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Hybrid aspens have long attracted scientific interest, but the research on their use as feedstocks for chemical applications are still very limited. The bark biomass of the poplar species contains many valuable extractives that can be utilized as value-added products. This paper examines the applicability of hybrid aspen (Populus tremula L. × P. tremuloides Michx.) bark extract as a precursor of rigid carbon foam and activated carbon. To explore this, the study considers 1) the basic chemical composition of the bark in terms of added value potential, 2) the basic chemical composition of the bark extract and the effect of its pretreatment on the extract composition, 3) the production of rigid carbon foam, and 4) the chemical activation of carbon foam with different impregnating agents. The study determines that the bark extract of the hybrid aspen can be used as a precursor for rigid carbon foam and further processed into an activated carbon product. Therefore, the bark extract of Populus tremula L. × P. tremuloides Michx. can be assessed as a potential value-added product that increases the use value of the hybrid aspen biomass. peerReviewed

Bark is currently used mainly to produce energy, but the extraction of valuable compounds before combustion offers an interesting cascading use for debarking biomass. Buffer storage is an inevitable part of bark biomass logistics, but substantial dry matter and extractive losses can degrade the properties and reduce the economic value of the raw material during storage. In this study, moisture and ash content, calorific value, and extractives content and composition of Scots pine (Pinus sylvestris) sawmill bark were determined over 2 months of buffer storage, and the change in energy content during storage was calculated. The results showed that the energy content (MWh m−3) of the bark increased 3% during storage, while at the same time the moisture content decreased 16%. The content of acetone-soluble extractives decreased markedly, with only 56% of the original amount remaining after 8 weeks of storage. In particular, hydrophilic, phenolic extractive compounds were rapidly lost after debarking and piling of the bark. About 60% of condensed tannins (CT) and about 26% of the quantified lipophilic compounds were lost after 2 weeks of storage. The fastest rate of decrease and the most significant changes in extractives content and composition occurred within the first 2 weeks of storage. Utilization of these valuable compounds necessitates fast supply of material for further processing after debarking. The comprehensive utilization of bark requires efficiency at all levels of the supply chain to ensure that tree delivery times are kept short and loss of bark is avoided during harvest and transport.

It will be necessary to make efficient use of our resources if our society is to be converted into a bio-based economy. Every year large side streams of bark are produced in sawmills and pulp mills. In addition to utilizing the bark for heat and electricity production, as happens today, high-value chemical components could be extracted prior to energy conversion. These components include tannins. Cationized tannins have already been indicated as promising renewable flocculants in wastewater treatment. However, today's industrial production of tannins uses species from subtropical or temperate climates, and there has so far been little attention to the use of tannins from Norway spruce (Picea abies), an important species in forestry in the subarctic climate. The present life-cycle assessment (LCA) was undertaken to understand the environmental performance of the production of cationized tannins from the bark of Norway spruce and how the environmental impact is distributed along the production system. This work was connected to the Interreg Botnia-Atlantica TanWat research project, which studies the production and use of cationized tannins from Norway spruce for wastewater treatment at a pilot scale. The present LCA shows that the main environmental impact stems from the reagents used in the cationization step. The purification step could also be a significant issue depending on the possibility of reusing the eluent (ethanol) and the lifetime of the resin. The importance of running the processes with as concentrated streams as possible to minimize the need of process water and energy was also confirmed (Less)

Polyphenolic stilbene glucosides are abundant in the fresh bark of Norway spruce (Picea abies [L.] Karst.) trees. Stilbene-rich bark extracts could be industrially utilized as preservatives due to their antioxidative, antifungal, and antibacterial properties. The postharvesting conditions, especially industrial debarking, influence the chemical properties of bark. Inherent variation in high-value compounds of bark is assumed to be offset by modifications within the bark supply chain; however, essential quantitative information is still rare. This study elucidated the magnitude of variation in the stilbenoid content and composition of Norway spruce bark due to (1) the geographical origin of Norway spruce seeds, (2) the geographical location of the growing site, (3) within-tree variability, and (4) industrial handling and pilot-scale extraction and fractioning processes. The inherent variation in stilbenoid content was large: the total average stilbenoid content of the inner bark varied from 70 to 110 mg/g of dry weight (DW). Sampling position in the stem and growing site explained over 50% of the total variance in stilbenoid content. Trees with a northern origin of seeds had a higher isorhapontin/astringin ratio than the trees with a southern origin of seeds, regardless of their growing site. Industrial bark from sawmills showed a significantly higher total stilbenoid content in winter than in summer, 22 mg/g and 1–3 mg/g DW, respectively. The inherent variation in the stilbenoid content was offset by the variation caused by the debarking process and experimental pilot-scale processing. To optimize the yield of stilbenoids from spruce bark, sampling of northern forests and short handling times in the supply chain are recommended.

