ASSESSMENT OF SITE-SPECIFIC ENVIRONMENTAL IMPACTS OF BIOENERGY AND BIO-BASED PRODUCTS FROM PERENNIAL GRASSES CULTIVATED ON MARGINAL LAND IN THE MEDITERRANEAN REGION

摘要

Considerations over the security of supplies, environmental concerns related to global warming and sustainability are promoting renewable and diversified systems. Perennial grasses and systems derived are being considered as viable substitutes to non-renewable chains. As bioenergy carriers or as bio-based products they offer ecological advantages by contributing to the reduction of greenhouse gases. Nonetheless, the intensive cultivation of theses grasses may lead to soil nutrient and water depletion, and impacts on the biological and landscape diversity. In this context, a study was conducted within the project OPTIMA (“Optimization of Perennial Grasses for Biomass Production”), funded by European Union (EU), which aimed to assess the local environmental impacts of the cultivation, processing and use of several perennial grasses, in the Mediterranean region, based on elements borrowed from Environmental Impact Assessment (EIA). Different end uses were investigated and, as ambitioned by the project, use of marginal land was considered for the biomass chains, being compared with use of standard soils. Results from EIA suggest that the biogenic system cultivated in marginal soils present higher environmental sideeffects than in standard soils, mostly due to the higher land area needed to produce the same amount of energy or biomass feedstock. Yet, this difference is not significant and in the cultivation phase, some aspects are beneficial, such as impacts on biodiversity and landscape. Compared to idle land, it was concluded that the cultivation of perennial grasses on marginal land in the Mediterranean provides comparatively minimal environmental side-effects. The reduced soil tillage and the high biomass production support the increased biological and landscape diversity, the lower erodibility potential and improvement of soil properties, namely structure and soil organic matter, and the hydrological impacts and effects on the NPK status are negligible. Miscanthus performs well at the local level because of its low nutrient demand and high yield. However, other crops perform better regarding specific impacts, e.g., cardoon’s flowering effect on biodiversity and landscape. Regarding the best performing use option, small CHP and domestic heat use options are considerably more beneficial than conversion to ethanol or 1,3-propanediol. However, process optimizations are expected and therefore use options need to be continuously reviewed.