Abstract
The aim of the study was to determine the quantitative and qualitative changes taking place in biomass components actively participating in methane fermentation, i.e., in carbohydrates, as a result of chemical pretreatment. Analyses were conducted on agricultural waste (corn stover, also called corn straw, and corncobs) as materials most commonly used in methane fermentation, as well as poplar wood, a material relatively rarely used in biogas production. Pretreatment with the aim of increasing efficiency of methane fermentation was carried out with the use of acid and alkaline solutions of different concentrations. The effect of pretreatment on carbohydrates was analyzed based on the quantitative and qualitative changes in this component. Due to the structural heterogeneity of carbohydrates, their varied reactivity and fermentability were determined in terms of holocellulose, cellulose, and pentosans. The chemical structure of cellulose was also analyzed. It is shown in this study that chemical pretreatment causes transformations of carbohydrate components, which differ quantitatively and qualitatively in the compared raw materials. It was found that the alkaline treatment caused smaller changes in the percentage shares of the carbohydrate biomass components as compared to the acid treatment. Moreover, it was observed that the compared materials differ in terms of quantitative changes in their chemical composition depending on the composition of the raw material prior to pretreatment. In the case of corn waste subjected to the action of 1 and 3% NaOH, the share of pentosans in the biomass increased. It was established that this is a change with a positive effect on fermentation efficiency. The action of acids and alkalis on the biomass led to similar structural changes in cellulose, which are adverse for the fermentation process.
Highlights
Introduction published maps and institutional affilCarbon-neutral fuels from lignocellulosic biomass can play a significant role in mitigating challenges associated with climate change and meeting the planet’s energy and material demands [1,2,3]
Kačík et al [37], in their analyses of the chemical composition in different poplar varieties, recorded a higher holocellulose share compared to the levels presented in this study, i.e., ranging from 80.8 to 84.8%
As a result of the pretreatment using sulfuric acid, the percentage share of holocellulose decreased in the case of poplar wood, while it increased in corn waste
Summary
Introduction published maps and institutional affilCarbon-neutral fuels from lignocellulosic biomass can play a significant role in mitigating challenges associated with climate change and meeting the planet’s energy and material demands [1,2,3]. The cell wall content of compounds resistant to the action of bacteria hinders the energy use of biomass, in fermentation processes taking place under anaerobic conditions [4,5]. Chemical changes of cellulose and lignin during methane fermentation based on miscanthus and sorghum were described by Waliszewska et al [6] and Waliszewska et al [7], respectively. Knowledge regarding the methods as well as the advantages and disadvantages of the pretreatment of biomass in preparation for fermentation is extensive [8]. The literature presents very limited information concerning the analysis of chemical changes taking place during pretreatment, which are significant when predicting fermentation efficiency. The literature presents very limited information concerning the analysis of chemical changes taking place during pretreatment, which are significant when predicting fermentation efficiency. iations.
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