Dissertation/Thesis Abstract

Pretreatment to Enhance the Anaerobic Digestion of Recalcitrant Lignocellulosic Biomass Materials
by khan, Muhammad Usman, Ph.D., Washington State University, 2020, 198; 28027593
Abstract (Summary)

Energy consumption using fossil fuels creates environmental pollution including greenhouse gasses promoting climate changes throughout the world. To levitate these problems, renewable energy sources have been promoted as an alternative. Lignocellulose is one of the most abundant and renewable biomass resources on the earth which makes it an ideal feedstock for production of biofuels particularly biogas. However, AD of the lignocellulosic materials is also limited due to the crystallinity of cellulose and embedded connections to lignin within the cellulose and hemicellulose polymer. The primary hypothesis of this study is to manipulate different types of pretreatments to decrease the recalcitrance, improve the hydrolysis and biogas production from lignocellulosic materials. Wet explosion Pretreatment, Alkaline thermal pretreatment, Mono and combined alkali pretreatment were tested for AD of lignocellulosic materials.

The results revealed that increased severity of wet explosion pretreatment with base addition (2%) increased the biogas yield and lignin conversion (56%) during AD with demethoxylation up to 49%. The lignin samples having the highest NaOH concentration in addition to oxygen resulted in highest methane yield during anaerobic digestion.

The alkaline thermal pretreatment was used for AD of residual manure fibers after AD. The results of study showed that degradation of manure fibers was improved ca. 43.6% as a result of alkaline thermal pretreatment with 3% w/w NaOH added. Methane yield improved by 143.5 and 180.2% under mesophilic and thermophilic conditions, respectively. Compositional analysis of effluent after AD showed that 57.3% of cellulose, 70.1% of hemicellulose, 39.4% of acid soluble and 19.4% of acid insoluble lignin was converted to methane under thermophilic conditions while under mesophilic conditions, 50.8% of the cellulose, 59.5% of the hemicellulose, 39.9% of acid soluble and 21.7% of acid insoluble lignin was converted to methane. The lime (CaO), NaOH and CaO+NaOH pretreatment was tested for AD of digested manure fibers. The methane yield improved by 115.7, 127.1 and 148.7% by CaO, NaOH and NaOH + CaO pretreatment respectively. The VS degradation was found to be 40.6, 42.6 and 46.4% by CaO, NaOH and NaOH + CaO pretreatment respectively.

Indexing (document details)
Advisor: Ahring, Birgitte K.
Commitee: Garcia-Perez, Manuel, Lei, Hanwu
School: Washington State University
Department: Biological and Agricultural Engineering
School Location: United States -- Washington
Source: DAI-A 82/5(E), Dissertation Abstracts International
Subjects: Agricultural engineering, Materials science, Sustainability, Climate Change, Alternative Energy, Environmental management
Keywords: Anaerobic digestion, Cellulose, Hemicellulose, Lignin, Lignocellulosic materials, Pretreatment, Energy consumption, Environmental pollution, Greenhouse gases, Renewable energy, Biomass, Fossil fuels
Publication Number: 28027593
ISBN: 9798698542308
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