• Energy Research

In Mediterranean environments, few perennial grass species are available for cultivation in rainfed systems and marginal lands, where plants with excellent adaptation are required. The aim of the present work was to determine the potentiality of five native Mediterranean perennial grasses for lignocellulosic biomass production. Wild accessions of three hemicryptophytes (Ampelodesmos mauritanicus, Hyparrhenia hirta, and Piptatherum miliaceum) and two geophytes (Saccharum spontaneum ssp. aegyptiacum and Sorghum halepense) were collected at three Mediterranean sites (Sicily, Sardinia and Majorca), and their morphological, physiological, productivity and quality traits were evaluated in the field. The species differed in height, with S. spontaneum and A. mauritanicus being the tallest. The leaf mass ratio ranged from 0.23 to 1.0 g g -1 among species. Maximum net photosynthesis was measured in the C 4 species S. spontaneum and S.halepense (26.6 and 23.8 mmol CO 2 m -2 s -1 , respectively). A. mauritanicus showed the lowest transpiration rate and the highest instantaneous water use efficiency (2.7 mmol H 2 O m -2 s -1 and 6.9 mmol CO 2 mmol H 2 O -1 , respectively). S. spontaneum was the most productive species, yielding more than 18 Mg DM ha -1 as a three-year average. The highest content of acid detergent lignin was found in P. miliaceum, while A. mauritanicus was the species richest in hemicellulose and cellulose and poorest in ash. S. spontaneum showed the highest moisture content at harvest. Overall, the studied species showed interesting morphological, physiological, productive and qualitative traits. Nevertheless, additional research is necessary to investigate their long-term performance under different management strategies.

This review describes the multiple utilization of perennial grasses as resilient crops for a multifunctional agriculture. Beyond its role of producing food, feed and fiber, the concept of multifunctional agriculture includes many other functions, such as ecosystem services, renewable energy production and a contribution to the socio-economic viability of rural areas. Traditionally used for feed, some perennial grasses—known as perennial energy grasses (e.g., miscanthus—Miscanthus × giganteus Greef et Deuter, giant reed—Arundo donax L., switchgrass—Panicun virgatum L., reed canary grass—Phalaris arundinacea L.)—have been recommended as a biomass source for both energy and non-energy applications, and ecosystem services. Perennial grasses are lignocellulosic, low-cost feedstock, able to grow in variable environments including marginal lands. Due to their high yield, resilient traits, biomass composition, energy and environmental sustainability, perennial grasses are a candidate feedstock to foster the bio-based economy and adapt to a changing agriculture. However, perennial grasses for biomass production are largely undomesticated crops, or are at early stages of development. Hence, a great potential for improvements is expected, provided that research on breeding, agronomy, post-harvest logistic and bioconversion is undertaken in order to deliver resilient genotypes growing and performing well across a broad range of environmental conditions, climatic uncertainty, marginal land type and end-use destinations.

According to the RED II (2018/2001/EU), Member States must supply a minimum of 14% of the energy consumed in road and rail transport by 2030, of which the contribution of advanced biofuels and biogas must reach at least 3.5%. Reduce biomass recalcitrance of high-yielding lignocellulosic crops by means of agronomic strategies would significantly contribute to the advanced biofuel production goal. Lignocellulose is the lowest cost raw material on earth, it is a no-food biomass and its use alone or in mix with other biomasses can strongly increase the biomass availability for advanced biomethane production. The present study evaluated the suitability of the lignocellulosic, herbaceous Arundo donax as a biomass feedstock for advanced biomethane production. Harvest time and nitrogen fertilization treatments were adopted to reduce biomass recalcitrance thereby increasing biomethane yield. Biochemical Methane Potential (BMP) was evaluated on batch anaerobic fermenters in mesophilic conditions. The BMP at 30 days of incubation was influenced by the investigated treatments, the incubation time and the interaction of these two factors. The trend showed a lag phase for the first 5 days of testing, due probably to the adaptation of the bacterial flora to the lignocellulosic matrix, followed by an exponential increase up to approximately 18 days; after that a slight increase tending to an asymptotic trend in the final phase (up to day 30) was observed. The highest BMP was reached by the combination of winter harvest (W) and 80 kg N ha-1 (123.4 Nml CH4 g-1 SV), followed by the autumn harvest (A) and 80 kg N ha-1 (118.1 Nml CH4 g-1 SV). The unfertilized treatments showed an opposite BMP, with the autumn higher than winter harvest (106.2 and 100.3 Nml CH4 g-1 SV, respectively). In terms of biomethane yield per unit land area, WN80 showed the highest (1717 ± 203 m3 CH4 ha-1) and WN0 the lowest (859 ± 93 m3 CH4 ha-1). Nitrogen fertilization looks a promising strategy to reduce biomass recalcitrance for bioconversion by anaerobic digestion mainly due to the higher content of neutral detergent soluble and protein; however, it should be proved by an energy, economic and environmental analysis to ascertain an overall sustainability. Proceedings of the 28th European Biomass Conference and Exhibition, 6-9 July 2020, Virtual, pp. 222-227

