Wouter Achten

Towards domestication of Jatropha curcas

Jatropha curcas L. attracts a lot of interest as a biofuel crop, triggering large investments and rapid expansion of cultivation areas, and yet, it should still be considered as a (semi-)wild, undomesticated plant. To use the full potential of Jatropha and to support further expansion and systematic selection, breeding and domestication are a prerequisite. This review reveals and identifies gaps in knowledge that still impede domestication of Jatropha. Prebreeding knowledge is limited. In particular, the regeneration ecology and the degree of genetic diversity among and within natural populations in and outside the center of origin are poorly studied. There is only a limited understanding of the Jatropha breeding system and the effect of inbreeding and outbreeding. This review presents all currently available and relevant information on the species distribution, site requirements, regeneration ecology, genetic diversity, advances in selection, development of varieties and hybridization. It also describes possible routes to a better Jatropha germplasm, gives recommendations for tackling current problems and provides guidance for future research. We also discuss the participatory domestication strategy of Jatropha integration in agroforestry.

Global mapping of Jatropha curcas yield based on response of fitness to present and future climate.

Although acclaimed as a biofuel crop with high potential to sustainably replace fossil fuels, Jatropha curcas L. remains a poorly studied plant. Reliable yield assessments with conventional methods require agroclimatic and physiological knowledge, which is not yet available for Jatropha. To fill this gap, we tested a novel two‐step approach integrating knowledge from biogeography and population biology with available Jatropha field data. In the first step, using MaxEnt, a widely implemented model in biogeography, we predicted Jatropha fitness in response to climate by relating natural occurrence recorded in herbaria with bioclimatic geodatasets. In the second step, we relied on population biology principles supported by seed mass addition experiments to relate fitness to reproductive potential, hence seed yield. Jatropha seed yield in response to climate was mapped worldwide for actual (1950–2000 average) and future (2020) climate conditions. The modelled Jatropha seed yield was validated against a set of on‐field yield assessments (R2=0.67, P<0.001). The discrepancies between estimated and measured yields were partially explained by model uncertainties, as quantified by the sensitivity analysis of our modelling (R2=0.57, P=0.001). Jatropha has a pan‐tropical distribution, plus specific adaptability to hot temperate areas. Climate variables most significantly affecting modelled yield response were annual average temperature, minimum temperature, annual precipitation and precipitation seasonality.

Implications of biodiesel-induced land-use changes for CO2 emissions: case studies in Tropical America, Africa, and Southeast Asia

Biofuels are receiving growing negative attention. Direct and/or indirect land-use changes that result from their cultivation can cause emissions due to carbon losses in soils and biomass and could negate any eventual greenhouse gas (GHG) reduction benefit. This paper evaluates the implications of land-use change emission on the climate-change mitigation potential of different biofuel production systems in 12 case studies in six countries. We calculated carbon debts created by conversion of different land-use types, ranging from annual cropland to primary forest. We evaluated case studies using three different biofuel crops: oil palm, Jatropha, and soybean. The time needed for each biofuel production system to pay back its carbon debt was calculated based on a life-cycle assessment of the GHG reduction potentials of the system. Carbon debts range from 39 to 1743.7 Mg C0 2 ha -1. The oil palm case studies created the largest carbon debts (472.8-1743.7 t C0 2 ha -1) because most of the area expansion came at the expense of dense tropical forest. The highest debt was associated with plantation on peatland. For all cases evaluated, only soybean in GuarantA£ do Norte and Alta Floresta, Brazil needed less than one human generation (30 years) to repay the initial carbon debt. Highest repayment times were found for Jatropha (76-310 years) and oil palm (59-220 years) case studies. Oil palm established in peatlands had the greatest repayment times (206-220 years). High repayment times for Jatropha resulted from the combined effects of land-cover change and low CO 2 emission reduction rate. These outcomes raise serious questions about the sustainability of biofuel production. The carbon implications of conversion of (semi-)natural systems with medium to high biomass indicate that, in order to generate climate benefits, cultivation of biofuel feedstocks should be restricted to areas that already have low carbon content. © 2011 by the author(s).

