A Cleaner Delignification of Urban Leaf Waste Biomass for Bioethanol Production, Optimised by Experimental Design

Abstract

This work is focused on optimising a low-temperature delignification as holocellulose purification pretreatment of Platanus acerifolia leaf waste for second-bioethanol production. Delignification was accomplished by acid-oxidative digestion using green reagents: acetic acid and 30% hydrogen peroxide 1:1. The effect of reaction time (30–90 min), temperature (60–90 °C), and solid loading (5–15 g solid/20 g liquid) on delignification and solid fraction yield were studied. The process parameters were optimised using the Box–Behnken experimental design. The highest attained lignin removal efficiency was larger than 80%. The optimised conditions of delignification, while maximising holocellulose yield, pointed to using the minimum temperature of the examined range. Analysis of variance on the solid fraction yield and the lignin removal suggested a linear model with a negative influence of the temperature on the yield. Furthermore, a negative effect of the solid loading and low effect of temperature and time was found on the degree of delignification. Then the temperature range was extended back to 60 °C, providing 71% holocellulose yield and 70% while improving energy efficiency by working at a lower temperature. Successful lignin removal was confirmed using confocal laser scanning microscopy. As evaluated by scanning electron microscopy, the solid structure presented an increased exposition of the cellulose fibre structure.

Cellulose Enzymatic Saccharification Intensified by Nonionic Surfactants

“…The process was carried out under orbital agitation for 60 min at 90 °C with a solid/liquid relationship of 5g/20 mL, conditions for which around 85% delignification was obtained. 23 The solid yield under these conditions was 47% containing 14% lignin. The pretreated leaves were washed with tap water before being used for saccharification.…”

“…Leaf litter was obtained from the Buenos Aires city cleaning service and belonged to P. acerifolia trees. They were mechanically treated as described in Kildegaard et al Afterward, they were subjected to acid oxidative hydrolysis with HPAC (50% v/v) for delignification. The process was carried out under orbital agitation for 60 min at 90 °C with a solid/liquid relationship of 5g/20 mL, conditions for which around 85% delignification was obtained .…”

“…They were mechanically treated as described in Kildegaard et al Afterward, they were subjected to acid oxidative hydrolysis with HPAC (50% v/v) for delignification. The process was carried out under orbital agitation for 60 min at 90 °C with a solid/liquid relationship of 5g/20 mL, conditions for which around 85% delignification was obtained . The solid yield under these conditions was 47% containing 14% lignin.…”

“…Different precursors with different pretreatment methods were studied, resulting generally in a positive influence attributed to the reduced inhibitory effects of lignin or toxic compounds. In the last years, an acid oxidative pretreatment method, using acetic acid and hydrogen peroxide (HPAC), has been put forward as a successful way of attaining highly delignified LCB under moderate pressure and temperature without the generation of toxic compounds. , Hence, the effect of adding nonionic surfactants to the enzymatic hydrolysis of two LCBs delignified by this method was also tested. In particular, Eucalyptus sawdust, generally used to produce paper and thus with a fiber structure similar to that of filter paper, and Platinum acerifolia leaves, with very different structure, were used.…”

Sodium Hydroxide Hydrothermal Extraction of Lignin from Rice Straw Residue and Fermentation to Biomethane

“…The primary problem is that the majority of the energy is derived from fossil fuels, which are expensive and generate greenhouse gases. Anaerobic digestion is a sustainable process for producing bioenergy from lignocellulosic waste biomass [3,4].…”