The Joint Research Center (JRC) has set a series of thresholds to define marginal lands in terms of biophysical constraints. We focus on climate limitation given by the ratio between precipitations and potential evapotranspiration (P/PET). Indeed, the Mediterranean climates are characterized by long drought periods during summer, with low rainfall and high evapotranspiration, what limits plant CO2 assimilation and biomass production, particularly of spring-summer crops. The present study ascertained the potential and actual yield of African fodder cane (Saccharum spontaneum ssp. aegypticum), a perennial, herbaceous, rhizomatous perennial grass, native from North Africa and widespread in South Mediterranean regions. Saccharum was grown under different water regimes (I0 - rainfed, I50 – 50% ETm and I100 – 100% ETm restoration) for six successive growing seasons, namely from the 7th to the 12th. Throughout the experimental period, the dryness index greatly changed among the six growing seasons: three out of the six (2012, 2013 and 2014) were much lower than the threshold of 0.6 set in the JRC report, indicating severe drought seasons, two were quite similar to the threshold value (2015 and 2016), while the 2011, which was the wettest season overall, had a dryness index higher than the threshold. Actual biomass yield was mostly driven by meteorological conditions through the growing seasons. However, even in the driest seasons, Saccharum was able to maintain satisfactory biomass yield and good yield persistence. As compared to the potential yield (I100), the relative yield reduction over the six years was in the range of 31% in the most stress condition (I0), but the energy productivity and the water footprint improved by 62% and 32%, respectively, indicating a higher sustainability of the cropping system when irrigation water was not provided. When the irrigation level was raised to the 50% of the maximum evapotranspiration restoration (ETm), the relative yield, over the six growing seasons, reduced by 16.5%; the energy productivity and the water footprint improved of only 14 and 22%, respectively. This study underlines the importance for strategic selection of crops for a given environmental condition dominated by a specific biophysical constraint and the agronomic practices leading to increase the energy productivity while reducing the pressure on Mediterranean freshwater. Proceedings of the 28th European Biomass Conference and Exhibition, 6-9 July 2020, Virtual, pp. 34-40

Long-storage tomato is a drought-tolerant plant traditionally cultivated under no water supply in semi-arid areas of Italy. In 2009, physiological traits of ten "long-storage" tomato lines cultivated under no irrigation were screened for low soil water tolerance. Leaf relative water content (RWC), proline content and leaf transpiration (E) were measured throughout the growing season. Instantaneous leaf water use efficiency was also calculated on a single date, as the ratio between net photosynthesis (A) and E. Close relationships were observed among the physiological parameters, positive for E vs. RWC and inverse for RWC and E vs. proline. Results indicate that the increase in proline concentration involves a water stress tolerance, and genotypes more sensitive to soil water deficit respond to drought stress through less proline in leaves. Close significant linear relationships (positive with RWC and E, negative with proline) were also found between fruit yield and all the physiological parameters examined. Among them, the most reliable indicator for yield prediction under water restriction was leaf transpiration rate as measured at the flowering stage. The study made it possible to understand the complex relationships between physiological processes, drought tolerance, and plant productivity in long-storage tomato, and to identify those traits that regulate plant physiology under low water availability.

Bioenergy crops are expected to play an important role in reducing CO2 emission, in energy supply and in European energy policy. However, a sustainable bioenergy supply must be resilient to climate change and the impacts on agriculture at both global and regional scale. The purpose of this study was to forecast the potential distribution of several bioenergy crops based on agronomic and environmental constrains under current conditions and future scenarios (2020 and 2030) in European Union. Potential biomass yield, according to the category end use product achievable in each environmental zone of Europe at present and in the future available land have been also studied. Future yields were assessed according to two factors: technological development and climate change: the former was based on prospect of DG-Agriculture for conventional crops and expert judgments for bioenergy crops, while the latter based on relevant research papers and literature reviews which used site-specific crop growth models. Yields are expected to increase in northern Europe due to climate change and technological development, while in southerneastern Europe the negative effect of climate change will be mitigated by the technological development. The estimated total biomass production in Europe, on the basis of future yields and surplus land made available for energy crops, may not be sufficient to meet the needs of bioenergy supply as claimed in the European directive 2009/28/EC.

Miscanthus, a C4 perennial grass native to Eastern Asia, is being bred to provide biomass for bioenergy and biorenewable products. Commercial expansion with the clonal hybrid M. × giganteus is limited by low multiplication rates, high establishment costs and drought sensitivity. These limitations can be overcome by breeding more resilient Miscanthus hybrids propagated by seed. Naturally occurring fast growing indigenous Miscanthus species are found in diverse environments across Eastern Asia. The natural diversity provides for plant breeders, the genetic resources to improve yield, quality, and resilience for a wide range of climates and adverse abiotic stresses. The challenge for Miscanthus breeding is to harness the diversity through selections of outstanding wild types, parents, and progenies over a short time frame to deploy hybrids that make a significant contribution to a world less dependent on fossil resources. Here are described the strategies taken by the Miscanthus breeding programme at Aberystwyth, UK and its partners. The programme built up one of the largest Miscanthus germplasm collections outside Asia. We describe the initial strategies to exploit the available genetic diversity to develop varieties. We illustrate the success of combining diverse Miscanthus germplasm and the selection criteria applied across different environments to identify promising hybrids and to develop these into commercial varieties. We discuss the potential for molecular selections to streamline the breeding process.