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Bioenergy will be one of the most important renewable energy sources in the conversion from fossil fuels to bio-based products. Short rotation coppice Salix could be a key player in this conversion since Salix has rapid growth, positive energy balance, easy to manage cultivation system with vegetative propagation of plant material and multiple harvests from the same plantation. The aim of the present paper is to provide an overview of the main challenges and key issues in willow genetic improvement toward sustainable biofuel value chains. Primarily based on results from the research project "Optimized Utilization of Salix" (OPTUS), the influence of Salix wood quality on the potential for biofuel use is discussed, followed by issues related to the conversion of Salix biomass into liquid and gaseous transportation fuels. Thereafter, the studies address genotypic influence on soil carbon sequestration in Salix plantations, as well as on soil carbon dynamics and climate change impacts. Finally, the opportunities for plant breeding are discussed using willow as a resource for sustainable biofuel production. Substantial phenotypic and genotypic variation was reported for different wood quality traits important in biological (i.e., enzymatic and anaerobic) and thermochemical conversion processes, which is a prerequisite for plant breeding. Furthermore, different Salix genotypes can affect soil carbon sequestration variably, and life cycle assessment illustrates that these differences can result in different climate mitigation potential depending on genotype. Thus, the potential of Salix plantations for sustainable biomass production and its conversion into biofuels is shown. Large genetic variation in various wood and biomass traits, important for different conversion processes and carbon sequestration, provides opportunities to enhance the sustainability of the production system via plant breeding. This includes new breeding targets in addition to traditional targets for high yield to improve biomass quality and carbon sequestration potential.

Wood is widely used in buildings but its low thermal mass limits its energy efficiency for internal use. The thermal mass of wood can be improved by incorporation of PCMs into its porous structure, and thus can control energy intermittency inside buildings. In this study, coconut oil fatty acids mixed with linoleic acid in 4:1 (w/w), with a phase transition temperature in the range of human comfort (18-25 ºC), were integrated into thermally treated spruce. The impregnation uptake was 60% and the stability of the PCM in wood structure was evaluated by subjecting impregnated wood samples to leaching tests, and found to be 5%. Thermal characteristics of the wood/BPCM composite including phase transition temperature, enthalpy, heat capacity and thermal conductivity were investigated with DSC, T-history and heat flow meter method, and respectively found to be in the range of 22.4-25.5 °C, 39 J/g, 4 J/(g K) and 0.13 W/(m K).

Salix (willow) is a well-known coppice plant that has been used as a source for bioenergy for decades. With recent developments in changing from a fossil-based to a circular bioeconomy, greater interest has been orientated towards willow as a potential source of biomass for transport biofuels. This has created increasing interest for breeding strategies to produce interesting genotypic and phenotypic traits in different willow varieties. In the present study, 326 genetically distinct clones and several commercial varieties of S. viminalis were analyzed using complementary approaches including density, chemical, image, histochemical, and morphometric analyses. A systematic approach was adopted whereby the basal regions of harvested stems were separated and used in all studies to aid comparisons. Density analyses were performed on all clone individuals, and from the results, 20 individual plants representing 19 clones were selected for the more in-depth analyses (chemical, image analysis, histochemical, and morphometric). The absolute dry density of the clones selected varied between ca. 300 and 660 kg/m3 with less variation seen in the commercial S. viminalis varieties (ca. 450–520 kg/m3). Selected clones for chemical analysis showed the largest variation in glucose (47.3–60.1%; i.e., cellulose) and total sugar content, which ranged between ca. 61 and 77% and only ca. 16 and 22% for lignin. Image analyses of entire basal stem sections showed presence of tension wood in variable amounts (ca. 7–39%) with characteristic G-fibers containing cellulose-rich and non-lignified gelatinous layers. Several of the clones showing prominent tension wood also showed high glucose and total sugar content as well as low lignin levels. A morphometric approach using an optical fiber analyzer (OFA) for analyzing 1000 s (minimum 100,000 particles) of macerated fibers was evaluated as a convenient tool for determining the presence of tension wood in stem samples. Statistical analyses showed that for S. viminalis stems of the same density and thickness, the OFA approach could separate tension wood fibers from normal wood fibers by length but not fiber width. Results emphasized considerable variability between the clones in the physical and chemical approaches adopted, but that a common aspect for all clones was the occurrence of tension wood. Since tension wood with G-fibers and cellulose-rich G-layers represents an increased source of readily available non-recalcitrant cellulose for biofuels, S. viminalis breeding programs should be orientated towards determining factors for its enhancement.

