Use of inadequate data and methodological errors lead to a dramatic 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. One of the most remarkable findings of this study was the very high water footprint of this species, which has serious management consequences. 

However, these results are in apparent contrast with recent findings on this species. We present evidence that several errors were made by the authors when calculating the water footprint of jatropha, which has lead to a dramatic overestimation. These errors include weaknesses concerning the data used for the calculation of the water footprint, as well as flaws in the calculation method, as we demonstrate in the letter. Based on peer-reviewed data, we furthermore provide a more correct, still rough, first estimate for the water footprint of this species, which would place it amongst the more water efficient bioenergy crops. 

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Proposing a life cycle land use impact calculation methodology

The Life Cycle Assessment (LCA) community is yet to come to a consensus on a methodology to incorporate land use in LCA, still struggling with what exactly should be assessed and which indicators should be used. To solve this problem we start from concepts and models describing how ecosystems function and sustain, in order to understand how land use affects them. Earlier our research group presented a methodology based on the ecosystem exergy concept. This concept as based on the hypothesis that ecosystems develop towards more effective degradation of exergy fluxes passing through the system and is derived from two axioms: the principles of (i) maximum exergy storage and the (ii) maximum exergy dissipation. This concept aiming at the area of protection natural environment is different from conventional exergy analysis in LCA focusing on natural resources. To prevent confusion, the ecosystem exergy concept is further referred to as the MAximum Storage and Dissipation concept (MASD concept). In this paper we present how this concept identifies end-point impacts, mid-point impacts and mid-point indicators. The identified end-point impacts to assess are Ecosystem Structural Quality (ESQ) and Ecosystem Functional Quality (EFQ). In order to quantify these end-point impacts a dynamic multi-indicator set is proposed for quantifying the mid-point impacts on soil fertility, biodiversity and biomass production (quantifying the ESQ) and soil structure, vegetation structure and on-site water balance (quantifying the EFQ). Further we present an impact calculation method suitable for different environmental assessment tools and demonstrate the incorporation of the methodology in LCA

Proposing a life cycle land use impact calculation methodology

The Life Cycle Assessment (LCA) community is yet to come to a consensus on a methodology to incorporate land use in LCA. Earlier our research group presented a methodology based on the ecosystem exergy concept. The ecosystem exergy concept suggests that ecosystems develop towards more effective degradation of energy fluxes passing through the system. The concept is argued to be derivable from two axioms: the principles of (i) maximum exergy storage and the (ii) maximum exergy dissipation. In this paper we present a methodology to assess impacts of human induced land use occupation, in which we make a difference between functional and structural land use impacts. The methodology follows a dynamic multi-indicator approach looking at mid-point impacts on soil fertility, soil structure, biomass production, vegetation structure, on-site water balance and biodiversity. The impact scores are calculated as a relative difference with a reference system. We propose to calculate the impact by calculating the land quality change between the former and the actual land use relative to the quality of the potential natural vegetation. Impact scores are then aggregated, as endpoint impacts, in (i) structural land use impact (exergy storage capacity) and (ii) functional land use impact (exergy dissipation capacity). For aggregation of the relative mid-point impact scores no characterization factor is used. In order to fit this impact calculation in the LCA framework the end-point impact scores are multiplied by a LCA component, a component that enables us to report the impact per functional unit

EFO-LCI: A New Life Cycle Inventory Database of Forestry Operations in Europe

Life cycle assessment (LCA) has become a common methodology to analyze environmental impacts of forestry systems. Although LCA has been widely applied to forestry since the 90s, the LCAs are still often based on generic Life Cycle Inventory (LCI). With the purpose of improving LCA practices in the forestry sector, we developed a European Life Cycle Inventory of Forestry Operations (EFO-LCI) and analyzed the available information to check if within the European forestry sector national differences really exist. We classified the European forests on the basis of "Forest Units" (combinations of tree species and silvicultural practices). For each Forest Unit, we constructed the LCI of their forest management practices on the basis of a questionnaire filled out by national silvicultural experts. We analyzed the data reported to evaluate how they vary over Europe and how they affect LCA results and made freely available the inventory data collected for future use. The study shows important variability in rotation length, type of regeneration, amount and assortments of wood products harvested, and machinery used due to the differences in management practices. The existing variability on these activities sensibly affect LCA results of forestry practices and raw wood production. Although it is practically unfeasible to collect site-specific data for all the LCAs involving forest-based products, the use of less generic LCI data of forestry practice is desirable to improve the reliability of the studies. With the release of EFO-LCI we made a step toward the construction of regionalized LCI for the European forestry sector

Potential Ecosystem Services of Urban Agriculture

Abstract Urban agriculture (UA) is increasingly proposed as an environmentally friendly answer to global challenges including urbanization, public health, food security and climate change. We provide an overview of present evidence of ecosystem services delivered by UA that could potentially increase the sustainability of the urban ecosystem, including the often claimed reduced greenhouse gas emissions. There is general agreement that UA is important for local food production, especially in the south; that UA has a role in regulating green and blue water flows, organic waste flows and pollination; and that UA has important socio-cultural values, including an improved quality of city life and increased local community capacity. There is some evidence that UA may also improve human health because of dietary changes in certain social classes, but these are potentially confounded by environmental pollution in the city. Quantitative evidence is very limited for all ecosystem services, but the available data nevertheless suggests that the overall food productivity and the total reductions in greenhouse gas emission are low at global or city-wide scale despite the fact that UA has potential strong effects on food security at the local scale. The current eagerness of industrialized cities to integrate UA into their food policies as an approach to become "climate neutral" or to rely on ecosystem services to become more resilient calls for life cycle assessment studies that accurately quantify emission reductions and other urban ecosystem services of urban agriculture

Effects of accession, spacing and pruning management on in-situ leaf litter decomposition of Jatropha curcas L. in Zambia

Jatropha curcas L. leaf litter decomposition and subsequent nutrient release was monitored in three experimental J. curcas plantations in Zambia, comparing accessions from six countries, pruned versus non-pruned and different plant spacings. Leaf litter production was low (267-536 kg ha-1 at the end of the growing season) and contained, on average, 1.23% N, 0.14% P and 2.61% K. Litter decomposed rapidly, losing 80% of total mass by 70 to 105 days after incubation in the field and followed a negative exponential pattern with an average decomposition constant, k, of 0.08 week-1. No significant effects of plant accession, plant spacing or pruning on the decomposition rate were detected. K, P, Mg and Na had nutrient release rates exceeding mass loss, explained by their high mobility and solubility, together with high soil temperature and rainfall conditions. Others, such as Ca and Mn, were initially retained in the decaying leaf litter before later release. The rate of N release closely approached that of mass loss. Jatropha curcas litter can be a supplemental source of nutrients in areas known for nutrient deficiency and low organic matter, which represents an additional input in intercropping systems above biofuel production. In addition J. curcas, sheds its leaves during the dry season and these can be used as mulch to minimize soil desiccation at least during the first dry period. Considering that the total primary nutrient input through J. curcas litterfall to the soil is limited (for example, for nitrogen between 9.7 and 14.2 g kg–1 and for phosphorus between 0.8 and 1.9 g kg–1), organic or mineral fertilizer application remains crucial to satisfy fully the nutrient requirements of surrounding crops