Short Rotation Coppice Research Articles

A financial and environmental sustainability of circular bioeconomy: A case study of short rotation coppice, biochar and greenhouse production in southern Finland

Business opportunities of circular bioeconomy have been proposed to lessen the socio-economic challenges of rural areas and to conserve diminishing natural resources. Recently, the financial and environmental sustainability of circular bioeconomy has gained considerable research interest. This study examines three promising operational models for circular bioeconomy development in southern Finland: willow cultivation on marginal lands, wood-based biochar production and wood chip heated greenhouse production. The feasibility of these models is assessed by analysing their financial and environmental sustainability using a multi-methodological approach. Financial sustainability is analysed using net present value and internal rate of return indicators via cash flow analysis. Environmental sustainability is examined using carbon footprint indicator in a life cycle assessment and a closed loop analysis. The results reveal correlations between both types of indicators, suggesting that a circular bioeconomy may lead to win–win situations. Potential closed loops are identified, and a circular bioeconomy model is suggested for improving security of supply and the flexibility of raw materials. Imbalanced revenue allocations between primary and secondary production are recognised as a potential threat to financial feasibility. Understanding financial and environmental sustainability of divergent operational models supports decision making and the legitimacy of change.

Phytoextraction of toxic elements and chlorophyll fluorescence in the leaves of energy willow (Salix sp.), treated with wastewater solids and wood ash

Open-field small plot long-term experiment was set up during 2011 with willow (Salix triandra × S. viminalis ‘Inger’), grown as a short rotation coppice energy crop in Nyíregyháza, Hungary. The sandy loam Cambisol with neutral pH was treated three times (2011, 2013, and 2016) with 15 t ha–1 municipal sewage sludge compost (MSSC) and with 600 kg ha–1 (2011, 2013) or 300 kg ha–1 (2016) wood ash (WA). In 2018 the MSSC-treated plots were amended with 7.5 t ha–1 municipal sewage sediment (MSS), and 300 kg ha–1 WA. MSSC and WA or MSS and WA were also applied to the soil in combinations during all treatments. Control plots remained untreated since 2011. Repeated application of wastewater solids (MSSC, MSS) and wood ash (WA) significantly enhanced the amounts of As (up to +287%), Ba, Cd (up to +192%), Cu, Mn, Pb, and Zn in the topsoil of willows. The combined application of MSSC+MSS+WA resulted in significantly higher Mn and Zn and lower As Ba, Cd Cr, and Pb concentrations in topsoil than MSSC+MSS treatment of soil without WA. Nitrogen concentrations in leaves of treated plants were generally slightly lower or similar to control. All soil treatments significantly enhanced the uptake or accumulation of nutrient elements (Ca, K, Mg, P) and potentially toxic elements (As, Ba, Cd, Cr, Cu, Mn, Ni, Pb, and Zn) in the leaves of willows during 2018, 2019, and 2020. Significantly higher Mn or Zn concentrations were measured in MSSC+MSS+WA than in MSSC+MSS treatments. Significant amounts of Cd (up to 1.11 mg kg–1) or Zn (up to 183 mg kg–1) can be translocated (phytoextracted) from a soil amended with wastewater solids or wood ash to willow leaves. In 2018 the treatments decreased the chlorophyll fluorescence values, while in 2019 and 2020 the light adapted fluorescence yield (Y) values were higher in treated than in control plants.

Wastewater-Fertigated Short-Rotation Coppice, a Combined Scheme of Wastewater Treatment and Biomass Production: A State-of-the-Art Review

