Assessment of bene fits and risks of growing Jatropha(Jatropha curcas)as a biofuel crop in sub-Saharan Africa:a contribution to agronomic and socio-economic policies

Keotshephile Kashe·Donald L.Kgathi·Mike Murray-Hudson·Kelebogile B.Mfundisi

Introduction

In sub-Saharan Africa(SSA),two-thirds(about 620 million)of the total population live without electricity(IEA 2014).This has created growing demand for energy in the region and has opened an opportunity for biofuels-production systems,a new economic opportunity(Mitchell 2011).Consumption oftransportfuelsin SSA has increased at a rate of 7%per year,as a result of growth in the economic activities within the region(Mulugetta 2008).In rural areas,where a majority of the community may not be able to afford fossil fuel,Jatropha biofuel systems are important energy alternative that can improve smallholder livelihoods,as the oil can be easily extracted with a simple technology and used for cooking in stoves,lighting in lamps,and simple generators(Muys et al.2013).Bioenergy in SSA becomes even more relevant because of poor access to energy,and vulnerability of agricultural production systems and natural vegetation to climate change.(van Eijck et al.2012).Furthermore,this region has large tract of land with high capacity for biofuels production(Enweremadu and Alamu 2010).Currently,yields in these vast areas of agricultural land are signi ficantly lower than what is potentially feasible(van Eijck et al.2012).Therefore,biofuels production can play a signi ficant role in energy security,employment creation,and rural development(Faaij and Domac 2006;Maltsoglou et al.2013;van Eijck et al.2014).

The production of biomass for energy generation has gained planetary signi ficance(Barney and DiTomaso 2008;Fletcher et al.2011)due to its potential to reduce greenhouse gas(GHG)emissions and climate change(Fargione et al.2008;Buddenhagen et al.2009;Charles 2009;Kgathi et al.2012;Koc?ar and Civas?2013).The reduction in GHG emissions can be achieved,provided that farmers are not tempted by higher prices for biofuels and do not convert forest and grassland to biofuel crop production(Searchinger et al.2008).Diverting ecosystems to biodiesel production may create a biofuel carbon debt and increase GHG emissions(Fargione et al.2008).Biofuels are also perceived to be a strategy for achieving foreign exchange savings,economic growth,and rural development(Gasparatos et al.2015).

Fossil fuel is the major energy source,constituting 80.3%of the global energy,with 57.7%used in the transport sector(IEA 2006).Fossil fuels are responsible for a signi ficant amount of GHG emissions(Escobar et al.2009).As a result of these negative consequences,scientists and policymakers have opted for renewable sources of energy.The European Union(EU)has set a target to replace 10%of transport fuel with biofuel by 2020(Rao et al.2012).Similarly,the U.S congress instituted a 5%increase in the use of bioenergy(Basili and Fontini 2012).It has been projected that biofuel production could contribute up to 33%of the global energy supply by the year 2050(van Vuuren et al.2009;Dornburg et al.2010).Recently,biofuel crops,such as perennial grasses,woody,and annual crops,are being widely evaluated for biofuels production(Zegada-Lizarazu and Monti 2012).

In India,Southeast Asia,and Africa,Jatropha is emerging as an attractive option for biodiesel production largely because it is perceived as high yielding on marginal lands(von Maltitz et al.2014;Achten et al.2015).The production of Jatropha on marginal land suggests that such areas have little value for commercially viable agriculture and would not compete with food production(Brittaine and Lutaladio 2010;Singh et al.2013a).However,recent literature has revealed that cultivation of Jatropha in marginal land may be associated with low yields,a factor which hampers viability of Jatropha projects.

Jatropha was introduced to Africa as a biofuel feedstock mainly through non-governmental organizations(NGOs)and private companies(Romijn and Caniels 2011;ADB 2012;Muys et al.2013).These stakeholders viewed Jatropha as miracle crop that can create not only local employment and pro fit to investors,but also contribute to a reduction in GHGs and energy security(von Maltitz et al.2014).The global area under Jatropha cultivation was estimated at 900,000 hectares in 2008,with projections of a total of 12.8 million hectares by 2015(GEXSI 2008).The largest cultivated region,about,80%,was in Asia,15%in Africa and the rest in Latin America(Brittaine and Lutaladio 2010).In India,their national mission on biodiesel has promoted Jatropha cultivation on a massive scale(Singh et al.2013a).In addition,the biodiesel has been certi fied as a fuel and fuel additive by the Environmental Protection Agency(Debnath and Bisen 2008).

Unfortunately,many plants proposed for biofuels production,including Jatropha,possess attributes for invasiveness(DiTomaso et al.2007;Buddenhagen et al.2009;Low et al.2011).Despite concerns about the adverse environmental impacts of biofuels,Jatropha continues to attract increasing attention worldwide,especially in Asia and Africa where it is expected to be planted on larger scale.However,it is important to assess the potential agricultural and ecological risks that may be associated with the introduction of this exotic species to agroecosystems.This article aims to evaluate the bene fits and risks of cultivating Jatropha with its high degree of invasiveness,for biodiesel production.Given that one of the main target of biofuel sector progress is reduction in GHGs,this work will also highlight the potential impact of Jatropha cultivation on GHGs.

The choice of Jatropha

Jatropha seed-oil content ranges from 31–35%by weight(Debnath and Bisen 2008;Soo-Young 2011).This high oil content is promising for agro-industrial use because its biodiesel has physical and chemical properties similar to conventional biodiesel(Martinez-Herrera et al.2006;Abdelgadir and van Staden 2013).In addition,its drought tolerance makes it much more suitable for biodiesel production(King et al.2009;Biswas et al.2010;Ricci et al.2012).The seed oil can be easily extracted and used as biodiesel that meets the international standards(Azam et al.2005;Tiwari et al.2007).These desirable properties have prompted investors and governments to consider Jatropha as a substitute for conventional fossil fuels in an attempt to mitigate climate change(Achten et al.2008).

Almost all of the commercially available biofuels are from first generation crops produced from food crops;for example,grains and sugarcane,as well as from vegetable oils(rapeseed,palm,and sun flower)(Mohr and Raman 2013;Tang and Tang 2014;Ziolkowska 2014).The use of edible crops for biofuels production raises the ‘fuel versus food’debate as it is likely to affect agricultural production(Kgathi et al.2012;Koc?ar and Civas?2013).However,Jatropha is the exception because it does not compete with food production.Moreover,it can be cultivated on marginal land because of its lower fertilizer and water needs.It is crucial to emphasize that cultivation of Jatropha in marginal land is associated with low potential for commercially viable agriculture and may therefore not compromise food-security issues(Basili and Fontini 2012:Singh et al.2013a).

Jatropha was initially known for ethnomedicine use and as livestock-proof hedgerow(Henning 2004).It is even suggested that it was literally unknown to academia,government and investors globally,especially in southern Africa(von Maltitz et al.2014).By 2007,111,000 ha of Jatropha were reported to have been planted in 52 projects within southern Africa(GEXSI 2008).The report further forecasted an increase in hectarage to 2.2 million hectares by 2015.In India,government and international investors promoted commercial cultivation of Jatropha on large plantations(Heller 1996;Kumar et al.2012).These stakeholders glori fied Jatropha as versatile crop that could grow on marginal land to create employment and generate revenue to the local communities and investors(von Maltitz et al.2014).These claims about the positive performance of Jatropha in poor agricultural land and low inputs are being challenged because they are not based on any credible scienti fic evidence(Openshaw 2000;Fairless 2007;Achten et al.2008).

While Jatropha is promoted as an economically and environmentally sustainable feedstock for biofuel production(Renner 2007),there is limited information about its cultivation and management(Achten et al.2010).For Jatropha to be an economically viable biofuel crop,it is a pre-requisite to develop varieties and other technologies that will address local climatic and agro-ecological constraints(Singh et al.2013a),since its economic viability as a biomass for biodiesel production under its current state as a wild plant are questionable(Basili and Fontini 2012;Singh et al.2013a).Experimental studies in India by Singh et al.(2013b)have concluded that for Jatropha to be economically important biodiesel crop it must produce a minimum yield of 4–5 t ha-1with oil content of about 35–40%.Yield assessment of Jatropha plantations in the semi-arid tropical location at International Crops Research Institute for the Semi-arid Tropics(ICRISAT)in Patancheru,indicated that seed yield ranged from 600 kg ha-1at third year to 1560 kg ha-1,in fluenced mainly by distribution of rainfall during the season(Rao et al.2012).

