Short Rotation Coppice Cultivation Research Articles

A review of Willow (Salix spp.) as an integrated biorefinery feedstock

Throughout history, the genus Salix (willow) has been an incredibly useful temperate plant for humans, with widespread global distribution and species indigenous to all continents except Antarctica. Estimations of the number of species range from 450 to 520 worldwide, and there are still more natural hybrids and multi-hybrid combinations. Several biomass willow breeding programmes have been established across the globe. All of these attempt to produce fast-growing, high-yielding stems with a straight habit and minimal side branching that are highly adaptable to different sites and are also disease and pest resistant. Short rotation coppice (SRC) cultivation involves growing willow at close spacings with a stocking rate of around 15,000 per hectare with harvests every 2–4 years. The crop is mechanically harvested, typically using a forager, and material has recently been used for bioenergy applications. Trial plots have achieved yields of up to 20 odt/ha/yr, whilst well-tended commercial crops have yielded up to 14 odt/ha/yr. Global willow breeding programmes have produced a wide variety of commercial genotypes that have suitable properties for easy planting and harvesting and have the added benefit of elevated levels of bioactive compounds , including salicin , present in the bark, which can be used in medical and veterinary applications. These high-yielding willow varieties grow well in the wetter regions of the globe, including NW Europe, and afford multiple harvests before re-planting. Salix's versatility and adaptability and the SRC cultivation process make them an ideal candidate feedstock for use in an integrated biorefinery to produce a range of biobased materials, including pharmaceuticals, and biocomposites , fuels, energy and fertiliser. • Willow is a pioneer species and grows well in the wetter regions of the world. • Willow plantation can yield 8–9 harvests collected every three years over 25 years before re-planting. • Commercial willow varieties cultivated over the last 20 years were developed for bioenergy. • Cultivation of willow in flood-prone areas offers the potential for flood risk mitigation. • Willow has high potential as an integrated biorefinery feedstock for the manufacture of biobased products.

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.

The Effect of Willow Short Rotation Coppice Cultivation on the Biodiversity Quality of Ground-Layer Invertebrates

The biodiversity quality of ground-layer invertebrates within the cropped area of a plantation of the biomass crop willow short-rotation coppice (SRC) grown within a floodplain was compared to the biodiversity quality of the neighbouring plots of floodplain grassland and a mixed deciduous woodland plantation. Pitfall traps were used to collect ground beetles (Carabidae) and arachnids (Araneae and Opiliones) in the plots over a period of two years. A range of biodiversity indices was used to assess the biodiversity quality of each of the three plots, and the willow SRC was compared to each of the controls using Mann-Whitney tests. The willow SRC transitioned from almost bare ground to young woodland during the two years of the study, which affected comparisons with alternative land uses as the habitat during the second year was very different from the habitat at the start of the study. Compared to plantation woodland, in the first year, the effect was mostly positive, but this declined in the second year. Compared to grassland there was a largely negative effect in both years. However, when in combination with other habitats, willow SRC cultivation on floodplain land may have an overall positive effect on invertebrate biodiversity quality.

Modelling investments in short rotation coppice under uncertainty: A value chain perspective

Short rotation coppice (SRC) for biomass production seems to be an interesting form of land use both from an ecological and economic perspective. However, farmers still behave reluctant in cultivating SRC. Recent investigations show that the high (partially irreversible) investment costs and the uncertainty of the future returns, in the literature jointly known as the real options approach, are main reasons for this reluctance. For complexity reasons, these studies do not, amongst others, consider interactions between different stages of the value chain of woody biomass, which, however, are existent in reality and can affect SRC cultivation decisions. Examples for this are the maximum capacities of biomass heating stations (BHSs), which could represent de facto production restrictions for the surrounding farmers, or possible incentive measures implemented by BHSs to increase farmers' willingness to cultivate SRC. This paper develops an agent-based real options model, which considers these interactions and comprises all stages of the value chain of woody biomass, from farmers who cultivate SRC, over the BHS which converts the wood chips into heat, to end consumers to whom the heat is delivered. Within this framework, the model analyzes farmers' optimal SRC cultivation decisions and the respective effects of potential incentive measures to the farmers implemented by the BHS to increase its utilization. Under a given stimulation of the total quantity of wood chips supplied by the farmers, investment subsidies are advantageous to price floors because they lead to a stronger increase in the profitability of the BHS.

