Short Rotation Coppice Systems Research Articles

Design, implementation, and evaluation of a short rotation coppice system for wastewater treatment and resource recovery in India

Despite growing health concerns and increasing water scarcity, adequate wastewater treatment and reuse remains limited in India. Low-cost, decentralised, and nature-based on-site sanitation systems could play a key role in a circular water approach. This paper evaluates the performance of a Wastewater Fertigated Short Rotation Coppice (wfSRC) system based on willow, poplar, and bamboo species as a potential solution, offering low-cost, efficient water treatment, and high biomass production. Through a full-scale wfSRC pilot plant (250 m3·day−1 municipal wastewater on 6864 m2) established at Aligarh Muslim University, Uttar Pradesh, India, treatment capacities, biomass production rates, and contamination tolerance of different willow, poplar, and bamboo species were investigated. The chemical compositions of incoming wastewater, percolation water, soil, and biomass were monitored regularly. Despite the high load, all plant sections of the wfSRC system showed efficient removal of wastewater-originated pollutants. BOD5 and COD removal efficiencies were up to 99% and 95% respectively. Removal efficiencies for PO4-P reached 93% and for TN 91%. In general, total nitrogen and phosphate loads appear to be the limiting design parameters under the conditions at Aligarh to meet all discharge limits in India. Biomass production was projected to be >225 tDM·ha−1·yr−1 for bamboo, 65 tDM·ha−1·yr−1 for willow, and 206 tDM·ha−1·yr−1 for poplar. The pilot, conducted from March 2022 to June 2023, showcased how these densely planted agroforestry systems can effectively treat wastewater through natural processes such as oxidation, microbial degradation, and plant uptake. The findings demonstrate wfSRC's potential to serve as a nature-based, sustainable approach to wastewater treatment, particularly beneficial for suburban and rural areas in India and similar regions worldwide. This paper also provides recommendations for future implementation of wfSRC systems, emphasizing the need for careful planning regarding plant selection, system design, and operational strategies to maximize treatment efficiency and biomass production.

Application Potential of Wastewater Fertigated Short Rotation Coppice Systems in a Selected Region (Aligarh, UP, India)

In many Indian regions, increased wastewater is both a threat to public health and the environment, but it also presents an opportunity as a source of water and nutrients. With less than one-third of India’s wastewater treated and an alarming water scarcity situation, efficient wastewater treatment and reuse schemes are needed to face impending water and fertiliser shortages. This study explores the application potential of wastewater fertigated Short Rotation Coppice systems (wfSRC) as a cost-efficient and promising solution for treating and reusing wastewater in a specific region (400 km2, 184 settlements) of Aligarh (UP), India. Based on real data from a local wfSRC pilot site using bamboo, willow, and poplar, we analysed the system’s treatment performance, nutrient recovery, carbon sequestration potential, land requirements, biomass production potential, and cost–benefit, under various scenarios. The results show that the pilot wfSRC system is efficiently treating 250 m3/day of domestic wastewater on 6864 m2 of land, and serving 2500 people. The land requirements for wfSRC systems vary depending on local conditions (e.g., climate, soil type, wastewater composition) and user demands (e.g., water reuse efficiency, type, and amount of biomass). The calculated areas ranged from 2.75 to 25.7 m2/PE, which equates to a required land area in the whole study region of between 108 and 1006 ha in 2036. This would produce up to 100 DM t/ha/year of valuable biomass. Early local stakeholder involvement and the monitoring of pollutants are recommended as priorities during the planning process for the large-scale implementation of wfSRC systems in India.

Growth Characteristics of Seven Willow Species Distributed in Eastern Japan in Response to Compost Application

To establish a short rotation coppice (SRC) system in the temperate region of East Asia, planting was conducted for cuttings from seven species, including Salix eriocarpa, S. gilgiana, S. gracilistyla, S. integra, S. sachalinensis, S. serissaefolia, and S. subfragilis, with wide distribution in eastern Japan. During cultivation, cheap compost derived from swine manure and containing high concentrations of various nutrients was added. Three treatment groups, including control, low manure (5 Mg ha−1), and high manure (10 Mg ha−1) treatments, were established, and seven willows were grown for two complete growing seasons to obtain the clone density of 10,000 cuttings ha−1. The manure treatments accelerated the growth of all the willow species after two growing seasons. The averages of annual biomass production of seven willows grown under the control, low manure, and high manure treatments were 0.2 Mg ha−1yr−1, 5.3 Mg ha−1yr−1, and 8.5 Mg ha−1yr−1, respectively. By comparing with the biomasses of seven willows, the largest annual biomass production rates of 14.1 and 13.7 Mg ha−1yr−1 were observed in the high manure treatments of S. sachalinensis and S. subfragilis, respectively. For two species under the high manure treatment, S. sachalinensis had the thickest shoots, and S. subfragilis had the tallest shoots. These growth characteristics of S. sachalinensis and S. subfragilis originate from their high biomass production. Overall, these results suggest that S. sachalinensis and S. subfragilis are potentially feasible candidates for the SRC system in temperate regions of East Asia.

