Low-external Input Rice Production – Chapter 5 – Use of Rice Plant By-products Batulandak.info

Improving the taste and nutrient availability of rice straw

Enriching the rice straw

Livestock raising can be an efficient way of converting edible but relatively undigestible and unmarketable nutrients produced on the farm (like rice straw) into valuable animal products. Even though their feed value is low, the crop residues are plentiful and low cost. By using simple methods, these residues can be improved to become important components of livestock feeds.

Rice straw has a low feed value — not only because of its small amount of nutrients, but also because the nutrients that exist are not readily available to the livestock. Enriching the rice straw with nitrogen or high-quality fodder (such as leaves from leguminous trees) makes the nutrients in the rice straw more available. The bacteria in the rumen of cattle, goats or carabaos use the nitrogen to multiply quickly and they, in turn, break down rice straw nutrients into forms that can be utilized by the livestock.

Rice straw can be enriched directly by mixing it with the nutrients before feeding or indirectly by feeding the improved fodder/feeds separately and allowing the mixing of the straw and the improved feeds to take place in the rumen of the animal. Some simple methods are described below:

A. Mixing dry rice straw with fresh grasses or legume fodder in equal amounts.

B. Sprinkling salt solution (a handful of salt to 1 gallon of water) or molasses on a portion of rice straw to be given in a single feeding.

C. Treating straw with urea

1. Dissolve 400 9 (roughly 1/2 li) urea in 10 liter water (half a kerosene can). Urea increases the nutrient content of the straw.

2. Sprinkle the solution over 10 kg dry rice straw (about 2 sacks, tightly packed).

3. Mix thoroughly.

4. Tightly pack the mixture in an airtight container (concrete or clay container, barrel or drum, or pit lined with plastic or clay).

5. Seal the top with plastic so the ingredients will ferment in 10-21 days.

6. Once the container is opened, the treated rice straw should be consumed within 14-21 days.

D. Providing urea, molasses and water as a healthful drink to ruminants above 6 months old.

When animals are stall-fed with rice straw, they must be provided with this drink at least twice a day, in addition to tap water. Prepare the drink at least two hours before it is given to the animals.

1. Mix 1 tbsp urea granules into 15 liter clean water.

2. Mix the solution until the urea is dissolved. Allow the solution to stand for 2 hours so the ammonia is released.

3. Add 4 tbsp molasses before giving the drink to the animal. (NOTE: Be careful not to put more urea than is required. Harmful effects of urea toxicity range from drowsiness, excessive salivation or going off feed. The most severe reaction is death.)

E. Salting Hay

Sprinkle 10-20 Ibs (5-10 kg) salt on each ton of damp rice straw. This can help prevent mold and undue heating. Salting makes poor quality hay more palatable. However, it does not ensure against spoilage (Morrison, 1961).

F. Providing low-cost molasses-urea block.



Original %

Current %















Agricultural Lime





Wheat bran/Rice bran




Water (liters)







* Contains calcium carbonate, adds nutrients and serves to bind the formula ingredients.

1. In one container, mix half of the salt (2.5%) in 5.6 liter water, then incorporate the cement (or lime). Add more water if necessary.

2. In a separate container, mix the wheat bran or rice bran, the remaining half of the salt (2.5%) and the urea thoroughly. Add the molasses until they are evenly mixed.

3. Combine the two mixtures and mix into a fine slop.

4. Line a mould or receptacle with plastic sheets to facilitate removal of the block. (Plastic pails or empty biscuit cans will do.) Another cheap method is to arrange 4 wooden boards on the ground in a 2 m x 3 m x 20 cm high rectangular mould. Pour the mixture into the mould without compressing and let it set for 24 hours.

5. The following day, cut the mass with a flat spade into 20 cm x 20 cm blocks, each one weighing about 10 kg.

6. The molasses-urea block can be given to the animals on a self-feeding box when they return from pasture or when stall-fed. The average consumption is about 250-700 g/day for an adult animal weighing 250 kg or more.

Briquettes: fuel from farm wastes

1. To make good use of rice hulls and cow dung (if available).
2. Briquettes are convenient to store in homes than loose rice hulls.
3. Saves on wood fuel and other fuel resources.

Mix one part rice hull to five parts fresh cow dung.

Mould the mix in tin cans opened both ends.

Sundry for three days

Push one end of the briquette when dry

It may then be used for cooking

Making charcoal from rice hulls

1. Char the rice hulls in a carbonizer (or a rice hull stove, but make sure that the rice hulls are not turned to ashes). Soak in water immediately to prevent char from turning to ashes.

Char the rice hulls in a carbonizer

2. Mix with as little binding material as possible, just enough to hold the charred hulls together when moulded. Paddy soil or fresh cow dung may be used as binder.

Mix with as little binding material as possible

3. Mould the mixture by hand, or by using a briquettor.

Mould the mixture by hand

4. Dry under the sun for about three days

Dry under the sun

5. When dried, the briquettes are reedy for cooking or drying grain crops.

The briquettes are reedy

(Adapted from IRRI and UPLB brochures)

Rice-hull stoves

The unmindful cutting of trees for firewood, poles and other uses has depleted available resources in most villages. Lowland areas are particularly affected as areas are cleared for paddy rice and/or vegetable production.

The increasing price of firewood demands the need to search for fuelwood substitutes. Rice hull, often regarded as a waste product of rice processing, can be the answer to such a quest. Rice hulls can be obtained free or at very minimal costs. This sheet discusses stove designs based on rice hulls as the energy source. Promoting their use will conserve valuable tree resources.


Packed Stoves. The rice hulls are packed tightly into the stove, leaving empty channels through the fuel mass for air, smoke, flames and hot grasses to pass. There are one to three vents at the base of the stove and cook pots are placed on an opening at the top.

1. Position 2 thick pieces of wood in the stove as shown.

2. Pour rice hulls in and pack them with piece of wood and mallet.

5. When the chamber is filled up to 1-2 inches from the

top, carefully remove the pieces of wood, leaving on air vent and a chimney.

4. Dip a narrow stick in kerosene, light it, and push it into the hole as shown.

Packed Stoves

Natural Draft Stove The husks are fed into the stove above the fire and fall down a slanted grate as they burn. The air intake is located under this grate, forcing all air drawn into the stove to pass through the burning fuel. The stove ash is raked out from below the grate. The Thailand and Philippine models below are widely used in the provinces of Bulacan, Laguna and Cavite. The Philippine model comes in different sizes and is widely available in local markets.

Perspective view

Front view

Cross sectional side-view

Rear view

Perspective view

Top view

Cross sectional side-view

Adapted from Rice Hulls as Fuel by Craig Thorbum, 1982.

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