Abstract
ABSTRACT Overliming is an effective way of neutralizing and reducing the toxicity of the hydrolysates generated from acidic pretreatment of lignocellulosic biomass for ethanol production and others biotechnological products. Overliming generates a solid residue whose inadequate disposal may represent an environmental problem. This work aimed at the chemical characterization of the solid residue generated during the detoxification of the sugarcane bagasse hemicellulosic hydrolysate and evaluation of its behavior in soil. The solid residue was submitted to physicochemical and granulometric analysis and determination of the contents of sugars, metals and toxic compounds (acetic acid, furfural, hydroxymethylfurfural and phenols). The potential of the residue as corrective of soil acidity was determined by analyzing the quality attributes of soil correctives (neutralizing power – NP, relative total neutralizing power – RTNP, Ca and Mg contents and granulometry). The residue was also evaluated for its influence on soil microbial communities and toxicity through bioassays with Lactuca sativa seeds. The residue contributed to the overall improvement of soil chemical attributes. The levels of Ca, Mg, C, OM and CEC were increased, nutrients such as Zn, Fe, Ni, Cr and Mn were detected, and microbial communities were stimulated. Besides, the residue showed no significant values of toxic compounds and no toxicity to L. sativa seeds. The residue was able to reduce the soil pH and to keep it stable throughout the study period. As a higher amount of the residue was necessary to reach pH 7 than limestone, it should be used as an auxiliary corrective of acidity.
Highlights
The growing demand for fuel has led to an increase in the use of liquid fuels, the availability of energy from nonrenewable sources is limited and their exploration, transformation and use can generate serious impacts on the environment
The process of chemical hydrolysis, in which diluted acid is used, is a technique commonly used as a pretreatment to increase the enzymatic accessibility of cellulose and, at the same time, to obtain a hemicellulosic hydrolysate rich in xylose, glucose and arabinose, which can be fermented to ethanol (Camargo et al 2014)
According to Abreu Júnior et al (2001), these cations are related to the values of index (V%) and potential soil acidity
Summary
The growing demand for fuel has led to an increase in the use of liquid fuels, the availability of energy from nonrenewable sources is limited and their exploration, transformation and use can generate serious impacts on the environment. The hemicellulosic fraction has been used in bioprocesses to obtain other products of industrial interest, such as xylitol (Hernandéz-Pérez et al.2016), poly-3-hydroxybutyrate (Dietrich et al 2018) and coproduction of ethanol and butanediol (Sharma et al 2018), in addition to transforming aliphatic alcohols derived from hemicellulose into alkanes for better carbon utilization (Sun et al 2018). These processes contribute to the efficient utilization and valorization of this fraction as biorefinery feedstock (Arora et al 2018)
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