Upflow anaerobic solid-state (UASS) digestion of horse manure: Thermophilic vs. mesophilic performance.

This research article investigates the potential to use horse manure-based straw as an efficient source of energy production through a technique called upflow anaerobic solid-state (UASS) digestion. It is found that thermophilic conditions have a significantly higher efficiency compared to mesophilic conditions.

Objective of the Research

• The primary objective of this study is to assess the efficiency of the UASS digestion of horse manure-based straw under thermophilic and mesophilic conditions. The researchers aimed to explore the potential of using complex lignocellulosic wastes like straw-based manures for energy production.

Methodology of the Research

• The team used the UASS process to analyze the digestion of horse manure under both thermophilic and mesophilic conditions.
• The organic loading rate was increased from 2.5 to 5.5gvsL−1d−1 to observe any changes in methane production rate and yield.
• A single-stage and two-stage process design was used to observe if there were any significant performance differences in the UASS digestion.
• Additional biochemical methane potential (BMP) tests were carried out with different types of horse manure and four different types of bedding materials.

Findings of the Research

• The study found that increasing the organic loading rate enhanced the average methane production rate.
• Performing the process under thermophilic conditions (higher temperatures) significantly increased the efficiency, showing around 60% increase in both methane yield and methane production rate compared to mesophilic conditions (moderate temperatures).
• The single-stage and two-stage process design did not show any significant performance difference.
• The BMP tests revealed that wheat straw rendered the highest biochemical methane potential amongst the bedding materials tested.

Significance of the Findings

• The results highlight the potential of using horse manure-based straw for efficient energy recovery through the UASS process. Given the global interest in the energetic use of complex lignocellulosic wastes, these findings carry considerable importance.
• The increased efficiency under thermophilic conditions suggests that adopting such conditions could optimize energy recovery from straw-based manures.
• The discovery that wheat straw has the highest BMP indicates it could be the most suitable bedding material for harnessing energy in this way.