Vegetated filters based on short-rotation coppice (SRC) can be used to treat various industrial and municipal wastewater while producing valuable biomass in an economical and sustainable way, showing potential in the field of pollution control and bio-based circular economy. This study provides an overview of the state of the art in wastewater-fertigated SRC systems (wfSRCs) worldwide. Different designs, wastewater sources, tree species and varieties, planting schemes, geographic locations, and climates for wfSRC implementation were identified after conducting a literature review. The performance review includes standard water quality parameters, BOD5, COD, nitrogen, phosphorous, and potassium, as well as the extent of pathogen and emergent contaminant removal and biomass production rates. Identified knowledge gaps and important factors to support the practical implementation of wfSRCs are highlighted. Europe leads the research of wfSRC, followed by North America and Australia. The available publications are mainly from developed countries (73%). The most applied and studied tree species in wfSRC systems are willows (32%), followed by eucalyptus (21%) and poplars (18%). Most of the reviewed studies used domestic wastewater (85%), followed by industrial wastewater (8%) and landfill leachate (7%). Most data show high BOD5 and COD removal efficiencies (80%). There are large differences in the documented total nitrogen and total phosphorus removal efficiencies (12%–99% and 40%–80%, respectively). Enhanced biomass growth in wfSRC systems due to wastewater fertigation was reported in all reviewed studies, and biomass production varied from 3.7 to 40 t DM/ha/yr. WfSRCs seem to have high potential as viable and cost-effective wastewater treatment alternatives to conventional treatment technologies.

Comparative economics of Sida hermaphrodita (L.) Rusby and Silphium perfoliatum L. as bioenergy crops in Europe

The purpose of this research was to fill the identified gap on financial data of Sida hermaphrodita (L.) Rusby (Sida) and Silphium perfoliatum L. (Silphium), two perennial bioenergy crops that potentially provide a more sustainable alternative/complement to other bioenergy crops. Using discounted cash flow analysis, the Net Present Values of Sida and Silphium were compared to a rotation of other arable crops including maize, and the two energy crops of short rotation coppice and Miscanthus. The analysis was completed using the SidaTim analysis tool for the UK, Italy, Germany and Poland, producing a total of four independent models. The results showed that with no subsidies, cultivating Sida was unattractive in all four countries relative to other crop options. However, Silphium, was an economically viable option in each country. Both Sida and Silphium can offer greater environmental benefits than other arable crops, and the profitability of each crop would be further enhanced if additional payments for such public services were made to farmers, and if there were secure markets for the sale of the biomass. This study is the first comparative economic analysis in West and Central Europe of the two novel energy crops in comparison to more common energy crops and an arable rotation.

Entwicklung der Laufkäferfauna (Coleoptera: Carabidae) einer Kurzumtriebsplantage über einen Zeitraum von 9 Jahren

In order to evaluate the importance of short-rotation coppice (SRC) as habitat for ground beetles, a SRC with stands of different tree species (poplar, willow, rowan) in the municipality of Schapen (NW-Germany) was investigated during several years and different rotation-phases using pitfall traps. Regardless of the plantation-age, the cultivated tree species and the rotation-phase, the ground beetle fauna of the surveyed SRC was dominated by widespread and common generalists. Species of conservation concern (exclusively xerothermophilic species) were found only sporadically and had their main occurrence in the two years following the establishment of the plantation. During this phase, Harpalus griseus, a rare and threatened species in Lower Saxony, was detected in large numbers. After 8 and 9 years respectively, species numbers as well as the number of specimens on the entire SRC and within its different stands were considerably lower than in the early establishment phase. The partial harvest of the poplar and willow stands caused a significant change in ground beetle communities and a strong increase in the activity of openland species. However, openland generalists were the main beneficiaries, while pioneer species like Harpalus griseus occurred only sporadically. Woodland species were found only rarely even in the 9th year after establishment. We conclude that the conservational value of SRC as habitat for ground beetles is generally limited, decreases with increasing plantation-age and that a mosaic of different tree stands, rotation-phases and headlands is not sufficient to promote pioneer species of conservation concern. In order to provide permanently suitable conditions for these species, additional measures extending beyond the regular management of the plantations are required. These should aim at the creation of sun-exposed ruderal habitats with a patchy herb layer and high proportions of bare ground within accompanying structures of SRC like headlands or rides.

