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The dwindling availability of agricultural land, caused by factors such as rapid population growth, urban expansion, and soil contamination, has significantly increased the pressure on food production. To address this challenge, cultivating non-food crops on contaminated land has emerged as a promising solution. This approach not only frees up fertile soil for food production but also mitigates human exposure to contaminants. This work aimed to examine the impact of soil contamination with Cd, Pb, Ni, and Zn on the growth, productivity, metal accumulation, and the tolerance of five lignocellulosic non-food crops: switchgrass ( Panicum virgatum L.), biomass sorghum ( Sorghum bicolor L. Moench), giant reed ( Arundo donax L.), African fodder cane ( Saccharum spontaneum L. spp. aegyptiacum Willd. Hackel), and miscanthus ( Miscanthus × giganteus Greef et Deu.). A two-year pot experiment was conducted in Greece, Italy, and Portugal, following the same protocols and applying various levels of metals: Cd (0, 4, 8 mg kg -1 ), Pb and Zn (0, 450, 900 mg kg -1 ), and Ni (0, 110, 220 mg kg -1 ). The experimental design was completely randomized, with three replicates for each treatment. The results showed that switchgrass and sorghum generally maintained their height and productivity under Cd and Pb stress but were adversely affected by high Zn and Ni concentrations. Giant reed and African fodder cane showed reduced height and productivity at higher Ni and Zn levels. Miscanthus exhibited resilience in height but experienced productivity reductions only at the highest Zn concentration. Heavy metal uptake varied among crops, with switchgrass and sorghum showing high Cd and Pb uptake, while giant reed accumulated the most Cd and Zn. Miscanthus had the highest Ni accumulation. The tolerance indices indicated that switchgrass and sorghum were more tolerant to Cd and Zn at lower concentrations, whereas miscanthus had lower tolerance to Cd but a higher tolerance to Zn at higher concentrations. Giant reed and African fodder cane demonstrated stable tolerance across most heavy metals. Accumulation indices highlighted the effectiveness of switchgrass and sorghum in Cd and Pb uptake, while miscanthus excelled in Ni and Zn accumulation. The cluster analysis revealed similar responses to heavy metal stress between African fodder cane and giant reed, as well as between sorghum and miscanthus, with switchgrass displaying distinct behavior. Overall, the study highlights the differential tolerance and accumulation capacities of these crops, indicating the potential for phytoremediation applications and biomass production in heavy metal-contaminated soils.

Demand for sustainably produced biomass is expected to increase with the need to provide renewable commodities, improve resource security and reduce greenhouse gas emissions in line with COP26 commitments. Studies have demonstrated additional environmental benefits of using perennial biomass crops (PBCs), when produced appropriately, as a feedstock for the growing bioeconomy, including utilisation for bioenergy (with or without carbon capture and storage). PBCs can potentially contribute to Common Agricultural Policy (CAP) (2023-27) objectives provided they are carefully integrated into farming systems and landscapes. Despite significant research and development (R&D) investment over decades in herbaceous and coppiced woody PBCs, deployment has largely stagnated due to social, economic and policy uncertainties. This paper identifies the challenges in creating policies that are acceptable to all actors. Development will need to be informed by measurement, reporting and verification (MRV) of greenhouse gas emissions reductions and other environmental, economic and social metrics. It discusses interlinked issues that must be considered in the expansion of PBC production: (i) available land; (ii) yield potential; (iii) integration into farming systems; (iv) R&D requirements; (v) utilisation options; and (vi) market systems and the socio-economic environment. It makes policy recommendations that would enable greater PBC deployment: (1) incentivise farmers and land managers through specific policy measures, including carbon pricing, to allocate their less productive and less profitable land for uses which deliver demonstrable greenhouse gas reductions; (2) enable greenhouse gas mitigation markets to develop and offer secure contracts for commercial developers of verifiable low-carbon bioenergy and bioproducts; (3) support innovation in biomass utilisation value chains; and (4) continue long-term, strategic R&D and education for positive environmental, economic and social sustainability impacts., Competing Interests: The authors declare that progress reported in this paper, which includes input from industrial partners, is not biased by their business interests., (© 2023 The Authors. GCB Bioenergy Published by John Wiley & Sons Ltd.)

