• Energy Research

Whereas life cycle assessment (LCA) is more and more used for assessing the environmental load of waste management systems and of biomass production and valorization systems, various scientific issues are still to be dealt with. The purpose of this paper is to enlighten these scientific issues and to describe the current attempt to overcome them. The method used has been to go through the steps of the LCA standardized framework (ISO 14040) and to outline at each step the points that could be improved and still deserve research efforts. The various identified issues are: in step 1 (goal and scope), the choice of attributional/consequential modelling, the difficult choice of the functional unit due to the highly multi-functional nature of such systems, the allocation choices and the need for spatial differentiation; in step 2 (inventory), the thorny issue of modelling such complex systems and properly estimating field emissions; in step 3 (impact assessment), the lack of appropriate impacts (such as odours) in current LCA impact categories; in step 4 (interpretation and use), research efforts are needed to understand and facilitate the way actors take over and use LCA multi-criteria results. A transversal issue, i.e. uncertainty characterization and reduction, is also analyzed. These various scientific bottlenecks are currently under study; some are handled by this “Waste and Biomass Valorization” special topic, which includes a selection of papers presented in 2011 at the Ecotech&Tools conference (Montpellier, France).

The greenhouse gas (GHG) balance of biofuels largely hinges on the magnitude of nitrous oxide (N2O) emissions from arable soils during feedstock production, which are highly variable. Here, used an agro-ecosystem model to generate these emissions at a high resolution over the Ile-de-France region in Northern France, for a range of feedstocks. The emissions were input to a life-cycle assessment of candidate biofuel pathways: bioethanol from wheat and sugar-beet, biodiesel from oilseed rape, and ethanol from miscanthus. Compared to the widely-used methodology based on fixed emission factors, ecosystem modelling lead to 55% to 70% lower estimates for N2O emissions, emphasizing the importance of regional factors. The life-cycle GHG emissions of 1st generation biofuels were 50% to 70% lower than fossile-based equivalents, and 85% lower for cellulosic ethanol. Indirect land-use change effects negated these savings for bio-diesel and wheat ethanol, but were offset by direct effects for cellulosic ethanol.

Abstract The environmental sustainability of biofuel production is still a debated issue in the world bio-economy development. Therefore, different researches are undergoing to evaluate the sustainability of ethanol production in different countries. This study aimed at analyzing the environmental performance of ethanol production in Ethiopia, considering energy balance and emission reduction using a life cycle assessment approach. It is also intended to identify the environmental hotspots so that possible improvement option can be devised. The life cycle assessment methodology was applied considering three alternative scenarios: 1) Base Case, which is the current situation, 2) Alternative 1, which considers the utilization of biogas from vinasse and bioslurry, and 3) Alternative 2, which includes mechanical harvesting and avoids pre-harvest cane trash burning. The results show that agricultural stage is greatly contributing to the pollutant emissions. The contribution of cane trash burning was significant to all the impact categories considered and avoiding pre-harvest cane trash burning significantly reduced the emissions contributing to global warming, acidification, stratospheric ozone depletion, ozone formation, particulate matter and eutrophication. On the other hand, the introduction of mechanical harvesting to avoid pre-harvest cane trash burning increased ecotoxicity, human toxicity and resource consumption (land, water and mineral) impacts. The net energy balance is positive for all the alternatives considered. In addition to using by-products, proper management of fuel utilization at the agricultural stage can further enhance benefits from the sector. Sensitivity analysis revealed that the price of molasses highly influences both energy ratio and greenhouse gas emissions since it completely shifts the allocation of upstream emissions from sugar to molasses.

Perennial crops globally provide a lot of fruit and other food products. They may also provide feedstock for bioenergy and have been, notably to this end, the subject of several LCA-based studies mostly focusing on energy and GHG balances. The purpose of this review was to investigate the relevance of LCAs on perennial crops, especially focusing on how the perennial crop specificities were accounted for in the farm stage modelling. More than 100 papers were reviewed covering 14 products from perennial crops: apple, banana (managed over several years), orange and other citrus fruits, cocoa, coconut, coffee, grape fruit, Jatropha oil, kiwi fruit, palm oil, olive, pear and sugarcane. These papers were classified into three categories according to the comprehensiveness of the LCA study and depending on whether they were peer-reviewed or not. An in-depth analysis of the goal and scope, data origin for farming systems, modelling approach for the perennial cropping systems and methods and data for field emissions helped reveal the more critical issues and design some key recommendations to account better for perennial cropping systems in LCA. In the vast majority of the reviewed papers, very little attention was paid on integrating the perennial cropping cycle in the LCA. It is especially true for bioenergy LCA-based studies that often mostly focused on the industrial transformation without detailing the agricultural raw material production, although it might contribute to a large extent to the studied impacts. Some key parameters, such as the length of the crop cycle, the immature and unproductive phase or the biannual yield alternance, were mostly not accounted for. Moreover, the lack of conceptual modelling of the perennial cycle was not balanced by any attempt to represent the temporal variability of the system with a comprehensive inventory of crop managements and field emissions over several years. According to the reviewed papers and complementary references, we identified the gaps in current LCA of perennial cropping systems and proposed a road map for scientific researches to help fill-in the knowledge-based gaps. We also made some methodological recommendations in order to account better for the perennial cycle within LCA considering the aim of the study and data availability.

Oil palm cultivation has drastically increased in the last decades and has become a key crop to meet the global vegetable oil demand, while raising environmental issues linked to deforestation, fertiliser or pesticide uses. Guidelines on best practices have been developed to limit these environmental impacts. However, there is little evidence on the field reality of concrete declination of these general guidelines and on the room for improvement of practices in light of the local diversity of oil palm systems. This study aimed to investigate in the field the actual practices in two contrasted areas in Indonesia, the first global palm oil producer. We carried out field surveys in Riau and Jambi provinces and collected data on annual applications of two synthetic mineral fertilisers, two herbicides and yields. We characterised the cropping systems of 88 smallholders’ and 45 industrial plantation units including potential practice drivers. Both qualitative and quantitative analyses showed contrasted practices across growers. Fertiliser rates were variable across all grower types, while pesticide rates especially distinguished between industrial and smallholders’ practices. Practices and performances were particularly variable amongst smallholders, and significantly different in Jambi compared to Riau. This study highlighted the great diversity of practices and potential environmental impacts. It stresses the need for a more systematic accounting of the local specificities of the cropping systems and their rationales in order to promote more adapted and efficient best practices recommendations.

Key messages: - Several sustainability certification schemes have been developed for palm oil; however, the field impacts of these schemes remain highly uncertain. The Sustainable Palm Oil Production (SPOP) project, funded by the French National Research Agency (ANR), was aimed at consolidating and deepening the scientific basis of these schemes. - SPOP field work undertaken in Indonesia and Cameroon highlighted the large variability in practices and impacts of oil palm systems. Our main results related to the uncovering of the multiplicity of growers and their trajectories, and identifying room for improvement and the need for recommendations adapted to the various grower contexts and strategies. - The SPOP project made it explicit that visions of sustainability and global challenges vary greatly among growers and other stakeholders involved in the palm oil sector. These diverging conceptions are most likely to induce bottlenecks in the definition and implementation of good practices and should be accounted for in the refinement of sustainability criteria. - Within the SPOP project, we investigated possible futures for oil palm using participatory prospective analyses and multi-agent-based modeling work. Our research work showed that capacity development and the organizational capacity of smallholders, fair partnerships and combined forms of governance are key drivers in ensuring the uptake of good practices and sustainable development at the landscape scale. (Resume d'auteur)