| 1. |
- Dimitriou, Ioannis, et al.
(author)
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Impact of Populus plantations on water and soil quality
- 2017
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In: BioEnergy Research. - : Springer Science and Business Media LLC. - 1939-1234 .- 1939-1242. ; 10, s. 750-759
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Journal article (peer-reviewed)abstract
- Trees of genus Populus (in our context primarily poplars) are predominantly grown in Sweden in small plantations on arable land in southern and central parts of the country to produce biomass for energy and other purposes. This study evaluated the effects (i) of poplar plantations on groundwater quality, by determining differences in leaching of nitrogen and phosphorus to groundwater, and (ii) of poplar and hybrid aspen plantations on soil quality in terms of carbon in the top- and subsoil. The study was conducted comparing Populus plantations in Sweden with adjacent fields with cereals and grasslands. The experiment concerning the groundwater leaching was conducted in eight poplar plantations along three growing seasons (2012-2015). For the soil carbon experiments, 19 poplar and two hybrid aspen plantations and the respective reference fields were sampled. NO3-N leaching from poplar plantations was significantly lower than that from reference fields with cereals, but not when compared with grasslands. Spring NO3-N leaching was significantly lower in poplars than in the reference fields, whereas leaching of NO3-N in autumn did not differ. Concentrations of PO4-P in the groundwater of poplar plantations were lower compared to the respective ones of the reference fields. There were no clear trends observed when comparing carbon concentrations in the topsoil of the poplar and hybrid aspen plantations compared to the respective adjacent reference fields. For the subsoil, the average carbon concentrations in the poplar and hybrid aspen plantations were equal to the respective ones of cereals, but were higher when compared to grassland.
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| 2. |
- Edelfeldt, Stina, et al.
(author)
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Effects of Cutting Length, Orientation and Planting Depth on Early Willow Shoot Establishment
- 2015
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In: BioEnergy Research. - : Springer Science and Business Media LLC. - 1939-1234 .- 1939-1242. ; 8, s. 796-806
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Journal article (peer-reviewed)abstract
- To assess the effects of different planting systems on early performance (survival, shoot emergence time, number of shoots, maximum shoot height and biomass shoot production) of willow, cuttings of varying lengths were planted horizontally at different depths and compared with vertically planted cuttings. Cutting lengths of (i) 25-200 cm and (ii) 7-21 cm were studied in a field experiment and in a box experiment, respectively. Shorter cuttings planted deeper had a lower survival rate and emerged a few days later compared to longer cuttings planted shallower. The performance was considerably higher at the apical part of the cuttings, regardless of cutting length. Longer cuttings planted shallow had a higher performance. Vertically planted cuttings produced more biomass and shoots per length unit than horizontally planted cuttings. We conclude that planting systems based on the use of longer horizontally planted cuttings would probably lead to an uneven establishment and gaps in the stand caused by apical dominance. Also, to achieve the same performance, the need of planting material would be considerably higher compared to systems with vertically planted cuttings. To obtain a fast and more even early establishment of willows, we recommend the use of vertically planted cuttings with a length of at least 20 cm. If cuttings are planted horizontally, they should not be planted deeper than 5 cm.
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| 3. |
- Edelfeldt, Stina, et al.
(author)
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Establishment and Early Growth of Willow at Different Levels of Weed Competition and Nitrogen Fertilization
- 2016
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In: BioEnergy Research. - : Springer Science and Business Media LLC. - 1939-1234 .- 1939-1242. ; 9, s. 763–772-
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Journal article (peer-reviewed)abstract
- To evaluate the effects of weed competition and nitrogen fertilization on the early growth performance of willow, cuttings of the clone Tora (Salix schwerinii x S. viminalis) were planted in buckets together with model weeds (spring barley or white mustard) sown 15, 26, and 30 days after willow planting. The buckets were fertilized with 30 or 90 kg N ha(-1). Willow with weeds sown after 15 days produced less biomass and smaller leaf area and had a lower maximum shoot height compared to willow planted without weeds and willow with weeds sown after 26 or 30 days. Fertilization with 90 kg N ha(-1) gave higher willow biomass production in willow with weeds sown after 26 or 30 days. Type of model weed had no effect on willow performance. Weed biomass and maximum shoot height were higher in weeds planted without willows compared to the willow-weed mixtures. A high nitrogen level gave more weed biomass when planted without willows and in the willow-weed mixture with weeds sown after 15 days. We conclude that for the given high density of willow, competition from weeds emerging soon after willow planting had strong effect on early production. Furthermore, if there is a risk of weed infestation, fertilization should be delayed.
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| 4. |
- Hammar, Torun, et al.
