G. Ragaglini

Biomass production and energy balance of a 12-year-old short-rotation coppice poplar stand under different cutting cycles

Given todays 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−1 yr−1 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−1 yr−1. 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.

Suitability of giant reed (Arundo donax L.) for anaerobic digestion: Effect of harvest time and frequency on the biomethane yield potential

This study aimed to investigate the potential of giant reed for biomethane production by examining the influence of harvest time and frequency on the Biochemical Methane Potential (BMP), the kinetics of biomethane accumulation in batch reactors and the expected methane yield per hectare. The crop was cut at five different times, regrowths from early cuts were harvested in autumn and BMP of each cut was assessed. The highest BMP (392 NL kg VS(-1)) and the best kinetics of methane production were associated to juvenile traits of the crop. By coupling the early cuts with the corresponding regrowths (double harvest), the dry biomass (from 35 to 40 Mg ha(-1)) equaled that obtained by a single cut at end of the season (38 Mg ha(-1)), while the methane yield per hectare (11,585-12,981 Nm(3) ha(-1)) exceeded up to 35% the methane produced with a single harvest at crop maturity (9452 Nm(3) ha(-1)).

Evapotranspiration, crop coefficient and water use efficiency of giant reed (Arundo donax L.) and miscanthus (Miscanthus × giganteus Greef et Deu.) in a Mediterranean environment.

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.

Energy conversion of biomass crops and agroindustrial residues by combined biohydrogen/biomethane system and anaerobic digestion.

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 18.9NLkgVS(-1)) and wheat bran the highest methane potential (243.5NLkgVS(-1)). In one-stage AD, giant reed, maize and wheat bran showed the highest methane production (239.5, 267.3 and 260.0NLkgVS(-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.

Miscanthus × giganteus nutrient concentrations and uptakes in autumn and winter harvests as influenced by soil texture, irrigation and nitrogen fertilization in the Mediterranean

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).

Influence of soil texture and crop management on the productivity of miscanthus (Miscanthus × giganteus Greef et Deu.) in the Mediterranean

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.

Agroindustrial residues and energy crops for the production of hydrogen and poly-β-hydroxybutyrate via photofermentation.

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 320.3mLL(-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.

Large‐scale simulation of temperature‐dependent phenology in wintering populations of Bactrocera oleae (Rossi)

To implement Area‐Wide Pest Management protocols at a regional scale (Liguria, northern Italy), egg deposition and adult flight of olive fruit fly, Bactrocera oleae, were monitored during 2009, 2010 and 2011. The consequence of complete generation in late winter – early spring was also examined. The reliability of a degree‐day model was tested to simulate the insect cycle, starting from October oviposition and considering a 379.01°C cumulative degree‐day (CDD) needed to complete development. The model was validated and then used to simulate olive fruit fly phenology in the region of Liguria, using a GIS approach and the agrometeorological network in the region. The output of the CDD model was mapped with two different spatialization modelling techniques, geostatistical autocorrelation and regression correlation, and altitude, aspect and distance from the sea were assessed as elements of variability. The regression correlation model provided a more accurate indication of B. oleae diversity at the local scale than the geostatistical autocorrelation model and identified the high spatial climatic variability of Liguria. The potential application of the distribution of days after oviposition and prediction error maps in support of pest management planning is discussed.

Biotransformation of water lettuce (Pistia stratiotes) to biohydrogen by Rhodopseudomonas palustris

Aim of the paper was to assess the feasibility of producing hydrogen as a biofuel by photofermentation of fermented water lettuce (Pistia stratiotes L.) waste biomass, after a nitrogen‐stripping treatment.

Anaerobic digestion and Co-digestion of oleaginous Microalgae residues for biogas production

Anaerobic Digestion And Co-Digestion of Oleaginous Microalgae Residues for Biogas Production Federica Barontini*, Enrico Biagini, Federico Dragoni, Elisa Corneli, Giorgio Ragaglini, Enrico Bonari, Leonardo Tognotti, Cristiano Nicolella Università di Pisa Dipartimento di Ingegneria Civile e Industriale Largo Lucio Lazzarino, 56122 Pisa, Italy Centro di Ricerca Interuniversitario Biomasse da Energia (CRIBE) Via Vecchia di Marina, 6, 56122 Pisa, Italy Scuola Superiore Sant’Anna – Institute of Life Sciences Via Santa Cecilia, 3, 56127 Pisa, Italy federica.barontini@unipi.it