Lignin, sugar, and furan production of industrial hemp biomass via an integrated process

Abstract

Traditional pretreatment of lignocellulosic biomass is often accompanied by washing and disposal of wastewater, which leads to overuse of water and loss of by-products. The objectives of this study were to validate the potential of an acid-base integrated process for simultaneous sugars, furans, and lignin production without washing and wastewater discarding. The difference in conversion performance among different biomass resources was also demonstrated. Parallel acetic acid (HOAc, pH = 2.25) and sodium hydroxide (NaOH, pH = 13.46) pretreatments followed by solid and liquid integration were applied to four genotypes of industrial hemp (Cannabis sativa L.) biomass that were harvested from two planting locations (Haysville and Manhattan, KS). Results showed that genotype, planting location, and their interaction had notable influences on biomass composition and its conversion to bioproducts but exhibited different trends. Glucan content of biomass from Haysville, ranging from 47.29 to 50.05%, were higher than those of 42.49–48.38 % from Manhattan with the lowest being Vega (Manhattan) and the highest being Hlukouskii (Haysville). Xylan and lignin contents in all the hemp genotypes were 11.70–13.88 % and 10.45–15.14 %, respectively. The integration process effectively rendered the pH of the integrated filtrate and slurry to approximately 4.80. The highest lignin recovery of 73.13 g/kg biomass was achieved by Rigel from Manhattan. Fourier transform infrared spectroscopy (FTIR) characterization showed that only lignin derived from Vega (Haysville) and Anka (Manhattan) was comparable to the commercial alkali lignin. Retaining monosaccharides (2.24–3.81 g/L) enhanced sugar concentrations (glucose: 40.40–45.71 g/L; xylose: 7.09–8.88 g/L) and conversion efficiencies (glucose: 71.19–77.71 %; xylose: 45.42–52.03 %). Besides, furans including 0.79–1.25 g/L of hydroxymethylfurfural (HMF) and 0.99–1.59 g/L of furfural coupling with 1.96–2.95 % and 10.00–14.65 % conversion efficiencies, respectively, were obtained in the final hydrolysate. Biomass from Haysville produced relatively higher glucose concentrations than those from Manhattan. Based on mass balance, the most productive genotype was Rigel. This study offers essential information to reduce water and chemical overconsumption and to understand the effects of genotype and planting location on biomass valorization.