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.     

Selected environmental impacts of the technical production of wood chips from poplar short rotation coppice on marginal land

The use of marginal land for Short Rotation Coppice (SRC) might contribute to a sustainable energy supply in future. We assessed the environmental impacts of common production chains for manufacturing wood chips from SRC with poplar, including all the processes necessary to produce and deliver chips to a plant gate in 50 km distance from the field site (“cradle-to-plant gate”).To do so, we carried out a Life Cycle Analysis (LCA) including upstream processes. Results showed clearly that the specific environmental impacts were mainly caused by the processes “harvesting” and “transport”. Using a cut-and-chip harvesting system with a forage harvester generated low impacts during harvesting because of its high productivity. Using a cut-and-storage harvesting system with a whole rod harvester, however, didn't require accompanying tractor-trailer units during harvesting and allowed storing stems before chipping thereby, reducing the moisture content to approximately 30%. Consequently, the transport to the plant caused significantly lower environmental impacts at the same distance (50 km) which lead to a better result when looking at the overall production chain (26 vs. 36 kg CO₂-eq Mg_dm⁻¹). Respective energy output to energy input ratios were 23:1 and 26:1.We also analysed the impacts of irrigation and fertigation as they might be options to increase biomass yield. Both treatments lead to considerably increased environmental impacts in all analysed categories which might be balanced only if the biomass yields increase substantially; an effect which could not be verified within the current study.     

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.     

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.     

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.     

Productivity,stand dynamics and the selection effect in a mixed willow clone short rotation coppice plantation

Short Rotation Coppice (SRC) is a promising method of biomass production for energy purposes, but there have been concerns about the low diversity of these stands, including the risk for pest outbreaks. Mixing different clones has been advised as a way to tackle this problem and improve yields through positive diversity effects. Recent research into the relationship between biodiversity and ecosystem functioning supports these recommendations, but also raises worries about mechanisms that may confound results, such as a selection effect due to dominant clones outcompeting weaker ones. However, the few available studies on diversity effects in SRC plantations did not allow the disentangling of the mechanisms at play.We used data from an experimental SRC site, which incorporated three Swedish Salix clones in a row-based mixing design. Productivity was expected to be greater in mixtures and we attempted to elucidate whether this was due to a complementarity or a selection effect. We found that complementarity effects were generally larger than selection effects, yet the total diversity effect on yield was not significant. Leaf surface temperature measurements indicated that drought stress was unlikely to be the factor underlying this distorted diversity productivity relationship. We also found that a less-productive clone (Gudrun) had a different stem biomass distribution when in monoculture, which may have repercussions for the quality of the harvested product and points at a so far less recognized potential benefit of mixing.     

The effects of policy incentives in the adoption of willow short rotation coppice for bioenergy in Sweden

The effect of policy incentives in the development of short rotation willow plantations for bioenergy is studied by using an aggregate adoption model based on sigmoidal curves for the Swedish municipalities. A total of 56 municipalities were studied, with 891 farmers that planted willow during the period 1986–1996. The model included variables related to the subsidies applied, the taxation on fossil fuels, the development of the wood-fuel consumption by the district heating systems, and the geographical and socio-economic characteristics of the municipality. Results of the simulations using the model show an increment of almost 70% of farmers planting willow during the period studied when the subsidy and tax incentives and the increments of the wood-fuel capacity by the district heating system took place. This study gives tools for future policy implementations in order to achieve the goals of the energy strategies.     

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.     

Willow clones with high biomass yield in short rotation coppice in the southern region of Tohoku district (Japan)

The present study was conducted to select willow (Salix spp.) clones with a high potential for use as biomass energy crops in the southern region of Tohoku district in Japan. Cuttings of 8 willow clones were planted on an abandoned farmland near Sendai (av. annual temp., 10.9 °C) in March 2006, grown throughout the year and cut back in late December 2006 to resprout from the remaining stools in March 2007. The biomass yield in December 2007, after the first growing season, was highest in Salix pet-susu clone KKD, followed by Salix pseudolinearis clone FXM and Salix sachalinensis clone SEN. The biomass yield on December 2008, after the second growing season, was again highest in clone KKD followed by clone FXM, S. pet-susu clone HB471 and S. sachalinensis clone SEN; the average annual yield of dry mass after the second growing season being 3.09, 2.58, 2.17 and 1.85 kgDM plant^?1 for the clones in this order. Plant growth form differed among the clones. Clones FXM and SEN had several shoots of almost uniform base diameter, whereas clones KKD and HB471 showed plagiotropic growth with one thick and several thin shoots. The calorific values of dried stem segments were similar among clones, ranging from 18.7 to 19.1 kJ g^?1. The dried stem segments contained 78.9–81.2 wt.% hollocellulose, 27.2–32.3 wt.% lignin and 2.1–4.0 wt.% extractives with ethanol-benzene, depending on clones. Based on these results, we could select four clones (KKD, FXM, HB471 and SEN) suitable for biomass production by SRWC in this area.     