Unweaving the population structure and genetic diversity of Canadian shrub willow

Perennial shrub willow are increasingly being promoted in short-rotation coppice systems as biomass feedstocks, for phytoremediation applications, and for the diverse ecosystem services that can accrue. This renewed interest has led to widespread willow cultivation, particularly of non-native varieties. However, Canadian willow species have not been widely adopted and their inherent diversity has not yet been thoroughly investigated. In this study, 324 genotypes of Salix famelica and Salix eriocephala collected from 33 sites of origin were analyzed using 26,016 single nucleotide polymorphisms to reveal patterns of population structure and genetic diversity. Analyses by Bayesian methods and principal component analysis detected five main clusters that appeared to be largely shaped by geoclimatic variables including mean annual precipitation and the number of frost-free days. The overall observed (HO) and expected (HE) heterozygosity were 0.126 and 0.179, respectively. An analysis of molecular variance revealed that the highest genetic variation occurred within genotypes (69%), while 8% of the variation existed among clusters and 23% between genotypes within clusters. These findings provide new insights into the extent of genetic variation that exists within native shrub willow species which could be leveraged in pan-Canadian willow breeding programs.

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.

Soil nutrients and maize yields responses to indigenous agroforestry tree post-fallows management in Tanzania

Agriculture is characterized by low production and expansion into forests and woodlands rather than increased productivity leading to deforestation and land degradation in sub-Saharan Africa. Use of appropriate low input agricultural and other land management technologies may increase production and benefit smallholder farmers through increased productivity in already degraded land. A field experiment was established to assess tree fallows and tree coppice intercropping of indigenous agroforestry tree species (Albizia harveyi and Albizia versicolor) for soil fertility and maize yield improvements in Morogoro, Tanzania. A. versicolor tree fallows recorded significantly (p < 0.05) highest amounts of soil total nitrogen, extractable phosphorus, calcium, magnesium and potassium in 0 - 15 cm soil depth compared to the A. harveyi tree fallows and continuous cropping. A. harveyi tree fallow recorded significantly (p < 0.05) higher amounts of organic carbon and calcium than the continuous cropping system. In comparison with continuous cropping, amount of organic carbon was higher by 41% and 56% in A. harveyi and A. versicolor tree fallows, respectively. During the first cropping season, yields of grains (1.26 Mg ha−1), cobs (0.3 Mg ha−1) and stovers (2.43 Mg ha−1) in maize intercropped with A. versicolor coppices were significantly (p < 0.05) higher than those of maize intercropped with A. harveyi coppices (0.74 Mg ha−1, 0.2 Mg ha−1, 1.49 Mg ha−1) and maize in continuous cropping system (0.29 Mg ha−1, 0.06 Mg ha−1 and 1.06 Mg ha−1). During the second cropping season, yields of maize stovers, height and diameter growth were lower in intercropped maize relative to continuous cropping by 98% to 98.7%, 14.8% to 15.3% and 46.4% to 81.0% respectively; due to increasing competition imposed by growing coppices. The studied indigenous agroforestry tree species are recommended for rotational woodlots and short rotation coppice systems to enhance agricultural productivity and safeguard the environment.

