Arnaud Hélias

Life-cycle assessment of microalgae culture coupled to biogas production.

Due to resource depletion and climate change, lipid-based algal biofuel has been pointed out as an interesting alternative because of the high productivity of algae per hectare and per year and its ability to recycle CO(2) from flue gas. Another option for taking advantage of the energy content of the microalgae is to directly carry out anaerobic digestion of raw algae in order to produce methane and recycle nutrients (N, P and K). In this study, a life-cycle assessment (LCA) of biogas production from the microalgae Chlorella vulgaris is performed and the results are compared to algal biodiesel and to first generation biodiesels. These results suggest that the impacts generated by the production of methane from microalgae are strongly correlated with the electric consumption. Progresses can be achieved by decreasing the mixing costs and circulation between different production steps, or by improving the efficiency of the anaerobic process under controlled conditions. This new bioenergy generating process strongly competes with others biofuel productions.

Environmental assessment of nutrient recycling from biological pig slurry treatment – Impact of fertilizer substitution and field emissions

Pig slurry treatment is an important means in reducing nitrogen loads applied to farmland. Solid phase separation prior to biological treatment further allows for recovering phosphorus with the solid phase. The organic residues from the pig slurry treatment can be applied as organic fertilizers to farmland replacing mineral fertilizers. The environmental impacts of nutrient recycling from aerobic, biological pig slurry treatment were evaluated applying the life cycle assessment (LCA) methodology. LCA results revealed that direct field emissions from organic fertilizer application and the amount of avoided mineral fertilizers dominated the environmental impacts. A modified plant available nitrogen calculation (PAN) was introduced taking into account calculated nitrogen emissions from organic fertilizer application. Additionally, an equation for calculating the quantity of avoided mineral fertilizers based on the modified PAN calculation was proposed, which accounted for nitrogen emissions from mineral fertilizer application.

Life-Cycle Assessment of Microalgal-Based Biofuels

Abstract Fossil-fuel depletion and attempts at global-warming mitigation have motivated the development of biofuels. Several feedstock and transformation pathways into biofuel have been proposed as an alternative to the usual fuels. Recently, microalgae have attracted a good deal of attention because of the promise of reduced competition with food crops and lowered environmental impacts. Over the last years, several life-cycle assessments (LCAs) have been realized to evaluate the energy benefit and potential global-warming reduction of biofuel and bioenergy produced from microalgae. This chapter presents a bibliographic review of 15 LCAs of microalgae production and/or transformation into biofuel. These studies often differ by the perimeter of the study, the functional unit, and the production technologies or characteristics. Methods for environmental impact assessment and the energy balance computation also diverge. This review aims to identify the main options and variations among LCAs and concludes with some recommendations and guidelines to improve the contribution of an LCA and to facilitate comparisons among studies.

How to take time into account in the inventory step: a selective introduction based on sensitivity analysis

PurposeLife cycle assessment is usually an assessment tool, which only considers steady-state processes, as the temporal and spatial dimensions are lost during the life cycle inventory (LCI). This approach therefore reduces the environmental relevance of certain results, as it has been underlined in the case of climate change studies. Given that the development of dynamic impact methods is based on dynamic inventory data, it seems essential to develop a general methodology to achieve a temporal LCI.MethodsThis study presents a method for selecting the steps, within the whole process network, for which dynamics need to be considered while others can be approximated by steady-state representation. The selection procedure is based on the sensitivity of the impacts on the variation of environmental and economic flows. Once these flows have been identified, their respective timescales are compared to the inherent timescales of the impact categories affected by the flows. The timescales of the impacts are divided into three categories (days, months, years) based on a literature review of the ReCiPe method. The introduction of a temporal dynamic depends on the relationship between the timescale of the environmental and economic flows on the one hand and that of the concerned impact on the other hand.Results and discussionThis approach is illustrated by the life cycle assessment of palm methyl ester and ethanol from sugarcane. In both cases, the introduction of a temporal dynamic is limited to a small proportion of the total number of flows: 0.1xa0% in the sugarcane ethanol production and 0.01xa0% in the palm methyl ester production. Future developments of time integration in the LCI and in the life cycle impact assessment (LCIA) are also discussed in order to deal with the need of characterization functions and the recurrent problem of waiting times.ConclusionsThis work provides a method to select specific flows where the introduction of temporal dynamics is most relevant. It is based on sensitivity analyses and on the relationship between the timescales of the flows and the timescale of the involved impact. The time-distributed LCI generated by using this approach could then be coupled with a dynamic LCIA proposed in the literature.

Review on Land Use Considerations in Life Cycle Assessment: Methodological Perspectives for Marine Ecosystems

Land use within the life cycle assessment (LCA) methodology deals with the impacts on the environment of occupation and transformation of a piece of land for human activities. Land quality can be altered in its ability to ensure ecosystem services. The present article reviews the different methods used to assess land use impacts on ecosystem quality during life cycle impact assessment (LCIA). Details are provided on the choice of the reference state, areas of protection, indicators and methods which can be used for the assessment. Then the study focuses on the different methodological aspects which need to be investigated to take into account impacts on marine ecosystems marine use in LCA, based on the terrestrial methodological framework previously detailed.