Background and Aims: The development of Arundo donax as a biomass crop for use on drought-prone marginal lands in areas with warm to hot climates is constrained by the lack of variation within this species. We investigated the effect of morphological and physiological variation on growth and tolerance to drought under field conditions in three ecotypes of A. donax collected from habitats representing a climate gradient: a pre-desert in Morocco, a semi-arid Mediterranean climate in southern Italy and a warm sub-humid region of central Italy., Methods: The three A. donax ecotypes were grown under irrigated and rain-fed conditions in a common garden field trial in a region with a semi-arid Mediterranean climate. Physiological and morphological characteristics, and carbohydrate metabolism of the ecotypes were recorded to establish which traits were associated with yield and/or drought tolerance., Key Results: Variation was observed between the A. donax ecotypes. The ecotype from the most arid habitat produced the highest biomass yield. Stem height and the retention of photosynthetic capacity later in the year were key traits associated with differences in biomass yield. The downregulation of photosynthetic capacity was not associated with changes in foliar concentrations of sugars or starch. Rain-fed plants maintained photosynthesis and growth later in the year compared with irrigated plants that began to senescence earlier, thus minimizing the difference in yield. Effective stomatal control prevented excessive water loss, and the emission of isoprene stabilized photosynthetic membranes under drought and heat stress in A. donax plants grown under rain-fed conditions without supplementary irrigation., Conclusions: Arundo donax is well adapted to cultivation in drought-prone areas with warm to hot climates. None of the A. donax ecotypes exhibited all of the desired traits consistent with an 'ideotype'. Breeding or genetic (identification of quantitative trait loci) improvement of A. donax should select ecotypes on the basis of stem morphology and the retention of photosynthetic capacity., (© The Author(s) 2018. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Genetic improvement through breeding is one of the key approaches to increasing biomass supply. This paper documents the breeding progress to date for four perennial biomass crops (PBCs) that have high output-input energy ratios: namely Panicum virgatum (switchgrass), species of the genera Miscanthus (miscanthus), Salix (willow) and Populus (poplar). For each crop, we report on the size of germplasm collections, the efforts to date to phenotype and genotype, the diversity available for breeding and on the scale of breeding work as indicated by number of attempted crosses. We also report on the development of faster and more precise breeding using molecular breeding techniques. Poplar is the model tree for genetic studies and is furthest ahead in terms of biological knowledge and genetic resources. Linkage maps, transgenesis and genome editing methods are now being used in commercially focused poplar breeding. These are in development in switchgrass, miscanthus and willow generating large genetic and phenotypic data sets requiring concomitant efforts in informatics to create summaries that can be accessed and used by practical breeders. Cultivars of switchgrass and miscanthus can be seed-based synthetic populations, semihybrids or clones. Willow and poplar cultivars are commercially deployed as clones. At local and regional level, the most advanced cultivars in each crop are at technology readiness levels which could be scaled to planting rates of thousands of hectares per year in about 5 years with existing commercial developers. Investment in further development of better cultivars is subject to current market failure and the long breeding cycles. We conclude that sustained public investment in breeding plays a key role in delivering future mass-scale deployment of PBCs., Competing Interests: The authors declare that progress reported in this paper, which includes input from industrial partners, is not biased by their business interests.