Agronomy of Jatropha

Jatropha(Euphorbiaceae)is a multi-purpose and droughtresistant perennial plant,gaining importance as an economically justi fiable alternative to conventional diesel(Jones and Miller 1992;Ranade et al.2008;Sachdeva et al.2011).There are about 170 different species of Jatropha(Ranade et al.2008;Basili and Fontini 2012;Sabandar et al.2013)being distributed worldwide(Schmook and Seralta-Peraza 1997;Deore and Johnson 2008).Even though it can be propagated from seed,seedlings,and cuttings(Misra and Misra 2010;Patil et al.2015),direct seeding is constrained by low seed germination and cuttings have poor root development(Openshaw 2000;Purkayastha et al.2010).Its height ranges from two to three meters,but under favourable conditions it can reach a height of ten meters(Achten et al.2008;Debnath and Bisen 2008).How long Jatropha plants can live largely depends on climatic and agro-ecological regions varying from 40 to 50 years(Kaushik et al.2007;Achten et al.2010).The plant takes two to three years to start producing fruits and reach full fruit bearing in the fourth or fifth year(Debnath and Bisen 2008).

Jatropha growswithin the temperature range of 15–40 °C(Kumar and Sharma 2008)and is susceptible to frost(Gour 2006;Orwa et al.2009).The latest studies in Botswana demonstrated that cold weather causes severe damage to Jatropha trees,which delays their sprouting in spring(Inafuku et al.2013).The plant can be grown on a wide range of soils,but loose soils with good aeration are preferred as they are less likely to be water logged(Foidl et al.1996;Heller 1996).For example in India,river sand was found to be the best germination medium than vermiculite(Mariappan et al.2014).Therefore,the plant should not be cultivated in heavy soils(Biswas et al.2006;Singh et al.2006),because such soils have poor drainage and aeration that will retard root formation and development(Heller 1996).

Jatropha is still considered a wild plant that grows well under rain-fed conditions from low(250 mm)to high amounts of(3000 mm per annum)rainfall(Foidl et al.1996).However,there is a gap in knowledge about the management and yield potential of promising clones in different agro-ecological zones(Rao et al.2012).Seed yields from undomesticated Jatropha plant were reported to be not more than 1 t ha-1(van Eijck et al.2010).

Interestingly,because it is adapted to marginal soils with low nutrient content,Jatropha can be used to rehabilitate degraded land(Openshaw 2000;Jongschaap et al.2007;Garg et al.2011).Furthermore,it is capable of producing seedyieldsofgoodqualityunderminimum water requirements compared to other crops(Kheira and Atta 2009).Seed yield is quite variable and varies from 0.2 to＞2 kg seeds from a single plant or 0.4–12 t ha-1(Francis et al.2005;Achten et al.2008;Wani et al.2012).The variation in seed yield is strongly linked to diverse environments where it is cultivated(Behera et al.2010;Srivastava et al.2011).In Tanzania,large-scale Jatropha oil production,seed yield of 2–5.4 t ha-1a-1were obtained under optimum conditions,i.e.fertilizer and good soil(Segerstedt and Bobert 2013).

Lands in arid and semi-arid areas have always been favored as ideal places for biofuel production,as it is doubtful that any signi ficant contribution to food production can be made(Achten et al.2013).Jatropha is well adapted to arid and semi-arid conditions where it is used to protect soil from erosion,rehabilitate land,and serve as a livestock-proof hedgerow(Martinez-Herrera et al.2006;Abdelgadir and van Starden 2013).However,yields under arid and semi-arid areas were found to be signi ficantly lower than expected(Sanderson 2009).Romijn(2011),quoting personal communication with Y.W.Franken reported that in Honduras,Mali and Mozambique,oil yields ranged from more than 1250 L ha-1a-1in favorable conditions to a meager 250 L ha-1a-1based on minimal water supply and low soil fertility.

Uses of Jatropha

About 69%of the world’s poorest people rely on biomass for their daily energy needs,and Jatropha is the principal crop for biofuels production(ENDA 2008).The main sources of energy in these poor communities are fuelwood and charcoal(Wiskerke et al.2010).Because Jatropha oil properties are similar to those of conventional diesel(Berchmans and Hirata 2008)and when combined with an uncomplicated extraction methodology,such biofuel is an ideal option for poor countries and can be used directly in cooking,lighting,and simple generators.In view of these desirable oil properties,biodiesel from Jatropha has turned into very suitable energy choice for the remote areas in SSA,where fossil fuel is expensive and its supply unreliable(Basili and Fontini 2012;Muys et al.2013).

According to Muys et al.(2013),economic models postulated that when Jatropha biofuel systems are economically viable,they could result in oil prices of≥$70 US dollars per barrel.The same source also cautioned that even when the oil prices were higher than the baseline price,there was no viable Jatropha projects as poor returns resulted in abandonment of most large-scale commercial plantations.

Jatropha was first commercialized by exportation of its seed oil from Cape Verde to Portugal for soap production and lamps(Gübitz et al.1999).The seeds are highly harmful as they contain several toxins(phorbol esters,curcin,trypsin inhibitors,lectins and phytates)as well as allergic proteins(Abdu-Aguye et al.1986;Lioglier 1990;Becker and Makkar 1998;Maciel et al.2009).However,after detoxi fication,the seed cake can provide a highly nutritious and cheap protein(50–60%)supplement for animal feed(Makkar et al.1998).The seed cake contains more nutrients than both chicken and cattle manure(Francis et al.2005),and can be used as an organic fertilizer and the organic waste products can be used in the production of biogas(Lopez et al.1997;Staubmann et al.1997;Gübitz et al.1999).

Its nitrogen content ranges from 3.2 to 3.8%(Kumar and Sharma 2008).A fertilizer trial by Henning(2004)on pearl millet indicated that the this crop reached its maximum potential yield in Jatropha oil cake(5 t ha-1)compared with farm-yard manure(5 t ha-1)and NP fertilizer(100 kg ammonium phosphate and 50 kg urea ha-1).Nitrogenbased fertilizers based on Jatropha seedcake are likely to reduce N2O emissions(Basili and Fontini 2012).Jatropha plants can easily regenerate from cuttings and are therefore mostly planted as a hedge to protect homesteads and fields as it is too poisonous and unpalatable to be browsed by cattle or other animals(Henning 2004;Martínez-Herrera et al.2006).It can also be used to control soil erosion,and to rehabilitate agricultural wastelands(Francis et al.2005).

Jatropha species are traditionally used for treatment of several diseases in Africa,Asia and Latin America(Burkill 1994;Abdelgadir and van Staden 2013).In Senegal,Nigeria,Congo,and East Africa,stem sap or dried powdered plant is applied on fresh wounds to stop bleeding(Abdelgadir and van Staden 2013).In Congo,dried sap is also used as ‘penicillin.’Jatropha oil seed is known for its laxative effect,which heals digestive system symptoms such as abdominal pains and looseness of the bowels(Sabandar et al.2013).However,Lioglier(1990)advised to the contrary and warned that the seeds of Jatropha species are highly toxic and should not be considered for herbal medicine.The seeds contain curcin,a phytotoxin that causes vomiting,bloody diarrhea,and central nervous system depression(Abdu-Aguye et al.1986).It is stated that the seeds can cause nausea,vomiting and dizziness,and in extreme conditions,even death(Becker and Makkar 1998).Other uses of Jatropha include the manufacture of lubricants,soaps and candles,astringents and coloring dye(Jain 1991;Ambasta 1994).

While Jatropha is widely used in traditional medicine in most regions of Africa,a review on the uses of different parts of Jatropha plants in folk and traditional medicine by Abdelgadir and van Staden(2013)did not indicate any medicinal uses in Southern Africa.However,Henning(2004)reported the main uses of Jatropha in Southern Africa as medicinal and animal-proof hedgerow.It was practically unknown to academics and governments in Southern Africa until 2000,when it started to be promoted as a biodiesel crop(von Maltitz et al.2014).While it is also being promoted as an energy crop in the region,it is banned in South Africa because it is considered a noxious weed(Blanchard et al.2011).

