Final Report Summary - BESOS (BioEnergy, Soil and Climate Change: factors and mechanisms on C storage and N2O emissions after bioenergy by-products application in soil) The project BESOS (BioEnergy Soil and Sustainability) has focused on understanding the impact of bioenergy by-products soil amendment on soil C and N balances, paying especial attention to greenhouse gas emissions.SCIENTIFIC RESULTS. A comprehensive study in collaboration with Cornell University (2011) led to the publication of a paper in the new open access journal from Nature: Biochar and denitrification in soils: when, how much and why does biochar reduce N2O emissions? Scientific Reports 3, Article number: 1732. The results of these experiments provide important scientific information on how biochar (a by-product of pyrolysis) affects N2O emissions from soil under denitrification conditions. Agriculture is the main contributor to N2O emissions, mainly due to the extensive use of N fertilizers. In this study we observed a consistent and significant decrease in N2O emissions through denitrification after application of biochar in 15 agricultural soils with different texture, pH and from different geographical areas (USA, Spain and Brazil). This information might be very useful for future policy decisions related to the use of biochar as soil amendment and its impact on greenhouse gas emissions in agriculture. We also demonstrated that biochar favors the last step of denitrification (i.e. the transformation of N2O to N2), which advances in the knowledge on key mechanisms controlling this process.Short term laboratory incubations have been carried out within the framework of this project with the aim of investigating how biochar influences N2O produced in soil by other mechanisms different to denitrification. We identified a soil where biochar increased N2O emissions, which seemed to contradict previous findings. The reasons of this atypical behaviour were studied by isotopic techniques and the use of inhibitors. Moreover, a parallel study was set up in collaboration with the University of Naples to study the interactions of biochar with mineral N in soil, mechanisms of priming effects and the dynamics of mineralization of biochar-N compounds. The results of these experiments are being analysed and two articles are expected to be published.A field experiment has been initiated in an experimental farm (olive orchard), located in South East Spain. The experimental field consists of 12 plots amended with biochar, compost or a mixture of both and a control. C and N dynamics, greenhouse gas emissions and enzymatic activity are being monitored. A review and meta-analysis on N2O emissions and biochar has been performed in collaboration with Wageningen University (The Netherlands) and the Department of Primary Industries (Australia). The paper has been published in Agriculture, Ecosystems & Environment. The results of this study demonstrate the significant impact of biochar in N2O emissions from soil, with an average of 54% less N2O emitted in soils amended with biochar in comparison to control soils. Factors like the feedstock used for biochar production, biochar application rate, biochar C/N, fertilizer applied in combination with biochar, soil pH have been found to have an impact on biochar effectiveness to decrease emissions. IMPACT ON RESEARCHER’S CAREER. New achievements and responsibilities during the Marie Curie reintegration grant: • “Ramon y Cajal Fellowship”, by participating in an open competitive call in the National Programme for Recruitment and Incorporation of Human Resources. This new contract starts on November 2013 and will last five years. • Lecturer in two Master courses in: (i) Universidad M. Hernández de Elche (Master on Management, Treatment and Valorization of Organic Residues) and (i) Universidad de Vigo (Master on Terrestrial Ecosystems, Sustainable Use and Environmental Impacts).• Appointed as member of the training Committee in the International Biochar Initiative. • Appointed as assistant editor for the open access journal “Frontiers in Environmental Science”.• Co-supervising two PhD students, which are now in their second year of their PhD.• Hosted two visiting scientists from University of Abertay Dundee (UK) and University of Naples (Italy).• The researcher has applied for a “Conference Sponsorship” to the OECD to organize an international workshop on biochar in 2014. • The researcher has applied for two projects as principal investigator in a regional open competitive call (regional agency of science and technology) and in a crowd-funding platform. The results about the success of these applications are expected for the end of 2013.