Optimising the Environmental Sustainability of Short Rotation Coppice Biomass Production for Energy

Background and Purpose: Solid biomass from short rotation coppice (SRC) has the potential to significantly contribute to European renewable energy targets and the expected demand for wood for energy, driven mainly by market forces and supported by the targets of national and European energy policies. It is expected that in the near future the number of hectares under SRC will increase in Europe. Besides producing biomass for energy, SRC cultivation can result in various benefits for the environment if it is conducted in a sustainable way. This paper provides with an overview of these environmental benefits. Discussion and Conclusions: The review of existing literature shows that SRC helps to improve water quality, enhance biodiversity, prevent erosion, reduce chemical inputs (fertilizers, pesticides) and mitigate climate change due to carbon storage. To promote and disseminate environmentally sustainable production of SRC, based on existing literature and own project experience, a set of sustainability recommendations for SRC production is developed. In addition to numerous environmental benefits, sustainable SRC supply chains can bring also economic and social benefits. However, these aspects of sustainability are not addressed in this paper since they are often country specific and often rely on local conditions and policies. The sustainable practices identified in this manuscript should be promoted among relevant stakeholder to stimulate sustainable local SRC production.

Analysis of commercial short rotation coppices in Bavaria, southern Germany

The total area of short rotation coppice (SRC) in Germany has increased to about 6000 ha in the last decade, without the benefit of subsidies. About 15% of Germany's total SRC area is in Bavaria. Up to now, the main focus of studies of SRC has been on experimental sites. Hence, as yet there have been no studies analyzing the sites used to cultivate SRC commercially, the management practices used, or the characteristics of the farmers who cultivate SRC. To fill this knowledge gap, we used a standardized questionnaire to gather information about SRC operators in Bavaria and their SRCs. SRC farmers differed from farmers who did not grow SRC: They had larger farms, often farmed organically, and the proportion of land they leased from other owners was lower. Furthermore, the relative forest area of SRC farmers was greater, whereas the relative area of permanent grassland was lower. The sites used for SRC cultivation showed below-average land rents, but generally were well supplied with water. The tree species cultivated in 98% of the cases was poplar. Biomass was predominantly harvested motor-manually after five to ten years for use in private wood chip heating systems. The use of marginal lands with sufficient water supply for biomass production with SRC in relatively long rotation cycles seems to be a favorable method of biomass production in southern Germany. This management practice on marginal land might be interesting for other countries because the competition with food production is low. However, economic analyses are needed.

Biomass Production in the Short Rotation Coppice of Poplar Species Treated with Low-Concentrated Liquid Fertilizer

A short rotation coppice (SRC) refers to cultivation systems using fast-growing tree species with the ability to re-sprout from the stump after harvest. Harvest in SRC cultivation occurs in short intervals, 2-6 years, and management practices are more similar to those of agricultural annual crops than to forestry. The SRC for production of biomass for heat and electricity is considered a very promising means to meet the different targets set to increase the amount of renewable energy. This study was conducted to analyze growth characteristics and biomass production of poplar clones in the SRC under the treatment of slurry composting and biofiltration liquid fertilizer (SCBLF). The average survival rate of poplar clones at SCBLF treatment was 95.0% and that at control was 92.5%, respectively. The average number of shoot at the treatment was 11.8 ea/clone and that of control was 11.5 ea/clone. ’72-31’, ‘Bonghwa1’ and ‘Clivus’ from Populus alba × P. glandulosa were superior clones for the number of shoot with 17.1 ea/clone, 14.5 ea/clone and 13.8 ea/clone at the treatment of SCBLF. For the average of leaf area, the SCBLF treatment showed 35% broader leaf (71.0 cm) than control (52.3 cm). The annual average of above-ground biomass production showed 51% better at the SCBLF treatment (8.5 ton/ha) than control (5.6 ton/ha). ‘Clivus’, ‘72-31’ and ‘Bonghwa1’ clones from P. alba × P. glandulosa were superior for the annual average of above-ground biomass production with 15.2 ton/ha, 14.0 ton/ha and 11.6 ton/ha at the treatment of SCBLF.