An economic overview of Populus spp. in Short Rotation Coppice systems under Mediterranean conditions: An assessment tool for decision-making

Poplar Short Rotation Coppices can provide lignocellulosic raw material, promote employment in rural areas, contribute to achieving a low carbon bioeconomy and supply environmental benefits. Nevertheless, the economic feasibility of these plantations is a matter of concern and hampers the expansion of commercial initiatives. In this regard, this work aims to identify the most critical cost factors of poplar plantations under Mediterranean conditions. Data from an extensive network located at 30 different sites were used, in particular, detailed cost data for 2 rotations was available for 6 sites within the network. This study evaluates the critical factors that affect profitability, analysing the influence of the discount rate and biomass price under two productive scenarios derived from the network and evaluated as green biomass yield for the first rotation: Baseline (30.56 Mg ha−1 yr−1) and an Optimum (56.52 Mg ha−1 yr−1). Net Present Value after 12 years (4 rotations of 3 years each), ranges from −1105.54 € ha−1 (Baseline) to 9620.30 € ha−1 (Optimum). According to the findings of this study, profitability of poplar plantations will be achieved by ensuring optimum productivity, through an increase in current market prices (40 € Mg-1) or by valuing the ecosystem services, which are not currently quantified. Sensitivity analyses were performed for the most critical cost factors: land rent (31.88 %), irrigation (16.61 %), and cut-and-chip harvesting (11.87 %), revealing that the influence of the former factor was decisive. Management diagrams that combine the discount rate, yield and biomass price are provided as tools for decision makers.

Life Cycle Assessment of Agricultural Wood Production\u2014Methodological Options: a Literature Review

In Europe, poplar and other fast-growing tree species are considered valuable resources for meeting the required wood demand of the rising bioeconomy. The agricultural technique of short rotation coppice (SRC) has gained relevance to ease the pressure of the demand for wood from forests. Previous studies have implemented the life cycle assessment (LCA) methodology to evaluate such systems’ potential environmental impacts. These studies present different outcomes, though a general pattern on the potential benefit of SRC is observed. The variation of relevant methodological options, such as goal and scope, system boundary, functional unit, reference system, data source, characterization models, and impact categories assessed can significantly affect the results. A consequence of this discrepancy is its effect on results’ interpretation, making the absolute comparison of case studies challenging and hindering the understanding of the potential impacts of SRC LCAs in support of developing a sustainable bioeconomy. Therefore, the current research attempts to understand the methodological implementation of LCA in assessing SRC value chains. Through literature research, studies are analyzed based on the four LCA phases. One of the results of this study shows how most of the articles focus on assessing the impact category related to climate change, while other environmental issues that are particularly relevant for agricultural woody biomass systems are seldomly evaluated. By discussing the state of the art of SRC LCA, this review paper attempts to suggest improvements that will allow future LCA studies to reach a more comprehensive understanding of the overall environmental impact of SRC systems.

Antioxidant Activity and Chemical Characteristics of Supercritical CO2 and Water Extracts from Willow and Poplar.

Renewable feedstock from perennial industrial crops, including those cultivated on marginal land in a short-rotation coppice system, could be an important contribution to the bioeconomy. The majority of data available on the topic are limited to the production of bioenergy from this type of biomass. According to the concept of bioeconomy, biomass-based bioproducts have priority over energy production. This paper characterizes the chemical composition and antioxidant activity of extracts from bark (b), wood (w) or a mixture of bark and wood (b + w) from Salix purpurea, Salix viminalis and Populus nigra obtained using supercritical carbon dioxide (scCO2), scCO2 and water (1%, w/w) or only water. Generally, a high concentration of polyphenols was obtained after extraction with scCO2 and water, while the lowest concentration was found in extracts obtained with scCO2. The highest concentration of polyphenols (p < 0.05) was obtained in an extract from P. nigra (b) (502.62 ± 9.86 mg GAE/g dry matter (d.m.)) after extraction with scCO2 and water, whereas the lowest polyphenol concentration was observed in an scCO2 extract from S. purpurea (b) (6.02 ± 0.13 mg GAE/g d.m.). The flavonoids were effectively separated by extraction with scCO2 (0.88–18.37 mg QE/g d.m.). A positive linear relationship between the antioxidant activity determined by DPPH and ABTS assays and the concentration of polyphenols was demonstrated, R2 = 0.8377 and R2 = 0.9568, respectively. It is most probable that the concentration of flavonoids, rather than the concentration of polyphenols, determines the chelating activity of Fe2+. The Fe2+-chelating activity of scCO2 extracts ranged from 75.11% (EC50 = 5.41 mg/cm3, S. purpurea, b + w) to 99.43% (EC50 = 0.85 mg/cm3, P. nigra, b + w). The lowest chelating activity was demonstrated by the extracts obtained with scCO2 and water (maximum 26.36%, S. purpurea, b + w). In extracts obtained with scCO2 and water, p-hydroxybenzoic acid (210–428 µg/g), p-coumaric acid (56–281 µg/g), saligenin (142–300 µg/g) and salicortin (16–164 µg/g) were the dominant polyphenols. All of these chemical compounds occurred mainly in the free form. The S. purpurea, S. viminalis and P. nigra biomass proved to be an attractive source of biologically active compounds for various possible applications in food, drugs or cosmetics. These compounds could be extracted using an environmentally friendly method with scCO2 and water as a co-solvent.