Norway spruce (Picea abies (L.) Karst.) bark contains marked amounts of polyphenolic compounds. Condensed tannins (CTs) and stilbenes show commercial potential as antioxidants, antimicrobials, preservatives in food and cosmetic applications, technochemical products, and pharmaceuticals. Storing of bark before the conversion process leads to substantial losses of extractives compounds. In the present study, the potential of thermal drying for maintaining extractives content was assessed based on an experiment in which bark samples were dried in convection kilns at 40, 50, 60, and 70 °C temperatures. The development of CTs and stilbene contents and CT degradation were followed for 28–34 h. CTs were analysed from bark samples with thiolysis. Quantities of stilbene glycosides and stilbene aglycones in water-acetone extracts were analysed applying gas chromatography with flame-ionization detection (GC-FID). Multilevel regression analysis was used to analyse the statistical differences in moisture content and extractives composition between the drying schemes. The initial CT content of 35–36 mg g−1 in dry bark material declined to 25–31 mg g-1 in 28–34 h. The average degree of polymerisation (DP) decreased slightly, and the relative proportion of prodelphinidins in CTs increased significantly in the 60 and 70 °C schemes. The proportion of A-type linkages slightly increased with the increase in drying temperature. The initial mean stilbene contents varied from 19 mg g−1 to 22 mg g−1 in dry bark mass. Isorhapontin was the major stilbene constituent, with a proportion of 45–49 % of the total stilbenes. Stilbene losses of up to 60 % were detected during the drying processes. In 10 h, for example, 36–43 % of total stilbenes were lost. Degradation activities by enzymes released from the bark and oxidative reactions after crushing at the debarking phase were concluded to be the primary mode of degradation. The results indicate that bark CT content can be preserved at a moderate temperature not exceeding 50 °C, but the degradation of CTs may affect their suitability for various applications. Sufficient stilbene content for industrial processes is unlikely to be maintainable through thermal drying. The permanence of the post-drying extractives content should be assessed based on a practical-scale storage experiment using bark dried to varying moisture contents. peerReviewed

Environmental concerns and depletion of fossil fuels along with government policies have led to the search for alternative fuels from various renewable and sustainable feedstocks. This review provides a critical overview of the chemical composition of common commercial plant oils, i.e., palm oil, olive oil, rapeseed oil, castor oil, WCO, and CTO and their recent trends toward potential biofuel production. Plant oils with a high energy content are primarily composed of triglycerides (generally > 95%), accompanied by diglycerides, monoglycerides, and free fatty acids. The heat content of plant oils is close to 90% for diesel fuels. The oxygen content is the most important difference in chemical composition between fossil oils and plant oils. Triglycerides can even be used directly in diesel engines. However, their high viscosity, low volatility, and poor cold flow properties can lead to engine problems. These problems require that plant oils need to be upgraded if they are to be used as a fuel in conventional diesel engines. Biodiesel, biooil, and renewable diesel are the three major biofuels obtained from plant oils. The main constraint associated with the production of biodiesel is the cost and sustainability of the feedstock. The renewable diesel obtained from crude tall oil is more sustainable than biofuels obtained from other feedstocks. The fuel properties of renewable diesel are similar to those of fossil fuels with reduced greenhouse gas emissions. In this review, the chemical composition of common commercial plant oils, i.e., palm oil, olive oil, rapeseed oil, castor oil, and tall oil, are presented. Both their major and minor components are discussed. Their compositions and fuel properties are compared to both fossil fuels and biofuels.

Fresh bark from spruce Picea abies was milled and extracted with hot water. The extracts were purified in a number of steps in order to get tannin-extracts pure enough to prepare tannin-based carbon foams. The chemical composition of the extracts were analyzed. The foams were maturated and thermally treated to obtain desired properties, such as specific surface area, porosity, and compressive strength. It was possible to produce carbon foams even if they contained carbohydrate impurities. Differences in the properties of the carbon foams such as compressive strength, specific surface areas, and pore size distributions might be related to the compositions of the extracts. The foams were finally activated chemically and physically and were tested in adsorption of methylene blue. Results from the adsorption tests showed that adsorption was highly related to the total pore volume and the amount of mesopores created inside the foam structure during the thermal treatment.

Wood bark is one of the major feedstocks in bioenergy and bioeconomy scenarios in Finland. Currently it is used mainly for producing heat and power, which make buffer storage essential due to seasonal variations in the demand for energy. The storage of bark is associated with problems like the occurrence of self-heating, biomass losses, and the reduction of its quality as fuel. Extraction of valuable extractives from the bark before burning is an interesting option when aiming to increase the value of this side-stream. However, the content of extractives starts to decrease immediately after tree felling and this degradation continues during storage. This study examined changes in fuel quality and extractive amounts during the storage of Norway spruce (Picea abies) bark from sawmills. The moisture content of the bark decreased five percent during the storage period of eight weeks. The temperature in the storage pile rose within one week to over 50° and there was evidence of appreciable initial biological activity within the bark. The dry matter losses of spruce bark were on average six % per month. The content of acetone-soluble extractives decreased significantly, being 66.2% of the original amount after eight weeks’ storage. The most significant changes in extractive content occurred within the two first weeks of storage when 30% of the extractives were lost. This means that in order to utilize these valuable compounds, the material should be sent for further processing as soon as possible after debarking.