Comparison of wood and foliage production of four Eucalyptus species using management of short rotation coppice in the Koushkak reaserch station

Comparison of wood and foliage production of four Eucalyptus species using management of short rotation coppice in the Koushkak reaserch station

Water Use of Hybrid Poplar (Populus deltoides Bart. ex Marsh timesP. nigra L. “AF2”) Growing Across Contrasting Site and Groundwater Conditions in Western Slovakia

The water use by short rotation coppices (SRC) has been a focus of ongoing research in the last decades. Nevertheless, investigations that consider site factors and present long-term monitoring of the components of the water balance are rare. This research quantified the tree-based transpiration in the 4th growing season of uncoppiced 1st rotational hybrid poplar stands (Populus deltoides Bart. ex Marsh × P. nigra L. “AF2”) in western Slovakia. The aim of the study was to determine the influence of meteorological and soil-related site conditions on transpiration rates. Three experimental plots were located in the Morava River floodplains, on loamy sand-textured soils with different groundwater accessibilities: higher, low, and fluctuating groundwater level. We measured sap flow (Heat Ratio Method), volumetric water content, matric potential, groundwater level, and meteorological variables throughout the growing season in 2019. The results indicated that transpiration in the three sites was almost constant during that period, which was characterized by distinct conditions. The average cumulative transpiration at the site with a higher groundwater level (1105 mm) was larger than at the site with a lower groundwater level (632 mm) and the site with fluctuating groundwater (863 mm). A principal component analysis (PCA) and correlation analysis identified that the contribution of meteorological and soil-related site variables to transpiration differed among the sites. Soil water availability and groundwater accessibility are critical variables for the water use of poplar SRC. We concluded that the combination of site conditions needs to be reconsidered for the expansion of sustainable short rotation plantations in Europe.

Assessment of Working Performance and Costs of Two Small-Scale Harvesting Systems for Medium Rotation Poplar Plantations

Considering the increasing need to produce energy from renewable sources, the interest towards Medium Rotation Coppices (MRC) plantations has increased. One of the main issues that require tackling for the comprehensive sustainability of these plantations is related to the development of sustainable harvesting systems. Indeed, as a consequence of the average tree diameters at a breast height (dbh) of about 15 cm, single-pass harvesting typical of short rotation coppice is not applicable. Therefore, these plantations are generally harvested with machinery specifically developed for forest operations, as for instance harvesters, feller-bunchers and forwarders. In the Mediterranean area, the availability of such machines is still limited to a few big forest enterprises. Indeed, the majority of forest contractors carry out their activities in the framework of small-scale forestry, without the financial possibility of purchasing expensive machineries. Thus, the present study had the objective to evaluate the performance of two small-scale harvesting systems in a 7-year-old poplar plantation in Central Italy. The difference between the two systems was the different machinery applied for wood extraction, i.e., a forestry-fitted farm tractor equipped with winch (WINCH) and a fork lift prototype, attached to a crawler tractor (CFL). Extraction via CFL system reached very high working performance with about 21.5 m3 SMH−1 (Scheduled Machine Hours, including delays), comparable to the productivities reported in the literature for forwarders working in similar plantations. Harvesting costs with CFL were 24.74 EUR m−3, of which 4.48 EUR m−3 was for felling with chainsaw, 4.61 EUR m−3 for extraction with CFL prototype and 15.64 EUR m−3 for wood chipping. WINCH showed unsatisfactory results instead, possessing a wood chip production cost of 41.95 EUR m−3, which is practically equivalent to the market price of wood chips.

Short communication: A study case on polycyclic plantations (PP) as innovative models for sustainable combined production of noble hardwood and biomass

Aim of study: To verify the short rotation coppices (SRC) aboveground biomass production; to define the best planting intra-row spacing for walnut and poplar growth and wood production, with the last goal to assess the possibility of obtaining competitive yields in comparison to those produced by traditional monocultures.
 Area of study: Po Valley, municipality of Meleti (Northern Italy).
 Material and methods: A randomized block design with three replications was applied for the experimental design. The growth-monitoring activities started in 2009 and have continued for 5 years on the SRC, 10 years on poplar clone ˈI-214ˈ, whereas on common walnut they are still going on but only data concerning the twelfth year are reported in this work. The normality of distribution was evaluated for growth and yield data of species in the SRC model; all data were analysed with ANOVA; growth data were included in a linear mixed model analysis to evaluate the effect of age, spacing and their interaction, and the effect of SRC rows on growth and yield of poplar and walnut.
 Main results: After 5 years of cultivation under SRC system, biomass yields obtained from the poplar clone ˈAF2ˈ were 39.9 Mg ha-1, from the elm 31.9 Mg ha-1 and from the plane 14.8 Mg ha-1. After 10 years high timber production was obtained from poplar clone ˈI-214ˈ (average volume 98.2 m3 ha-1). After 12 years, walnut trees reached a diameter at breast height (DBH) of 17.8±0.2, 18.9±0.2 and 18.7±0.3 cm, respectively, for planting distances of 6, 7 and 8 m, and showed diameter increments of 1.5-2.0 cm yr-1. With these growth rates, walnut can reach a merchantable dimension within 25-30-years.
 Research highlights: Polycyclic wood plantations are a recent arboriculture model able to produce, on the same site, different assortments using various crop trees characterized by different growth rates and turnovers. This new type of mixed plantation is more environmentally sustainable compared to monoculture and allows diversification of production, obtaining continuous wood yields over the years (5, 10, 20, 30 years).

