Assessment of uncertain returns from investment in short rotation coppice using risk adjusted discount rates

The increasing demand for renewable energy resources increases interest in the use of short rotation coppice (SRC) as alternative land use activity. The high uncertainty attached to returns from SRC is one of the key adoption barriers to farmers. One possibility to account for the role in investment assessments is the use of project specific risk adjusted discount rates (RADR). In this article, we revisit the theoretical background of RADR and illustrate different assumptions using an example of poplar based SRC. Time-invariant RADR used in the current literature on SRC assessment are found to over-emphasize the role of risk for project assessment and usually give to little weights to returns in future periods, which are of particular relevance for long-term investments in SRC. Thus, the use of time invariant RADR is found to lead to biased recommendations towards the attractiveness of SRC and optimal policy support.     

Stakeholder opinion on constrained 2030 bioenergy scenarios for North West England

English farmers are subsidised by the UK government to plant (short rotation coppice—SRC) willow as an energy crop. This study incorporates the outputs of techno-economic and environmental life cycle assessment modelling of bioenergy power and combined heat and power (CHP) plants within a simple spreadsheet model that enables users to partially modify bioenergy scenarios for SRC willow. The model is intended as an opinion-elicitation device. It is restricted in scope, reflecting the electrical power emphasis of the first phase of the Supergen Biomass and Bioenergy research programme. Bioenergy policy stakeholders in North West (NW) England were asked to use the model to develop 2030 scenarios for SRC willow fuelling eight types of bioenergy power and CHP plant. Users allocate finite land inputs to the different power and CHP plant types and the sheet outputs the energy supply, environmental and agricultural employment implications. Policy stakeholders are shown to hold widely differing views of how the bioenergy heat and power sector might and should look in 2030. If the policy stakeholders’ 2030 scenarios prove accurate, the percentage of regional households likely to be electrically supplied by willow coppice grown in NW England will be small, at some 3.6%.     

Sustainable use of eucalypt biomass grown on short rotation coppice for bioenergy

Bioenergy is one of the alternatives to reduce the dependence of global energy on fossil fuels. The short rotation coppice (SRC) of eucalypt species appears as an interesting option for forest biomass production in a short time. However, the harvesting of whole trees (included the crown) in SRC systems has implications on sustainable land use. More information is required on the increase of biomass as renewable energy resource to achieve the sustainability of these crops. The main objective of this research was to evaluate the sustainable use of biomass from very high-density eucalypt plantations, managed at tropical conditions for bioenergy. To accomplish this objective, the tree was fractionated into three fractions: stem, branches, and leaves, and there was determination of the dry matter, energy yield, and nutrients export. This experiment used a short rotation coppice, a hybrid clone of Eucalyptus urophylla × Eucalyptus grandis, of 2 years old. According to the results obtained, the density planting and fertilization levels have a greater influence on the dry matter yield, energy yield, and nutrient exports. The higher density planting reaches mean values of 30.9 tonnes of dry matter per hectare (t DM ha⁻¹) and 743.3 GJ ha⁻¹. Considering the biomass yield and nutrients export of short rotation coppice of eucalypt, the higher density planting with the lower dose of fertilization is more indicative of sustainable use. The leaves have an important participation in nutrients export and should be retained in the soil of forest.     

Moisture content determination in solid biofuels by dielectric and NIR reflection methods

One near infrared (NIR) reflectance and five dielectric moisture meters were tested for their capability of measuring moisture content (MC) in solid biofuels. Ninety-eight samples were tested at up to eight moisture levels covering the MC range from fresh fuel to approximately 10% MC (w.b.). The fuel types ranged from typical solid biofuels such as coniferous and deciduous wood chips over short rotation coppice (SRC) to sunflower seed and olive stones. The most promising calibrations were obtained with the NIR reflection method and two dielectric devices where the sample is placed in a container integrated in the device. The calibration equations developed show that there is a profound influence from both laboratory and fuel type. It is suggested that individual calibrations that are based on the specific fuel types used at the individual heating plant could be applied.     