Economics of poplar short rotation coppice plantations on marginal land in Germany

Although there is a need for biomass and a potential for short rotation coppice (SRC), farmers hesitate to establish SRC, even on marginal agricultural land on which annual crops show low productivity. Probably the most important factor explaining this reluctance might be the uncertain economic prospects of the cultivation of SRC. Therefore, the aim of this study is to analyse the economy of a typical SRC supply chain by calculating the annuities which can be expected by German farmers who establish SRC on their marginal land.The result shows that the yearly annuity of a 20-year SRC cultivation is about 70 € y−1 ha−1 when poplar SRC is harvested every 4 years with a forage harvester (one-step system). The result includes the establishment, cultivation and transport of the fresh wood chips to a plant 50 km away. However, this result is not competitive with the result of annual crops (226–462 € y−1 ha−1) and is also lower than the CAP subsidy payments that farmers receive from the EU (300 € y−1 ha−1). To achieve higher annuities, four options were analysed possibly leading either to higher biomass yields or to higher market prices (extension of rotation cycle, implementation of irrigation, technical drying of fresh wood chips, using a two-step harvesting system). The implementation of drip irrigation to increase biomass yield turned out to be uneconomic. An extension of the rotation cycle from 4 to 5 years can be recommended as it leads to an annuity of 255 € y−1 ha−1 (instead of 69 € y−1 ha−1). Results also show that the technical drying of chips using (cheap) surplus heat can be very profitable if the added value is reflected in higher market prices. Furthermore, it is shown that the use of an alternative two-step harvesting system with natural interim drying of the rods can be an attractive option for farmers to increase the annuity of their SRC.

Differential patterns of mono- and sesquiterpenes with leaf ontogeny influence pharmaceutical oil yield in Eucalyptus polybractea R.T. Baker

Pharmaceutical 1,8-cineole oil is commercially harvested from Eucalyptus polybractea R.T. Baker grown in short rotation coppice cultivation. Harvests occur throughout the year, with no consideration given to the proportion of leaves present at different ontogenetic stages, and the effect leaf ontogeny may have on harvested oil quality and quantity. To determine the optimal leaf stage to harvest pharmaceutical-grade oil, we quantified the relationship between leaf ontogeny and foliar oil quantity and quality, secretory cavity size, and abundance along branches of two E. polybractea clones. The results show that the desirable attributes of oil yield and 1,8-cineole proportion both reach their maximum in fully expanded leaves and that this coincides with maximum secretory cavity size. Across all leaf ages the amount of various monoterpenes were highly correlated with 1,8-cineole, suggesting a single, multi-product monoterpene synthase may be responsible. In the very young leaves, sesquiterpenes such as β-elemene were the most abundant constituents of the essential oil. This study suggests that there may be differential transcriptional regulation of mono- and sesquiterpene synthases with leaf ontogeny such that sesquiterpene biosynthesis is at a maximum only in young leaves, and that monoterpene biosynthesis dominates during leaf and concomitant cavity expansion. Given E. polybractea leaves are produced during major seasonal flushes, there are times throughout the year when the numbers of young leaves with inferior oil quantity and quality are likely to be proportionally decreased. Therefore harvesting times could be manipulated to take advantage of such times and ensure abundant high quality oil is harvested.

Assessing Environmental Impacts of Short Rotation Coppice (SRC) Expansion: Model Definition and Preliminary Results

Short rotation coppice (SRC) systems can play a role as feedstock for bioenergy supply contributing to EU energy and climate policy targets. A scenario depicting intensive arable crop cultivation in a homogeneous landscape (lacking habitat structures) was compared to a scenario including SRC cultivation on 20 % of arable land. A range of indicators was selected to assess the consequences of SRC on soil, water and biodiversity, using data from the Rating-SRC project (Sweden and Germany). The results of the assessment were presented using spider diagrams. Establishment and use of SRC for bioenergy has both positive and negative effects. The former include increased carbon sequestration and reduced GHG emissions as well as reduced soil erosion, groundwater nitrate and surface runoff. SRC can be used in phytoremediation and improves plant and breeding bird biodiversity (exceptions: grassland and arable land species) but should not be applied in dry areas or on soils high in toxic trace elements (exception: cadmium). The scenario-based analysis was found useful for studying the consequences of SRC cultivation at larger scales. Limitations of the approach are related to data requirements and compatibility and its restricted ability to cover spatial diversity and dynamic processes. The findings should not be generalised beyond the representativeness of the data used.

