Alternative energy sources: The case of Jatropha

SHARE   |   Monday, 13 March 2017   |   By Staff Writer
Jatropha crop Jatropha crop

The euphoria that engulfed many environmentalists and green technology geeks upon the discovery of widespread growth of bioenergy plant Jatropha in Botswana was deflated on Tuesday when researchers cast doubt on the viability of its commercial exploitation. Many had hoped that with the free-growing plant Botswana may have struck gold, which could reverse the debilitating energy deficits ravaging the country and the region. Now, five years of intensive research and experimentation through a collaboration between Japanese and local scientists with potential bioenergy plant Jatropha has produced mixed results, with very little to celebrate. A jatropha production project is considered economically sustainable if it is able to earn cash flow from the sale of seeds or oil to cover the cost of production and make profit over the life of a project, while having minimal negative social and environmental impacts. Presenting on Economic, Social and Environmental Impacts of Jatropha production and biomass Use Professor G. Mmopelwa said the cultivation of Jatropha curcas as a bioenergy crop is a mixed bag of opportunities and challenges for societies, particularly rural societies. "At the moment it is neither the panacea of energy security and socio-economic development problems that it was initially touted to be, nor is it completely devoid of significant opportunities," he said. Scientists among them Mmopelwa, R. Chanda, D.L. Kgathi, M. Murry–Hudson and K. Kashe carried out research in main Jatropha growing countries of the Southern African Development Community (SADC) countries of Mozambique, Tanzania, South Africa and Zambia, with examples drawn from other African and Asian countries for comparisons.  They found that the literature on Jatropha biofuels in sub-Saharan Africa suggests that the global potential of this Jatropha biofuel production was greatly exaggerated during the period 2000–2008, and this state of affairs they referred to as the “global Jatropha biofuel hype”. These exaggerations were found in jatropha's drought tolerance, pest and disease resistance, low nutritional requirements, ability to grow on a wide range of soil and climatic condition and its ability to rehabilitate marginal lands. Researchers found that most large scale projects collapsed due to lower anticipated yields (economic viable yield is 4-5 t ha-1yr-1), underestimation of production costs and changes in price of crude oil and delays in production. On the other hand small-scale biofuel projects (e.g. Soap production) have been found to be more economically viable with the potential to contribute positively to human well-being through better access to energy, capacity building, poverty reduction and rural development. In fact, jatropha hedge cultivation has been reported as one of the most economically viable farming business models especially due to its low inputs and opportunity cost of land.

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Jatropha crop is still a wild plant and little is known about its agronomy. It was promoted on expectations of high seed yield in marginal land with limited rainfall and low fertility, but seed yield have been found to be significantly lower, rendering production of the crop non-economically viable particularly on large scale production. There is need for serious research and technical efforts to fully understand the basic agronomic properties (spacing, stress tolerance, growth and yield response to inputs) optimization of seed yield under diverse agro-ecological zones. Breeding programmes should select and improve suitable germ plasm before cultivation on a large-scale. Appropriate policies and legislation for the management of Jatropha should be introduced and the experience of successful countries in biofuel development such as Brazil should serve as a benchmark, taking into consideration that the biophysical and socio-economic conditions of Botswana are different. Finally, an attempt should be made to ensure that all Jatropha biofuel projects are piloted before they are implemented in order to test their economic viability.

Cure for BCL poisoning
The little solace Botswana will take from the jatropha research is that the plant has been found to be capable of being used for phytoremediation. A study was carried out to assess the level of contamination by heavy metals and soil acidity on soils collected from eastern and western side of the BCL Copper/Nickel mine smelter and also to identify plants which can be used for phytoremediation of the area. Soil samples were collected from 2.5km east, 2.5km west, 20km west and 55km west of mine smelter and soil pH and heavy metal content were measured. Soil east and west of the mine was shown to be acidic and pH is lowest closest to the mine smelter on the western side (2.5kmwest) and increases with distance from the mine smelter towards the west. The eastern side is however less acidic than the west. Cu,Ni,Fe,Mn,Zn,As,Cd,Co,Cr,Mo,Pb,Se,Sn,Li and Pt were found to be present in the soil. Two accessions of Jatropha curcas[GKM09-Tsamaya and Mosetse were raised in pots in the greenhouse in soil with and without coal fly ash from the smelter in October 2013 to January 2014 and October 2014 to January 2015. Soils east and west of the BCLCu/Ni mine in Selebi-Phikwe, Botswana have been shown to be acidic. Soil pH was found to be lowest closest to the mine and increases with distance from the mine smelter towards the west. Addition of coal fly ash increased soil pH to above neutral. Both accessions of Jatropha curcas did not survive in soil collected from 2.5 km west of mine smelter (without ash) but survived in soil where ash was added. Jatropha curcas was able to accumulate heavy metals but more so in roots than in shoots. Jatrophacurcas failed to hyper accumulate heavy metals therefore is not a viable candidate for the phytoextraction treatment of soils closest to Selebi-Phikwe mine (2.5 km west and east and 20 km west). Application of coal fly ash also reduced heavy metal translocation from the soil to the plants. Translocation factor and bioaccumulation factors were higher in Jatropha plants grown in soil without ash as compared to with ash.
Jatropha curcas can be used for revegetating the area provided soil pH is increased and heavy metals are stabilized with coal fly ash.