Life cycle assessment of a palm oil system with simultaneous production of biodiesel and cooking oil in Cameroon.

The use of palm oil as a biofuel has been heavily debated for its land-use conflict with nature and its competition with food production, being the number one cooking oil worldwide. In that context, we present a life cycle assessment of a palm oil production process yielding both biodiesel and cooking oil, incorporating the land-use impact and evaluating the effect of treating the palm oil mill effluent (POME) prior to disposal. The results show that the nonrenewable energy requirement, global warming potential (GWP; exclusive land-use change), and acidification potential are lower than those of the fossil alternative. However, the system triggers an increase in eutrophication potential (EP) compared to the fossil fuel reference. This system shows less energy requirement, global warming and acidification reduction, and less eutrophication increase compared to the reference than the same system converting all palm oil into biodiesel (no cooking oil production). The land occupation of palm oil triggers ecosystem quality (EQ) loss of 30-45% compared to the potential natural vegetation. Furthermore, such land-use change triggers a carbon debt neutralizing the GWP reduction for 45-53 years. The POME treatment scenarios reveal a trade-off between GWP and EP.

Global greenhouse gas implications of land conversion to biofuel crop cultivation in arid and semi-arid lands: lessons learned from Jatropha

Biofuels are considered as a climate-friendly energy alternative. However, their environmental sustainability is increasingly debated because of land competition with food production, negative carbon balances and impacts on biodiversity. Arid and semi-arid lands have been proposed as a more sustainable alternative without such impacts. In that context this paper evaluates the carbon balance of potential land conversion to Jatropha cultivation, biofuel production and use in arid and semi-arid areas. This evaluation includes the calculation of carbon debt created by these land conversions and calculation of the minimum Jatropha yield necessary to repay the respective carbon debts within 15 or 30 years. The carbon debts caused by conversion of arid and semi-arid lands to Jatropha vary largely as a function of the biomass carbon stocks of the land use types in these regions. Based on global ecosystem carbon mapping, cultivated lands and marginal areas (sparse shrubs, herbaceous and bare areas) show to have similar biomass carbon stocks (on average 4e 8tCh a � 1 ) and together cover a total of 1.79 billion ha.

Use of inadequate data and methodological errors lead to an overestimation of the water footprint of Jatropha curcas

In their recent article, Gerbens-Leenes et al. (1) calculated the water footprint (WF), the amount of water required to produce 1 GJ of energy, of several bioenergy crops. The water footprint of Jatropha curcas was remarkably high (8.6 times higher than the WF of sugar beet, the most water-efficient crop), which may have serious implications for its future management.

Benchmarking the Environmental Performance of the Jatropha Biodiesel System through a Generic Life Cycle Assessment

In addition to available country or site-specific life cycle studies on Jatropha biodiesel we present a generic, location-independent life cycle assessment and provide a general but in-depth analysis of the environmental performance of Jatropha biodiesel for transportation. Additionally, we assess the influence of changes in byproduct use and production chain. In our assessments, we went beyond the impact on energy requirement and global warming by including impacts on ozone layer and terrestrial acidification and eutrophication. The basic Jatropha biodiesel system consumes eight times less nonrenewable energy than conventional diesel and reduces greenhouse gas emissions by 51%. This result coincides with the lower limit of the range of reduction percentages available in literature for this system and for other liquid biofuels. The impact on the ozone layer is also lower than that provoked by fossil diesel, although eutrophication and acidification increase eight times. This study investigates the general impact trends of the Jatropha system, although not considering land-use change. The results are useful as a benchmark against which other biodiesel systems can be evaluated, to calculate repayment times for land-use change induced carbon loss or as guideline with default values for assessing the environmental performance of specific variants of the system.