Time-course foliar dynamics of poplar short rotation plantations under Mediterranean conditions. Responses to different water scenarios

Poplar (Populus spp.) Short Rotation Coppice (SRC) systems are characterized by high short-term biomass productivity and play a key role in promoting employment in rural areas as well as supplying environmental benefits. However, in the context of climate change with expected reduced water availability in the Mediterranean area, the productivity of these plantations may be seriously limited. In this regard, the aim of this work is to analyse the monthly dynamic responses of relevant variables at foliar level throughout the entire first rotation of a poplar short rotation plantation under two water scenarios: optimal scenario (with irrigation to field capacity (FC)) versus restrictive scenario (with 50% FC irrigation).This data came from 590 trees in a poplar short rotation plantation of the highly productive genotype ‘AF2‘. LAImax values of 2.39, 7.47 and 9.34 were found for the three-year rotation cycle, pointing to significantly lower values after the establishment year under the restrictive water scenario. SLA mean values displayed a downward trend, with 12.25 m2 kg−1, 10.82 m2 kg−1 and 10.47 m2 kg−1 for years 1, 2 and 3 respectively, no significant differences being observed between water scenarios. NPK foliar concentrations decreased over the rotation, being the values lower under the restrictive scenario. Additionally, the selected genotype, ‘AF2’, displayed tight stomatal control under conditions of water stress, maintaining high photosynthetic levels.The responses observed in this study can potentially be used to better understand the behavior of these variables which most affect production of poplar plantations in face of climate change.

Agroforestry systems as new strategy for bioenergy — Case example of Czech Republic

The paper deals with the analysis of economic efficiency of innovative agroforestry systems (AFS) using coppiced tree belts (CTB), which combine the advantages of traditional alley cropping with the short rotation coppice (dense plantation of fast-growing trees for biomass — SRC) on an agricultural field. We have analyzed and compared such innovative agroforestry system (AFS-CTB) with conventional food crops production in conventional 4 crop year rotation (winter barley, winter wheat, rapeseed and corn). The minimum price of production, (based on net present value criterion), was performed to enable simultaneous assessment of annual and perennial crops over time in order to obtain also economic evaluation and comparison. Our results show that AFS-CTB generate similar income and profits as from conventional annual crops when cultivating on suitable sites and adhering to good farming principles.

Beyond Monetary Cost-Benefit Analyses: Combining Economic, Environmental and Social Analyses of Short Rotation Coppice Poplar Production in Slovakia

Rising demand for bio-based products exerts a growing pressure on natural resources such as wood. Sustainable solutions are becoming increasingly important to meet the demand. In this study, 20-year poplar Short Rotation Coppice (SRC) plantations located in Western Slovakia are investigated with respect to (socio)-economic, environmental and social sustainability. The cost–benefit methodology is applied to assess the economic profitability of a switch from conventional annual crops (corn maize and winter rye) to perennial SRC. To compare economic profitability of the land management, net present value (NPV), payback time (PBT), internal rate of return (IRR) and benefit–cost ratio (BCR) are calculated. The study was enhanced by adopting the concept of regional value added to indicate the local value creation. The results for the three scenarios yield an NPV equal to 12,156 euros ha−1 for corn maize, 9763 euros ha−1 for winter rye and 2210 euros ha−1 with a PBT of 14.13 years for poplar SRC production. The regional value added for the corn maize scenario was estimated with 10,841 euros ha−1, the winter rye with 7973 euros ha−1 and the poplar SRC with 1802 euros ha−1. To appraise non-monetized social values, semi-structured interviews (N = 4) were conducted among experts familiar with SRC management in Eastern Europe. Non-monetary benefits for the stakeholder groups society, farmers or landowners and the industry were identified in terms of land fragmentation, carbon sequestration and an increase in biodiversity within the plantations, farm diversification and higher independency from wood markets. The relatively poor image of SRC, farmers or landowners having concerns about being tied on long-term contracts and legal restrictions may become obstacles in the establishment of SRC. For estimating the capability of carbon sequestration in SRC plantations the RothC model was utilized, resulting in the potential soil organic carbon (SOC) average increase of 29% during the 20 years. However, a transition in land use patterns must involve thorough considerations of all three pillars of sustainability to ensure long-term viability of the establishment.