Modelling farmer uptake of perennial energy crops in the UK

The UK Biomass Strategy suggests that to reach the technical potential of perennial energy crops such as short rotation coppice (SRC) willow and miscanthus by 2020 requires 350,000 hectares of land. This represents a more than 20-fold increase on the current 15,546 hectares. Previous research has identified several barriers to adoption, including concerns over security of income from contracts. In addition, farmers perceive returns from these crops to be lower than for conventional crops. This paper uses a farm-level linear programming model to investigate theoretical uptake of energy crops at different gross margins under the assumption of a profit-maximising decision maker, and in the absence of known barriers to adoption. The findings suggest that while SRC willow, at current prices, remains less competitive, returns to miscanthus should have encouraged adoption on a wider scale than at present. This highlights the importance of the barriers to adoption. Recently announced contracts for miscanthus appear to offer a significant premium to farmers in order to encourage them to grow the crops. This raises the question of whether a more cost-effective approach would be for government to provide guarantees addressing farmers concerns including security of income from the contracts. Such an approach should encourage adoption at lower gross margins.     

The influence of soil and coppice cycle on the rooting habit of short rotation poplar and willow coppice

The increased demand for renewable energy sources has led to large areas of former agricultural land being proposed for short rotation coppice (SRC) establishment. Concerns expressed over the potential impacts of tree roots on buried archaeological evidence led to a study into the rooting habit of SRC. Roots were exposed in trenches dug within a variety of willow and poplar clonal stands grown on brown earth, pelosol, ground-water gley and surface-water gley soils. Root depths and diameters were recorded in each of the 33 trenches. In total, over 18,000 roots were measured on 264 coppice stools. The rotation length, species and stool location within a block were all found to influence the maximum size of root produced. Soil type had some influence on the root number and depth, but the pattern of root distribution down the soil profile was similar for both species.     

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.     

SRC-willow (Salixviminalis) as a resource for flower-visiting insects

The potential habitat value of commercial short rotation coppice (SRC)-willow plantations for flower-visiting insects was investigated. During 1998–2000, at a single typical intensive Danish farmland site, 11 Salix viminalis plantations were sampled by late April to quantify willow catkin abundance and flower sex. Mean plantation size was 1.1 ha and included one or more of clones: orm, rapp, ulv, jorr, christina and jorrun. Plot-year means of catkin abundance and of proportion of willows flowering were related to the coppicing cycle, i.e. the number of growth years since last harvest of plot (‘year’ 0–4). In 1998, the ground layer vegetation was sampled. Monitoring flower-visiting insects by means of line-transect counts failed due to the local scarcity of bees. At the plantation scale, flowering was discontinuous across the harvest cycle as it was totally absent in the year immediately following harvest. In successive years (1–4), individual willows flowered frequently and, occasionally, at high abundances, and catkin abundance increased with time. Within 3–4 year of harvest cycle, all plots flowered in most years with most plots exhibiting at least some flowering in any 1 year. Thus, willow catkin abundance was generally high in the total area due to: high frequency of flowering in plots, occasional high flowering abundance, plots not being harvested simultaneously and large total number of willows within plots and landscape. Similarly, flower sex ratio, and thus flower value, varied greatly between plots while variation was damped across plots. Alternative simultaneous flower resources in ground layer vegetation were few except for Dandelion. SRC willow may constitute an important resource for bees, even under the stress of the harvest cycle, and recommendations are given for improving this biodiversity aspect.     

Potential of Short Rotation Coppice plantations to reinforce functional biodiversity in agricultural landscapes

We compared communities of vascular plants and arthropods in ten Short Rotation Coppice (SRC)–maize pairs, to (1) quantify the difference in diversity and composition between these two alternative land-use types and (2) to assess the potential of SRC plantations to increase functional biodiversity values in agricultural landscapes. In each SRC plantation and maize field, the vegetation was surveyed and arthropods were sampled by applying pitfall and pan trapping. The composition of the vegetation and of the epigeic and vegetation inhabiting arthropod communities strongly differed between the crop types. This differentiation was mainly due to true species turnover and only to a lesser extent to the occurrence of nested subsets. On average, the total cover of the vegetation was 10 times higher in the SRC plantations and taxonomic and trait diversity were also consistently higher in SRC. Arthropod activity densities were significantly higher, sometimes almost double, in SRC plantations. Significantly higher effective species numbers in SRC were only retrieved for Hymenoptera and Coleoptera. Regarding functional groups, the activity densities of omnivores, detritivores, mycophages, phytophages and parasitoids were significantly higher in SRC. While activity densities of predators were not different among the crop types, their effective species number was higher in SRC, indicating a more evenly distributed and diverse predator community. To conclude, we have shown that SRC can significantly increase vegetation and arthropod abundance and/or diversity in agricultural landscapes when replacing annual biomass crops, such as maize.     

