Bark represents 10 % dry weight of spruce trees and is a major side stream from pulp production. Currently, pulp mills burn bark to produce energy with a low economic value, directly emitting biogenic carbon dioxide to the atmosphere. Biorefining bark using a continuous flow-through fractionation process generates high added-value compounds (tall oil, starch, phenol, and pulp) that allow for extended carbon storage durations. This study assesses the potential future environmental impacts of valorising bark instead of burning it. We conduct a LCA study combining a prospective consequential modelling perspective with an input-related functional unit and account for the effects of storing biogenic carbon in the bark-based products. Our findings show that biorefining bark maintains lower environmental impacts than combustion, reducing time-differentiated climate impacts by up to 30 %, but only when the carbon dioxide used for pulping is recirculated and the fractionation processes are integrated with a co-located pulp mill supplying surplus waste energy, considered to have no associated environmental impacts. Storing biogenic carbon for a longer period of time has a positive effect on mitigating short-term climate impacts. However, our analysis reveals that while time-dependent climate impacts decrease, there is an increase in human toxicity and ecotoxicity impacts, with combustion performing better in these categories. This highlights the importance of expanding the scope of LCA studies to include impacts beyond climate change. Overall, this work demonstrates that combining a prospective consequential modelling perspective with an input-related functional unit is a relevant approach to study potential future impacts of emerging biorefineries and thus supports the development of a sustainable circular bioeconomy.

This study presents a sequential fractionation of spruce bark employing a flow-through system that enables continuous extraction without the need to change the chamber during the process. Various bark components such as lipophilic extractives, noncellulosic sugars, and lignin were extracted under mild conditions and within short timeframes compared to the batch process. The utilization of the flow-through system enabled efficient extraction without degradation of products that were observed during the batch process. By recirculating the solvents containing extracted components, the solvent/biomass ratio could be reduced considerably, without degradation of the products. The results demonstrate an energy efficient approach to obtaining valuable components from spruce bark, paving the way for a future biorefinery.

Maximizing products of high value and minimizing incineration of side-streams is key to realize future biorefineries. In current textile production from forestry, hemicellulose is removed by prehydrolysis before delignification. The resulting prehydrolysis liquor is incinerated in the recovery boiler at low efficiency. This additional burden on the limiting recovery boiler reduces the pulp production. In this study, we demonstrate that prehydrolysis liquor can be upgraded, in 5 steps, to yield aviation fuels. Prehydrolysis liquors were dehydrated to furfural by zeolite catalysis. Furfural was selectively reduced to furfuryl alcohol by Au@NC. Rhenium-catalysed Achmatowicz rearrangement gave a C₅ intermediate susceptible to self [2 + 2] cycloaddition to give the C₁₀ oxygenated precursor. By using a combination of Ru/C and zeolites, full hydrodeoxygenation was achieved. The overall transformation from furfural to hydrocarbons resulted in a 48% carbon yield. The resulting hydrocarbons, containing an anticipated strained four-membered ring, are preferred aviation fuel components. This is an important step to show that aviation fuels can be produced sustainably from existing industrial side-streams. A comparative life cycle assessment was applied to evaluate the environmental impact of the proposed valorization approach, demonstrating benefits in the climate change impact category when implementing this technology in a pulp mill compared to the incineration of pre-hydrolysis liquor scenario.

The development of novel pathways for valorizing low-value streams from pulp, forest, and agricultural industries is crucial for realizing a circular bioeconomy and addressing the needs of both platform chemicals and fuels. Utilizing hemicellulose and lignin as biomass-derived feedstocks facilitates the production of sustainable liquid hydrocarbons, with catalytic hydrodeoxygenation being a key process. 

In the utilization of hemicellulose for the synthesis of liquid hydrocarbons, the approach involves recovering hemicellulosic sugars from wood and transforming them into furfural, which undergoes catalytic hydrodeoxygenation using a noble metal/zeolite tandem catalyst. This results in the production of pentane as the primary product. The process also generates C₇–C₁₀ hydrocarbons through bimolecular condensation of oxygenated intermediates alongside the formation of aromatic structures. Another approach involves a three-step transformation of furfural, including furanic ring rearrangement and [2+2] cycloaddition, which produces a C₁₀ oxygenated precursor with a 4-membered ring. Catalytic hydrodeoxygenation of this precursor results in the formation of cyclobutane-containing hydrocarbons for sustainable aviation fuel applications.

In the utilization of lignin for the synthesis of liquid hydrocarbons, the approach involves lignin isolation from biomass and its direct catalytic hydrodeoxygenation into valuable platform chemicals and fuels. Guaiacol serves as a lignin model compound, facilitating optimization of the hydrotreatment process and giving insights into the distribution of the products. The hydrodeoxygenation of two different lignins, isolated from biomass by organosolv and soda pulping, yields bio-oils rich in hydrocarbons and suitable for transportation fuel applications.

