Rheological evolution of straw-cattle manure (SCM) treated by dry anaerobic digestion in batch and in continuous...

Area of Science:

• Biomass rheology
• Anaerobic digestion engineering
• Sustainable waste management

Background:

• Understanding biomass rheological evolution during dry anaerobic digestion (D-AD) is crucial for reactor design, modeling, and operation.
• Straw-cattle manure (SCM) rheology was investigated to assess its behavior in D-AD processes.

Purpose of the Study:

• To measure the evolution of yield stress, cohesion, and friction angle of SCM during D-AD.
• To compare rheological changes in different D-AD reactor types (batch leach-bed and plug flow).
• To establish the relationship between biomass degradation and rheological properties.

Main Methods:

• Rheological analysis using slump tests and shear-box tests.
• Monitoring solid degradation via volatile solids (VS) content, fiber analysis, and biochemical methane potential (BMP).
• Utilizing two reactor types: 60 L batch leach-bed reactors (LBR) and a 500 L plug flow reactor (PFR).

Main Results:

• VS content decreased by approximately 10-11% over 30 days in both PFR and LBR, driven by hemicellulose and cellulose consumption.
• D-AD induced a significant reduction in yield stress (24-28% over 30 days) in both reactor types.
• Cohesion and friction angle showed similar evolutionary patterns in both LBR and PFR samples.

Conclusions:

• Dry anaerobic digestion significantly alters the rheological properties of straw-cattle manure.
• The degree of solid biomass degradation is closely linked to changes in its rheological characteristics.
• Findings provide valuable insights for optimizing D-AD reactor performance and design.