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Energy crops have proved to be a viable alternative to fossil fuels. However, high biomass production always means that large quantities of nutrients from the soil are removed at harvest. The goal of this work was to estimate nutrient (nitrogen, phosphorous, potassium) use efficiency (NUE) and nitrogen balance in an eight-year-old Populus deltoides clone Lux, short rotation forestry under two cutting cycles, every two (biennial) and three (triennial) years, carried out under Mediterranean climate conditions. Results indicate that NUE, for all the analyzed elements, contained variations with slightly higher values for nitrogen and phosphorous in the triennial cycle. Although poplar cultivation has a positive nutrient efficiency, in terms of nitrogen, there is significant loss of this element in the crop cycle. [ABSTRACT FROM AUTHOR]

In the Mediterranean rainfed systems, perennial warm-season grasses are profitable crops for the production of herbage as forage or feedstock for bioenergy purposes. During summer, when the production of cool-season crops is scarce, warm-season grasses can improve the productivity and stability of forage cropping systems. In Italy, switchgrass (Panicum virgatum L.) can be cultivated for herbage production or as energy crop. The objective of this work was evaluating if relay intercropping with cool-season legumes could be suited to convert a mature stand of switchgrass from energy to dual, energy and forage, production, together with improving the productivity and the quality of the harvestable biomass. All these things considered, a field experiment was carried out in Central Italy, on mature stands of two switchgrass varieties, Alamo and Blackwell, overseeded with two legumes: sulla (Hedysarum coronarium L.) and crimson clover (Trifolium incarnatum L.). The intercropping system was compared with fertilized and un-fertilized pure switchgrass stands. After two years of study, data showed that the intercropping increased the total above ground biomass (AGB) productivity. In the second year, the increase in total AGB production for switchgrass mixtures compared with the pure stands was greater for sulla, a biennial legume, than crimson clover. [ABSTRACT FROM AUTHOR]

Aiming to improve the sustainability of biogas supply chains, the research for alternative feedstocks is a key issue and giant reed (Arundo donax L.) is a promising no-food crop to be used in anaerobic digestion. In fact, giant reed is a perennial species characterised by low nutrient requirements and is able to provide promising biogas yields. Its suitability for anaerobic digestion is influenced by harvest time, since plant characteristics vary noticeably along the season. Moreover, ensiling is a storage technique that can assure a good preservation of the biomass over time, but also influence the methane yields. Therefore, the aim of this study was to assess the suitability for biogas production of giant reed silage, according to different cutting regimes, and to evaluate the efficiency in saving land and nitrogen for fuelling biogas plants, in comparison with maize and two sorghum varieties. Methane yields per hectare (Nm³ CH4 ha-1) were determined by multiplying the biochemical methane potential of each substrate by the aboveground biomass of the corresponding crop. The land use coefficient (LU), namely the land needed to fuel one kW power (ha kWe-1), was calculated from the estimated methane yields per hectare. Finally, nitrogen utilisation efficiency (NUtE), which is the ratio between the estimated methane yield and the nitrogen uptake per hectare (Nm³ CH4 kgN-1), was determined for each crop species and according to the harvest time and frequency of giant reed. Overall, a good suitability for ensiling was observed in giant reed. When harvested in September, the crop yielded about 9900 Nm³ CH4 kgN-1, while in double harvest systems biomethane was about 12,000 Nm³ CH4 kgN-1, +35% and +70% than maize and sorghum respectively. Moreover, giant reed under double harvest management was the most land-conservative option, as LU was about 0.22 ha kWe-1, while in annual crops it was about 0.35 ha kWe-1. The higher NUtE was observed in single harvests (up to 64 Nm³ CH4 kgN-1), while double harvests showed remarkably lower values, averaging 48 Nm³ CH4 kgN-1. Annual crops were less efficient, since NUtE ranged from 28 Nm³ CH4 kgN-1 (maize) to 40 Nm³ CH4 kgN-1 (fibre sorghum). In conclusion, giant reed can be an alternative for biogas making, potentially providing land and nitrogen savings compared with conventional annual crops. [ABSTRACT FROM AUTHOR]