Carbon Budget of an Agroforestry System after Being Converted from a Poplar Short Rotation Coppice

Poplar (Populus L. spp.) Short Rotation Coppice systems (SRCs) for bioenergy production are being converted back to arable land. Transitioning to Alley Cropping Systems (ACSs) could be a suitable strategy for integrating former tree rows and arable crops. A field trial (Pisa, Central Italy) was set up with the aim of assessing the C storage of an ACS system based on hybrid poplar and sorghum (Sorghum bicolor L. Moench) and comparing it with that of an SRC cultivation system. The carbon budget at the agroecosystem scale was assessed in the first year of the transition using the net biome production (NBP) approach with a simplified method. The overall NBP for the SRC was positive (96 ± 40 g C m−2 year−1), highlighting that the system was a net carbon sink (i.e., NBP &gt; 0). However, the ACS registered a net C loss (i.e., NBP &lt; 0), since the NBP was −93 ± 56 g C m−2 year−1. In the first year of the transition, converting the SRC into an ACS counteracted the potential beneficial effect of C storage in tree belowground biomass due to the high heterotrophic respiration rate recorded in the ACS, which was fostered by the incorporation of residues and tillage disturbance in the alley. Additional years of heterotrophic respiration measurements could allow for an estimate of the speed and extent of C losses.

Coppicing improves the growth response of short-rotation hybrid aspen to elevated atmospheric humidity

Aspens are fast-growing clonal trees with a wide circumboreal distribution range, suitable for the production of pulp and bioenergy. The adaptability of aspen short-rotation coppice systems to climate change has rarely been investigated. For a large part of aspens’ northern range, climate models predict an increase in precipitation and, consequently, in atmospheric humidity. Our aim was to clarify the long-term effect of elevated air humidity on vegetative reproduction capacity and dynamics of above-ground growth and size structure in aspen stands. We analysed tree growth data from two consecutive 6-year rotations (a planted and a coppice generation) in experimental short-rotation hybrid aspen (Populus tremula L. × P. tremuloides Michx.) stands in the Free Air Humidity Manipulation (FAHM) experiment in Estonia. In three plots, mean relative air humidity was elevated by 7% and three plots were controls. Across two rotation periods, the humidification effect on tree height and/or stem basal area increment was year-dependent (p < 0.001): negative in 4 years, positive also in 4 years and non-significant in 3 years. Mean basal area of humidified (11.6 ± 0.8 cm2) and control trees (15.0 ± 1.0 cm2) differed significantly (p = 0.035) at the end of the first but not the second rotation period (9.3 ± 0.9 cm2 and 9.3 ± 1.2 cm2, respectively). Average growth differences levelled out already in the beginning of the second rotation, suggesting that some root-level acclimation must have taken place. The annual size-growth relationships (SGR) indicated a more size-symmetric growth in humidified (SGR = 1.00 ± 0.05) and a size-asymmetric growth (SGR = 1.12 ± 0.04) in control stands, implying a greater role of root-competition in humidified stands. In humidified stands, the growth of re-sprouting trees was more strongly determined by parent tree size, indicating a stronger carry-over of size hierarchy. The tree height diversity fluctuated more in control stands, where mortality was higher, especially after dry years. To summarise, short- and long-term responses of hybrid aspen to elevated air humidity varied, emphasizing the importance of long-term climate manipulations with trees. Generally, hybrid aspen short-rotation coppice forests showed promising acclimation capacity with future more humid climate predicted for northern latitudes.