Growth in planted areas of Miscanthus for biomass in Europe has stagnated since 2010 due to technical challenges, economic barriers and environmental concerns. These limitations need to be overcome before biomass production from Miscanthus can expand to several million hectares. In this paper, we consider the economic and environmental effects of introducing seed based hybrids as an alternative to clonal M. x giganteus ( Mxg ). The impact of seed based propagation and novel agronomy was compared with current Mxg cultivation and used in 10 commercially relevant, field scale experiments planted between 2012 and 2014 in the United Kingdom, Germany, and Ukraine. Economic and greenhouse gas (GHG) emissions costs were quantified for the following production chain: propagation, establishment, harvest, transportation, storage, and fuel preparation (excluding soil carbon changes). The production and utilization efficiency of seed and rhizome propagation were compared. Results show that new hybrid seed propagation significantly reduces establishment cost to below £900 ha -1 . Calculated GHG emission costs for the seeds established via plugs, though relatively small, was higher than rhizomes because fossil fuels were assumed to heat glasshouses for raising seedling plugs (5.3 and 1.5 kg CO 2 eq. C Mg [dry matter (DM)] -1 ), respectively. Plastic mulch film reduced establishment time, improving crop economics. The breakeven yield was calculated to be 6 Mg DM ha -1 y -1 , which is about half average United Kingdom yield for Mxg ; with newer seeded hybrids reaching 16 Mg DM ha -1 in second year United Kingdom trials. These combined improvements will significantly increase crop profitability. The trade-offs between costs of production for the preparation of different feedstock formats show that bales are the best option for direct firing with the lowest transport costs (£0.04 Mg -1 km -1 ) and easy on-farm storage. However, if pelleted fuel is required then chip harvesting is more economic. We show how current seed based propagation methods can increase the rate at which Miscanthus can be scaled up; ∼×100 those of current rhizome propagation. These rapid ramp rates for biomass production are required to deliver a scalable and economic Miscanthus biomass fuel whose GHG emissions are ∼1/20th those of natural gas per unit of heat.

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., (Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.)

In scale-up, the potential of ethanol production by dilute sulfuric acid pretreatment using corncob was investigated. Pretreatments were performed at 170 °C with various acid concentrations ranging from 0% to 1.656% based on oven dry weight. Following pretreatment, pretreated biomass yield ranged from 59% to 67%. More than 90% of xylan was removed at 0.828% of sulfuric acid. At same pretreatment condition, the highest glucose yield obtained from pretreated biomass by enzymatic hydrolysis was about 76%, based on a glucan content of 37/100 g. In hydrolysate obtained by pretreatment, glucose concentration was low, while xylose concentration was significantly increased above 0.368% of sulfuric acid. At 1.656% of sulfuric acid, xylose and glucose concentration was highest. In subsequent, fermentation with hydrolysate, maximal ethanol yield was attained after 24 h with 0.368% of sulfuric acid. The fermentation efficiency of hydrolysate obtained by enzymatic hydrolysis reached a maximum of 75% at an acid charge of 0.368%.

Saccharum (Saccharum spontaneum L. ssp. aegyptiacum (Willd.) Hack.), is a rapidly growing, wide ranging high-yield perennial, suitable for second generation bioethanol production. This study evaluated oxalic acid as a pretreatment for bioconversion. Overall sugar yields, sugar degradation products, enzymatic glucan hydrolysis and ethanol production were studied as effects of temperature (150-190 degrees C), reaction time (10-40 min) and oxalic acid concentration 2-8% (w/w). Time and temperature were combined into a single parameter, Severity Factor (SF) [Log(R(0))], and related to oxalic acid using a response surface methodology. Maximum total sugar yield was attained at a SF of 2.93 and 6.79% (w/w) oxalic acid, while maximum formation of sugar degradation products was observed at the highest SF (4.05) and 5% (w/w) oxalic acid. These were also the conditions for maximum simultaneous saccharification and fermentation (SSF) of the residual solids. Commercial cellulases and Saccharomyces cerevisiae attained 89.9% glucan conversion and 17.8 g/l ethanol. Pichia stipitis CBS 6054 fermented hemicellulosic hydrolysates from less severe conditions to ethanol with a yield of 0.35 (g(e)/g(s)). Maximal product yields were 69% of theoretical value and 90% of the SSF conversion efficiency for hydrolysate fermentation and SSF, respectively., (Published by Elsevier Ltd.)