Fertilization has a great impact on GHG emissions and crop nutrient requirements play an important role on the sustainability of cropping systems. In the case of bioenergy production, low concentration of nutrients in the biomass is also required for specific conversion processes (e.g. combustion). In this work, we investigated the influence of soil texture, irrigation and nitrogen fertilization rate on nitrogen, phosphorus and potassium concentrations and uptakes in Miscanthus × giganteus when harvested at two different times: early (autumn) and late (winter). Our results confirmed winter harvest to significantly reduce nutrient removals by as much as 80% compared to autumn. On the other hand, a few attempts have been made to investigate the role of soil texture and irrigation on nutrients in miscanthus biomass, particularly in the Mediterranean. We observed an effect of soil mainly on nutrient concentrations. Similarly, irrigation led to higher nutrient concentrations, while its effect on nutrient uptakes was less straightforward. Overall, the observed differences in miscanthus nutrient uptakes as determined by the crop management (i.e. irrigation and nitrogen fertilization) were highlighted for autumn harvest only, while uptakes in all treatments were lowered to similar values when winter harvest was performed. This study stressed the importance of the time of harvest on nutrient removals regardless of the other management options. Further investigation on the environmental and economic issues should be addressed to support decisions on higher yields-higher nutrient requirements (early harvest) vs. lower yields-lower nutrient requirements (late harvest). [ABSTRACT FROM AUTHOR]

Biomass productivity is the main favorable trait of candidate bioenergy crops. Miscanthus × giganteus is a promising species, due to its high-yield potential and positive traits including low nutrient requirements and potential for C sequestration in soils. However, miscanthus productivity appears to be mostly related to water availability in the soil. This is important, particularly in Mediterranean regions where the risk of summer droughts is high. To date, there have been no studies on miscanthus responses under different soil conditions, while only a few have investigated the role of different crop managements, such as irrigation and nitrogen fertilization, in the Mediterranean. Therefore, the effects of contrasting soil textures (i.e. silty-clay-loam vs. sandy-loam) and alternative agricultural intensification regimes (i.e. rainfed vs. irrigated and 0, 50, 100 kg ha−1 nitrogen fertilization), on miscanthus productivity were evaluated at three different harvest times for two consecutive years. Our results confirmed the importance of water availability in determining satisfactory yields in Mediterranean environments, and how soil and site characteristics strongly affect biomass production. We found that the aboveground dry yields varied between 5 Mg ha−1 up to 29 Mg ha−1. Conversely, nitrogen fertilization played only a minor role on crop productivity, and high fertilization levels were relatively inefficient. Finally, a marked decrease, of up to −40%, in the aboveground yield occurred when the harvest time was delayed from autumn to winter. Overall, our results highlighted the importance of determining crop responses on a site-by-site basis, and that decisions on the optimal harvest time should be driven by the biomass end use and other long-term considerations, such as yield stability and the maintenance of soil fertility. [ABSTRACT FROM AUTHOR]

Giant reed ( Arundo donax L.) and miscanthus ( Miscanthus × 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 ( ETc), crop coefficients (Kc) 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 ETc was 7.4 and 6.2 mm in giant reed and miscanthus respectively. The Kc 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−1 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. [ABSTRACT FROM AUTHOR]

The present study was aimed at assessing the biotransformation of dark fermented agroindustrial residues and energy crops for the production of hydrogen and poly-β-hydroxybutyrate (PHB), in lab-scale photofermentation. The investigation on novel substrates for photofermentation is needed in order to enlarge the range of sustainable feedstocks. Dark fermentation effluents of ensiled maize, ensiled giant reed, ensiled olive pomace, and wheat bran were inoculated with Rhodopseudomonas palustris CGA676, a mutant strain suitable for hydrogen production in ammonium-rich media. The highest hydrogen producing performances were observed in wheat bran and maize effluents (648.6 and 320.3 mL L −1 , respectively), both characterized by high initial volatile fatty acids (VFAs) concentrations. Giant reed and olive pomace effluents led to poor hydrogen production due to low initial VFAs concentrations, as the original substrates are rich in fiber. The highest PHB content was accumulated in olive pomace effluent (11.53%TS), ascribable to magnesium deficiency. [ABSTRACT FROM AUTHOR]

Aim of this study was to evaluate the suitability of ensiled giant reed, ensiled maize, ensiled olive pomace, wheat bran for combined systems (CS: dark fermentation + anaerobic digestion (AD)) producing hydrogen-rich biogas (biohythane), tested in batch under basic operational conditions (mesophilic temperatures, no pH control). Substrates were also analyzed under a single stage AD batch test, in order to investigate the effects of DF on estimated energy recovery (ER) in combined systems. In CS, maize and wheat bran exhibited the highest hydrogen potential (13.8 and 18.9 NL kgVS −1 ) and wheat bran the highest methane potential (243.5 NL kgVS −1 ). In one-stage AD, giant reed, maize and wheat bran showed the highest methane production (239.5, 267.3 and 260.0 NL kgVS −1 ). Butyrate/acetate ratio properly described the dark fermentation, correlating with hydrogen production ( r = 0.92). Wheat bran proved to be a promising residue for CS in terms of hydrogen/methane potential and ER. [ABSTRACT FROM AUTHOR]