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This study aimed to evaluate the environmental impacts (i.e. global warming potential (GWP) and resource depletion (RD)) of the bio-based levoglucosan production process through fast pyrolysis of cotton straw via life cycle assessment (LCA). An LCA model consisting of feedstock transportation, biomass pretreatment, fast pyrolysis, bio-oil transportation, bio-oil recovery and levoglucosan extraction was developed. Results indicated that GWP and RD of bio-based levoglucosan production were approximately 2 and 32.5 times less than that of the petroleum-based counterpart. Sensitivity analysis showed that the GWP and RD of levoglucosan production were highly sensitive to plant size, hydrochloric acid usage, cooling energy, levoglucosan yield and bio-oil yield. The results of this research could provide a framework for robust decision making at an industrial level, which is useful for the commercial-scale production of levoglucosan.

A rapid method for the quantification of levoglucosan in pyrolysis liquids using high-performance liquid chromatography (HPLC) was developed. The method avoids the tedious and time-consuming sample preparation required by current analytical methods In this method, levoglucosan has better separation of xylose, glucose and fructose so as to avoid interference. The calibration curve coefficient of determination on levoglucosan was >0.990 determined by an evaporative light scattering detector (ELSD). The relative standards for the new method were ≤1.34% at low concentration and ≤2.56% at high concentration. The spiked levoglucosan recovery on the pyrolysis liquid samples were between 96.79 and 99.13%. The research demonstrates that it is possible to obtain excellent accuracy and efficiency using HPLC to quantificate levoglucosan found in fast pyrolysis bio-oils.

The knowledge about adsorption/desorption of cellulase on/from residual lignin is essential for efficient cellulose hydrolysis by recycling the cellulase from residual solid fraction. Herein, the impact of alkali pretreatment at different alkali strength on the adsorption/desorption of enzymatic residual lignins (ERLs) with cellulase was investigated. ERLs pretreated at stronger alkali strength had higher molecular weights and negative zeta potentials, but lower hydrophobicity. The inhibition of ERL to the enzymatic cellulose digestion was mitigated by alkali pretreatment, and inhibition degrees decreased from 21.5 % (with un-pretreated ERL) to 18.9 %, 12.9 %, and 10.8 % with the addition of ERLs treated with 0.5 %, 1.0 %, and 1.5 % (w/w) sodium hydroxide aqueous solution, respectively. The affinity of ERLs with cellulase diminished after alkali pretreatment, and the binding strength decreased from 183.0 to 130.7 mL/g with the alkali strength increasing, retaining more cellulase activities in supernatant. Desorption capacity of bound-cellulase from ERL increased after alkali pretreatment, and the recovery increased from 65.3% to 73.1% with the alkali strength increasing. The cellulase released after desorption exhibited hydrolytic activity, and higher glucose yields were obtained by the bound-cellulase on alkali-pretreated ERLs compared with that of un-pretreated ERL. The results provide references for the development of alkali pretreatment and recycling cellulase from residual lignin for efficient lignocellulosics digestion.

Evaluating the technical feasibility and economic viability of citric acid production at the commercial scale is challenging because it depends on several factors including type of feedstock, process parameters and production routes. In this research, techno-economic and environmental impacts of citric acid production from corn are comparatively evaluated for three scenarios. In the production process Aspergillus niger is used for corn fermentation in a commercial scale of 6400 kg/h citric acid production rate. The scenarios are defined based on application of three recovery methods, including calcium precipitation, solvent extraction, and ion exchange. From three investigated scenarios, the lowest selling price of citric acid is achieved in a scenario using solvent extraction recovery method, followed by the scenario with calcium precipitation recovery method. Sensitivity analysis shows that the minimum selling price of citric acid is highly sensitive to electricity cost, by-product credit, corn supply cost, fermentor cost and wastewater treatment cost. Environmental impacts of citric acid production in three scenarios are assessed using the life cycle assessment approach. Citric acid production with ion exchange recovery method is the most environment-friendly scenario. The results of this research are useful for the development of citric acid production in commercial scale.