Economic viability of short rotation coppice for energy production for reuse of caesium-contaminated land in Belarus

Following the Chernobyl accident, changed land use such that the products of the land are radiologically acceptable and assure an economic return is a potentially sustainable remediation option. In this study, Short rotation coppice (SRC) for energy production is evaluated as an alternative land use in contaminated areas. If the radiological and technical feasibility criteria are met, the economic viability of the SRC wood production and conversion of the biofuel to energy is a prerequisite for promotion of this alternative landuse.Data were collected for Belarus conditions and the economics of SRC production and conversion side were modelled using the Renewable Energy Crop Analysis Programme (RECAP).The profitability of SRC production largely depends on crop yield, harvesting method and price of the delivered biofuel, labour and machinery cost playing a minor role. The required internal rate of return (IRR) of 5% at the production side is only obtained with high biofuel prices $\text{(40}\text{EUR}\text{t}{}^{\mathrm{-1}}\text{)}$ and a biomass yield of at least $\text{6}\text{t}\text{ha}{}^{\mathrm{-1}}$. For appropriate soil conditions, potential SRC yields are high (10–$\text{12}\text{t}\text{ha}{}^{\mathrm{-1}}\text{yr}{}^{\mathrm{-1}}\text{)}$. However, in Belarus, most soils are sandy for which yield estimates are too low $\text{(5}\text{t}\text{ha}{}^{\mathrm{-1}}\text{)}$ to make production profitable. Cut and chip harvesting is more profitable than stick harvesting.On the conversion side, heat and power plant investment schemes are only profitable when industrial energy prices are considered. Systems are not viable at lower domestic rates with IRR being always smaller than the 10% required for industry in Belarus. Large-scale heat conversion systems are the most profitable and revenue may be considerable with the IRR between 16% and 59%. Electricity routes are usually unprofitable. Waste disposal costs are only a small fraction of the total costs and revenue.     

Interaction of willow (Salix) clones grown in polyclonal stands in short rotation coppice

Stool survival of Salix spp. clones is reduced when growing in polyclonal stands as compared to monoclonal stands. Stools growing in polyclonal stands show increased vigour with compensation of weak or dead stools from adjacent stools. In monoclonal stands the stools tend to be less vigorous but there is also less variation between stools. When a clone, which has become highly susceptible to rust infection, is included in the mixture, e.g. Salix burjatica Korso, it will die out completely within two years.     

Open-air storage of fine and coarse wood chips of poplar from short rotation coppice in covered piles

The cultivation of short rotation coppices (SRC) on agricultural land represents an economically and environmentally promising option for sustainable provision of bioenergy. Not only the further development of efficient harvesting machinery, but also the development of harvest-optimised storage systems are necessary to implement cost-efficient cultivation and use strategies for SRC in practice. The storage of fine wood chips from poplar harvest with a forage harvester results in high dry matter losses of up to 25%. Tractor-mounted mower-chippers can harvest coarse wood chips that might possess more favourable storage and drying properties. The main objective of the current research project was to develop and perform a storage experiment in which the storage behaviour of fine and coarse wood chips could be examined and compared in detail over a period of nine months. In this experiment two covered storage piles (height 3.5 m), with over 500 m³ fine and coarse wood chips respectively, were examined under practice scale conditions in Germany. After nine months of storage the fine chips in the core of the storage pile had dried to a moisture content of 34% with dry matter losses of 22%. Coarse chips, on the other hand, achieved a moisture content of 29% and dry matter losses of 21% in the same period. The maximum moisture content of 40% required by heating plants in practice is achieved by fine chips after 6.5 months and by the coarse chips already after 3.5 months.     

Slow expansion and low yields of willow short rotation coppice in Sweden; implications for future strategies

About 16 000 ha of commercial willow Short Rotation Coppice (SRC) fields for production of biomass for energy were planted in the early 1990s in Sweden. The cultivated with SRC area has remained almost stable and was slightly decreased during the last years despite the incentives and predictions for drastic increases. Similar incentives and predictions in other countries have been lately launched. The bioenergy produced in the planted SRC areas in Sweden has been lower than anticipated, partly due to the lower than expected biomass yields and the termination of some willow SRC plantations. Explanations for the low yields are depicted based on analyzing the results of a survey where 175 willow SRC growers participated. Lower biomass yields are attributed to: (i) the low input in management activities; (ii) the choice of land for the willow SRC plantation; (iii) and the level of personal involvement of the farmer. Understanding the reasons to earlier years’ performance of willow SRC is important for development of better performing systems in the future, in Sweden as well as in other countries.     