This study evaluated the potential of biochar impregnated with Fe3+ or Ca2+, or mixed with Polonite®, as a filter material for removal of phosphate (PO4-P) from wastewater in onsite wastewater treatment systems (OWTS). Four treatments with biochar were investigated: unimpregnated biochar (UBC), biochar impregnated with iron Fe3+ (FBC), biochar impregnated with calcium oxide (CBC), and biochar mixed with Polonite® (PBC). In a batch experiment using phosphate solution at concentrations 0.5, 3.3, 6.5, 13, and 26 mg PO4-P L–1, adsorption of PO4-P in the different treatments was modeled using Langmuir and Freundlich isotherms. Column filters (5 diameter × 55 cm height) packed with UBC, FBC, CBC, and PBC were then furnished with raw wastewater over 148 weeks. During this experiment, adsorption of PO4-P was investigated in response to increasing hydraulic loading rate (HLR; 56, 74, and 112 L m–2 day–1) and increasing phosphate loading rate (PLR; 195, 324, 653, and 1715 mg PO4-P m–2 day–1). Among the materials, FBC had the highest maximum adsorption capacity (Qm) based on Langmuir isotherms (3.21 ± 0.01 mg g–1). FBC and CBC showed robust performance with increasing HLR, while increasing PLR increased the amount of PO4-P retained in all filters. After 148 weeks of operation, removal of PO4-P (averaged over the last 18 weeks of operation) was 13 ± 16% for UBC, 40 ± 20% for CBC, 88 ± 12% for FBC, and 30 ± 18% for PBC. The PO4-P amount retained in filters over the 148 weeks was 84.75, 221.75, 358.38, and 152.36 g m–2 in UBC, CBC, FBC, and PBC, respectively. The adsorption capacity of the filters after 148 weeks was 1.50, 4.02, 6.41, and 2.75 mg g–1 for UBC, CBC, FBC, and PBC, respectively. The adsorption capacity values and breakthrough curves showed that low concentrations (i.e.

Additional file 1: Figure S1. Estimates of Klason lignin from py-MBMS versus values obtained by wet chemistry. Figure S2. Results of initial test runs to assess optimal pretreatment severity and enzyme loading. Figure S3. Results of second test run to better assess optimal enzyme loading.

Polyunsaturated fatty acid vinyl ester was synthesized via a transition-metal catalyzed transvinylation reaction between vinyl acetate and fatty acids from Tung oil. The ensuing fatty acid vinyl ester (vinyl α-eleostearate) was characterized by FTIR and NMR spectral analyses and used as reactive reagent for modification of wood veneers. The covalent grafting of polyunsaturated fatty acid moieties onto the wood was achieved through transesterification reaction between wood hydroxyl groups and fatty acid vinyl ester. The transesterification reaction was confirmed by FTIR, 13C CP MAS NMR spectroscopy and the level of modification was estimated by determining the weight percentage gain (WPG). The photostability of modified wood veneers was evaluated by exposing wood veneers to natural weathering in Uppsala (Sweden) during April-May 2018. Upon 5 weeks of exposure to natural weathering, unmodified wood showed quick color changes and degradation of lignin, while modification of wood vinyl α-eleostearate was very effective in suppressing light-induced color changes at wood surfaces.

In recent years, some vegetable oils such as linseed oil and soybean oil, have been used to preserve wood material, and contain no environmentally hazardous chemicals or chemicals harmful to humans. However, based on early studies related to vegetable oils, it was found that vegetable oils do not chemically bond with the wood structure, but rather only fill the cavities in the wood structure. This acts only to prevent the water uptake into wood. Because vegetable oils only act as a barrier to prevent water absorption, higher oil retentions (400 kg/m3 - 600 kg/m3) which are not cost-effective, would be needed to be effective in protecting wood. In this study, to reactivate oil and improve the bonding ability between oil and wood components, epoxidation of vegetable oil was targeted. Thus, more cost-effective oil retention levels between 80 kg/m3 and 270 kg/m3 were used due to treat the wood. With epoxidized vegetable oils, oil acids are able to bond to sites normally occupied by water molecules. This study also aimed to reduce leaching of boron compounds.

Diplôme : Dr. d'Université; Au cours de cette étude, une méthode inédite de fonctionnalisation chimique de la matière lignocellulosique a été développée. Des groupes acyles de taille et de fonctionnalité variées ont ainsi été greffés à l’intérieur du bois, grâce à une réaction de transestérification entre les esters d’énol et les groupes hydroxyles des polymères lignocellulosiques. Les greffages ont été confirmés grâce aux spectroscopies infrarouge et RMN du 13C en phase solide. La stabilité dimensionnelle du bois acétylé à partir de l’acétate de vinyle ainsi que sa résistance aux attaques fongiques a été également évaluée, de même que la photostabilité du bois estérifié à partir des esters de vinyle aromatiques.