Modelling new sustainable cropping systems for advanced biofuel production

Through the re-use of empirical functions and new model development, this study aims at contributing to the development of advanced biofuels in Europe. Four lignocellulosic crops were selected and tested in stand-alone (sunn hemp – Crotalaria juncea L.) and rotation system (sunn hemp, biomass sorghum - Sorghum bicolor x Sorghum sudangrass, kenaf - Hibiscus cannabinus L. and industrial hemp - Cannabis sativa L.) in different European environments. The first Chapter deals with a new model development (SunnGro) to reproduce sunn hemp, an interesting summer crop for advanced biofuels in Europe; in the second Chapter, the same model was used to simulate 20-year sunn hemp productivity across Europe. The SunnGro model reproduces sunn hemp development and growth, while providing a detailed description of leaf/branch size heterogeneity and its evolution during the vegetative season, depending on thermal time accumulation (GDD), sowing time (ST) and density (SD). The model was calibrated and evaluated using 20 sunn hemp field datasets collected in Greece, Spain and Italy. Interesting correlations were found between simulated and measured values of branch and leaf number (0.80<R2<0.92) and biomass accumulation (0.67<R2<0.82). Hence, SunnGro can be a valuable tool for estimating the potentialities of sunn hemp, either as main or intercropping, as feedstock for advanced biofuels across Europe. The third Chapter is dedicated to the in-season growth simulation of first-of-a-kind food/energy crop rotations aimed at providing lignocellulosic feedstock for advanced biofuels without increasing land pressure. The rotations with biomass sorghum, industrial hemp and sunn hemp resulted in the highest biomass yields, whereas kenaf was less productive. The presented models were developed to provide user-friendly tools to estimate the potentialities of the selected lignocellulosic crops across Europe. Even though these models need further ameliorations and extensions, to now, they represent reliable tools for preliminary assessments.