Risks associated with Jatropha cultivation and production

Jatropha has been praised on unproven claims of high oil yields without any scienti fic backing(Das et al.2012;von Maltitz et al.2014).For example,the large-scale Jatropha cultivation was carried out without use of improved varieties,on-farm evaluation,and assessment of appropriate management practices(Edrisi et al.2015).Large-scale cultivation and investments pose socio-economic and environmental hazards(Achten et al.2010,2015).In view of this uncertainty,it is imperative to examine potential dangers that might arise out of large-scale cultivation of Jatropha.

Invasiveness risk

One of the main challenges to this booming industry is how to meet biofuel demands ef ficiently and sustainably on the scarce land,while at the same time avoiding negative environmental consequences,such as the risk of invasiveness(Robertson et al.2008).A signi ficant number of crops proposed for biofuels production have the potential to become invasive(Buddenhagen et al.2009;Barney and DiTomaso 2011;von Maltitz et al.2014).This concern stems from the fact that desirable traits for an ideal biofuel crop—such as high productivity,tolerance to abiotic stress,low-input requirements and wide habitat breath—are the same physiologicaltraitsthatfacilitate invasiveness(Raghu et al.2006;Barney and DiTomaso 2011;Flory et al.2012).

In response to the potential invasiveness risk of biofuel crops,international organizations,such as Global Invasive Programme(GISP)and International Union for Conservation of Nature(IUCN),have produced a white paper to guide the selection of biofuel feedstocks and management strategies,including regulatory and policy reforms,created to prevent widespread invasion(Quinn et al.2013).Both organizations recommend that plant protection of ficers to be consulted before biofuel feedstocks are introduced(GISP 2007;IUCN 2009).Most biofuel crops are cultivated in areas outside their geographical origin,thus exacerbating the potential risk of future invasions(Barney and DiTomaso 2008).For example,the United States is evaluating miscanthus hybrids(Miscanthus×giganteus)as a potential biomass crop(Lewandowski et al.2003;J?rgensen 2011)which is native to Eastern Asia(Stewart et al.2009).Similarly,Jatropha originates in South America and Mexico(Makkar and Becker 2009;Achten et al.2010),but is currently widely promoted for biodiesel production in India,Southeast Asia,and Africa.

Invasive plants are those ones that grow vigorously when introduced into an exotic ecosystem,occupy large tracts of land and out-compete native species,destroying plant diversity and ecosystem services(IUCN 2009).Invasive species are only surpassed by habitat destruction in terms of their threat to biodiversity(Randall 1996;Vitousek et al.1997;Mack et al.2000;Wittenberg and Cock 2001;Clout and Williams 2009).The economic costs of invasive species to the economy can be signi ficantly high.The negative impact of invasive species is projected to be more than US$1.4 trillion,which is equivalent to five percent of the global economy(Pimentel et al.2001).Since Jatropha is classi fied as invasive crop(GISP 2008),its cultivation was forbidden in Australia(Royal Botanic Gardens Sydney 2008)and South Africa(Blanchard et al.2011;von Maltitz et al.2014).Conversely,most sub-Sahara African countries consider it as an important biofuel crop(Spaan et al.2004).

The proposed large-scale cultivation,transport,processing,and breeding for high-yielding varieties provide opportunities for successful ‘escape’and invasion of nearby agro-ecosystems(Richardson and Blanchard 2011;Barney 2014).The success of invasion however,is largely determined by the amount of seeds or other reproductive structures dispersed into that system(Lockwood et al.2005).The risks of invasiveness therefore increase with increasing number of propagules(Holle and Simberloff 2005).The anticipated large-scale of Jatropha plantings implies that it has many opportunities to escape because of high propagule pressure(Low et al.2011).Experimental studies in Zambia on Jatropha demonstrated that its seeds or cuttings were not able to escape and spread signi ficantly from deliberate plantings(Negussie et al.2013a).However,the plant has been predicted to be highly invasive when cultivated in regions where it does not naturally occur(Negussie et al.2013b).Such contradictory reports call for the importance of studies focusing on risk assessment of large-scale cultivation of Jatropha.

Another key concern is about whether biofuel crops can produce enough fuel to meet energy needs and become pro fitable on the domestic or international markets(Fargione et al.2008;Scharlemann and Laurance 2008).In Tanzania,the price for Jatropha seed in 2007–2009 ranged from 0.14 to 0.18$kg-1(Loos 2008;Mitchell 2008),whereas,in Kenya it ranged from 0.12–0.18$kg-1.Still in Tanzania,Wiskerke et al.(2010)found that the production cost of Jatropha oil makes it too expensive to be used as a substitute for fuelwood and concluded that smallholder Jatropha oil production as an alternative fuel for household cooking is not economically attractive.

Segerstedt and Bobert(2013)used an economic landevaluation assessment for large-scale Jatropha oil production in Tanzania,which showed that more fertilizer and as well as more labor are needed to achieve high seed yields(2–5.4 t ha-1).These high input costs will elevate the price of production and thus render the Jatropha biodiesel production system unpro fitable(Achten et al.2015).Market failures can contribute signi ficantly to the risk of Jatropha invasiveness.Many plantations were unsuccessful,due to lack of markets for the seeds(Sanderson 2009)or poor yields(Euler and Gorriz 2004;Ariza-Montobbio and Lele 2010).These low returns resulted in abandonment of commercial large-scale plantings with the risk of plant escapes into adjacent land use systems.

Jatropha seeds have been reported to be dispersed mainly anthropogenically and by gravitationalforce(Hannan-Jones and Csurhes 2008).Plant features can enhance its growth aggressiveness(Py?ek and Richardson 2007);for example:larger and more proli fic species naturally attract more dispersal agents and therefore ensuring its spreading(Jelbert et al.2015).Animals usually disperse seeds by consuming and ejecting them later through their digestive tract.However,the toxins in the Jatropha fruits and seeds make them inedible and unattractive food source for animals and therefore less likely to be dispersed by them(Negussie et al.2013b).

Rejmánek and Richardson(1996)showed that seed weight correlates negatively with dispersal distance.Large seeds are too heavy to be dispersed and would therefore require large animals and strong winds to be successfully dispersed physically(Kelly 1995).Jatropha seeds are quite large and range from 1.69×1.4×0.84 mm to 1.84×1.31×0.85 mm as length,width and breadth,respectively(Misra and Misra 2010).Given that for an invasion to occur,seeds or reproductive structures must be dispersed to suitable sites(Burns et al.2013;Lewis et al.2014);however,the risks of invasiveness associated with Jatropha cultivation might be low,owing to its large seed which would be too heavy to be dispersed.

Seeds and seedlings predation occurs mostly around the parent where seeds and seedlings are concentrated(Peres et al.1997;Hulme 1998;Willson and Traveset 2000).In Zambia,rodents and shrews were reported to be consuming Jatropha seeds(Negussie et al.2013a).Given that Jatropha seeds may not be dispersed further away from the parent plant,they are more likely to be destroyed by predators and pathogens.Furthermore,experimental studies in Botswana by Inafuku-Teramoto et al.(2013)demonstrated that Jatropha trees are susceptible to frost damage and can lose all their leaves when conditions become too cold.In China,Liang et al.(2007)observed that Jatropha is susceptible to chilling stress,especially at seedling stage.Additionally,the loss of leaves will delayed sprouting in spring.This observation substantiates the suggestion that risks of invasiveness from Jatropha cultivation would be low.

Jatropha susceptibility to low temperatures suggests that its recruitment from stumps or coppicing will be slow and further limit its invasiveness.The seeds of Jatropha are reported to have low viability(Rakkimuthu et al.2011),suggesting that germination rates from seed banks will be reduced over time.Once the seed bank is built,it gives the species opportunity to germinate and establish when conditions are favorable(Rejmánek 2000),making control and eradication dif ficult(Lewis et al.2014).However,it is unlikely that this will be the case with Jatropha seed bank,given its low seed viability.

Recent studies have challenged the production ef ficiency of biofuels crops and have called attention to the need of a large cultivation area,besides water use for irrigation.Such combined aspects would not be compensated as biofuel production is still low(Steer and Hanson 2015).There is also a chance of biofuels production becoming more pro fitable,tempting growers to convert agricultural land to biofuel crop cultivation.Another point would be the failure in producing economic yields of biofuel,leading its cultivation to be carried out in fertile arable areas(Fargione et al.2008).This scenario could occur with Jatropha due to its poor performance on marginal lands.

