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The yield of green energy from solid-state anaerobic co-digestion (SSAD) has recently been enhanced by incorporating innovative pretreatment methods and nanoparticles. However, the environmental consequences of employing new processes have not been fully examined. In this study, the environmental impacts of three high-methane-yielding scenarios including SSAD of corn stover blended with dairy manure (DM) denoted as (SYM1), calcium hydroxide-pretreated corn stover (CpCS) blended with DM (SYM2), and the CpCS blended with DM and nanoparticles (SYM3) were assessed and compared the baselines of solid-state and semi-solid-state anaerobic digestion using a life cycle assessment (LCA) approach. The approach investigated the best management practices that would result in high methane yield and low environmental impact. Results of the life cycle assessment indicate the inclusion of calcium hydroxide and nanoparticle has minimal negative environmental impact. There was an environmental gain in GWP when corn stover was co-digestion with DM (SYM1) relative to DM mono-digestions (baselines) and the carbon footprint of SYM1 was less by more than 85% compared to SYM2 and SYM3. However, the large volume of untreated corn stover harnessed for SYM1 scenario resulted in over 75% fossil fuel depletion compared to the other scenarios. The surplus methane from the SYM3 (at least twofold of other scenarios and baselines) in conjunction with being the least with the environmental implication makes the scenario the most attractive option for on-farm practice capable of harnessing the growing organic waste volume. These outcomes can guide trade-off between pretreatment and nanoparticle application to reduce solid-state anaerobic digestion's negative environmental impact. [ABSTRACT FROM AUTHOR]

Enzymatic hydrolysis at high solids loading has the potential to reduce both capital and operational expenditures. Here, pretreatment of rice straw (PRS) with dilute acid was carried out at a pilot scale (250 kg per day) at 162°C for 10 min and 0.35% acid concentration, followed by enzymatic hydrolysis at different total solids loadings. It showed that although the total sugar concentration increased from 48 to 132 g/l, glucan conversion reduced by 27% (84–66.2%) with increasing solids from 5 to 20% in batch mode. Therefore, two different fed-batch approaches were evaluated to improve the glucan conversion by the sequential addition of a substrate and/or enzyme. At 20% solid loadings and a 3 filter paper units/g enzyme dosage, the highest glucan conversion obtained was 66% after 30 h of hydrolysis in batch mode. However, in an optimized fed-batch approach, the glucan yield was improved to 70% by simply dividing the substrate feeding into three batches, that is, 50% at 0 h, 25% each after 4 h, and 8 h of hydrolysis reaction. The addition of surfactant (Ecosurf E6) further improved the conversion to 72% after 30 h. The role of critical factors, that is, inhibitors, enzyme–lignin binding, and viscosity, was investigated during the course of hydrolysis in the batch and fed-batch approaches. This study suggests a sustainable approach for improved hydrolysis at high solids loadings by fine-tuning a simple process.

Highlights • Highly effective DESs took only 6 min at 120 °C to remove 79% xylan and 82% lignin. • Ternary DESs were effective for biomass fractionation at 35% solid loading. • Rapid deconstruction led to concentrated sugar hydrolysate with 78.4% glucose yield. • Low enzyme loading of 5 mg protein/solid was used for hydrolysis at 20% solids. • Lignin properties were affected by constitutes of ternary DESs. Abstract Ternary deep eutectic solvents (DESs) were developed to enable rapid and high-solid biomass pretreatment as well as concentrated sugar hydrolysate production. Six ternary DESs constituted choline chloride (ChCl) or guanidine hydrochloride (GH) as a hydrogen bond acceptor (HBA), ethylene glycol (EG) or propylene glycol (PG) or glycerin (GLY) as a polyol-based hydrogen bond donor (HBD), and p -toluenesulfonic acid (PTSA) as an acidic HBD. GH-EG-PTSA was the most effective, evidenced by 79% xylan and 82% lignin removal in only 6 min at 120 °C and 10 wt% solid loading. Even at 35 wt% solid loading, both GH-EG-PTSA and ChCl-EG-PTSA still removed more than 60% xylan and lignin in 30 min. Using a 20% solid loading and a low enzyme loading of 5 mg protein/g solid, 128 g/L glucose and 20 g/L xylose was obtained, with a glucose yield of 78.4%. Overall, this study demonstrated novel and high-performance ternary DESs for effective lignocellulose deconstruction. [ABSTRACT FROM AUTHOR]