|Bioconversion of Organic Residues for Rural Communities (UNU, 1979)|
|Indian experience with treated straw as feed|
While experimental data are limited, we may nevertheless attempt to evaluate straw treatment in a wider context. Indeed, it is essential that we make the attempt at this stage when we are contemplating a rapid expansion in our research and extension programmes on straw treatment.
A major concern in India should be the high support-energy cost of alkali treatment. Support-energy is obtained by burning fossil fuels, from falling water, and nuclear fission as opposed to the energy of the sun that is trapped on the farm. In the systems of farming that have come into existence in Europe and North America during the era of cheap fossil fuels, support-energy costs have been found to be very high and are, in the present changed circumstances, a cause for concern. Krummel and Dritschilo (15) have calculated the support-energy cost of producing one MJ animal protein in the United States. These figures are 6 MJ for milk and 32 MJ for beef. The corresponding support-energy costs for feed alone are 4 and 20 MJ, respectively. The values for beef include, however, the maintenance of cow herds as well as the rearing of animals for slaughter. In India, support-energy costs for animal protein production are near zero, as by-products are fed and few chemicals or machines are used. The introduction of alkali treatment would, at one stroke, raise support-energy costs to as much as 5 MJ/MJ animal protein (Table 2, Annex 4).
If all 200 million tons of straw produced in India every year were to be treated, some 10 million tons of NaOH would have to be manufactured at an energy cost of 510 x 109 MJ. This is three times the amount of energy currently expended in manufacturing nitrogenous fertilizers in one year (1,774,000 tons N x 84,000 MJ/ton). Not only is the support-energy of this magnitude not available, it can also be argued that even if it were, it would best be used to manufacture more nitrogen fertilizer, which would provide more additional feed energy than the NaOH would, and at the same time solve many other problems. One example will serve to indicate the strength of this argument.
One kg of urea applied to crops in India, under favourable conditions, can return 10 kg of grain, or 100 kg of green forage. In the example given in Annex 4, a buffalo cow would consume 883 kg of NaOH in her lifetime. This is equivalent to 1,272 kg of urea which, if applied to crops, would produce enough additional grain to feed the buffalo 3 kg per day for life, much more - probably three times more - than would be needed to produce the increment of milk resulting from the treatment of straw. If this urea were applied to non-leguminous forage crops, the additional yield would be enough to feed the buffalo 30 kg of forage per day, again much more than would be needed to produce the increment of milk produced by straw treatment.
Aside from energy considerations, NaOH treatment may prove unacceptable in the long run because of the sodium pollution it would cause. Newer methods of NaOH treatment avoid river pollution at the treatment stage, but each 100 kg of treated straw fed contains 3 - 5 kg of sodium that will find its way into soil and rivers. In the humid countries of Northern Europe this may not be a cause for concern, but in an arid country like India, with vast areas already afflicted with soil salinity, it could be. In the German Democratic Republic, KOH is being used extensively in place of NaOH (A. Hennig, personal communication, 1978), but soils in that country must be fertilized with potassium; Indian soils need not be. Indian soils also do not need calcium, which makes Ca (OH)2 less attractive than it might otherwise be. In any case, these alkalis are also expensive to manufacture in terms of support-energy.
What, then, are the alternatives? There are several possibilities, and each of them is discussed briefly in the following paragraphs. Unfortunately, considerable research and development effort would be needed to develop these alternatives to alkali treatment. By drawing attention to these alternatives now, however, the necessary effort may be stimulated more quickly.
The biological fungal treatment of straws needs no support-energy, but the fungi derive some of the energy they need from carbohydrates in the straw that the ruminant could use itself. Thus, overall energy efficiency (milk energy output/straw energy input) might not be improved. However, there are inadequate data (4). More information should be obtained quickly in order to evaluate this method of treatment critically. There would be no pollution with this method.
Ammonia treatment offers the advantage that it can help meet the protein needs of the animal consuming the straw, and later on the same nitrogen in dung and urine can help to meet the nitrogen needs of crops. It does not cause pollution. However, the methods developed thus far for farm use employ NH3 gas and would, therefore, be difficult or impossible to use in Indian villages.
One interesting possibility is that suggested by Oji and Mowat (16). They sprayed straw with a urea solution and packed it in a silo so as to exclude air. The urea was broken down to NH3, thus subjecting the straw to an alkaline treatment and, at the same time, increasing its nitrogen content. This method deserves further testing. A disadvantage is the capital cost of constructing silos; only the more affluent farmers in India could afford to do so.
A final alternative is the breeding of varieties of cereal crops that have highly digestible straw. The extent to which this is possible is not known at present. The genetic variability that may exist would have to be ascertained. Next, the compatibility of highly digestible straw with high grain yields would also have to be determined. Some varietal differences do exist (17). Growing cereal varieties that produce straw of high intrinsic digestibility could be combined with urea treatment in a silo.