Impact on greenhouse gas emissions

Most studies have demonstrated that replacin g traditional fossil fuel with biofuels will reduce GHG emissions(Fargione et al.2008;Gallagher 2008;Naik et al.2010),because the growing biofuel crop sequesters carbon(Osamu and Carl 1989;Scarlat and Dallemand 2011).The GHG balance is largely in fluenced by the type of biofuel feedstock used,the crop management during cultivation,and whether there are land-use changes(Quirin et al.2004;Larson 2006;Dornburg et al.2010).Therefore,in the assessment of carbon debt or credit resulting from land-use change,the carbon bene fits of using land for biofuels should be taken into consideration,including carbon costs,carbon storage,and sequestration forfeited by converting land from its current uses(Searchinger et al.2008).

As with other biofuel crops,one of the most appealing aspects for Jatropha biofuel is to reduce GHG emissions.Tilman et al.(2009)recommended that plants that grow in degraded lands not suitable for agricultural production that also absorb carbon dioxide from the atmosphere should be considered for biofuel production.Jatropha meets these requirements and its cultivation does not induce land-use change(Basili and Fontini 2012)and thus will result in net GHG savings(Gallagher 2008).However,the application of nitrogen fertilizers can negate the net GHG savings through the emission of nitrous oxide(N2O)(Crutzen et al.2008),given that the nitrogen-based fertilizers will emit signi ficant amount of N2O(IPCC 2006).It is recommended that instead,seedcake,a by-product from Jatropha oil extraction,be used as an organic fertilizer(Basili and Fontini 2012).

Life cycle assessment(LCA)studies on Jatropha biodiesel,covering the system from crop cultivation in the field through burning biodiesel in generators and engines,are generally in agreement that there is a reduction in GHG emissions(Tobin and Fulford 2005;Ndong et al.2009;Achten et al.2010;Kumar et al.2012).LCA studies have demonstrated that replacing petroleum diesel with Jatropha biodiesel will reduce net GHG emissions by up to 62%(Whitaker and Heath 2008).Such reductions though,will only be achieved when both direct and indirect land-use change are avoided and by-products,such as seedcake,are used as organic fertilizer(Muys et al.2013).Achten et al.(2013)assessed the carbon balance of potential land-use change to Jatropha cultivation and found more carbon debt(70–118 t C ha-1)in 1.15 billion ha of forested areas under arid and semi-arid climates than in 0.75 billion ha shrubland(24–28 t C ha-1).Importantly,they projected that the carbon debts will be repaid within 30 years,with a seed yield of 3.5–3.9 and 5 t ha-1a-1in shrubland and forested areas,respectively.

Kritana and Gheewala(2006)investigated GHG emissions from Jatropha production in Thailand using LCA and concluded that GHG emissions from Jatropha biodiesel production was 77%lower than in production and use of fossil diesel.Similarly,in West Africa,Jatropha biodiesel production saved 72%in GHG emissions compared with conventional diesel fuel(Ndong et al.2009).

Romijn(2011)used data from extant forestry and ecology of Miombo Woodland to estimate GHG emissions resulting from the introduction of large-scale Jatropha cultivation in these woodlands.The study concluded that Jatropha cultivation in these ecosystems will lead to emissions of considerable amounts of GHG that will subsequently undermine any GHG savings from the whole of the production chain,resulting in carbon debt.With the current potential seed yield of 5 t ha-1a-1,it will take about30 yearsto repay thatdebt(Achten etal.2008,2013).

Conclusion

Jatropha is a promising biofuel feedstock that can contribute to sustainable rural development and employment creation,especially in Southern Africa.However,for it to be economically and environmentally sustainable,a standard set of practices for diverse environmental conditions needs to be developed.Jatropha’s low performance in marginal areas suggests that like any other crop,it needs fertilizer and water to attain economic yield.

The risks of invasion resulting from Jatropha being introduced for biodiesel production have received little attention.The potential invasive risks seem to be quite low;however,its cultivation should be regulated given the expected large–scale cultivation.To minimize the risk of invasiveness,it is recommended that Jatropha be classi fied as a noxious weed so that farmers or investors are obliged to request permission from plant protection of ficers before planting.This is essential to regulate and monitor Jatropha cultivation.

Large-scale cultivation of Jatropha will create increased propagule pressure and increase the risk of invasiveness.Jatropha as a new crop should be therefore subjected to a proven scienti fic risk-assessment protocol to determine if it will become invasive in areas of introduction.Governments should develop regulations on the cultivation of Jatropha for biodiesel production to curb its spread into other land-use systems,given the risks associated with large-scale cultivation,transportation,and seed processing.The rules should ensure that plantations are not abandoned without adequate management and eradication.

AcknowledgementsThis study was funded by the Government of Botswana and Japan.Finally,we would like to thank Mrs Frances Murray-Hudson for editing the first draft of this manuscript.

Abdelgadir HA,van Staden J(2013)Ethnobotany,ethnopharmacology and toxicity of Jatropha curcas L.(Euphorbiaceae):a review.S Afr J Bot 88:204–218.doi:10.1016/j.sajb.2013.07.021

Abdu-Aguye I,Sannusi A,Ala fiya-Tayo RA,Bhusnurmath SR(1986)Acute toxcity studies with Jatropha curcas L.Hum Toxicol 5(4):269–274.doi:10.1177/096032718600500409

Achten WMJ,Verchot L,Franken Y,Mathijs E,Singh V,Aerts R,Muys B(2008)Jatropha bio-diesel production and use.Biomass Bioenergy 32(12):1063–1084.doi:10.1016/j.biombioe.2008.03.003

Achten WMJ,Nielsen LR,Aerts R,Lengkeek AG,Kjaer ED,Trabucco A,Hansen JK,Maes WH,Gradual L,Akinnifesi FK,Muys B(2010)Towards domestication of Jatropha curcas.Biofuels 1(1):91–107

Achten WMJ,Trabucco A,Maes WH,Verchot LV,Aerts R,Mathijs E,Vantomme P,Singh VP,Muys B(2013)Global greenhouse gas implications of land conversion to biofuel crop cultivation in arid and semi-arid lands–lessons learned from Jatropha.J Arid Environ 98:135–145.doi:10.1016/j.jaridenv.2012.06.015

Achten WMJ,Dillen K,Trabucco A,Verbist B,Messemaker L,Muys B,Mathijs E(2015)The economics and greenhouse gas balance of land conversion to Jatropha:the case of Tanzania.Glob Change Bioenergy 7(2):302–315.doi:10.1111/gcbb.12160

ADB(African Development Bank)(2012)African Economic Outlook 2012.Joint publication of the ADB,Development Centre of the Organization for Economic Cooperation and Development,United Nations Development Programme and United Nations Economic Commission for Africa

Ambasta SP(1994)The useful plants of India.CSIR,New Delhi

Ariza-Montobbio P,Lele S(2010)Jatropha plantations for biodiesel in Tamil Nadu,India:viability,livelihood trade-offs,and latent con flict.Ecol Econ 70(2):189–195.doi:10.1016/j.ecolecon.2010.05.011

Azam MM,Waris A,Nahar NM(2005)Prospects and potential of fatty acid methyl esters of some non-traditional seed oils for use as biodiesel in India.Biomass Bioenergy 29(4):293–302.doi:10.1016/j.biombioe.2005.05.001

Barney JN(2014)Bioenergy and invasive plants:quantifying and mitigating future risks.Invasive Plant Sci Manag 7(2):199–209.doi:10.1614/IPSM-D-13-00060.1

Barney J,DiTomaso J(2008)Non-native species and bioenergy:are we cultivating the next invader?Bioscience 58(1):64–70.doi:10.1641/B580111

Barney JN,DiTomaso JM(2011)Global climate niche estimates for bioenergy crops and invasive species of agronomic origin:potential problems and opportunities.PLoS ONE.doi:10.1371/journal.pone.0017222.t001

Basili M,Fontini F(2012)Biofuel from Jatropha curcas:environmental sustainability and option value.Ecol Econ 78:1–8.doi:10.1016/j.ecolecon.2012.03.010

Becker K,Makkar HPS(1998)Effects of phorbolesters in carp(Cyprinus carpio L.).Vet Hum Toxicol 40(2):82–86

Behera SK,Srivastava P,Tripathi R,Singh JP,Singh N(2010)Evaluation of plant performance of Jatropha curcas L.under different agro-practices for optimizing biomass—a case study.Biomass Bioenergy 34(1):30–41.doi:10.1016/j.biombioe.2009.09.008

