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Abstract Sulphite addition during steam pretreatment of softwoods under acidic, neutral and alkaline conditions was assessed to try to minimize lignin condensation. Although pretreatment under neutral/alkaline conditions resulted in effective lignin sulphonation, non-uniform size reduction was observed. In contrast, acidic sulphite steam treatment at 210 °C for 10 min resulted in homogenous particle size reduction and water-insoluble component that was 62% carbohydrate and 33% lignin. This carbohydrate-rich substrate was readily hydrolyzed and fermented which indicated the lack of fermentation inhibitors in the steam-pretreated whole slurry. The use of high solid loading (25% w/v) resulted in a hydrolysis yield of 58% at an enzyme loading of 40 mg protein/g glucan and efficient fermentation (46.6 g/L of ethanol). This indicated that the addition of acidic sulphite at the steam pretreatment of softwoods improved both the enzymatic hydrolysis and fermentation of steam-pretreated whole slurries. Graphical Abstract

A pre-hydrolysis Kraft pulping (PHK) process that was used to make dissolving pulp was enhanced by replacing conventional white liquor (WL) neutralization with green liquor (GL) neutralization prior to Kraft pulping. This resulted in a 10% increase in dissolving pulp production, and significant chemical savings, without compromising pulp reactivity. When the possible influence of the alkaline charge on fibre properties was assessed using methods such as viscosity, Simon's stain, Size Exclusion Chromatography (SEC) and SEM, it was apparent that stronger alkaline treatments (WL) resulted increased cellulose degradation, a lower cellulose DP and a slightly larger surface area. When these methods were complemented with an assay based on the selective binding of site-specific carbohydrate-binding modules (CBMs), it was apparent that green liquor (GL) neutralization resulted in an increase in less-ordered cellulose being exposed. This likely contributed to its higher reactivity despite its lower overall surface area.

Several methods are currently used to track the bio-component of co-processed fuels including energy/mass balance, yield methods and radiocarbon techniques. The methods used to track or estimate the bio-component of fuels produced when bio and fossil feedstocks are processed together (co-processed) in oil refineries were analysed in detail, together with their advantages and disadvantages. Some methods, such as radiocarbon methods that allow the direct measurement of the bio-content in a fuel, have been criticised due to low accuracy at low blends. However, these reservations have tended to misinterpret the options available for carbon dating and to discount recent improvements in these tests. As much higher co-pressing mixtures are anticipated if published national decarbonisation targets are to be achieved, any challenges at very low co-processing ratios affecting the accuracy of the radiocarbon methods should not be an issue. Energy/mass balance and yield methods might be supplemented with carbon-tracking to determine the real the biogenic content.

The complex and heterogeneous polyphenolic structure of lignin confers recalcitrance to plant cell walls and challenges biomass processing for agroindustrial applications. Recently, significant efforts have been made to alter lignin composition to overcome its inherent intractability. In this work, to overcome technical difficulties related to biomass recalcitrance, we report an integrated strategy combining biomass genetic engineering with a pretreatment using a bio-derived deep eutectic solvent (DES). In particular, we employed biomass from an Arabidopsis line that expressed a bacterial hydroxycinnamoyl-CoA hydratase-lyase (HCHL) in lignifying tissues, which results in the accumulation of unusual C6C1 lignin monomers and a slight decrease in lignin molecular weight. The transgenic biomass was pretreated with renewable DES that can be synthesized from lignin-derived phenols. Biomass from the HCHL plant line containing C6C1 monomers showed increased pretreatment efficiency and released more fermentable sugars up to 34% compared to WT biomass. The enhanced biomass saccharification of the HCHL line is likely due to a reduction of lignin recalcitrance caused by the overproduction of C6C1 aromatics that act as degree of polymerization (DP) reducers and higher chemical reactivity of lignin structures with such C6C1 aromatics. Overall, our findings demonstrate that strategic plant genetic engineering, along with renewable DES pretreatment, could enable the development of sustainable biorefinery.

Abstract  Hybrid poplar (Populus nigra � P. maximowiczii) chips were pretreated using an organosolv ethanol process. The effect of pretreatment conditions (temperature, time, catalyst, and ethanol concentration) on the substrate characteristics, including fiber size, crystallinity, and degree of polymerization of cellulose, was investigated using an experimental matrix designed with response surface methodology. The conditions ranged 155–205�C, 26–94 min, 0.83–1.67% catalyst (H2SO4) on oven-dry wood chip (w/w), and 25–75% ethanol concentration (v/v). The results indicated that the substrate characteristics are controllable and predictable. Desirable substrates can be prepared by fine-tuning the processing parameters. The regression models developed, allowed the quantitative prediction of the substrate characteristics from the pretreatment conditions used. [ABSTRACT FROM AUTHOR]

Abstract  The development of bioconversion technologies for production of fuels, chemicals, and power from renewable resources is currently a high priority for developed nations such as the United States, Canada, and the European Union as a way to improve national energy security and reduce greenhouse gas emissions. The widespread implementation of such technologies will require a sustainable supply of biomass from forestry and agriculture. Forests are a major source of feedstocks for biofuels production in Canada. Woody biomass includes residues from logging and forest thinning, and from wood processing and pulp production. More recently, damaged wood caused by beetle infestations has become available on a large scale in Western Canada. This study evaluates beetle-killed British Columbian hybrid spruce (HS) (Picea glauca � P. engelmannii) as a feedstock for the production of bioethanol. In the past 30 yr, attack by the beetle Dendroctonus rufipennis and associated fungi has resulted in estimated losses of more than three billion board feet in British Columbia alone. Here we describe the chemical and some physical characteristics of both healthy (HHS) and beetle-killed (BKHS) British Columbian HS and evaluate the technical feasibility of using these feedstocks as a source of biomass for bioethanol production. Untreated HHS and BKHS did not differ significantly in chemical composition except for the moisture content, which was significantly lower in BKHS (approx 10%) compared with HHS (approx 18%). However, the yields of carbohydrates in hydrolyzable and fermentable forms were higher at mild pretreatment conditions (H-Factor 2000) pretreatment conditions HHS and BKHS behaved similarly. Organosolv pretreated HHS and BKHS demonstrated good ethanol theoretical yields, approx 70 and 80%, respectively. [ABSTRACT FROM AUTHOR]