Meeting Sustainability Requirements for SRC Bioenergy: Usefulness of Existing Tools, Responsibilities of Involved Stakeholders, and Recommendations for Further Developments

Short rotation coppice (SRC) is considered an important biomass supply option for meeting the European renewable energy targets. This paper presents an overview of existing and prospective sustainability requirements, Member State reporting obligations and parts of the methodology for calculating GHG emissions savings within the EU Renewable Energy Directive (RED), and shows how these RED-associated sustainability criteria may affect different stakeholders along SRC bioenergy supply chains. Existing and prospective tools are assessed on their usefulness in ensuring that SRC bioenergy is produced with sufficient consideration given to the RED-associated criteria. A sustainability framework is outlined that aims at (1) facilitating the development of SRC production systems that are attractive from the perspectives of all stakeholders, and (2) ensuring that the SRC production is RED eligible. Producer manuals, EIAs, and voluntary certification schemes can all be useful for ensuring RED eligibility. However, they are currently not sufficiently comprehensive, neither individually nor combined, and suggestions for how they can be more complementary are given. Geographical information systems offer opportunities for administrative authorities to provide stakeholders with maps or databases over areas/fields suitable for RED-eligible SRC cultivation. However, proper consideration of all relevant aspects requires that all stakeholders in the SRC supply chain become engaged in the development of SRC production systems and that a landscape perspective is used.

Sewage sludge and wastewater fertilisation of Short Rotation Coppice (SRC) for increased bioenergy production—Biological and economic potential

Application of municipal residues, e.g. wastewater or sewage sludge, to Short Rotation Coppice (SRC) is among the most attractive methods for attaining environmental and energy goals set for Europe. At current woodchip prices in Sweden, the gross margin for SRC cultivation is positive only if biomass production is >9 t DM/ha yr. The gross profit margin increases (by 39 and 199 €/GJ, respectively) if sewage sludge and wastewater are applied to SRC. Application of residues to SRC has proved to be an acceptable alternative treatment method, and the farmer’s profit can be markedly increased if compensation is paid for waste treatment. If all available sludge and wastewater were applied to SRC plantations, they could be grown on large agricultural areas in Europe, and c. 6000 PJ of renewable energy could be produced annually. However, a more economical landuse strategy, e.g. the use of more P-rich residues, appears more rational, and is biologically justifiable.

The influence of micropropagation on growth and coppicing ability of Eucalyptus polybractea

A micropropagation protocol was recently developed for Eucalyptus polybractea R.T. Baker, a commercially important eucalypt grown in short-rotation coppice cultivation and harvested for its foliar 1,8-cineole oil. Micropropagation of elite E. polybractea trees has resulted in selection gains for foliar oil traits, but decreased above-ground biomass accumulation has been observed in clones compared to related half-sibling families. This study aims to use a greenhouse study to investigate if micropropagation induces somaclonal variation that can account for the reduction in above-ground biomass in E. polybractea clones. Secondly, the study aims to compare the coppicing ability of micropropagated clones with related half-sibling seedlings using de-topped plantation-grown saplings. The results of the greenhouse study suggest that micropropagation of E. polybractea induces somaclonal variation that manifests in more mature leaf morphologies such as increased foliar oil concentrations and lower specific leaf area (SLA), attributable to an isobilateral arrangement of increased palisade mesophyll layers. Lower SLA, rather than differences in root allocation, is likely to be a key contributor to the lower relative growth rates observed in early sapling growth of micropropagated clones. In the field study, all micropropagated and seedling-derived E. polybractea saplings coppiced vigorously in the 12 months after de-topping. The coppice growth was so vigorous in the 12 months after de-topping that total above-ground biomass equalled that of the 27-month-old saplings, irrespective of propagation source. The morphological distinction between leaves of micropropagated and seed-derived plants was no longer evident in the coppice regrowth. The results presented here suggest that the micropropagated leaf morphology and the resultant growth reduction is transient and micropropagated plants coppice just as vigorously as seed-derived plants. Therefore, micropropagation is unlikely to detrimentally influence above-ground biomass accumulation beyond the first harvest rotation.

