Subabul (Leucaena leucocephala) is a fast-growing tree species. It provides a medium density wood (because of its fast growth); excellent high protein fodder from its leaves and fixes nitrogen in the roots which helps the soil. It was introduced in India from Hawaii in early 1980s for all the above benefits. It was a part of social forestry program spearheaded by the Government of India (GOI) to increase the green cover and also provide fuel for rural households.
There were also some programs initiated by DNES (forerunner of Ministry of New and Renewable Energy Sources (MNRE) for power generation via biomass gasifiers. However the cost of electricity production from gasifier was high hence with less uptake of wood by power producers, the program failed. Since Subabul was like a weed it could not be eradicated, and hence spread rapidly in all areas where it was planted. By late 1980s the GOI and others had lost interest in its propagation because there were no takers for its relatively soft wood (unfit for timber and also as fuel wood).
However, lately Subabul has become a very attractive fodder crop world over and I feel that it is this quality of Subabul as good fodder together with its value as a fuel and paper pulp crop that it has great potential for India.
Recently in November 2018 an International Conference on Leucaena took place in Brisbane, Australia. Researchers and workers from all over the world (we two were the only Indian delegates) discussed its various uses and how to expand its acreage. The fact that the conference was taking place after about 20 years (the last one took place in 1997 in Vietnam) attested to the new found love for Leucaena as a fodder crop.
Almost all scientists and researchers showed that Leucaena is an excellent fodder for animals both in good rainfall areas as well as in dry and drought-prone areas. Most of the data shown in the conference was for increased meat production by feeding Leucaena leaves alone though it is well-known that even small quantities of Leucaena can increase milk production thereby reducing or even eliminating the need for concentrate supplementation. In Australia we visited quite a number of large properties (3000-5000 acres) where the animals grazed on Leucaena-grass pastures only.
Leucaena contains an anti-nutrition compound Mimosine which can cause toxicity in animals. However researchers at the conference showed that in short time the gut of animals adapt and degrade Mimosine. Also researchers have identified bacteria which when fed to animals completely neutralized the toxicity of Mimosine.
There is a tremendous shortage of fodder in India. Large number of livestock camps attest to it. We need fodder for both large and small ruminants and in the absence of large areas of grazing land (as in Australia, Europe and America) there is a need to harvest the Leucaena leaves; prepare leaf meal and then feed it to the animals. Also for it to become popular so that farmers find it remunerative to plant, it needs to have other uses. Thus Subabul wood can be used both for energy and also as a raw material for pulp.
In India Subabul wood is already being used as raw material for paper pulp. Probably India is the only country in the world to use Subabul wood for pulp making. About 100,000 ha of Leucaena have been planted in India for this purpose. The program can spread even more if the import policy of GOI is made to help the local paper mills rather than the importers. Presently the import duty on pulp is very low; thus growing Subabul is becoming economically unviable.
However a better alternative will be to use Subabul for power generation. In early 1990s Nimbkar Agricultural Research Institute developed a taluka biomass policy of producing 10 MW power in each taluka using agricultural residues supplemented by Subabul wood. This policy which was implemented by MNRE and was the forerunner of the national biomass-based power plants. I feel 5-10 MW power can be produced in each taluka by dedicated Subabul plantations and the leaves can be processed into leaf meal and sold as an excellent fodder.
Thus the Subabul can become a source of producing both power and fodder. Our data has shown that for producing 5 MW of power an area of 1600 ha under Subabul plantation will be required. This can produce about 12,000 tons of dry edible biomass/year (leaves and small stems), enough for about 7500 livestock. Many such plants in different talukas all over the country can help in decentralized energy and fodder production.
On an average Subabul produces about 5-10 tons/ha-year of dry edible biomass and 40-50 tons/ha-year of fresh woody biomass. With the cost of high protein dry fodder at Rs. 12/kg a farmer can easily make around Rs. 60,000/ha-year from Leucaena fodder alone. This income will be supplemented by the wood supply at Rs. 2/kg. Thus a farmer can make about Rs. 1.4 lakh/ha-year.
Our data also shows that with Rs. 2/kg fresh woody biomass cost the electricity cost from Leucaena will be about Rs. 5.7/kWhr. This electricity is costlier than that produced via Solar PV but cheaper than that from diesel gensets. However, the attraction of this scheme is that it is decentralized and can be run year around irrespective of insulation.
What is needed to make this scheme a success is to develop machines to harvest wood and foliage and also to do excellent R&D to produce Leucaena varieties producing high leafy and woody biomass.
(The authors are with the Nimbkar Agricultural Research Institute (NARI). Phaltan, Maharashtra, India. They can be contacted at firstname.lastname@example.org)