Invasiveness risk of the tropical biofuel crop Jatropha curcas L. into adjacent land use systems: from the rumors to the experimental facts

Jatropha curcas L. produces seeds rich in non‐edible oil suitable for biodiesel but it has been categorized as invasive. Although not scientifically verified, this allegation has resulted in a cultivation ban in several countries. In this article we report an integrated series of observations and experimental findings from invasiveness research in Zambia. We studied the impacts of J. curcas plantations on adjacent land use systems focusing on spontaneous occurrence of seedlings, seed dispersal mechanisms, seed predation by animals, and germination success of dispersed seeds. No spontaneous regeneration was observed in land use systems adjacent to J. curcas plantations. Primary seed dispersal was limited, predominantly under the canopy of the mother plant. Rodents and shrews dispersed and predated J. curcas seeds and fruits. They transported the seeds up to 23 m from the sources and repositioned them in their burrows up to 0.7 m deep, but none of these seeds could establish. Germination experiments in adjacent land use systems revealed 4% germination success at the soil surface, and 65% if buried artificially at 1–2 cm depth, yet the latter is unlikely to occur under natural conditions. These findings show that J. curcas seeds may be dispersed by animals to adjacent land use systems, but no natural recruitment was observed given low germination on the surface and none in burrows. Altogether these results suggest that the plant currently does not show an elevated risk of invasion to adjacent land use systems, at least in the investigated case study. But more long‐term studies, also in other growing areas are needed to corroborate these results.

Floral display and effects of natural and artificial pollination on fruiting and seed yield of the tropical biofuel crop Jatropha curcas L.

Jatropha curcas L. is a tropical tree grown on large scale as a potential biofuel seed crop. However, little information on the reproductive ecology of the species is available. This lack of knowledge makes it hard to predict yield. The higher number of male flowers than female flowers results in a very low yield. In this context, field experiments were conducted in mature (site 1) and young (site 2) plantations in Zambia and mature plantation (site 3) in Malawi to study flowering characteristics and the effect of pollination methods on the fruiting and seed yield of J. curcas. Pollination treatments were open pollination, autogamous pollination, self‐pollination, cross‐pollination and pollen supplemented open pollination. The result showed J. curcas is not only of protandrous nature as reported earlier. The male female flower sex ratio was 17 : 1, 22 : 1 and 10 : 1, respectively, for site 1 and 2 in Zambia and site 3 in Malawi. The mean flower longevity periods were 1.80 ± 0.07 days for male and 4.5 ± 0.18 days for female. Fewer fruit set and seed yield were recorded from autogamous pollination in Zambia sites. In the case of Malawi, more matured fruits resulted from autogamous pollination but the fruits contained fewer seeds. High fruit and seed yield were recorded for open pollination similar to pollen‐supplemented pollination at Zambia sites, which indicates there was no pollen limitation in these sites. In the Malawi site there was no seed yield difference between pollination treatments. The experiment showed that J. curcas can be both protandrous and protogynous and able to produce seeds through both self‐and cross‐pollination. The natural fruit set and seed yield indicates that stimulating natural pollination will improve J. curcas fruit set and seed yield.

Gully erosion in South Eastern Tanzania: spatial distribution and topographic thresholds

Summary. Though gully erosion is often mentioned as a major process of land degradationin South Eastern Tanzania, little information is available on its distribution. The Makondeplateau and adjacent inland plains are of particular concern as they are densely populated andare major areas of cashew nuts production. The occurrence of gully erosion was assessed in 66villages selected by stratified random sampling in an area of 13,000 km 2 . Difference in suscep-tibility to gully erosion between landscape units was assess by determining topographicthreshold parameters of 22 gullies on the Makonde plateau and 14 in the inland plains. Over-all, gullies are common and spread equally over the different landscape units. Their occurrenceis positively associated with terrain roughness (Cramer’s V = 0.30; P = 0.05) and negatively withpopulation density ( V = 0.44; P 0.01). On the Makonde plateau occurrence of gully erosionis associated with the presence of roads, while on the inland plains it is predominantly foundin fields (