Pretreatment of lignocelluloses for enhanced biogas production: A review on influencing mechanisms and the importance of microbial diversity

Safoora Mirmohamadsadeghi, Keikhosro Karimi, Reza Azarbaijani, Laleh Parsa Yeganeh, Irini Angelidaki, Abdul Sattar Nizami, Rajeev Bhat, Kavya Dashora, Virendra Kumar Vijay, Mortaza Aghbashlo, Vijai Kumar Gupta*, Meisam Tabatabaei

*Corresponding author for this work

Research output: Contribution to journalReview articlepeer-review

Abstract

As one of the most efficient methods for waste management and sustainable energy production, anaerobic digestion (AD) countenances difficulties in the hydrolysis of lignocelluloses biomass. Different pretreatment methods have been applied to make lignocelluloses readily biodegradable by microorganisms. These pretreatments can affect biogas yield by different mechanisms at molecular scale, including changes in chemical composition, cellulose crystallinity, degree of polymerization, enzyme adsorption/desorption, nutrient accessibility, deacetylation, and through the formation of inhibitors. The present article aims at critically reviewing the reported molecular mechanisms affecting biogas yield from lignocelluloses via different types of pretreatments. Then, a new hypothesis concerning the impact of pretreatment on the microbial community developed (throughout the AD process from an identical inoculum) was also put forth and was experimentally examined through a case study. Four different leading pretreatments, including sulfuric acid, sodium hydroxide, aqueous ammonia, and sodium carbonate, were performed on rice straw as model lignocellulosic feedstock. The results obtained revealed that the choice of pretreatment method also plays a pivotally positive or negative role on biogas yield obtained from lignocelluloses through alteration of the microbial community involved in the AD. Considerable changes were observed in the archaeal and bacterial communities developed in response to the pretreatment used. Sodium hydroxide, with the highest methane yield (338 mL/g volatile solid), led to a partial switch from acetoclastic to the hydrogenotrophic methane production pathway. The findings reported herein undermine the default hypothesis accepted by thousands of previously published papers, which is changes in substrate characteristics by pretreatments are the only mechanisms affecting biogas yield. Moreover, the results obtained could assist with the development of more efficient biogas production systems at industrial scale by offering more in-depth understanding of the interactions between microbial community structure, and process parameters and performance.

Original languageEnglish
Article number110173
JournalRenewable and Sustainable Energy Reviews
Volume135
Early online date11 Aug 2020
DOIs
Publication statusFirst published - 11 Aug 2020
Externally publishedYes

Keywords

  • Anaerobic digestion
  • Influencing mechanism
  • Lignocellulosic substrate
  • Methane
  • Microbial community
  • Pretreatment

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