Abstract
Fungi can run feedstock pretreatment to improve the hydrolysis and utilization of recalcitrant lignocellulose-rich biomass during anaerobic digestion (AD). In this study, three fungal strains (Coprinopsis cinerea MUT 6385, Cyclocybe aegerita MUT 5639, Cephalotrichum stemonitis MUT 6326) were inoculated in the non-sterile solid fraction of digestate, with the aim to further (re)use it as a feedstock for AD. The application of fungal pretreatments induced changes in the plant cell wall polymers, and different profiles were observed among strains. Significant increases (p < 0.05) in the cumulative biogas and methane yields with respect to the untreated control were observed. The most effective pretreatment was carried out for 20 days with C. stemonitis, causing the highest hemicellulose, lignin, and cellulose reduction (59.3%, 9.6%, and 8.2%, respectively); the cumulative biogas and methane production showed a 182% and 214% increase, respectively, compared to the untreated control. The increase in AD yields was ascribable both to the addition of fungal biomass, which acted as an organic feedstock, and to the lignocellulose transformation due to fungal activity during pretreatments. The developed technologies have the potential to enhance the anaerobic degradability of solid digestate and untap its biogas potential for a further digestion step, thus allowing an improvement in the environmental and economic sustainability of the AD process and the better management of its by-products.
Highlights
The awareness about the environmental damage caused by the massive exploitation of fossil fuels has led to a green revolution in energy production models in favor of environmentally friendly, cost-effective, and sustainable energy systems [1]
This study aims to evaluate the role of pretreatments in order to transform lignocellulose and enhance the methane recovery
The total solids (TS) concentration significantly (p < 0.05) decreased 23.8%, 25.4%, and 28.5% in samples pretreated with C. aegerita, C. stemonitis, and C. cinerea, respectively
Summary
The awareness about the environmental damage caused by the massive exploitation of fossil fuels has led to a green revolution in energy production models in favor of environmentally friendly, cost-effective, and sustainable energy systems [1]. AD is a flexible technology since, theoretically, any organic substrate could be exploited as a feedstock [3]. It is a captivating technology for the treatment of a wide range of organic wastes [2]. The use of some feedstocks is often limited due to the process microbiology, plant technology, country legislation, and biomass properties [3]. Agricultural biogas plants (ABPs) that are more widely diffused in Europe operate in co-digestion with a mixture of zootechnical effluent, energy crops, and agriculture-related residues [2,3]. Alternative sustainable lignocellulosic biomasses, such as agro-industrial wastes and by-products (corn stover, wheat straw, and rice straw), may contribute to improve the overall sustainability of AD [6]
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