Berchmans HJ,Hirata S(2008)Biodiesel production from crude Jatropha curcas L.seed oil with a high content of free fatty acids.Bioresour Technol 99(6):1716–1721.doi:10.1016/j.bior tech.2007.03.051

Biswas S,Kaushik N,Srikanth G(2006)Biodiesel:technology and business opportunities—an insight.In:Singh B,Swaminathan R,Ponraj V(eds)Proceedings of the biodiesel conference toward energy independence—focus of Jatropha.Rashtrapati Bhawan,New Delhi,India,pp.303–330

Biswas KP,Pohit S,Kumar R(2010)Biodiesel from Jatropha:can India meet the 20% blending target? Energy Policy 38(3):1477–1484.doi:10.1016/j.enpol.2009.11.029

Blanchard R,Richardson DM,O’Farrell PJ,von Maltitz GP(2011)Biofuels and biodiversity in South Africa.S Afr J Sci 107(5–6):1–8.doi:10.4102/sajs.v107i5/6.186

Brittaine R,Lutaladio N(2010)Jatropha:a smallholder bioenergy crop—the potential for pro-poor development.In:Integrated crop management,vol 8.Food and Agriculture Organization of the United Nations,Rome

Buddenhagen CE,Chimera C,Clifford P(2009)Assessing biofuel crop invasiveness:a case study.PLoS ONE.doi:10.1371/journal.pone.0005261

Burkill HM(1994)The useful plants of west tropical Africa,vol 2.Royal Botanical Gardens,Kew

Burns JH,Pardini EA,Michele R,Schutzenhofer MR,Chung YA,Seidler KJ,Knight TM(2013)Greater sexual reproduction contributes to differences in demography of invasive plants and their noninvasive relatives.Ecology 94(5):995–1004.doi:10.1890/12-1310.1

Charles D(2009)Corn-based ethanol flunks key test.Science 324(5927):587.doi:10.1126/science.324_587

Clout MN,Williams PA(2009)Invasive species management:a handbook of principles and techniques.Oxford University Press,Oxford

Crutzen PJ,Mosier AR,Smith KA,Winiwarter W(2008)N2O release from agro-biofuel production negates global warming reduction by replacing fossil fuels.Atmos Chem Phys 8:389–395

Hannan-Jones M,Csurhes,S(2008)Pest plant risk assessment physic nut,PR 08–3681.Department of Primary Industries and Fisheries,Queensland Government,Queensland,Australia

Das S,Pries JA,Schweitzer C(2012)Modelling regional scale biofuel scenarios—a case study for India.Glob Change Bioenergy 4(2):176–192.doi:10.1111/j.1757-1707.2011.01114.x

Debnath M,Bisen PS(2008)Jatropha curcas L.a multipurpose stress resistant plant with a potential for ethnomedicine and renewable energy.Curr Pharm Biotechnol 9(4):288–306.doi:10.2174/138920108785161541

Deore AC,Johnson TS(2008)High-frequency plant regeneration from leaf-disc cultures of Jatropha curcas L.:an important biodiesel plant.Plant Biotechnol Rep 2:7–11.doi:10.1007/s11816-008-0042-y

DiTomaso JM,Barney JN,Fox AM(2007)Biofuel feedstocks:the risk of future invasions.Council for Agricultural Science and Technology Commentary QTA 2007–1,Ames,IA,p 8

Dornburg V,van Vuuren D,van de Ven G,Langeveld H,Meeusen M,

Banse M,van Oorschot M,Ros J,van den Born GJ,Aiking H,Londo M,Mozaffarian H,Verweij P,Lysen E,Faaij A(2010)Bioenergy revisited:key factors in global potentials of bioenergy.Energy Environ Sci 3:258–267.doi:10.1039/B922422J

Edrisi SA,Dubey RK,Tripathi V,Bakshi M,Srivastava P,Jamil S,Singh HB,Singh N,Abhilash PC(2015)Jatropha curcas L.:a cruci fied plant waiting for resurgence.Renew Sustain Energy Rev 41:855–862

ENDA(Environmental Development Action)(2008)Biofuels development in Africa:illusion or sustainable alternative?http://www.compete-bioafrica.net/publications/publ/ENDA%20Biofules%20Africa.pdf.Accessed 25 Feb 2016

Enweremadu CC,Alamu OJ(2010)Development and characteriza

tion of biodiesel from shea nut butter.Int Agrophys 24:29–34

Escobar JC,Lora ES,Osvaldo J,Venturini OJ,Edgar E,Yáu?ez EE,Edgar F,Castillo EF,Almazan O(2009)Biofuels:environment,technology and food security.Renew Sustain Energy Rev 13:1275–1287

Euler H,Gorriz D(2004)Case study Jatropha Curcas:Global facilitation unit for underutilized species.Deutsche Gesellschaft fu′r Technische Zusammenarbeit(GTZ),Frankfurt,http://www.underutilized-species.org/Documents/PUBLICATIONS/jatro pha_curcas_india.pdf.Accessed 22 Mar 2016

Faaij APC,Domac J(2006)Emerging international bio-energy markets and opportunities for socio-economic development.Energy Sustain Dev 10(1):7–19.doi:10.1016/S0973-0826(08)60503-7

Fairless D(2007)Biofuel:the little shrub that could–maybe.Nature 449:652–655.doi:10.1038/449652a

Fargione J,Hill J,Tilman D,Polasky S,Hawthorne P(2008)Land clearing and the biofuel carbon debt.Science 319(5867):1235–1238.doi:10.1126/science.1152747

Fletcher RJ Jr,Robertson BA,Evans J,Doran PJ,Alavalapati JRR,Schemske DW(2011)Biodiversity conservation in the era of biofuels: risks and opportunities. Front Ecol Environ 9(3):161–168.doi:10.1890/090091

Flory SL,Lorentz KA,Gordon DR,Sollenberger LE(2012)Experimental approaches for evaluating the invasion risk of biofuel crops.Environ Res Lett.doi:10.1088/17489326/7/4/045904

Foidl N,Foildl G,Sanchez M,Mittelbach M,Hackel S(1996)Jatropha curcas L.as a source for the production of biofuel in Nicaragua.Bioresour Technol 58(1):77–82.doi:10.1016/S0960-8524(96)00111-3

Francis G,Edinger R,Becker K(2005)A concept for simultaneous wasteland reclamation,fuel production,and socio-economic development in degraded areas in India:need,potential and perspectives ofJatropha plantations.NatResourForum 29(1):12–24

Gallagher E(2008)Review of the indirect effects of biofuels production.Renewable Fuels Agency.http://www.renewablefuel sagency.org.Accessed 12 Dec 2015

Garg KK,Karlberg L,Wani SP,Berndes G (2011)Jatropha production on wastelands in India:opportunities and trade-offs for soil and water management at the watershed scale.Biofuel Bioprod Biore fin 5:410–430.doi:10.1002/bbb.312

Gasparatos A,von Maltitz GP,Johnson FX,Lee L,Mathai M,de Oliveira JAP,Willis KJ(2015)Biofuels in sub-Sahara Africa:drivers,impacts and priority policy areas.Renew Sustain Energy Rev 45:879–901.doi:10.1016/j.rser.2015.02.006

GEXSI(Global Exchange for Social Investment)(2008)Global Market Study on Jatropha.Final report of The GEXSI,prepared for the World Wide Fund for Nature(WWF),London/Berlin

GISP(The Global Invasive Species Programme)(2007)Assessing the Risk of Invasive Alien Species Promoted for Biofuels.GISP

GISP(The Global Invasive Species Programme)(2008)Biofuels run the risk of becoming invasive species.http://www.gisp.org/whatsnew/docs/biofuels.pdf.Accessed 15 Mar 2016

Gour VK(2006)Production and practices including post-harvest management of Jatropha curcas.In:Singh B,Swaminathan R,Ponraj V(eds)Biodiesel conference towards energy independence—focus on Jatropha,Hyderabad,June 9–10,2006

Gübitz GM,Mittelbach M,Trabi M(1999)Exploitation of the tropical oil seed plant Jatropha curcas L.Bioresour Technol 67(1):73–82.doi:10.1016/S0960-8524(99)00069-3

Heller J(1996)Physic nut Jatropha curcas L promoting the conservation and use of underutilized and neglected crops,1st edn.International Plant Genetics and Crop Plant Research Institute,Gartersleben(IPGRI),Rome