Large-scale fuelwood production on agricultural fields in mesoscale river catchments – GIS-based determination of potentials in the Dahme river catchment (Brandenburg,NE Germany)

Woody biomass (dendromass) today already has an important role in bioenergy production and will even increase in the future as a renewable resource for energetic as well as for material use. In eastern Germany, an increasing demand for dendromass in renewable energy production is unlikely to be covered by sustainable forest wood production. Hence, a deficit for the federal state of Brandenburg of 4.02 million tonnes per year is predicted. Besides imports, one option of increasing dendromass supply in Brandenburg is short rotation coppice (SRC) on arable land. The potential of SRC on arable land is determined by the economic competitiveness of SRC compared to conventional annual crops. This factor is strongly influenced by the water supply, expressed as the transpiration water supply (TWS) in the growing season, and the soil quality.First evaluations of SRC potentials in Brandenburg identify large areas of arable land where SRC seems to be able to compete with annual crops.Potential areas in the Dahme river catchment, located in the south of Berlin, were identified at a regional scale through a GIS-based approach. The results indicate that lowland river catchments like the Dahme basin have great potentials for fuelwood production. Especially the large amount of arable land with accessible groundwater resources offers water for transpiration in a region where average annual precipitation and water storage capacity of soils is relatively low (550 mm and 100–150 mm m⁻¹ resp.) and thus too small to meet the demands of optimal SRC growth. In total, 340,000 tonnes fuelwood could be produced annually in the Dahme river catchment, if all potential sites were transformed into SRC. This accounts for 8.5% of the deficit produced on just 1.8% of the federal state of Brandenburg's total agricultural area by 2030 and meet the heating energy demand of approximately 130,000 people. The results show that the applied method is an effective way to identify biomass potentials in mesoscale river basins and demonstrates the relevance of the Dahme catchment for a sustainable energy supply in the future.     

Farm wood fuel and energy project

This paper describes the findings of the Farm Wood Fuel and Energy Project. It began in 1991 and ended in 1997 and was undertaken to provide a commercial demonstration for the establishment of 50 hectares of short rotation coppice (SRC) on six farms in southern England and the development of associated marketing activities. The Project:

• — taught farmers how best to grow the crop and will enable them to teach others;

• — determined that winter conditions in the UK are unsuitable for most harvesting equipment trialled and that both harvesting and chip storage need to be re-examined;

• — demonstrated that SRC has the potential to be competitive with fossil fuels;

• — gave confidence to Government to include a Band for energy crops under the NFFO electricity generating procedures

     

Assessment of potential bioenergy from coppice forests trough the integration of remote sensing and field surveys

A spatially explicit knowledge of forest resources is essential to support the sustainable use of wood as a fuel for producing energy (firewood).This paper describes the integrated use of remotely sensed data and sample based forest inventories to derive a biomass map for coppice forest, resulted estimated potential biomass available is contrasted with local domestic consumptions at the municipality level. The test was carried out in an environmentally and socially homogeneous district of Apennine Mountains (Alto Molise, south-central Italy) coupling multispectral high resolution Landsat 7 ETM+ satellite imagery and a local forest inventory trough the application of the non-parametric estimation procedure k-Nearest Neighbours (k-NN). Several forest management scenarios were applied in order to evaluate their impact on the potential availability of firewood from coppice forests.The paper introduces data and methods used and presents the achieved results both in terms of the accuracy of the biomass map produced by k-NN and of the relationship between the potential availability and demand for firewood.These results demonstrated that k-NN is able to estimate the biomass of coppice forest in the test area with an accuracy level comparable with recent similar application of k-NN carried out in Boreal regions (RMSE of 25.6%).The application of different forest management scenarios have a significant impact on local estimated firewood balance between potential supply from coppice forests and demand for domestic consumption, depending of the scenarios the net balance changed up to 84%.     

Nutrients and energy in proleptic branches and leaves of poplar under a short-rotation coppice

Renewable energy is often generated from biomass, produced in short-rotation coppice (SRC) cultures. These cultures are frequently established on former agricultural land with ample availability of plant nutrients as nitrogen, phosphorous, potassium, calcium and magnesium. Nevertheless, little is known about the annual recycling of these nutrients through the leaves, as well as about the amounts that are removed at harvest. We therefore quantified soil nutrient concentrations, as well as nutrient concentrations and the gross calorific value of the proleptic branches and of the leaves of 12 poplar (Populus) genotypes in the second rotation of an operational SRC (with two-year rotations). For the produced leaf biomass, we also quantified the standing energy stock and the nutrient stock of each genotype. After four years the P, K, Ca and Mg soil concentrations had not significantly changed, while the N concentration at 30–60 cm of soil depth had significantly increased. On average, the standing aboveground woody biomass of the 12 genotypes in 2013 was 13.75 Mg ha⁻¹ and the total leaf biomass was 3.54 Mg ha⁻¹. This resulted in an average standing energy stock in the leaves of 64.8 GJ ha⁻¹. Nutrient concentrations were lower in the proleptic branches as compared to the leaves, but the proleptic branches and leaf nutrient concentrations significantly varied among the genotypes.     