(author)
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Time-Dynamic Effects on the Global Temperature When Harvesting Logging Residues for Bioenergy
- 2015
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In: BioEnergy Research. - : Springer Science and Business Media LLC. - 1939-1234 .- 1939-1242. ; 8, s. 1912-1924
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Journal article (peer-reviewed)abstract
- The climate mitigation potential of using logging residues (tree tops and branches) for bioenergy has been debated. In this study, a time-dependent life cycle assessment (LCA) was performed using a single-stand perspective. Three forest stands located in different Swedish climate zones were studied in order to assess the global temperature change when using logging residues for producing district heating. These systems were compared with two fossil reference systems in which the logging residues were assumed to remain in the forest to decompose over time, while coal or natural gas was used for energy. The results showed that replacing coal with logging residues gave a direct climate benefit from a single-stand perspective, while replacing natural gas gave a delayed climate benefit of around 8-12 years depending on climate zone. A sensitivity analysis showed that the time was strongly dependent on the assumptions for extraction and combustion of natural gas. The LCA showed that from a single-stand perspective, harvesting logging residues for bioenergy in the south of Sweden would give the highest temperature change mitigation potential per energy unit. However, the differences between the three climate zones studied per energy unit were relatively small. On a hectare basis, the southern forest stand would generate more biomass compared to the central and northern locations, which thereby could replace more fossil fuel and give larger climate benefits.
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| 5. |
- Hjelm, Birger, et al.
(author)
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Diameter–Height Models for Fast-growing Poplar Plantations on Agricultural Land in Sweden
- 2015
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In: BioEnergy Research. - : Springer Science and Business Media LLC. - 1939-1234 .- 1939-1242. ; 8, s. 1759-1768
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Journal article (peer-reviewed)abstract
- There is increasing interest in using poplar plantations as sources of bioenergy in many countries, but optimizing their management, robust models for estimating and monitoring their structure, growth and biomass are required. The presented study explores the diameter-height relationships of poplars in 40 plantations on agricultural land located in central and southern Sweden, in order to provide tools for an easy estimation of standing biomass of poplar stands. Diameter and height measurements of 167 trees were included: 117 for calibration and 50 for validation. The constructed diameter-height equations were developed using a mixed-effect modelling approach to address the variations among sites of the plantations and obtain a flexible tool capable of providing locally calibrated estimates. Different models with various structures and stand variables, such as mean diameter and age, were tested. The best model presented R (2) values of 0.87 and 0.96, for the fixed and mixed model parts, respectively. Thus, it appears to be capable of providing useful estimates of heights of poplar stands from measurements of stem diameters in sample plots, thereby facilitating the planning and management of Swedish poplar plantations as future energy feedstock.
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| 6. |
- Li, Muyang, et al.
(author)
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Prediction of Cell Wall Properties and Response to Deconstruction Using Alkaline Pretreatment in Diverse Maize Genotypes Using Py-MBMS and NIR
- 2017
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In: Bioenergy Research. - : Springer. - 1939-1234 .- 1939-1242. ; 10:2, s. 329-343
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Journal article (peer-reviewed)abstract
- In this work, we explore the ability of several characterization approaches for phenotyping to extract information about plant cell wall properties in diverse maize genotypes with the goal of identifying approaches that could be used to predict the plant’s response to deconstruction in a biomass-to-biofuel process. Specifically, a maize diversity panel was subjected to two high-throughput biomass characterization approaches, pyrolysis molecular beam mass spectrometry (py-MBMS) and near-infrared (NIR) spectroscopy, and chemometric models to predict a number of plant cell wall properties as well as enzymatic hydrolysis yields of glucose following either no pretreatment or with mild alkaline pretreatment. These were compared to multiple linear regression (MLR) models developed from quantified properties. We were able to demonstrate that direct correlations to specific mass spectrometry ions from pyrolysis as well as characteristic regions of the second derivative of the NIR spectrum regions were comparable in their predictive capability to partial least squares (PLS) models for p-coumarate content, while the direct correlation to the spectral data was superior to the PLS for Klason lignin content and guaiacyl monomer release by thioacidolysis as assessed by cross-validation. The PLS models for prediction of hydrolysis yields using either py-MBMS or NIR spectra were superior to MLR models based on quantified properties for unpretreated biomass. However, the PLS models using the two high-throughput characterization approaches could not predict hydrolysis following alkaline pretreatment while MLR models based on quantified properties could. This is likely a consequence of quantified properties including some assessments of pretreated biomass, while the py-MBMS and NIR only utilized untreated biomass.
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| 7. |
- Mohan Pawar, Prashant, et al.
(author)
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QTL Mapping of Wood FT-IR Chemotypes Shows Promise for Improving Biofuel Potential in Short Rotation Coppice Willow (Salix spp.)
- 2018
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In: BioEnergy Research. - : Springer Science and Business Media LLC. - 1939-1234 .- 1939-1242. ; 11, s. 351-363
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Journal article (peer-reviewed)abstract
- 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 x 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.
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| 8. |
- Mola-Yudego, Blas, et al.