Henning R(2004)Jatropha curcas L.in Africa.Global Facilitation Unit for Underutilized Species,Rome

Holle BV,Simberloff D(2005)Ecological resistance to biological invasion overwhelmed by propagule pressure. Ecology 86(12):3212–3218.doi:10.1890/05-0427

Hulme PE(1998)Post-dispersal seed predation:consequences for plant demography and evolution.Perspect Plant Ecol 1(1):32–46

IEA(International Energy Agency)(2006).Key world energy statistics.Paris,France.https://www.iea.org/publications/freepu blications/publication/KeyWorld2016.pdf.Accessed 15 April 2016

IEA(International Energy Agency)(2014)World Energy Outlook 2014 Special Report:Africa Energy Outlook.http://www.worldenergyoutlook.org/.Accessed 15 April 2016

Inafuku-Teramoto S,Mazereku M,Coetzee T,Gwa fila C,Lekgari AL,Ketumile D,Fukuzawa Y,Yabuta S,Masukujane M,George DGM,Chite SM,Ueno M,Kawamitsu Y,Akashi K(2013)Production approaches to establish effective cultivation methods for Jatropha(Jatropha curcas L.)under cold and semiarid climate conditions.Int J Agron Plant Prod 4:3804–3815

IPCC(Intergovernmental Panel on Climate Change)(2006)N2O emissions from managed soils and CO2emissions from lime and urea application.In:Eggleston HS,Buendia L,Miwa K,Ngara T,Tanabe K(eds)‘IPCC Guidelines for National Greenhouse Gas Inventories:vol 4:agriculture,forestry and other land use’,pp.1–54.(The Institute for Global Environmental Strategies:Hayama,Japan)http://www.ipcc-nggip.iges.or.jp/public/2006gl/vol2004.htm[Veri fied 1 November 2010]

IUCN(International Union for Conservation of Nature)(2009)Guidelines on biofuels and invasive species.IUCN,Gland

Jain SK(1991)Dictionary of Indian folk medicine and ethnobotany.Deep Publications,New Dehli

Jelbert K,Stott I,McDonald RA,Hodgson D(2015)Invasiveness of plants is predicted by size and fecundity in the native range.Ecol Evol 5(10):1933–1943.doi:10.1002/ece3.1432

Jones N,Miller JH(1992)Jatropha curcas L:a multipurpose species for problematic sites.The World Bank,Washington DC

Jongschaap R,CorréW,Bindraban P,Brandenburg W(2007)Claims and facts on Jatropha curcas L.Global Jatropha curcas evaluation,breeding and propagation programme.Plant Research International BV,Wageningen

J?rgensen U(2011)Bene fits versus risks of growing biofuel crops:the case of Miscanthus. Curr Opin Environ Sustain 3(1–2):24–30.doi:10.1016/j.cosust.2010.12.003

Kaushik N,Kumar K,Kumar S,Kaushik N,Roy S(2007)Genetic variability and divergence studies in seed traits and oil content of Jatropha(Jatropha curcas L.)accessions.Biomass Bioenergy 31(7):497–502.doi:10.1016/j.biombioe.2007.01.021

Kelly CK(1995)Seed size in tropical trees:a comparative study of factors affecting seed size in Peruvian angiosperms.Oecologia 102(3):377–388.doi:10.1007/BF00329805

Kgathi DL,Mfundisi KB,Mmopelwa G,Mosepele K(2012)Potential impacts of biofuel development on food security in Botswana:a contribution to energy policy.Energy Policy 43:70–79.doi:10.1016/j.enpol.2011.12.027

Kheira AA,Atta NMM(2009)Response of Jatropha curcas L.to water de ficits:yield,water use ef ficiency and oilseed characteristics.Biomass Bioenergy 33(10):1343–1350.doi:10.1016/j.biombioe.2008.05.015

King AJ,He WJA,Freudenberger M,Ramiaramanana D,Graham IA(2009)Potential of Jatropha curcas as a source of renewable oil and animal feed.J Exp Bot 60(10):2897–2905.doi:10.1093/jxb/erp025

Koc?ar G,Civas?N(2013)An overview of biofuels from energy crops:current status and future prospects.Renew Sustain Energy Rev 28:900–916.doi:10.1016/j.rser.2013.08.022

Kritana P,Gheewala SH (2006)Energy and greenhouse gas implications of biodiesel production from Jatropha curcas L.Paper presented at the second joint international conference on sustainable energy and environment,Bangkok,21–23 November 2006

Kumar A,Sharma S(2008)An evaluation of multipurpose oil seed crop for industrial uses(Jatropha curcas L.):a review.Ind Crop Prod 28(1):1–10.doi:10.1016/j.indcrop.2008.01.001

Kumar S,Singh J,Nanoti SM,Garg MO(2012)A comprehensive life cycle assessment(LCA)of Jatropha biodiesel production in India.Bioresour Technol 110:723–729.doi:10.1016/j.biortech.2012.01.142

Larson ED(2006)A review of life-cycle analysis studies on liquid biofuel systems for the transport sector.Energy Sustain Dev 10(2):109–126.doi:10.1016/S0973-0826(08)60536-0

Lewandowski I,Scurlock JMO,Lindvall E,Chistou M(2003)The development and current status of perennial rhizomatous grasses as energy crops in the US and Europe.Biomass Bioenergy 25(4):335–361

Lewis KC,Read D,Porter RD(2014)Global approaches to addressing biofuel-related invasive species risks and incorporation into U.S.laws and policies.Ecol Monogr 84(2):171–201.doi:10.1890/13-1625.1

Liang Y,Chen H,Tang M,Yang P,Shen S(2007)Responses of Jatropha curcas seedlings to cold stress:photosynthesis related proteins and chlorophyll fluorescence characteristics.Physiol Plant 131(3):508–517.doi:10.1111/j.1399-3054.2007.00974.x

Lioglier HA (1990)Medicinal plants of Puerto Rico and the Caribbean.Iberoamericana,Editions Inc,San Juan

Lockwood J,Cassey P,Blackburn T(2005)The role of propagule pressure in explaining species invasions.Trends Ecol Evol 20(5):223–228.doi:10.1016/j.tree.2005.02.004

Loos TK(2008)Socio-economic impact of a Jatropha-project on smallholder farmers in Mpanda.Master Thesis,University of Hohenheim,Hohenheim

Lopez O,Foidl G,Foidl N(1997)Production of biogas from Jatropha curcus fruit shells.In:Gübitz GM,Mittelbach M,Trabi MM(eds)Proceedings of the Symposium on Jatropha 97,23–27 February 1997,Graz,Austria

Low T,Booth C,Sheppard A(2011)Weedy biofuels:what can be done?Curr Opin Environ Sustain 3(1–2):55–59.doi:10.1016/j.cosust.2010.12.007

Maciel FM,Laberty MA,Oliveira ND,Felix SP,Soares AMD,Verícimo MA,Machado OLT(2009)A new 2S albumin from Jatropha curcas L.and assessment of its allergenic properties.Peptides 30:2103–2107

Mack RN,Simberloff D,Lonsdale WM,Evans H,Clout M,Bazzaz F(2000)Biotic invasions:causes,epidemiology,global consequences and control.Ecol Appl 10(3):689–710.doi:10.2307/2641039

Makkar HPS,Becker K(2009)Jatropha curcas,a promising crop for the generation of biodiesel and value-added coproducts.Eur J Lipid Sci Technol 111(8):773–787.doi:10.1002/ejlt.200800244

Makkar HPS,Becker K,Schmook B(1998)Edible provenances of Jatropha curcas from Quintana Roo state of Mexico and effect of roasting on antinutrient and toxic factors in seeds.Plant Food Hum Nutr 52(1):31–36.doi:10.1023/A:1008054010079

Maltsoglou I,Koizumi T,Felix E(2013)The status of bioenergy developmentin developing countries.Glob Food Secur 2(2):104–109.doi:10.1016/j.gfs.2013.04.002

Mariappan N,Srimathi P,Sundaramoorthi L,Sudhakar K(2014)Effect of growing media on seed germination and vigor in biofuel tree species.J For Res 25(4):909–913.doi:10.1007/s11676-014-0484-8

Martínez-Herrera J,Siddhuraju P,Francis G,Davila-Ortiz G,Becker K (2006)Chemicalcomposition,toxic/antimetabolicconstituents,and effects of different treatments on their levels,in four provenances of Jatropha curcas L.from Mexico.Food Chem 96(1):80–899.doi:10.1016/j.foodchem.2005.01.059