The changing of the relationships between carbon footprints and final demand: Panel data evidence for 40 major countries

Global warming and environmental pollution have led many countries to begin to implement measures to reduce the use of fossil fuels. However, emissions reductions may have been reached because of the displacement of emissions intensive production. The objective of this study is to analyze the relationships between the emissions caused by countries from a demand point of view, the carbon footprints and the demand for goods and services in these countries, and especially in the European countries. With this aim, a two-step process was carried out. Firstly, carbon footprints were calculated during the 1995–2009 period. Secondly, the EKC hypothesis between these carbon footprints and the total final demands were tested by using panel data and a multilevel mixed-effects model. The results show that the EKC hypothesis is not supported when considering carbon footprints with respect to final demand. It is also shown that carbon footprints are slightly increasing with respect to final demand beyond proportionality. The carbon footprint elasticities are different between countries, their values increasing with the final demand per capita of countries.     

Economics of electricity and heat production by gasification or flash pyrolysis of short rotation coppice in Flanders (Belgium)

Short rotation coppice (SRC) seems attractive as an energy crop on degraded land. Gasification and flash pyrolysis are promising technologies for the conversion of SRC into energy or chemicals. A model has been developed to calculate the net present value (NPV) of the cash flows generated by an investment in gasification or flash pyrolysis of SRC for the production of electricity or for combined heat and power production. The NPV has been calculated and compared for (combined heat and) power stations with an electrical capacity (P_e) between 5 MW and 20 MW. Furthermore the minimal amount of heat that has to be sold to make combined heat and power production more profitable than pure electricity production has been determined. By performing Monte Carlo simulations, key variables that influence the NPV have been identified.In the case of small scale SRC conversion, i.e. at an electrical capacity of 5 MW-10 MW, flash pyrolysis is more profitable than gasification. At the smallest scale of 5 MW it is necessary to invest in combined heat and power production, as the sole production of electricity is not profitable at this low scale. At an electrical capacity of 10 MW flash pyrolysis for the sole production of electricity becomes profitable, but gasification for electricity production is still not viable. At this capacity however, the extra investments required in the case of combined heat and power production are already paid back if only 25% of the produced heat can be sold. At a higher capacity of 20 MW, the technology choice becomes unclear taking into account the most uncertain variables, i.e. investment cost parameters and energetic efficiencies.     

Early rotation short rotation willow coppice as a winter food resource for birds

Unlike a century ago when mixed arable/pastoral farms prevailed, the current Welsh pastoral landscape lacks arable crops for arable weed seeds as a winter food resource for granivorous birds. Biomass crops such as short rotation willow coppice (SRC) where Salix cultivars are grown at high density (10 000-40 000 per ha) and each plot harvested on a usually three year rotation may help redress this loss. SRC, certainly in its establishment phase, and, if suitably managed, in early post-harvest rotation, offers significant winter seed resource which within one resource, such as spear thistle (Cirsium vulgare), may change its bird availability depending whether it is upright when used by finches or fallen when utilised by ground feeding thrushes. If this crop becomes widespread in the landscape and it is managed in an environmentally friendly way, it will provide a food resource and possibly habitat “stepping stones” in countryside currently barren of such features.     

Comparative studies of stress-relief cracking in relaxation test specimens and in a full-scale weldment

An attempt is made to assess the susceptibility of stress-relief cracking (SRC) of simulated HAZ microstructures in heated specimens of SA508 Class 2 steel, using a notched bend relaxation test. The ability of this test to reproduce service conditions is explored by comparing cracking behaviour and the fractographic details of the cracks produced with observations made on stress-relief cracks in actual weldments of SA508 Class 2 obtained from the same manufacturer.It is shown that SRC in the relaxation test and in the weldments exhibited similar fractographic features and micromechanisms of cracking. From the test specimens, it was found that a critical value of stress-intensity factor was necessary to produce ‘severe’ cracking, and application of this value to the cracking observed in the weldments appears to be fully consistent with the details of weldment manufacture. It is proposed that a stress-intensity approach of this sort can provide a general method for the assessment of possible SRC in welded components.     