(author)
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How Much Yield Should We Expect from Fast-Growing Plantations for Energy? Divergences Between Experiments and Commercial Willow Plantations
- 2015
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In: BioEnergy Research. - : Springer Science and Business Media LLC. - 1939-1234 .- 1939-1242. ; 8, s. 1769-1777
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Journal article (peer-reviewed)abstract
- How representative are yields from experimental plots compared to large-scale commercial implementation? This study analyses the yields of fast-growing willow plantations for energy reported in experimental trials in Sweden during the period 1980-2012 compared with those from commercial willow plantations for the period 1986-2006. The study reviews 16 academic publications, which include 466 records from experimental plots, and records from 2073 commercial plantations across the country. The average yield recorded from experiments was 7.7 odt ha(-1) year(-1), compared to commercial plantations' yields 2.6 and 4.2 odt ha(-1) year(-1) for the first and second rotations, respectively. The measured area of the experimental plots seems to have an effect in the overestimation of the average yields, which can be attributed to extrapolation errors. In addition, to explain the broad differences between yield estimates, we identify the following as potential factors: near-optimal management practices and choice of land age differences and rotation lengths, edge effects, measurement methods, harvesting losses, increased mortality, and increased probability of hazard. The results can help to rationalize the expectations derived from experiments and to a more realistic planning of future plantation schemes.
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| 9. |
- Nielsen, Fredrik, et al.
(author)
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Sequential Targeting of Xylose and Glucose Conversion in Fed-Batch Simultaneous Saccharification and Co-fermentation of Steam-Pretreated Wheat Straw for Improved Xylose Conversion to Ethanol
- 2017
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In: Bioenergy Research. - : Springer Science and Business Media LLC. - 1939-1234 .- 1939-1242. ; 10:3, s. 800-810
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Journal article (peer-reviewed)abstract
- Efficient conversion of both glucose and xylose in lignocellulosic biomass is necessary to make second-generation bioethanol from agricultural residues competitive with first-generation bioethanol and gasoline. Simultaneous saccharification and co-fermentation (SSCF) is a promising strategy for obtaining high ethanol yields. However, with this method, the xylose-fermenting capacity and viability of yeast tend to decline over time and restrict the xylose utilization. In this study, we examined the ethanol production from steam-pretreated wheat straw using an established SSCF strategy with substrate and enzyme feeding that was previously applied to steam-pretreated corn cobs. Based on our findings, we propose an alternative SSCF strategy to sustain the xylose-fermenting capacity and improve the ethanol yield. The xylose-rich hydrolyzate liquor was separated from the glucose-rich solids, and phases were co-fermented sequentially. By prefermentation of the hydrolyzate liquor followed fed-batch SSCF, xylose, and glucose conversion could be targeted in succession. Because the xylose-fermenting capacity declines over time, while glucose is still converted, it was advantageous to target xylose conversion upfront. With our strategy, an overall ethanol yield of 84% of the theoretical maximum based on both xylose and glucose was reached for a slurry with higher inhibitor concentrations, versus 92% for a slurry with lower inhibitor concentrations. Xylose utilization exceeded 90% after SSCF for both slurries. Sequential targeting of xylose and glucose conversion sustained xylose fermentation and improved xylose utilization and ethanol yield compared with fed-batch SSCF of whole slurry.
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| 10. |
- Normark, Monica, et al.
(author)
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Biochemical Conversion of Torrefied Norway Spruce After Pretreatment with Acid or Ionic Liquid
- 2016
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In: Bioenergy Research. - : Springer Science and Business Media LLC. - 1939-1234 .- 1939-1242. ; 9:1, s. 355-368
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Journal article (peer-reviewed)abstract
- The chemical effects of torrefaction and the possibility to combine torrefaction with biochemical conversion were explored in experiments with five preparations of wood of Norway spruce that had been torrefied using different degrees of severity. Compositional analysis and analyses using solid-state CP/MAS C-13 NMR, Fourier-transform infrared (FTIR) spectroscopy, and Py-GC/MS showed small gradual changes, such as decreased hemicellulosic content and increased Klason lignin value, for torrefaction conditions in the range from 260 A degrees C and 8 min up to 310 A degrees C and 8 min. The most severe torrefaction conditions (310 A degrees C, 25 min) resulted in substantial loss of glucan and further increase of the Klason lignin value, which was attributed to conversion of carbohydrate to pseudo-lignin. Even mild torrefaction conditions led to decreased susceptibility to enzymatic hydrolysis of cellulose, a state which was not changed by pretreatment with sulfuric acid. Pretreatment with the ionic liquid (IL) 1-butyl-3-methylimidazolium acetate overcame the additional recalcitrance caused by torrefaction, and the glucose yields after 72 h of enzymatic hydrolysis of wood torrefied at 260 A degrees C for 8 min and at 285 A degrees C for 16.5 min were as high as that of IL-pretreated non-torrefied spruce wood. Compared to IL-pretreated non-torrefied reference wood, the glucose production rates after 2 h of enzymatic hydrolysis of IL-pretreated wood torrefied at 260 A degrees C for 8 min and at 285 A degrees C for 16.5 min were 63 and 40 % higher, respectively. The findings offer increased understanding of the effects of torrefaction and indicate that mild torrefaction is compatible with biochemical conversion after pretreatment with alternative solvents that disrupt pseudo-lignin-containing lignocellulose.
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