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Given today's political targets, energy production from agricultural areas is likely to increase and therefore needs to be more sustainable. The aim of this study was thus to carry out a long-term field trial based on the poplar short-rotation coppice (SRC), in order to compare dry matter, energy-use efficiency and the net energy yield obtainable from this crop in relation to different harvest frequencies (1-, 2-and 3-year cutting cycles). The results showed that poplar SRC performed very well under temperate climates as it can survive up to 12 years, providing a considerable annual biomass yield (9.9, 13.8, 16.4 t ha À1 yr À1 for annual T1, biannual T2 and triennial T3 cutting cycles, respectively). The system tested in southern Europe showed a positive energy balance characterized by a high energy efficiency. We found that the choice of harvest interval had huge consequences in terms of energy yields. In fact, the energy efficiency improved from T1 to T2 and T3, while the net energy yield increased from 172 to 299 GJ ha À1 yr À1. This study suggests that, with 3-year harvest cycles, poplar SRC can contribute to agronomic and environmental sustainability not only in terms of its high yield and energy efficiency but also in terms of its positive influence on limiting soil tillage and on the environment, given its low pesticide and nutrient requirements.

Abstract:The hydrothermal conversion of giant reed (Arundo donax L.) to furfural (FA) and levulinic acid (LA) was investigated in the presence of dilute hydrochloric acid. FA and LA yields were improved by univariate optimization of the main reaction parameters: concentration of the acid catalyst, solid/liquid ratio of the reaction mixture, hydrolysis temperature, and reaction time. The catalytic performances were investigated adopting the efficient microwave (MW) irradiation, allowing significant energy and time savings. The best FA and LA yields were further confirmed using a traditionally heated autoclave reactor, giving very high results, when compared with the literature. Hydrolysis temperature and time were the main reaction variables to be carefully optimized: FA formation needed milder reaction conditions, while LA more severe ones. The effect of the crop management (e.g., harvest time) on FA/LA production was discussed, revealing that harvest time was not a discriminating parameter for the further optimization of both FA and LA production, due to the very high productivity of the giant reed throughout the year. The promising results demonstrate that giant reed represents a very interesting candidate for a very high contemporary production of FA and LA of up to about 70% and 90% of the theoretical yields, respectively.

Giant reed (Arundo donax L.) is a perennial rhizomatous\ud grass that shows promise as a bioenergy crop in\ud the Mediterranean environment. The species has spread\ud throughout the world, catalyzed by human activity, though\ud also as a result of its intrinsic robustness, adaptability, and\ud versatility. Giant reed is able to thrive across a wide range of\ud soil types and is tolerant to drought, salinity, and flooding.\ud This tolerance to environmental stresses is significant and\ud could mean that growing energy crops on marginal land is\ud one possible strategy for reducing competition for land with\ud food production and for improving soil quality. We devised\ud an experiment in which we cultivated giant reed in a sandy\ud loam soil with low nutrient availability. Our goal was to\ud evaluate the dynamics of aboveground and belowground\ud biomass and assess the nutrient dynamics of this grass\ud species, focusing particularly on nutrient accumulation and\ud remobilization. The species demonstrated good productivity\ud potential: In the third year, aboveground dry biomass yield\ud reached around 20 tha−1, with a corresponding rhizome dry\ud biomass yield of 16 tha−1. Results for this species were\ud characterized by low nutrient contents in the aboveground\ud biomass at the end of the growing season, and its rhizome\ud proved able to support growth over the spring period and to\ud store nutrients in the autumn. Nevertheless, the adaptability\ud of giant reed to marginal land and the role of its belowground\ud biomass should be investigated over the long-term,\ud and any further research should focus on its potential to\ud reduce greenhouse gas emissions and maintain soil fertility

Evapotranspiration, crop coefficient and water use efficiency of giant reed (Arundo donax L.) and miscanthus (Miscanthus 3 giganteus Greef et Deu.) in a Mediterranean environment. AbstractGiant reed (Arundo donax L.) and miscanthus (Miscanthus 9 giganteus Greef et Deu.) are two perennial rhizomatous grasses (PRGs), considered as promising sources of lignocellulosic biomass for renewable energy production. Although the agronomic performance of these species has been addressed by several studies, the literature dedicated to the crop water use of giant reed and miscanthus is still limited. Our objective was thus to investigate giant reed and miscanthus water use by assessing crop evapotranspiration (ET c ), crop coefficients (K c ) and water use efficiency (WUE). The study was carried out in central Italy and specifically designed water-balance lysimeters were used to investigate the water use of these PRGs during the 2010 and 2011 growing seasons. Giant reed showed the highest cumulative evapotranspiration, with an average consumption of approximately 1100 mm, nearly 20% higher than miscanthus (900 mm). Crop evapotranspiration rates differed significantly between the species, particularly during the midseason (from June to September), when average daily ET c was 7.4 and 6.2 mm in giant reed and miscanthus respectively. The K c values determined in our study varied from 0.4 to 1.9 for giant reed and 0.3 to 1.6 for miscanthus. Finally, WUE was higher in miscanthus than in giant reed, with average values of 4.2 and 3.1 g L À1 respectively. Further studies concerning water use under nonoptimal water conditions should be carried out and an assessment of the response to water stress of both crops is necessary to integrate the findings from this study.

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