Variability and plasticity of productivity,water-use efficiency,and nitrogen exportation rate in Salix short rotation coppice

Short rotation coppice (SRC) willow plantations may play an important role in the future for biomass production purposes. However, the high planting density schemes combined with the frequent harvests occurring in such plantations could rapidly deplete soil resources. The use of genotypes able to produce greater amounts of biomass by using the least water and nutrients may help mitigating this risk. This study aimed at assessing among six willow genotypes (1) the variability of traits related to productivity (e.g. aboveground dry biomass or stem height), leaf and wood nitrogen (N) contents, N exportation rate and water-use efficiency (WUE) as estimated through bulk leaf carbon isotope discrimination (Δ¹³C), (2) the relationships among traits, and (3) the plasticity of these traits and of the relationships among them across different sites. The six genotypes were grown under SRC at three sites in northern France differing primarily in pedoclimatic characteristics for two years. A significant genotypic variability was found for all traits, except for the N exportation rate. The pedoclimatic context impacted the values of all traits, and the genotypic ranking for traits related to productivity and for Δ¹³C. Δ¹³C was negatively correlated with total shoot dry biomass and/or height irrespective of the site, meaning that the most productive genotypes were also the most efficient to use water. In conclusion, no antagonism was detected between biomass production and WUE. The most productive and most water-use efficient genotypes were the ones responsible for the highest nitrogen removal from the plantation during harvest.     

Biomass energy in organic farming—the potential role of short rotation coppice

One of the aims of organic farming is to “reduce the use of non-renewable resources (e.g. fossil fuels) to a minimum”. So far, however, only very little progress has been made to introduce renewable energy in organic farming. This paper presents energy balances of Danish organic farming compared with energy balances of conventional farming. In general, the conversion to organic farming leads to a lower energy use (approximately 10% per unit of product). But the production of energy in organic farming is very low compared with the extensive utilisation of straw from conventional farming in Denmark (energy content of straw used for energy production was equivalent to 18% of total energy input in Danish agriculture in 1996).Biomass is a key energy carrier with a good potential for on-farm development. Apart from utilising farm manure and crop residues for biogas production, the production of nutrient efficient short rotation coppice (SRC) is an option in organic farming. Alder (Alnus spp.) is an interesting crop due to its symbiosis with the actinomycete Frankia, which has the ability to fix up to 185 kg/ha nitrogen (N₂) from the air. Yields obtained at different European sites are presented and the R&D needed to implement energy cropping in organic farming is discussed.Possible win–win solutions for SRC production in organic farming that may facilitate its implementation are; the protection of ground water quality in intensively farmed areas, utilisation of wastewater for irrigation, or combination with outdoor animal husbandry such as pigs or poultry.     

Land use change to bioenergy: A meta-analysis of soil carbon and GHG emissions

A systematic review and meta-analysis were used to assess the current state of knowledge and quantify the effects of land use change (LUC) to second generation (2G), non-food bioenergy crops on soil organic carbon (SOC) and greenhouse gas (GHG) emissions of relevance to temperate zone agriculture. Following analysis from 138 original studies, transitions from arable to short rotation coppice (SRC, poplar or willow) or perennial grasses (mostly Miscanthus or switchgrass) resulted in increased SOC (+5.0 ± 7.8% and +25.7 ± 6.7% respectively). Transitions from grassland to SRC were broadly neutral (+3.7 ± 14.6%), whilst grassland to perennial grass transitions and forest to SRC both showed a decrease in SOC (−10.9 ± 4.3% and −11.4 ± 23.4% respectively). There were insufficient paired data to conduct a strict meta-analysis for GHG emissions but summary figures of general trends in GHGs from 188 original studies revealed increased and decreased soil CO₂ emissions following transition from forests and arable to perennial grasses. We demonstrate that significant knowledge gaps exist surrounding the effects of land use change to bioenergy on greenhouse gas balance, particularly for CH₄. There is also large uncertainty in quantifying transitions from grasslands and transitions to short rotation forestry. A striking finding of this review is the lack of empirical studies that are available to validate modelled data. Given that models are extensively use in the development of bioenergy LCA and sustainability criteria, this is an area where further long-term data sets are required.