Produção de biomassa de &lt;i&gt;Eucalyptus grandis&lt;/i&gt; Hill ex. Maiden em diferentes arranjos de espaçamentos de plantio simples e duplos

O objetivo deste trabalho foi avaliar o efeito dos espaçamentos de plantio em linhas simples e duplas na área basal, volume de madeira com casca por hectare, densidade básica do tronco e biomassa arbórea de Eucalyptus grandis Hill ex Maiden (clone G-21) manejado no sistema de curta rotação. O ensaio foi composto por quatro espaçamentos de plantio: 3,0 m × 1,0 m × 2,0 m (linha dupla), 3,0 m × 1,0 m (linha simples), 3,0 m × 1,0 m × 1,0 m (linha dupla) e 3,0 m × 0,5 m (linha simples), sendo avaliado aos 12 meses e 24 meses após o plantio. As principais diferenças significativas foram encontradas no segundo período de avaliação para os fatores de variação considerados – espaçamento e idade. A área basal aumentou com o adensamento das florestas, embora o volume não tenha seguido a mesma tendência aos 24 meses de plantio. A densidade básica aumentou com a idade apenas nos espaçamentos simples. No estudo da alocação de biomassa nos diferentes compartimentos da árvore, verificou-se uma maior proporção de biomassa de tronco com a idade, bem como nos espaçamentos mais adensados. Uma das maiores produções florestais (65 Mg ha-1) foi encontrada no espaçamento 3,0 m × 1,0 m aos 24 meses de idade.

Willow Short-Rotation Coppice as Model System for Exploring Ecological Theory on Biodiversity–Ecosystem Function

Plantations of willow (Salix spp.) are today grown as short-rotation coppice (SRC) for the sustainable production of biomass. While developing these production systems in the past, much ecological knowledge on plant–plant, plant–environment and trophic interactions has been generated. This knowledge can contribute to the further development of biodiversity–ecosystem function (BEF) theory, which frequently lacks a sound understanding of the complex mechanisms behind the observed patterns of diversity-productivity relationships. Thus, willow SRC systems are suitable models to explore BEF theory; they are simple enough to allow the study of the complex ecological mechanisms involved and they have many similarities to grassland systems in which much of recent BEF theory development has been achieved. This paper briefly reviews the current observational and mechanistic knowledge on diversity–productivity relationships in willow SRC, as well as the most important above- and below-ground trophic interactions that are likely to affect them. If the available knowledge is integrated and combined with further experimental work targeting mechanisms behind patterns, research on willow SRC as a model offers a great opportunity for filling the gaps in the understanding what presently hampers the development of predictive BEF theory.

Production and Regression Models for Biomass and Carbon Captured in Gmelina arborea Roxb. Trees in Short Rotation Coppice Plantations in Costa Rica

Mortality, diameter at 30 cm over ground level, height, biomass production, and carbon capture (CC) for different tree components (trunk, bark, branches, and leaves) in two locations in Costa Rica, during their first three years and with three plantation spacings (1.0 × 0.5 m, 1.0 × 1.0 m, and 1.0 × 2.0 m) were obtained for Gmelina arborea Roxb. trees growing in short rotation coppice systems (SRC). In addition, regression models were developed to predict biomass production and CC using location, age, spacing, and their interactions. Biomass production was measured by weight of trees without considering dendrometric variables. Results showed that mortality was lower than 15% for one location, with probable high fertility, and almost 85% for the other location. Diameter and height of trees increased with plantation age in both locations. The highest biomass production and CC were observed in the spacings of 1.0 × 0.5 m2 and 1.0 × 1.0 m2, with 20 Mg/ha/year and 8 Mg/ha/year, respectively. The models to predict biomass production in trunk with bark, branches, leaves, total biomass without leaves, and CC in trunk, branch, and total biomass were developed using this equation: Y = β1 + β2 (location × age) + β3 (age) + β4 (spacing). The R2 values varied from 0.66 to 0.84, with error from 0.88 to 10.75 and indicators of goodness of fit from 60 to 83%.

Willow production during 12 consecutive years—The effects of harvest rotation, planting density and cultivar on biomass yield

AbstractWillow biomass produced in short rotation coppice systems can potentially be used as biomass feedstock in Europe, the United States and Canada. However, most researchers focus on data from the first harvest rotation only, whereas multiple rotations have been rarely investigated. The aim of this study was to evaluate the effect of cultivar (5), planting density (12,000–96,000 cuttings/ha) and harvest rotation (annual, biennial, triennial) on willow biomass yields during 12 consecutive years in northern Poland. Every experimental factor and the interactions between factors significantly impacted willow yields. Biomass yield was highest in the triennial harvest rotation (13.3 Mg ha−1 year−1), 15.9% lower in the biennial rotation and 26.9% lower in the annual rotation. The highest average yield (14.6 Mg ha−1 year−1) was noted at a planting density of 24,000 cuttings/ha, and yields were 9.3%–46.0% lower at the remaining densities. Cultivar UWM 095 had the highest average yield (13.0 Mg ha−1 year−1), whereas the yield of the remaining cultivars was 4.6%–32.4% lower. During the 12‐year period, yields were higher after the first harvest in annual, biennial and triennial harvest rotations. This above implies that high biomass yields can be obtained after the first harvest rotation if willows are cultivated on fertile soils at higher planting density, well managed and coppiced after the first year. However, yields are unlikely to be higher in successive harvest rotations, and they can even be lower, but more stable than in the first harvest rotation.