Sea use impact category in life cycle assessment: characterization factors for life support functions

PurposeThe impact of human activities on marine environments is poorly addressed by the scope of life cycle impact assessment (LCIA). The aim of this study is to provide characterization factors to assess impacts of sea use such as fishing activities or seafloor destruction and transformation on the life support functions of marine ecosystems.MethodsThe consensual framework of land use for ecosystem services damage potential assessment was applied, according to the recent United Nations Environment Programme-Society for Environmental Toxicology and Chemistry (UNEP-SETAC) guidelines, using the free net primary production as a quality index of life support functions.Results and discussionThe impact of shading, biomass removal, seafloor destruction, and artificial habitat creation on the available quantity of organic biomass for the ecosystem functioning was quantified at the midpoint level with a common unit (kg of organic carbon equivalent). It included effects of human interventions on both the ecosystem production potential and the stock of biomass present within the ecosystem. Characterization factors (CF) for biomass removal vary from 0.1xa0kgCequ2009kg−1 for seaweed to 111.1xa0kgCequ2009kg−1 for tunas, bonitos, and billfishes. CF for seafloor destruction range from 0.164xa0kgCequ2009m−2 for a temperate seagrass ecosystem to 0.342xa0kgCequ2009m−2 for an intertidal tropical rocky habitat.ConclusionsThis study provides an operational method in order to compute sea use impact assessment.

Sea-use impact category in life cycle assessment: state of the art and perspectives

PurposeThe present study provides a review on sea-use impacts and how they are handled in life cycle assessments (LCA). It aims at defining the impact pathways for occupation and transformation impacts on marine ecosystems due to human activities (constructions, fishing, aquaculture, navigation).MethodsFirst, a review was performed on human interventions leading to environmental impacts in marine areas and on additional fishery-related impact categories used in LCA of seafood, in order to identify the main methodological deficiencies existing in LCA of seafood products. Second, the sea-use impact category has been defined, by detailing the human interventions leading to impacts on the marine environment and which should be accounted for in LCA. Subsequently, the identification and description of the possible impact pathways linking activities and interventions to impact categories are carried out at endpoint and midpoint levels. This assessment has been based on a review of existing methods of land use, and suggests the use of certain indicators, which could be available for different types of marine activities and ecosystems.ResultsThis study highlights the needs to account for impacts of human activities due to sea use. Additional indicators have often been added in LCA of seafood, to assess the impacts of seafloor destruction and biomass removal. By extending the scope to other activities than fisheries, many interventions lead to impacts on marine ecosystems: biomass removal and benthic construction, invasive species release, shading, artificial habitat creation, noise, turbidity, and changes in original habitat availability. The impact pathway definition and the identification of the most relevant methods for sea use highlighted the need to assess impacts on ecosystem services (life support functions, global material cycling, and detoxification of pollutants) and on biodiversity as well as biotic resource depletion.ConclusionsA consensus for biotic resource depletion assessment still needs to be found despite recent innovative proposals. For the sea-use impact assessment, methods using species-area relationships, as well as methods focusing on ecosystem services, appear particularly relevant. In a context of strong marine resource overexploitation, and limited marine biodiversity data, the deficiencies in biomass production capability (provisioning services) could be the first stage of sea-use development.

Time and Life Cycle Assessment: How to Take Time into Account in the Inventory Step?

Life cycle assessment is usually an assessment tool which only considers steady state processes: the temporal and spatial properties of extractions, usage and emissions are lost during the life cycle inventory step. This approach significantly reduces the environmental relevance of some results. As the development of dynamic impact methods is based on dynamic inventory data, it seems essential to develop a general methodology to achieve a temporal life cycle inventory. This study presents a method to select steps, in the whole network tree, for which dynamics have to be considered while the others are approximated by steady state representation. The selection procedure is based on the main contributors in term of impact. The approach is illustrated by the life cycle assessment of simplified rapeseed oil production as biofuel system.

Abstraction of continuous system trajectories into timed automata

Abstract This paper deals with the representation of continuous system dynamics into a timed discrete-event formalism to the end of system analysis. The continuous model of the system is first approximated using intervals and then translated into the timed automata formalism by comparison with thresholds defined on the state variables’ domains. The detection of thresholds crossing is characterised by two time instants corresponding respectively to the earliest and latest crossing dates. This approach is briefly illustrated with real data obtained from a 1 m wastewater treatment pilot plant.

RISK ASSESSMENT FOR SAFE RESTART OF ANAEROBIC DIGESTION PROCESSES

Abstract For several years, a 1 m 3 fixed bed anaerobic digestion process has been operated for the treatment of wine distillery wastewater. This reactor has been fully instrumented with the following variables available on-line: pH, temperature, liquid and gas flow rates, gas composition ( i.e. , CH 4 , CO 2 and H 2 ), concentration of bicarbonate, chemical oxygen demand, total organic carbon, volatile fatty acids and partial and total alkalinity. This paper deals with the problem of restarting the reactor after a period of time with missing information from the sensors. An approach has been developed to determine – while managing inherent uncertainty – the evolution of the inputs between the date of information loss and that of information recovered. It is then used together with a timed automata formalism and model checking capabilities to assess and analyse the induced risk in order to restart the process in safe conditions.