the promising option can be obtained by direct combustion of paddy straw or rice husk. Heat so produced can be used by either of the following methods:

- Steam route;
- Directly

The steam boiler operating in a farm environment will necessarily have to be a low pressure type, due to safety considerations.

Direct Utilization of Heat Obtained by Combustion of Biomass

Heat produced by combustion of biomass ca be directly used for drying by either of two methods, namely:

- Direct utilization of combustion gases.
- By hot air engineers to produce mechanical power and heat in combustion gases in cogeneration made.

In both the methods, a controlled combustion is required. The technology for controlled combustion of rice husk is well established. The technology for controlled combustion of paddy straw on a large scale is also established. However, controlled combustion of paddy straw on a small scale is yet to be established. The rout which shows promise consists of mechanical disintegration of paddy straw. Disintegrated paddy straw can be used in rice husk combustor with appropriate modification in the feeding mechanism.

17. Promising Options

Major requirement of a dryer for drying freshly harvested cereals are during adverse weather conditions. To improve the reliability of solar dryers under adverse weather conditions, a subsidiary heat source is essential. Major investment in solar dryer is towards establishment of solar component, which contributes towards little during adverse conditions, when the need felt for the dryer is maximum, also impact of this investment adversely affects the cost of drying. Nor, the solar component can be used for other farm related activities. Thus solar dryers are not likely to be a promising option under present environment.

Out of the options discussed, the following hold

i) Direct utilization of combustion gases: and
ii) Hot air engines

Neither of the above two options have been used for drying freshly harvested cereals on a commercial scale in the environment prevailing in the rural surroundings. In brief, hot air engine have the advantage of producing both hot air and power necessary to dry freshly harvested cereals. In addition, the engine can be used for farming related activities like irrigation, threshing, etc. Direct utilization of the combustion gases system can only provide hot air for drying. To effect controlled drying, the power required for forcing the hot air through the grains has to be obtained either through utility power or by the operation of diesel engine. From above it is apparent that hot air engines hold better promise due to their ability of :

- Simultaneous generation of power and heat: and
- multi-purpose to which they can be put.

However, although these engineers have been available for the past few years, they have not yet been widely used for drying. Similarly, though the technology of direct utilization of combustion gases has been widely used for other applications, its use for drying freshly harvested cereals on commercial scale has not been reported.

A detailed analysis of both the above options shows that hot air engines (stirring engines) show better promise, as they meet nearly all oft the basic requirement desired in the promising option outlined in Section 9 above. However, it will be prudent to test the efficiency of both the systems under rural environment to arrive at a conclusive result.

18. Further Actions Considered Necessary

To improve the acceptability of promising options for drying freshly harvested cereal, following investigations/developments are considered necessary:

i) Identification of suitable methods to obtain controlled combustion of paddy straw at a scale appropriate for rural application.

ii) Ambient air dilution system using combustion gases of paddy straw to obtain drying air with controlled temperature of 50 to 60?C.

iii) Identification of actions necessary to reduce cost of drying and installed capital costs.

iv) Development and availability of cost effective attachments to make the options amenable for use in other applications in the farm to improve the utilization of the capital investment.