Robinia pseudoacacia L.: A Lesser Known Tree Species for Biomass Production

Experiments with fast-growing tree species for biomass production in Germany have been mainly focused on the growth performance of Populus and Salix spp. Among the lesser-known species for energy plantations is Robinia pseudoacacia L. Special features of this species are its drought tolerance and its ability to fix nitrogen. Given the large share of marginal arable land in NE-Germany and the predicted climate change, R. pseudoacacia is expected to grow in importance. In order to evaluate the growth performance of this species under extreme conditions, four experiments were established in the post-mining landscape of the Lusatian lignite-mining district (NE-Germany). Biomass production was estimated for 3- to 14-year-old shoots on 4- to 14-year-old roots. Results for the annual production of oven-dried biomass of R. pseudoacacia ranged between 3 and 10 t ha−1, which was substantially greater than the biomass of poplar and willow clones established on the same site. Economic analysis results show that the rotation period, the duration of the plantation, and the harvesting costs are important parameters for the economic return and cash flow in short-rotation coppice cultivation. The results show that the cultivation of R. pseudoacacia is an economically competitive land-use strategy for the post-mining landscapes considered in our study.

Water-use efficiency of a mallee eucalypt growing naturally and in short-rotation coppice cultivation

This study compared matureEucalyptuskochii subsp.plenissima trees in inner regions or edges of natural bushland to young trees belt-planted through cleared agricultural land as uncut saplings or regenerating coppice over 2.7 years at Kalannie, Western Australia (320 mm annual rainfall). We assessed the ability of the species to alter its gas exchange characteristics, leaf physical attributes, and water-use efficiency of foliar carbon assimilation (WUEi) or of total dry matter production (WUEDM). Stomatal conductance (gs) varied five-fold between treatment means, with coppices exhibiting greatest values and mature bush least. Photosynthetic rates followed this trend. Leaf photosynthetic capacity estimated by chlorophyll content varied 1.3-fold parallel with variations in leaf thickness, with coppices rating lowest and mature edge trees most highly. WUEi varied 1.5-fold between treatments and was greatest in mature inner-bush and edge trees. Leaf photosynthetic capacity and gs were both correlated with WUEi. Carbon isotope composition (δ 13 C values) of new shoot dry matter produced early in a seasonal flush were similar to those of root starch but when averaged over the whole season correlated well with WUEi and gas exchange characteristics of trees of each treatment. Coppices showed poorestWUEi and most negative shoot tip δ 13 Cb ut their WUEDM was high. This discrepancy was suggested to relate to carbon allocation strategies in coppices favouring fast growth of replacement shoots but not of roots. Physiology of coppice growth of E. kochii is usefully geared towards both rapid and water-use efficient production of woody biomass in water limited environments.

The swedish programme for intensive shortrotation forests

The Section of Intensive Short-Rotation Forestry at the Swedish University of Agricultural Sciences incorporates several programmes on biomass production for energy and fibre and its integration with environmental aspects such as biofilters, waste recycling, etc. The major programmes are: Woody biomass production, optimization of woody biomass production of deciduous trees by irrigation and fertilization, deciduous forests on clay soil, utilization of sludge as a fertilizer in short-rotation forestry, and purification of ground water by short-rotation forestry. To achieve the goals, different production systems are being investigated on a wide range of different sites. The emphasis is on intensive short rotation coppice cultivation of Salix spp on agricultural land for production of biomass for energy. Other production systems presently under investigation are extensively cultivated, longer rotation willow plantations, single-tree poplar plantations and mixed deciduous forests.