Feedstock flexibility is highly advantageous for the viability of (solvent-based) biorefineries but comes with the considerable challenge of having to cope with the varying nature and typically high abundance of nonlignocellulose compounds in the most readily available residual biomass streams. Here, we demonstrate that mild aqueous acetone organosolv fractionation of various complex lignocellulosic raw materials (roadside grass, wheat straw, birch branches, almond shells, and a mixed stream thereof) is indeed negatively affected by these compounds and present a versatile strategy to mitigate this bottleneck in biorefining. A biomass pre-extraction approach has been developed to remove the detrimental extractives with (aqueous) acetone prior to fractionation. Pre-extraction removed organic extractives as well as minerals, primarily reducing acid dose requirements for fractionation and loss of hemicellulose sugars by degradation and improved the purity of the isolated lignin. We show how pre-extraction affects the effectiveness of the biorefinery process, including detailed mass balances for pretreatment, downstream processing, and product characteristics, and how it affects solvent and energy use with a first conceptual process design. The integrated biorefining approach allows for the improved compatibility of biorefineries with sustainable feedstock supply chains, enhanced biomass valorization (i.e., isolation of bioactive compounds from the extract), and more effective biomass processing with limited variation in product quality.

Lignin partial depolymerization by reduction (PDR) was developed as a strategy to tailor a technical lignin's molar mass and reduce its heterogeneity and to potentially increase the reactivity of lignin hydroxyl groups in polymer applications such as PU foams and coatings. The process aims to cleave remaining lignin β-O-4 linkages, thereby reducing the molar mass of large lignin fragments and overall lignin dispersity. Acetone organosolv lignin from pilot-scale fractionation of industrial-size wood chips was depolymerized using methanol, a Ru/C catalyst, and externally supplied hydrogen. The effect of reaction temperatures (in the presence and absence of the catalyst) was fully detailed using SEC, 31 P NMR, and 2D-HSQC NMR analyses of the depolymerized lignin. The Ru/C catalyst promoted molar mass reduction by hydrogenolysis and slightly increased the lignin aliphatic OH content. Process parameter screening showed effective depolymerization at high lignin concentrations but required relatively high catalyst loadings. PDR depolymerization efficiency proved to be dependent on the technical lignin's quality. A less-condensed lignin with a higher β-O-4 content showed improved ether cleavage, yielding a lower lignin molar mass after PDR and increased formation of 4-n-propanol end groups. Overall, the PDR process provides control over key lignin characteristics, which in turn offers potential to tailor biobased polymer properties for various applications.

Polyurethane (PU) coatings with high lignin content and tunable properties were made using a combination of fractionation and partial catalytic depolymerization as a novel strategy to tailor lignin molar mass and hydroxyl group reactivity, the key parameters for use in PU coatings. Acetone organosolv lignin obtained from pilot-scale fractionation of beech wood chips was processed at the kilogram scale to produce lignin fractions with specific molar mass ranges (M w 1000–6000 g/mol) and reduced polydispersity. Aliphatic hydroxyl groups were distributed relatively evenly over the lignin fractions, allowing detailed study of the correlation between lignin molar mass and hydroxyl group reactivity using an aliphatic polyisocyanate linker. As expected, the high molar mass fractions exhibited low cross-linking reactivity, yielding rigid coatings with a high glass transition temperature (T g). The lower M w fractions showed increased lignin reactivity, extent of cross-linking, and gave coatings with enhanced flexibility and lower T g. Lignin properties could be further tailored by lignin partial depolymerization by reduction (PDR) of the beech wood lignin and its high molar mass fractions; excellent translation of the PDR process was observed from laboratory to the pilot scale necessary for coating applications in prospective industrial scenarios. Lignin depolymerization significantly improved lignin reactivity, and coatings produced from PDR lignin showed the lowest T g values and highest coating flexibility. Overall, this study provides a powerful strategy for the production of PU coatings with tailored properties and high (>90%) biomass content, paving the path to the development of fully green and circular PU materials.

To fully exploit kraft lignin’s potential in material applications, we need to achieve tight control over those key physicochemical lignin parameters that ultimately determine, and serve as proxy for, the...

Reservoirs with the geometry of structural lows trap negatively buoyant fluids, mirroring the way structural highs trap positively buoyant fluids. In both scenarios, lateral flow of reservoir water alters the trapping geometry by causing fluid contacts to tilt. Tilt increases in proportion to hydraulic head gradient increases and the density contrast between the flowing and trapped fluids decreases. Positively buoyant, immiscible supercritical CO2 is at least 20% lighter than typical saline formation waters at CO2 subsurface storage pressures and temperatures, and would experience relatively low tilts, <1°, similar to hydrocarbon fields. On the other hand, CO2-saturated brines are within 1% of the density of CO2-free equivalent brine. This relatively low density contrast creates tilted contacts at much higher angles even at the low hydraulic head gradients that typify deep saline aquifers. For example, a fluid contact with 0.5% density contrast exceeds 2° tilt for hydraulic head gradients of only 15 cm/km. Many large and basin-scale synformal traps are formed with structural dips of just a few degrees and therefore cannot trap CO2 solutions under hydrodynamic conditions. This problem could be overcome by utilization of hydrodynamic traps or appropriately configured structural-stratigraphic traps for CO2 sequestration.