Misra M,Misra AN(2010)Jatropha:the biodiesel plant biology,tissue culture and genetic transformation–a review.Int J Pure Appl Sci Technol 1(1):1–24

Mitchell A(2008)The implications of smallholder cultivation of the biofuel crop,Jatropha curcas,for local food security and socioeconomic development in northern Tanzania.Masters Thesis,University of London(England),Department of Anthropology and Ecology of Development

Mitchell D(2011)Biofuels in Africa:opportunities,prospects,and challenges.World Bank,Washington,DC

Mohr A,Raman S(2013)Lessons from first generation biofuels and implications for the sustainability appraisal of second generation biofuels.Energy Policy 63:114–122.doi:10.1016/j.enpol.2013.08.033

Mulugetta Y(2008)Evaluating the economics of biodiesel in Africa.Renew Sustain Energy Rev 13(6–7):1592–1598.doi:10.1016/j.rser.2008.09.011

Muys B,Norgrove L,Alamirew T,Birech R,Chirinian E,Delelegn Y,Ehrensperger A,Ellison CA,Feto A,Freyer B,Gevaert J,Gmünder S,Jongschaap REE,Kaufmann M,Keane J,Kenis M,Kiteme B,Langat J,Lyimo R,Moraa V,Muchugu J,Negussie A,Ouko C,Rouamba MW,Soto I,W?rgetter M,Zah R,Zetina R(2013)Integrating mitigation and adaptation into development:the case of Jatropha curcas in sub-Saharan Africa.GCB Bioenergy 6:169–171.doi:10.1111/gcbb.12070

Naik S,Goud VV,Rout PK,Dalai AK(2010)Production of first and second generation biofuels:a comprehensive review.Renew Sustain Energy Rev 14(2):578–597.doi:10.1016/j.rser.2009.10.003

Ndong R,Montrejaud-Vignoles M,Saint Girons O,Gabrielle B,Pirot R,Domergue M,Sablayrolles C(2009)Life cycle assessment of biofuels from Jatropha curcas in West Africa:a field study.GCB Bioenergy 1(3):197–210.doi:10.1111/j.1757-1707.2009.01014.x

Negussie A,Achten WMJ,Aerts R,Norgrove L,Sinkala T,Hermy M,Muys B(2013a)Invasiveness risk of the tropical biofuel crop Jatropha curcas L.into adjacent land use systems:from the rumours to the experimental facts. GCB Bioenergy 5(4):419–430.doi:10.1111/gcbb.12011

Negussie A,Achten WMJ,Norgrove L,Hermy M,Muys B(2013b)Invasiveness risk of biofuel crops using Jatropha curcas L.as a model species.Biofuel Bioprod Biore fin 7(5):485–498.doi:10.1002/bbb.1416

Openshaw K(2000)A review of Jatropha curcas:an oil plant of unful filled promise.Biomass Bioenergy 19:1–15

Orwa C,Mutua A,Kindt R,Jamnadass R,Anthony S(2009)Agroforestree database:a tree reference and selection guide version 4.0. http://www.worldagroforestry.org/af/treedb/.Accessed 10 Feb 2016

Osamu K,Carl HW(1989)Biomass handbook.Gordon Breach Science Publisher,Philadelphia

Patil VK,Bandare P,Kulkani PB,Naik GR(2015)Progeny evaluation of Jatropha curcas and Pongamia pinnata with comparison to bioproductivity and biodiesel parameters.J For Res 26(1):137–142.doi:10.1007/s11676-014-0546-y

Peres CA,Schiesari LC,Dias-Leme CL(1997)Vertebrate predation of Brazil-nuts(Bertholletia excelsa,Lecythidaceae),an agoutidispersed Amazonian seed crop:a test of the escape hypothesis.J Trop Ecol 13(1):69–79

Pimentel D,McNair S,Janecka J,Wightman J,Simmonds C,O’Connell C,Wong E,Russel L,Zern J,Aquino T,Tsomondo T(2001)Economic and environmental threats of alien plant,animal,and microbe invasions.Agric EcosystEnviron 84(1):1–20.doi:10.1016/S0167-8809(00)00178-X

Purkayastha J,Sugla T,Paul A,Mazumdar P,Basu A,Solleti SK,Mazumdar P,Basu A,Mohommad A,Ahmed Z,Sahoo L(2010)Ef ficient in vitro plant regeneration from shoot apices and gene transfer by particle bombardment in Jatropha curcas.Biol Plant 54(1):13–20.doi:10.1007/s10535-010-0003-5

Py?ek P,Richardson DM(2007)Traits associated with invasiveness in alien plants:where do we stand?In:Nentwig W(ed)Ecological studies.Springer,New York

Quinn LD,Barney JN,McCubbins JSN,Endres AB(2013)Navigating the ‘noxious’and‘invasive’regulatory landscape:suggestions for improved regulation.Bioscience 63(2):124–131.doi:10.1525/bio.2013.63.2.8

Quirin M,G?rtner SO,Pehnt M,Reinhardt GA(2004)CO2mitigation through Biofuels in the transport sector—tatus and perspectives,IFEU Institute for Energy and Environmental Research,Heidelberg.http://www.ifeu.de

Raghu S,Anderson RC,Daehler CC,Davis AS,Wiedenmann RN,Simberloff D,Mack RN(2006)Adding biofuels to the invasive species fire?Science 313(22):1742

Rakkimuthu R,Nithya PS,Aravinthan KM(2011)In vitro propagation of Jatropha curcas L—a valuable multipurpose crop.Adv Biotech 11:24–25

Ranade SA,Srivastava AP,Rana TS,Srivastava J,Tuli R(2008)Easy assessment of diversity in Jatropha curcas L.plants using two single-primer ampli fication reaction(SPAR)methods.Biomass Bioenergy 32(6):533–540.doi:10.1016/j.biombioe.2007.11.006

Randall J(1996)Weed control for the preservation of biological diversity.Weed Technol 10(2):370–383

Rao AVRK,Wani SP,Singh P,Srinivas K,Rao ChS(2012)Water requirement and use by Jatropha curcas in semi-arid tropical location.Biomass Bioenergy 39:175–181.doi:10.1016/j.biom bioe.2012.01.013

Rejmánek M(2000)Invasive plants:approaches and predictions.AustralEcol25(5):497–506.doi:10.1046/j.1442-9993.2000.01080.x

Rejmánek M,Richardson DM(1996)What attributes make some plant species more invasive?Ecology 77(6):1655–1661.doi:10.2307/2265768

Renner R(2007)Green gold in a shrub.Entrepreneurs target the Jatropha plant as the next big biofuel.Sci Am 296:20–23.doi:10.1038/scienti ficamerican0607-20

Ricci A,Chekhovskiy K,Azhaguvel P,Albertini E,Falcinelli M,Saha M(2012)Molecular characterization of Jatropha curcas L.Resources and identi fication of population-speci fic markers.Bioenergy Res 5(1):215–224.doi:10.1007/s12155-011-9150-6

Richardson DM,Blanchard R(2011)Learning from our mistakes:minimizing problems with invasive biofuel plants.Curr Opin Env Sustainability 3(1–2):36–42.doi:10.1016/j.cosust.2010.11.006

Robertson GP,Dale VH,Doering OC,Hamburg SP,Melillo JM,Wander MM,Parton WJ,Adler PR,Barney JN,Cruse RM,Duke CS,Fearnside PM,Follett RF,Gibbs HK,Goldemberg J,Mladenoff DJ,Ojima D,Palmer MW,Sharpley A,Wallace L,Weathers KC,Wiens JA,Wilhelm WW(2008)Agriculture.Sustainable biofuels redux.Science 322:49–50.doi:10.1126/science.1161525

Romijn HA(2011)Land clearing and greenhouse gas emissions from Jatropha biofuels on African Miombo Woodlands.Energy Policy 39:5751–5762.doi:10.1016/j.enpol.2010.07.041

Romijn HA,Caniels MCJ(2011)The Jatropha biofuels sector in Tanzania 2005–2009:evolution towards sustainability?Res Policy 40(4):618–636.doi:10.1016/j.respol.2011.01.005