Legal Framework for the Sustainable Production of Short Rotation Coppice Biomass for Bioeconomy and Bioenergy

The production of lignocellulose biomass on dedicated plantations is an option that facilitates the implementation of sustainable development policy. The novelty of this type of research is that it involves the use of various types of methods—economic and legal analyses within a particular subject. This makes it possible to obtain a holistic view of the chosen case study. The purpose of this study was to determine whether setting up a Short Rotation Coppice (SRC) plantation of willow (Salix spp.) and poplar (Populus spp.) was economically profitable and if the legal regulations supported this type of production. The economic data are based on an experimental case study. The economic profitability of the plantations was assessed through an analysis of discounted cash flows, net present value (NPV), internal rate of return (IRR), and profitability index (PI). The legal analysis of the relevant EU and Polish legal solutions was based on a dogmatic approach. The study demonstrated that SRC cultivation was mostly hindered by economic factors, including the low selling price of biomass as an energy resource and the high costs of harvest. Meanwhile, in the analysed period, i.e., from 2015 to 2020, there were no additional legal or economic forms of support for this type of production that was addressed directly to lignocellulose biomass producers, with the exception of the standard support under the Common Agricultural Policy framework. The results of this study provide information for decisionmakers about the opportunities and challenges experienced during the development of SRC plantations.

Woodchips or potato chips? How enhancing soil carbon and reducing chemical inputs influence the allocation of cropland

ContextFarmers are facing increasing pressure to practice multifunctional agriculture. Producing woody biomass through short rotation coppices (SRC) provides an economic opportunity for farmers to diversify their agricultural income while potentially providing environmental benefits. ObjectiveUsing multi-objective, robust optimization we investigate the extent to which SRC may help farmers to reconcile the economic objective of profit maximization with ecological concerns related to enhancing soil carbon and reducing the use of chemical inputs (nitrogen fertilizers and pesticides). MethodsTo evaluate the costs and benefits of SRC relative to conventional agricultural crops, we use empiric and modelled data from Bavaria, Germany. Based on this performance data our optimization model determines the best mix of land-uses (land-use portfolio) for reconciling multiple objectives under uncertainty. We compare the optimal portfolios for two decision perspectives: profit oriented (in which the decision-maker only considers economic return) and multifunctional (in which the three ecological objectives are considered in addition to economic return). Both perspectives consider that farmers seek protection against downside risks. Results and conclusionsFrom the profit-oriented perspective, SRC was selected in the optimal portfolios (comprising 34% of the land area) derived for more risk-tolerant decision-makers, but was absent from the portfolio optimized for a strongly risk-averse decision-maker. Instead, higher woodchip prices may be required to make SRC economically attractive for strongly downside risk-averse farmers. In contrast, SRC was selected in the multifunctional portfolio (with 24-33% land-use shares) for all levels of risk aversion. We found that the selection of SRC helped to mitigate the financial costs of multifunctionality, increasing both the average and worst-case economic return of the multifunctional portfolio. SignificanceOur study reveals new insights concerning the influence of uncertainties and downside risk associated with SRC on anticipated farmer decisions and suggests that cultivating SRC can help reduce trade-offs between economic and ecological objectives.

