Santiago Lopez-Ridaura

Environmental evaluation of transfer and treatment of excess pig slurry by life cycle assessment.

Slurry management is a central topic in the agronomic and environmental analysis of intensive livestock production systems. The objective of this study is to compare the environmental performance of two scenarios of collective slurry management for the disposal of excess nitrogen from animal manure. The scenarios are the transfer of slurry and its injection to crop land, and the treatment of slurry in a collective biological treatment station. The study is based on a real case in the West of France, where a group of farmers is developing a collective plan for the disposal of almost 7000 m(3) of excess pig slurry. The evaluation is carried out by Life Cycle Assessment, where emissions and resource consumption are quantified and aggregated into four environmental impact categories: eutrophication, acidification, climate change, and non-renewable energy use. Ammonia emitted is the most important contributor to acidification and eutrophication, while methane contributes most to climate change. Both ammonia and methane are mostly emitted during the storage of slurry and, in the case of the treatment scenario, also during composting the solid fraction of the slurry. The two management strategies are similar with respect to climate change, whereas eutrophication and acidification are twice as large for treatment relative to transfer. Electricity needed for the treatment process is the main contributor to non-renewable energy use for the treatment scenario, while the transfer scenario represents a net energy saving, as energy saved by the reduction of mineral fertiliser use more than compensates for the energy needed for transport and injection of slurry. The overall environmental performance of transfer is better than that of treatment, as it involves less acidification, eutrophication and non-renewable energy use. The method employed and the results obtained in this study can provide elements for a transparent discussion of the advantages and disadvantages of contrasting excess slurry management scenarios as well as the identification of the main aspects determining their environmental performance.

Sustainability indicators, alternative strategies and trade-offs in peasant agroecosystems: analysing 15 case studies from Latin America

In view of the urgent need to improve agroecosystem sustainability, several efforts have been made to evaluate the effect of alternative strategies on key environmental and socioeconomic variables at the farm, community and regional levels. Most peasant farmers manage complex and diverse agroecosystems, and constantly adapt management strategies with multiple aims. A sustainability evaluation framework for peasant systems has been applied in over 40 case studies in Latin America, from which 15 were analysed, focusing on the choice of indicators, the effect of alternative strategies on agroecosystem sustainability and the trade-offs involved. Common indicators include yields, income, agrodiversity and external input dependence. Alternative strategies include crop/product diversification and soil conservation practices. Yields, income and agrodiversity improved in most cases, but in some cases the establishment costs increased external input use. Trade-offs observed include improved performance of a subsystem (i.e. crops) vs. decreased one in others (livestock, forestry) and increases in productivity vs. decreases in stability, resilience and reliability. The difficulty of assessing systems in transition towards alternative management was acknowledged by some evaluation teams. Applying the framework to such a variety of cases allowed making the sustainability concept operational, promoted alternative strategies and generated knowledge on agroecosystem processes among stakeholders.

Prospective and participatory integrated assessment of agricultural systems from farm to regional scales: Comparison of three modeling approaches

Evaluating the impacts of the development of alternative agricultural systems, such as organic or low-input cropping systems, in the context of an agricultural region requires the use of specific tools and methodologies. They should allow a prospective (using scenarios), multi-scale (taking into account the field, farm and regional level), integrated (notably multicriteria) and participatory assessment, abbreviated PIAAS (for Participatory Integrated Assessment of Agricultural System). In this paper, we compare the possible contribution to PIAAS of three modeling approaches i.e. Bio-Economic Modeling (BEM), Agent-Based Modeling (ABM) and statistical Land-Use/Land Cover Change (LUCC) models. After a presentation of each approach, we analyze their advantages and drawbacks, and identify their possible complementarities for PIAAS. Statistical LUCC modeling is a suitable approach for multi-scale analysis of past changes and can be used to start discussion about the futures with stakeholders. BEM and ABM approaches have complementary features for scenarios assessment at different scales. While ABM has been widely used for participatory assessment, BEM has been rarely used satisfactorily in a participatory manner. On the basis of these results, we propose to combine these three approaches in a framework targeted to PIAAS.