Delignification of Halophyte Atriplex crassifolia by Green Recyclable Deep Eutectic Solvents for Enhanced Production of Biogas

Abstract

Deep eutectic solvents (DESs) have upgraded the practices of valorizing lignocellulosic feedstock by lessening biomass recalcitrance through delignification in precise and economical manner. In this study, the influence of a series of deep eutectic mixtures was evaluated on the halophyte Atriplex crassifolia for achieving elevated biogas production. Initially, the biomass was pretreated via several DESs with varying hydrogen bond donors (HBDs) including carboxylic acids, amine/amide, and polyols/glycols. DES composed of choline chloride (ChCl) and lactic acid (LA) evidenced as the most effective solvent in achieving high lignin removal rates and was further optimized by evaluating the parameters of molar ratio of DES components, solid-to-liquid ratio, and solvent addition. A maximum delignification value of 89.5% was achieved by 15% diluted ChCl: LA (1:2) DES at a biomass loading of 1:15. The solubilization rate of diluted ChCl: LA was also raised up to 38%. FT-IR analysis revealed significant lignin elimination from ChCl: LA pretreated substrates. Moreover, ≥88% of ChCl: LA DES was recovered after up to three pretreatment cycles, retaining ≥85% delignification efficiency. Fresh DES-pretreated Atriplex crassifolia recorded 32.2 mL/g of biogas production yield due to increased cellulosic content. The findings validated Atriplex crassifolia as an efficient feedstock for biogas production and confirmed the affectivity of ChCl: LA pretreatment in eliminating the lignin barrier, ultimately making cellulosic sugars readily biodegradable and highly accessible for anaerobic microorganisms.

Exploring the Potential of Halophyte Biomass for Green Biorefinery Applications

“…Cayenne et al [104] measured the biomethane potential of Salicornia europaea and S. ramosissima to be up to 250 mL CH4/g VS and 300 mL CH4/g VS, respectively. Nawaz et al [105] reported de-lignification with deep eutectic solvent to increase biomass yield from Atriplex crassifolia by making it less recalcitrant and accessible for micro-organisms and measured biogas yield of 32.2 mL/g from the fresh solvent-treated sample. Akinshina et al [106] studied the biogas potential of wild and cultivated halophytes and emphasised their importance for the development of marginal and salt-affected environments in Central Asia, Karelinia caspia being the most promising species with biogas potential of 310.6 mL/g VS.…”