Royal Botanic Gardens Sydney(2008)Australia’s Virtual Herbarium.Royal Botanic Gardens,Sydney,Australia.http://avhtas.tmag.tas.gov.au/.Accessed 12 Dec 15

Sabandar CW,Ahmat N,Jaafar FM,Sahidin I(2013)Medicinal property,phytochemistry and pharmacology of several Jatropha species(Euphorbiaceae):a review.Phytochemistry 85:7–29.doi:10.1016/j.phytochem.2012.10.009

Sachdeva K,Garg P,Singh M,Srivastava B(2011)Wound healing potential of extract of Jatropha curcas L.(stem bark)in rats.Pharmacogn J 3(25):67–72.doi:10.5530/pj.2011.25.12

Sanderson K(2009)Wonder weed plans fail to flourish.Nature 461(7262):328–329.doi:10.1038/461328a

Scarlat N,Dallemand JF(2011)Recent developments of biofuels/bioenergy sustainability certi fication:a global overview.Energy Policy 39(3):1630–1646.doi:10.1016/j.enpol.2010.12.039

Scharlemann J,Laurance W(2008)How green are biofuels?Science 319:43

Schmook B,Seralta-Peraza L(1997)Jatropha curcas:distribution and uses in the Yucatan Peninsula of Mexico.In:Gübitz GM,Mittelbach M,Trabi M(eds)Biofuels and industrial products from Jatropha curcas.Graz

Searchinger T,Heimlich R,Houghton RA,Dong F,Elobeid A,Fabiosa J,Tokgoz S,Heyes D,Yu TH(2008)Use of U.S.croplands for biofuels increases greenhouse gases through emissions from land use change. Science 319(5867):1238–1240.doi:10.1126/science.1151861

Segerstedt A,Bobert J(2013)Revising the potential of large-scale Jatropha oil production in Tanzania:an economic land evaluation assessment.Energy Policy 57:491–505.doi:10.1016/j.enpol.2013.02.023

Singh L,Bargali SS,Swamy SL(2006)Production,practices and post-Harvest Management in Jatropha.In:B Singh,R Swaminathan,V Ponraj(eds)Proceedings of the biodiesel conference toward energy independence—focus of Jatropha.Rashtrapati Bhawan,New Delhi

Singh B,Singh K,Shukla G,Goel VL,Pathre UV,Rahi TS,Tuli R(2013a)The field performance of some accessions of Jatropha curcas L.(biodiesel plant)on degraded sodic land in North India.Int J Green Energy 10(10):1026–1040.doi:10.1080/15435075.2012.738336

Singh BSK,Rao GR,Chikara J,Kumar D,Mishra DK,Saikia SP,Pathre UV,Raghuvanshi N,Rahi TS,Tuli R(2013b)Agrotechnology of Jatropha curcas for diverse environmental conditions in India.Biomass Bioenergy 48:191–202.doi:10.1016/j.biombioe.2012.11.025

Soo-Young N(2011)Inedible vegetable oils and their derivatives for alternative diesel fuels in CI engines:a review.Renew Sustain Energy Rev 15(1):131–149.doi:10.1016/j.rser.2010.08.012

Spaan W,Bodnár F,Idoe O,De Graaff J(2004)Implementation of contour vegetation barriers under farmer’s conditions in Burkina Faso and Mali.Q J Int Agric 43(1):21–38

Srivastava P,Behera SK,Gupta J,Jamil S,Singh N,Sharma YK(2011)Growth performance,variability in yield traits and oil content of selected accessions of Jatropha curcas L.growing in a large scale plantation.Biomass Bioenergy 35(9):3936–3942.doi:10.1016/j.biombioe.2011.06.008

Staubmann R,Foidl G,Foidl N,Gübitz GM,Lafferty RM,Arbizu VM,Steiner W(1997)Biogas production from Jatropha curcas press cake.Appl Biochem Biotech 63–65:457–467

Steer A,Hanson C(2015)Biofuels are not a green alternative to fossil fuels.http://www.theguardian.com/environment/2015/jan/29/bio fuels-are-not-the-green-alternative-to-fossil-fuels-they-are-soldas.Accessed 15 Nov 15

Stewart JR,Toma Y,Fernabdez FG,Nishiwaki A,Yamada T,Bollero G(2009)The ecology and agronomy of Miscanthus sinensis,a species important to bioenergy crop development,in its native range in Japan:a review.GCB Bioenergy 1:126–153.doi:10.1111/j.1757-1707.2009.01010.x

Tang W,Tang AY(2014)Transgenic woody plants for biofuel.J.For Res 25(2):225–236.doi:10.1007/s11676-014-0454-1

Tilman D,Socolow R,Foley JA,Hill J,Larson E,Lynd L,Pacala S,Reilly J,Searchinger T,Somerville C,Williams R(2009)Bene ficial biofuels–The food,energy and environment trilemma.Science 325(5938):270–271.doi:10.1126/science.1177970

Tiwari AK,Kumar A,Raheman H(2007)Biodiesel production from Jatropha(Jatropha curcas)with high free fatty acids:an optimized process.Biomass Bioenergy 31(8):569–575.doi:10.1016/j.biombioe.2007.03.003

Tobin J,Fulford DJ(2005)Life cycle assessment of the production of biodiesel from Jatropha.Masters Dissertation,The University of Reading(UK)

van Eijck J,Smeets E,Jongschaap R,Romijn H,Balkema A(2010)Jatropha assessment;agronomy,socio-economic issues and ecology,facts from literature.Copernicus Institute,Utrecht University,Eindhoven University of Technology and Wageningen PRI,Utrecht.http://www.agentschapnl.nl/content/reportjatrophaassessment

van Eijck J,Smeets E,Faaij A(2012)The economic performance of jatropha,cassava and eucalyptus production systems for energy in an East African smallholder setting.Global Change Bioenerg 4(6):828–845.doi:10.1111/j.1757-1707.2012.01179.x

van Eijck J,Romijn H,Smeets E,Bailis R,Rooijakkers M,Hooijkaas N,Verweij P,Faaij A(2014)Comparative analysis of key socioeconomic and environmental impacts of smallholder and plantation based jatropha biofuel production systems in Tanzania.Biomass Bioenergy 61:25–45.doi:10.1016/j.biombioe.2013.10.005

van Vuuren DP,van Vliet J,Stehfest E(2009)Future bio-energy potential under various natural constraints.Energy Policy 37(11):4220–4230.doi:10.1016/j.enpol.2009.05.029

Vitousek PM,Mooney HA,Lubchenco J,Melillo JM(1997)Human domination of earth’s ecosystem.Science 277(5325):494–499.doi:10.1126/science.277.5325.494

von Maltitz G,Gasparatos A,Fabricius C(2014)The rise,fall and potential resilience bene fits of Jatropha in Southern Africa.Sustainability 6(6):3615–3643.doi:10.3390/su6063615

Wani TA,Kitchku S,Ram G(2012)Genetic variability studies for morphological and qualitative attributes among Jatropha curcas L.accessions grown under subtropical conditions of North India.S Afr J Bot 79:102–105.doi:10.1016/j.sajb.2011.10.009

Whitaker M,Heath G(2008)Life cycle assessmentof the use of Jatropha biodiesel in Indian locomotives.Technical Report NREL/TP-6A2-44428,National Renewable Energy Laboratory,US Department of Energy,Golden,CO.http://www.osti.gov/bridge

Willson MF,Traveset A(2000)The ecology of seed dispersal.In:Fenner M(ed)Seeds:The ecology of regeneration in plant communities.CABI International,Wallingford,pp 85–110

Wiskerke WT,Dornburg V,Rubanza CDK,Malimbwi RE,Faaij APC(2010)Cost/bene fit analysis of biomass energy supply options for rural smallholders in the semi-arid eastern part of Shinyanga Region in Tanzania.Renew Sustain Energy Rev 14(1):148–165.doi:10.1016/j.rser.2009.06.001

Wittenberg R,Cock MJW(2001)Invasive alien species:A toolkit of best prevention and management practices.CAB International,Wallingford

Zegada-Lizarazu W,Monti A(2012)Are we ready to cultivate sweet sorghum as a bioenergy feedstock?A review on field management practices.Biomass Bioenergy 40:1–12.doi:10.1016/j.biombioe.2012.01.048

Ziolkowska J(2014)Optimizing biofuels production in an uncertain environment:conventional vs.advanced technologies.Appl Energy 114:366–376.doi:10.1016/j.apenergy.2013.09.060