Intégration de l'analyse du cycle de vie dans le processus de prise de décision : application à la bioraffinerie à base de triticale en Alberta

Le concept de développement durable et la prise de conscience de nos impacts sur l’environnement ont rendu nécessaire la prise en compte de l’environnement dès les premières phases de développement de projets à long terme. L’analyse de cycle de vie (ACV) est un outil reconnu qui permet d’évaluer les impacts potentiels d’un produit sur l’ensemble de son cycle de vie, cependant ses résultats sont difficiles à intégrer dans une prise de décision. Le travail présenté dans ce mémoire s’intéresse d’une part à la comparaison de différentes technologies de bioraffinerie et d’autre part à l’intégration des résultats d’ACV dans le processus de prise de décision; notamment à l’identification de critères environnementaux pertinents à un contexte spécifique. Une méthodologie basée sur un panel d’analyse décisionnelle multicritères a été développée et appliquée à un ensemble de technologies de bioraffinerie à base de triticale qui se divisent en trois plateformes : les biocarburants, les bioplastiques et les biomatériaux. Le triticale, qui est une céréale issue du croisement entre le blé et le seigle est utilisé car son rendement, actuellement légèrement supérieur au blé, a un fort potentiel de croissance et son grain a une haute teneur en amidon ce qui lui donne un bon potentiel pour l’utilisation industrielle. Du point de vue de la prise de décision, l’étude a montré que la normalisation est une étape méthodologique critique pour l’interprétation d’indicateurs issus de l’ACV car c’est elle qui donne de l’information sur l’amplitude des impacts évalués mais qu’il n’existe pas de solution idéale. Les quatre critères identifiés comme les plus importants dans le contexte d’un investissement dans une bioraffinerie d’acide polylactique en Alberta sont les émissions de GES, la consommation de ressources non renouvelables, l’occupation de terres agricoles et la santé humaine. Ces critères ont été introduits dans une prise de décision globale fictive, incluant des aspects de performance économique et de compétitivité sur le marché et les émissions de GES ont été jugées être le deuxième critère décisionnel le plus important. La méthodologie mise en place pour identifier les critères environnementaux pertinents a donc amené les décideurs fictifs à ne pas négliger l’environnement dans leur prise de décision. Les ACV conséquentielles faites au cours du projet ont montré que pour les trois plateformes, l’utilisation d’un procédé de mouture humide mène à des impacts totaux plus élevés qu’avec une mouture à sec et qu’ajouter une étape de décorticage en début de ligne de grain n’influe pas sur les performances environnementales des bioraffineries. D’autre part, la conversion de la paille en éthanol par fermentation mène à des impacts plus élevés que par gazéification et une unité d’ultrafiltration dans la production de PLA permet de diminuer les impacts sur toutes les catégories. Enfin, pour toutes les plateformes, produire plus d’électricité à partir de résidus agricoles réduit les émissions de GES, la consommation des ressources et l’acidification aquatique, mais augmente les impacts sur la qualité des écosystèmes et l’occupation des terres agricoles. ---------- In order to reach a sustainable development, environment must be integrated in decision-making process at early stage of development. Life cycle analysis (LCA) is a recognised tool to evaluate potential impacts of a product or process on environment considering all its life cycle, however its results are hard to integrate in decision-making. This work is therefore on the integration of LCA results indecision-making process and especially on the identification of relevant environmental criteria in a specific context. A methodology based on a multi-criteria decision-making panel was developed and applied to three triticale-based bioraffineries platforms: biofuel, biochemical and biomaterial. Triticale is a biomass of interest because it has a high yield growth potential and a high content of starch that give it a good potential for industrial use. The project has shown that normalization is a critical step for LCA indicators interpretation because it is normalization that gives information on the significance of the results. The four criteria identified to be the most important in a fictive decision-making for investment in biochemical platform in Alberta were greenhouse gas (GHG) emissions, non-renewable resources, cropland occupation and human health. These criteria were included in a global decision-making along with economic and competitiveness and GHG emissions were considered to be the second most important criterion. The methodology developed to identify relevant environmental criteria lead therefore the fictive decision-makers to consider seriously environmental issues in their choice. The LCAs performed on the three platforms lead to different conclusions on process unit choices that should be considered acknowledging that a consequential approach was taken and that hypotheses were made. On all platforms, wet milling process lead to higher impacts that dry milling and adding a pearling unit at the beginning of the grain line do not affect environmental performances. Ethanol production through fermentation creates more impacts than through gasification and ultrafiltration enable significant saving on all categories compared to the classic separation unit. Finally, for all platforms, maximising electricity production by burning all the straw reduces GHG emissions, non-renewable resources and aquatic acidification but increase impacts on ecosystem quality and cropland occupation