Life cycle assessment of biomass chains: Wood pellet from short rotation coppice using data measured on a real plant

This paper presents a LCA study about household heat from Short Rotation Coppice wood pellets combustion. The overall process, from field growth to ash disposal, was considered; environmental analysis was carried out using a LCA software programme (Simapro 7.0) and adopting the EcoIndicator 99 model for the evaluation of the global burden; analysis with EPS 2000 and EDIP methodologies were also carried out, in order to compare the different approaches. For the pellet production process, mass and energy flows were measured on an existing Italian plant, while other data were obtained from the Literature; a comparison between results obtained using only data from Literature and using data from the existing plant was made, showing for the pelleting phase a value of about 23% lower if measured data are used. The LCA study showed that agricultural operations account for most of the environmental impact if evaluated both with EcoIndicator 99 and EPS 2000; EDIP gave results that were not very reliable for this chain, due to the high weight given to the infra-structures and machinery construction. The comparison between data obtained considering and not considering the infra-structures contribution in the LCA analysis with EcoIndicator 99 showed a modest contribution of infra-structures on the final score (about 2%). The overall impact evaluated with EcoIndicator 99 is considerably less than the one caused by natural gas heating. The Energy Return Ratio was finally calculated; a value of 3.25 was found, good if compared to the one for the methane combustion, equal to 6.     

The influence of canopy density on willow leaf rust (Melampsora epitea) severity in willow short rotation coppice

Willow short rotation coppice is used as a renewable energy source and also as a vegetation filter for purifying wastewater. Wastewater irrigation might change microclimatic conditions and increase the canopy density in plantations, which might decrease production due to leaf rust (Melampsora epitea). The aim of this study was to estimate the impact of the canopy density on rust abundance on willows. For that, we counted rust pustules on leaves of five different willow clones from dense and sparse areas in both the wastewater irrigated and control part of the plantation. The results demonstrated clear differences between clones; clone ‘81090’ was very susceptible, ‘78183’ susceptible, ‘78021’ fairly tolerant and ‘Tora’ rust resistant. Clone ‘Gudrun’, which was previously reported resistant, had severe rust damages in Estonia. In the case of clones ‘78183’ and ‘78021’ there were significantly more rust pustules per leaf unit area at areas with denser canopy, which confirmed that higher plant density could result in biomass losses caused by leaf rust. No differences, however, were detected between dense and sparse areas of hybrid clone ‘Gudrun’, most probably because in this particular case leaves from upper canopy layer were used. There was a tendency detected that clones with a higher number of shoots per plant had more rust damages on their leaves, however, the correlation was not statistically confirmed. In conclusion, the impact of canopy density on rust abundance is clone-specific and significant in the case of clones on which infection starts from the lower part of the canopy.     

Growth and production of a short rotation coppice culture of poplar. II. Clonal and year-to-year differences in leaf and petiole characteristics and stand leaf area index

Twelve different poplar (Populus) clones, belonging to different species and interspecific hybrids were studied during the first and second growing seasons of the second rotation of a high density coppice culture. Leaf size, leaf area, leaf nitrogen and specific leaf area (SLA) were examined at two different canopy levels, together with petiole length and petiole diameter. Leaves in the upper canopy layer were larger, heavier and had a lower SLA. They also had longer and thicker petioles, as well as a higher nitrogen concentration per unit dry weight than lower canopy leaves. Significant clonal variation was observed in leaf and petiole characteristics in both growing seasons. Leaf area index (LAI), scaled-up from allometric relationships, showed significant clonal variation in the two growing seasons, and increased for all clones in the second growing season. LAI increment was related to a significantly increased diameter of all shoots. Our study demonstrates (i) that light significantly affects leaf and petiolar characteristics, and nitrogen concentrations of foliage elements, and (ii) that year-to-year differences in foliar characteristics are related to stand aging rather than to increased shading due to larger LAI.     

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.     

Impact of different establishment methods in terms of tillage and weed management systems on biomass production of willow grown as short rotation coppice

To date little information is available on methods including soil preparation and weed control in SRC. For this purpose, in 2010, a field trial with willow cv. ‘Tordis’ was established in southwest Germany. Three different tillage systems (mouldboard plough, chisel plough + ley crop, no-till) were implemented in the establishment year in combination with eight chemical and mechanical weed management systems. Over a period of three years, plant and weed specific parameters were collected to determine the effect of tillage systems and weed treatments on final biomass production of willow. The highest biomass yields were obtained by mouldboard plough with chemical weed control (14.0 Mg ha⁻¹ dry matter) as well as by mouldboard plough with rotivation and band spraying of herbicides (14.2 Mg ha⁻¹ dry matter), followed by 13.7 Mg ha⁻¹ dry matter in no-till with broadcast application of herbicides. Chisel ploughing with ley crop led to lower willow yields in most weed treatments. It was assumed that chisel ploughing + ley crop would lead to a high competition for light, water and nutrients especially in the first year. Consequently, it is not recommended as an establishment method for willow. Additionally, mulching with wood chips and no weed management generally resulted in low biomass yields. Overall, the results suggest that the tillage system in combination with effective chemical or mechanical weed control is of major importance for the success of willow establishment.