Life cycle assessment of a short-rotation coppice willow riparian buffer strip for farm nutrient mitigation and renewable energy production

As agricultural activity intensifies across Europe there is growing concern over water quality. Agricultural run-off is a leading cause of freshwater degradation. Simultaneously there is a continually increasing drive to promote renewable energy and reduce greenhouse gas emissions. Willow coppice planted as a riparian buffer has been suggested as a solution to help mitigate these problems. However, there is limited research into the use of such a system and several key knowledge gaps remain, such as, the energy ratio of the system is not known, and a fully harvested site has yet to be analysed in the literature. The aim of this research is to fill these knowledge gaps to help inform agri-environmental policy. To do this a life cycle assessment was carried out on an established willow buffer system, considering the global warming potential, eutrophication potential, acidification potential and cumulative energy demand impact categories, alongside the calculation of the energy ratio. To our knowledge it is the first site to be fully harvested and for which a full life cycle assessment has been carried out. The willow was combusted to fuel a district heating system. Key results showed emissions of 4.66 kg CO2eq GJheatout−1 and 0.01 kg SO2eq GJheatout−1, both of which are significant reductions compared to an oil heating system (95% reductions for both impact categories). The system also resulted in the permanent nutrient removal of 55.36 kg PO43−eq ha−1 yr−1 and had an energy ratio of 17.4, which could rise to 64 depending on the harvest method.

Response of Poplar Leaf Transcriptome to Changed Management and Environmental Conditions in Pure and Mixed with Black Locust Stands

Mixed cropping in short rotation coppice can be an alternative to monocultures. To design optimized mixtures, field trials are needed. Poplar, as an economically important and fast-growing species, and black locust, as a nitrogen-fixing species, are promising candidates for such studies. RNA sequencing (RNA-seq) was used to monitor effects of mixed and pure cultivations on the gene expression of poplar along with growth measurements during 2017 and 2018. Both biomass production and leaf transcriptomes revealed a strong competition pressure of black locust and the abiotic environment on poplar trees. Gene expression differed between the two study sites and pure and mixed stands. Shading effects from black locust caused the downregulation of photosynthesis and upregulation of shade avoidance genes in mixed stands in 2017. As a result of higher light availability after cutting black locust, plant organ development genes were upregulated in mixed stands in 2018. Drought conditions during the summer of 2018 and competition for water between the two species caused the upregulation of drought stress response genes in mixed stands and at the unfavorable growing site. Further investigations are required to discover the mechanisms of interspecific competition and to develop stand designs, which could increase the success and productivity of mixed plantations.

Long-Term Effects of Soil Remediation with Willow Short Rotation Coppice on Biogeographic Pattern of Microbial Functional Genes.

Short rotation coppice (SRC) is increasingly being adopted for bioenergy production, pollution remediation and land restoration. However, its long-term effects on soil microbial communities are poorly characterized. Here, we studied soil microbial functional genes and their biogeographic pattern under SRC with willow trees as compared to those under permanent grassland (C). GeoChip analysis showed a lower functional gene diversity in SRC than in C soil, whereas microbial ATP and respiration did not change. The SRC soil had lower relative abundances of microbial genes encoding for metal(-oid) resistance, antibiotic resistance and stress-related proteins. This indicates a more benign habitat under SRC for microbial communities after relieving heavy metal stress, consistent with the lower phytoavailability of some metals (i.e., As, Cd, Ni and Zn) and higher total organic carbon, NO3−-N and P concentrations. The microbial taxa–area relationship was valid in both soils, but the space turnover rate was higher under SRC within 0.125 m2, which was possibly linked to a more benign environment under SRC, whereas similar values were reached beyond thisarea. Overall, we concluded that SRC management can be considered as a phytotechnology that ameliorates the habitat for soil microorganisms, owing to TOC and nutrient enrichment on the long-term.

Which Large- and Medium-Sized Mammals Use Commercial Short-Rotation Coppice as Habitat?