IMPACT World+: a globally regionalized life cycle impact assessment method

Purpose This paper addresses the need for a globally regionalized method for life cycle impact assessment (LCIA), integrating multiple state-of-the-art developments as well as damages on water and carbon areas of concern within a consistent LCIA framework. This method, named IMPACT World+, is the update of the IMPACT 2002+, LUCAS, and EDIP methods. This paper first presents the IMPACT World+ novelties and results and then analyzes the spatial variability for each regionalized impact category. Methods With IMPACT World+, we propose a midpoint-damage framework with four distinct complementary viewpoints to present an LCIA profile: (1) midpoint impacts, (2) damage impacts, (3) damages on human health, ecosystem quality, and resources & ecosystem service areas of protection, and (4) damages on water and carbon areas of concerns. Most of the regional impact categories have been spatially resolved and all the long-term impact categories have been subdivided between shorterterm damages (over the 100 years after the emission) and long-term damages. The IMPACT World+ method integrates developments in the following categories, all structured according to fate (or competition/scarcity), exposure, exposure response, and severity: (a) Complementary to the global warming potential (GWP100), the IPCC Global Temperature Potentials (GTP100) are used as a proxy for climate change long-term impacts at midpoint. At damage level, shorter-term damages (over the first 100 years after emission) are also differentiated from long-term damages. (b) Marine acidification impact is based on the same fate model as climate change, combined with the H+ concentration affecting 50% of the exposed species. (c) For mineral resources depletion impact, the material competition scarcity index is applied as a midpoint indicator. (d) Terrestrial and freshwater acidification impact assessment combines, at a resolution of 2° × 2.5° (latitude × longitude), global atmospheric source-deposition relationships with soil and water ecosystems’sensitivity. (e) Freshwater eutrophication impact is spatially assessed at a resolution grid of 0.5° × 0.5°, based on a global hydrological dataset. (f) Ecotoxicity and human toxicity impact are based on the parameterized version of USEtox for continents. We consider indoor emissions and differentiate the impacts of metals and persistent organic pollutants for the first 100 years from longer-term impacts. (g) Impacts on human health related to particulate matter formation are modeled using the USEtox regional archetypes to calculate intake fractions and epidemiologically derived exposure response factors. (h) Water consumption impacts are modeled using the consensus-based scarcity indicator AWARE as a proxy midpoint, whereas damages account for competition and adaptation capacity. (i) Impacts on ecosystem quality from land transformation and occupation are empirically characterized at the biome level. Results and discussion We analyze the magnitude of global potential damages for each impact indicator, based on an estimation of the total annual anthropogenic emissions and extractions at the global scale (i.e., Bdoing the LCA of the world^). Similarly with ReCiPe and IMPACT 2002+, IMPACT World+ finds that (a) climate change and impacts of particulate matter formation have a dominant contribution to global human health impacts whereas ionizing radiation, ozone layer depletion, and photochemical oxidant formation have a low contribution and (b) climate change and land use have a dominant contribution to global ecosystem quality impact. (c) New impact indicators introduced in IMPACT World+ and not considered in ReCiPe or IMPACT 2002+, in particular water consumption impacts on human health and the long-term impacts of marine acidification on ecosystem quality, are significant contributors to the overall global potential damage. According to the areas of concern version of IMPACT World+ applied to the total annual world emissions and extractions, damages on the water area of concern, carbon area of concern, and the remaining damages (not considered in those two areas of concern) are of the same order of magnitude, highlighting the need to consider all the impact categories. The spatial variability of human health impacts related to exposure to toxic substances and particulate matter is well reflected by using outdoor rural, outdoor urban, and indoor environment archetypes. For Bhuman toxicity cancer^ impact of substances emitted to continental air, the variability between continents is of two orders of magnitude, which is substantially lower than the 13 orders of magnitude total variability across substances. For impacts of water consumption on human health, the spatial variability across extraction locations is substantially higher than the variations between different water qualities. For regionalized impact categories affecting ecosystem quality (acidification, eutrophication, and land use), the characterization factors of half of the regions (25th to 75th percentiles) are within one to two orders of magnitude and the 95th percentile within three to four orders of magnitude, which is higher than the variability between substances, highlighting the relevance of regionalizing. Conclusions IMPACT World+ provides characterization factors within a consistent impact assessment framework for all regionalized impacts at four complementary resolutions: global default, continental, country, and native (i.e., original and non-aggregated) resolutions. IMPACT World+ enables the practitioner to parsimoniously account for spatial variability and to identify the elementary flows to be regionalized in priority to increase the discriminating power of LCA