Category: Biogas Chemistry • Read Time: 8 min
Introduction
Landfill gas (LFG) generation is one of the most important processes in waste management. Understanding the chemistry behind methane formation is essential for designing efficient gas extraction systems, forecasting emissions, and reducing environmental impact.
Municipal solid waste decomposes through a predictable four-phase anaerobic decomposition process, each driven by unique microbial communities.
Hydrolysis (Stage 1)
This initial phase breaks down complex organic materials such as carbohydrates, proteins, and lipids.
Key reactions:
Polymers → amino acids, fatty acids, simple sugars
Enzymes released by hydrolytic bacteria begin dissolution of solids
Importance: Hydrolysis determines how quickly waste becomes bioavailable for microorganisms.
2. Acidogenesis (Stage 2)
Fermentative bacteria convert hydrolysis products into:
Volatile fatty acids (VFAs)
Alcohols
Hydrogen
CO₂
Ammonia
This phase lowers pH and creates acidic conditions.
Acetogenesis (Stage 3)
Acetogenic bacteria transform VFAs into acetate, hydrogen, and carbon dioxide — the primary substrates for methane-forming microorganisms.
Environmental factors that influence this stage:
Temperature
pH
Moisture
Methanogenesis (Stage 4)
Methanogenic archaea convert acetate, hydrogen, and CO₂ into methane (CH₄) and carbon dioxide (CO₂).
Key pathways:
Acetoclastic methanogenesis
Hydrogenotrophic methanogenesis
Understanding these pathways allows engineers to optimize gas extraction efficiency and minimize fugitive emissions.
Why This Matters
A deep understanding of LFG chemistry helps waste management operators:
Predict gas production curves
Design effective well-field systems
Improve energy recovery potential