Assessing the impact of fertilizer application on net soil-derived emission budgets from a temperate willow (Salix miyabeana) short rotation coppice system

Willow (Salix spp.) short-rotation coppice (SRC) systems are productive bioenergy feedstocks that can be cultivated on marginal land and generate high yields when amended with nitrogen (N) fertilizers. However, fertilizer application results in greater N2O emissions and negates the potential carbon (C) neutrality of willow bioenergy systems. We evaluated 1) the effect of N fertilizer application on the soil-atmosphere exchange of CO2-C and (N2O-N emissions, soil NH4+-N and NO3−-N); 2) emissions generated during winter and freeze-thaw cycles (FTCs); and 3) the net annual emission (CO2-equivalents [CO2-eq]) from willow SRC systems. CO2-C emissions followed seasonal trends with elevated emissions occurring in the spring and summer. Significantly greater (p < 0.05) CO2-C emissions were observed during the growing season, whereas only 7.2%–13.4% of the total CO2-C emissions occurred during the winter. Freeze-thaw cycles (FTCs) did not significantly (p < 0.05) increase CO2-C emissions. Nitrogen fertilizer application increased soil NH4+ and NO3− availability resulting in an N2O-N hot moment following fertilizer application in the spring. There was a N2O-N hot moment following FTC events, and winter N2O-N emissions were minimal. Overall, N2O-N emissions accounted for 2.2–3.4% of the total annual emissions. Willow SRC systems were a C sink in fertilized treatments with a C sequestration potential of 10.79 Mg CO2-eq ha−1 yr−1. Unfertilized treatments were a slight C source, with net emissions of 1.19 Mg CO2-eq ha−1 yr−1. We recommend a low rate of fertilizer application to willow SRC systems to maintain these systems as a long-term C sink.

Genetic variation and growth stability of hybrid poplars in high-density short-rotation coppice stands in central Chile

Short-rotation coppice (SRC) using hybrid poplars for biomass production may be a productive alternative in Mediterranean zones. However, the degree of genetic control and the growth stability of poplar clones in high-density plantations remain unknown, and information is needed to reduce the selection time in SRC systems. The genetic variation and stability of growth traits with the age of hybrid clones (from interspecific crosses of Populus deltoides [D], P. trichocarpa [T], P. nigra [N] and P. maximowiczii [M]) were investigated under two planting densities (5000 and 10000 trees ha−1). The basal diameter and height of dominant shoots were measured at ages 1, 2 and 4 years. The total above-ground fresh weight of individual trees was also measured as an indicator of cumulative biomass at age 4 years. Clonal performance was not significantly changed by the planting density. Repeatability increased slightly from age 1 (0.58) to age 2 (0.65) but decreased by age 4 years (0.33). The highest clonal repeatability (0.54) value for above-ground fresh weight was observed for the T✕D cross, whereas the minimum value (0.27) was obtained when genotypes of all crosses were pooled. The age-to-age genetic correlations indicate high clonal stability over time. With respect to the complexities and time required for screening a large number of genotypes under SRC, the results of this study indicate that traits measured during the first growing season are stable indicators of clonal performance in SRC systems.

QTL Mapping of Wood FT-IR Chemotypes Shows Promise for Improving Biofuel Potential in Short Rotation Coppice Willow (Salix spp.)