Valorizing industrial side-streams that are burnt to a low value are important to make biorefining more sustainable. In this work, hemicellulose obtained as a pre-hydrolysis liquor from kraft pulping was converted to furfural in a 19 wt% yield based on hemicellulose content in raw biomass using a beta zeolite as a catalyst. Furfural was then directly hydro-processed to yield pentane and higher hydrocarbons in 60%. It was found that a combination of Pd/C and ZSM-5 gave full hydrodeoxygenation. Depending on reaction conditions, aromatic or aliphatic compounds could be generated. By using pentane as a carrier liquid, a 100% renewable hydrocarbon stream is possible. Off gases, comprising <C₅ hydrocarbons (23% yield), could be reformed to green hydrogen to yield renewable hydrocarbon products. This way, the pulp mill is de-bottlenecked and thus can increase the production of pulp, and at the same time, another valuable product stream is generated.

The increased interest in utilizing lignin as a feedstock to produce various aromatic compounds requires advanced chemical analysis methods to provide qualitative and quantitative characterization of lignin samples along different technology streamlines. However, due to the lack of commercially available chemical standards, routine quantification of industrially relevant lignin oligomers in complex lignin samples remains a challenge. This study presents a novel method for universal quantification of lignin dimers based on supercritical fluid chromatography with charged aerosol detection (CAD). A series of lignin-derived dimeric compounds that have been reported from reductive catalytic fractionation (RCF) were synthesized and used as standards. The applicability of using linear regression instead of quadratic calibration curves was evaluated over a concentration range of 15–125 mg/L, demonstrating that the former calibration method is as appropriate as the latter. The response factors of lignin dimeric compounds were compared to assess the uniformity of the CAD signal, revealing that the CAD response for the tested lignin dimers did not differ substantially. It was also found that the response factors were not dependent on the number of methoxy groups or linkage motifs, ultimately enabling the use of only one calibrant for these compounds. The importance of chromatographic peak resolution in CAD was stressed, and the use of a digital peak sharpening technique was adopted and applied to address this challenge. The developed method was verified and used for the quantification of lignin dimers in an oil obtained by a RCF of birch sawdust. 

To achieve a viable forest-based biorefinery, both the carbohydrate and lignin parts of the raw material should be valorized. While lignin-first approaches have successfully been applied to hardwoods, where up to 50% of the lignin -close to the 'theoretical maximum yield'- has been transformed to valuable monophenols; limited studies have targeted softwoods. Softwood lignin comprises lower amount of beta-ether bonds and this results in lower theoretical and observed yields of monophenols in reductive catalytic fractionation (RCF): below 5 wt% yield of initial biomass has been reported. In this study, we use beetle infected spruce, a softwood, as raw material. A fast fractionation was developed to give a pulp and a lignin fraction in the absence of transition metal catalysts. The carbohydrate matrix was valorized to dissolving grade pulp in 37 wt% from biomass (86% yield), and suc-cessfully spun to Lyocell fibers. The lignin fraction was dissolved in furfural -operating as green 'solubility-enhancing-agent'- to blend lignin in inert carrier liquids to promote controlled hydrotreatment to yield biofuels in 10 wt% (60% carbon yield) from initial biomass. Life cycle assessment (LCA) of the value-chain showed improved sustainability in several footprint categories compared to cotton production. Thus, upgrading of a considered forestry waste to high value textile fibers and biofuels has been achieved: in case of lignin beyond the 'theoretical maximum yield'. This is an important step to mitigate a future growing demand of textiles without negatively affecting irrigation or land use.

To make biorefining more environmentally sustainable, preferably residues from forestry should be used and more than one fraction should be upgraded. A third of raw materials from forestry & horbar;tops and branches (T & B)― are either left in the forests or collected and incinerated to a low value. Herein, we apply a fast fractionation to valorize two of the fractions of this forestry residue. The cellulose is converted to textile fibers and all the lignin to hydrocarbons. The environmental sustainability of the novel value chain was studied by life cycle assessment (LCA), and benefits were found in four out of five impact categories. These are important steps to increase fiber production without affecting environmental impact, making biorefining competitive.

Coconut Coir Pith (CCP) is a relatively unexplored type of lignocellulosic waste from the coconut industry. As a feedstock that is highly enriched in lignin (Klason lignin content of 40.9 wt % found in this study), CCP is a potential source for renewable lignin-derived materials. We have performed a systematic study on the characterization and valorization of lignin from CCP. We have investigated two different valorization approaches: reductive catalytic fractionation (RCF) and soda pulping followed by catalytic hydrodeoxygenation. During RCF, the lignin was converted into monomeric products in 7.6 wt %. Using soda pulping conditions, we were able to isolate lignin from CCP in 74% yield. Subsequent hydrotreatment of the lignin over a Pt/MoO3/TiO2catalyst resulted in the formation of hydrogenated oil in 43 wt % yield, suitable for the production of biobased diesel fuels and lubricant base oils.