We surveyed occurrence and activity of large- and medium-sized mammals on six commercial mini-rotation short-rotation coppice (SRC) plantations in northern Germany by camera trapping in different seasons (winter, late summer). In total, eleven species (6–9 per site) were detected. This corresponds to the majority of mammal species occurring in the study region. Roe deer, wild boar and red fox were found across all sites. All other species were detected on fewer sites and some in only one of the seasons. Roe deer was the most active species both in terms of visit frequency (days with detection) and use intensity (detection numbers). With few exceptions on individual sites, all other species showed significantly lower activity. Number of detected species and activity of most of the species did not differ between seasons. Furthermore, there were no differences between near-edge and central areas of the crops with regard to the activity of the occurring species. Activity of individual species on different sites, however, differed considerably in some cases. Our results show that a wide range of mammal species are basically able to include SRC into their habitat utilisation. However, the sporadic use by most species indicates a rather limited current habitat value of the surveyed plantations. Options to increase the habitat value of SRC for mammals are suggested, but their effectiveness needs to be tested in future studies. Since the spatial and temporal scope of our study was limited and only SRC of a uniform age-class were considered, our results are not immediately applicable to other landscapes, seasons or types and management phases of SRC. Therefore, further research is required that considers these aspects as well as species-specific patterns of habitat selection in comparison to other habitat types.

Assessing the economic profitability of Paulownia as a biomass crop in Southern Mediterranean area

The increase of renewable energy production worldwide, occurred in the last years, is also attributable to some agroforestry species cultivated according to the short rotation coppice technique. Although these species are able of enhancing abandoned or marginal land leading to numerous environmental benefits, an increasing number of farmers are introducing them in place of agricultural crops. Therefore, since for a farmer economic sustainability is one of the main factors to introduce a biomass crop, the study aimed at evaluating the profitability of Paulownia, a species that has been spreading in recent years. In particular, an economic analysis has been carried out in a Southern Italian farm in which Paulownia has recently replaced a vineyard, by adopting a discounted cash flow approach. The results show that the Paulownia for both timber and woodchip production, with an annual gross margin equal to 357.91 € ha−1, can represent a valid alternative compared to wine grape (237.41 € ha−1), while Paulownia for exclusively biomass production has almost zero profitability (4.22 € ha−1). However, the profitability depends not only on the product typology but also on the future market price fluctuations, on the subsidies or incentives, as well as on adequate choices by entrepreneurs for the creation of sustainable supply chains also from an environmental and social point of view.

Acid-Catalyzed Liquefaction of Biomasses from Poplar Clones for Short Rotation Coppice Cultivations.

Liquefaction of biomass delivers a liquid bio-oil with relevant chemical and energetic applications. In this study we coupled it with short rotation coppice (SRC) intensively managed poplar cultivations aimed at biomass production while safeguarding environmental principles of soil quality and biodiversity. We carried out acid-catalyzed liquefaction, at 160 °C and atmospheric pressure, with eight poplar clones from SRC cultivations. The bio-oil yields were high, ranging between 70.7 and 81.5%. Average gains of bio-oil, by comparison of raw biomasses, in elementary carbon and hydrogen and high heating, were 25.6, 67, and 74%, respectively. Loss of oxygen and O/C ratios averaged 38 and 51%, respectively. Amounts of elementary carbon, oxygen, and hydrogen in bio-oil were 65, 26, and 8.7%, and HHV averaged 30.5 MJkg−1. Correlation analysis showed the interrelation between elementary carbon with HHV in bio-oil or with oxygen loss. Overall, from 55 correlations, 21 significant and high correlations among a set of 11 variables were found. Among the most relevant ones, the percentage of elementary carbon presented five significant correlations with the percentage of O (−0.980), percentage of C gain (0.902), percentage of O loss (0.973), HHV gain (0.917), and O/C loss (0.943). The amount of carbon is directly correlated with the amount of oxygen, conversely, the decrease in oxygen content increases the elementary carbon and hydrogen concentration, which leads to an improvement in HHV. HHV gain showed a strong positive dependence on the percentage of C (0.917) and percentage of C gain (0.943), while the elementary oxygen (−0.885) and its percentage of O loss (0.978) adversely affect the HHV gain. Consequently, the O/C loss (0.970) increases the HHV positively. van Krevelen’s analysis indicated that bio-oils are chemically compatible with liquid fossil fuels. FTIR-ATR evidenced the presence of derivatives of depolymerization of lignin and cellulose in raw biomasses in bio-oil. TGA/DTG confirmed the bio-oil burning aptitude by the high average 53% mass loss of volatiles associated with lowered peaking decomposition temperatures by 100 °C than raw biomasses. Overall, this research shows the potential of bio-oil from liquefaction of SRC biomasses for the contribution of renewable energy and chemical deliverables, and thereby, to a greener global economy.