An increasing interest to convert lignocellulosic biomass into biofuels has highlighted the potential of using willows for this purpose, due to its fast growth in short rotation coppice systems. Here, we use a mapping population of 463 individuals of a cross between Salix viminalis and S. viminalis × S. schwerinii to investigate the genetic background of different wood chemical traits, information of importance for breeding towards different uses of wood. Furthermore, using a subset of the mapping population, the correlation between biogas production and chemical traits was investigated. The phenotyping of wood was carried by Furrier-transformed-Infrared spectrometry (FT-IR) and water content analysis. Quantitative trait loci (QTLs) analysis was used to identify regions in the genome of importance for the phenotypic variation of these chemical traits. We found 27 QTLs for various traits. On linkage group (LG) VI-1, QTLs for signals assigned to G-lignin, lignin, and the S/G ratio were collocated and on LG XIV we found a cluster of QTLs representing signals assigned to lignin, cellulose, hemicellulose, and water. The QTLs explained from 3.4 to 6.9% of the phenotypic variation indicating a quantitative genetic background where many genes influence the traits. For the biogas production, a positive and negative correlation was seen with the signals assigned to acetyl and lignin, respectively. This study represents a first step in the understanding of the genetic background of wood chemical traits for willows, information needed for complementary studies, mapping of important genes, and for breeding of varieties for biofuel production purposes.

Policy analysis of perennial energy crop cultivation at the farm level: Short rotation coppice (SRC) in Germany

Perennial energy crop production methods such as short rotation coppice (SRC) have gained interest among farmers and policy makers. SRC is characterised by rapid biomass production, low inputs, and high managerial flexibility. SRC plantations also provide environmental advantages relative to annual crop production and contribute to the transition towards renewable energy. Yet, the combination of high sunk costs and high uncertainty hampers SRC adoption among farmers. Policy instruments currently implemented to foster SRC adoption exhibit limited success. In this paper we assess the performance of different policy measures intended to stimulate SRC adoption in terms of efficiency and farm-level effects, taking into account related uncertainty. We use a combination of stochastic programming and the real options approach in our model featuring SRC poplar cultivation in Germany. We analyse four policy measures intended to foster SRC adoption: an establishment subsidy, a price floor, a guaranteed price, and increasing the “Ecological Focus Area” (EFA) value for SRC systems within the European Union Common Agricultural Policy. Our results indicate that a guaranteed price can stimulate immediate SRC adoption; however, it is inferior to the other instruments in other dimensions. An establishment subsidy as recently implemented in the study area might incentivise farmers to adopt SRC by contributing substantially to farm income, but should be modified because it may encourage postponement of SRC adoption. Increasing the EFA coefficient and a price floor are more efficient measures in terms of governmental expenditures, while having limited positive effects on bioenergy produced.

Short-rotation coppice agroforestry for charcoal small business in Papua New Guinea

ABSTRACTFuelwood is an integral part of the Papua New Guinea domestic economy, with consumption estimated at 1.8 m3 person–1 year–1. Social stress in many districts is evident by high prices for and the conflict generated by competition for fuelwood. This paper describes three related activities designed to develop small businesses based on short-rotation coppice (SRC) agroforestry systems for fuelwood. These activities are: 1) a survey of domestic fuelwood consumers and vendors (n = 4110) in fuelwood-stressed districts in urban and rural areas of lowlands and highlands; 2) field trials of ten candidate SRC species, at two spacings, in 2–3 year rotations, with measurements of wood volume after two years, coppice vigour, burning characteristics, and market acceptance; and 3) facilitating the establishment of SRC-grown charcoal businesses. The survey found the fuelwood economy has a very short, direct supply chain in a completely informal environment. This paper summarises the fuelwood economy and illustrates the opportunity to create a new fuelwood supply chain that could deliver sustainably harvested and value-added fuelwood to consumers, especially in urban areas and the commercial sector. The SRC systems appealed to landholders because they could intercrop vegetables in the first year, and had the option of carrying over some trees to grow on to poles. The best SRC woodlot species were Eucalyptus grandis for the highlands and E. tereticornis for the lowlands. Calliandra calothrysus is also a suitable SRC species for alley systems in highland gardens. In the highlands, SRC firewood and charcoal production yield higher estimated returns to labour (43 and 24 PNG Kina person–1 day–1, equivalent to $US 20–11 person–1 day–1) compared with the main alternative crops of sweet potato and coffee (21 and 15 Kina person–1 day–1 respectively). As SRC-grown wood appears different from the normal, wild-collected wood for sale, there was resistance to it in the market. As a value-adding option, the establishment of charcoal producer groups was facilitated in Mt Hagen and Lae. The group business structures in the two centres were very different, reflecting their socio-cultural contexts. A flourishing SRC-based biomass energy sector will require a multi-sectoral national fuelwood policy.