Digester Degritting

Maximising Biogas Production: The Importance of Anaerobic Digestion Plant Digester Cleaning


Anaerobic digestion plants play a crucial role in biogas production. However, even with a well-designed and efficient mixing system installed, issues like sediment buildup and crust formation can impede performance over time. This blog explores the significance of digester cleaning in maintaining optimal operations.

What is Anaerobic Digestion Plant Digester Cleaning?

The accumulation of grit, silt, and sand in biogas tanks over time can significantly impact their efficiency. These sediments compact and solidify, affecting the tank's performance by requiring increased feeding for sustained biogas production. This reduced retention time within the tank directly impacts biogas yield, potentially affecting the operational capacity of systems like Combined Heat and Power (CHP) or upgraders.

Another common issue arises when materials form a layer at the tank's surface, leading to crust formation. The development of such crusts often stems from a reduction in the tank's hydraulic retention time due to silt build-up. Fibrous solids that can't be efficiently digested tend to accumulate, forming a disruptive layer on the tank's surface. This accumulation not only affects the tank's overall capacity due to silt at the base but also directly impacts mixing efficiency, reducing gas production and increasing the frequency of tank maintenance and cleaning.

Degritting / digester cleaning is a crucial process that eliminates unwanted debris from tanks, thereby restoring digesters to their optimal biogas output levels. The initial step involves draining the tank to assess the volume of solids remaining. Depending on various factors such as the material, gas lines, digester operating clusters, and tank access points, specific methods for debris removal are chosen. These methods often include the use of mechanical tools like hydraulic clamshells, industrial vacuum equipment, separators, and specialised machinery.

Once the tank is completely emptied, it presents a great opportunity to conduct comprehensive inspections for any required remedial work. These inspections involve thorough checks on internal equipment, such as mixer inspections, structural integrity tests for the tank, examinations of metal infrastructure, assessments of roof support structures, inspections of desulphurization nets, membrane evaluations, and assessments of tank linings. Planning necessary replacements during operational downtime is crucial to enhance process efficiency.

Pros and Cons of Digester Cleaning


  • Maintenance Efficiency – Longevity of components due to reduced sediment
  • Increased Gas production – Increasing the hydraulic retention time will provide more time to fully digest the feedstocks, resulting in releasing the full biomethane potential of the feedstocks introduced into the digester tank.
  • Improved Mixer efficiency – Minimised solid accumulation prevents surface crust formation.



  • Cost Considerations: Expense associated with cleaning and resulting downtime.
  • Downtime Impact: Scheduled cleaning disrupts regular plant operations.

What to expect from Circular Renewables

For successful digester cleaning, Circular Renewables offers specialised expertise in challenging environments.  Understanding each phase of the project is key to planning, our trained team ensures a thorough understanding of each project stage, adherence to safety regulations, and minimum downtime. We source necessary parts and equipment, resolving any issues promptly to get your plant back to full operation efficiently.  Every project undertaken comes with a comprehensive project plan and all Health & Safety documentation underscored by our CHAS accreditation, ensuring compliance with industry’s regulations.  Depending on the plant design, we may effectively take a digester offline while maintaining production efficiency.


Prioritising safety and efficiency, Circular Renewables guarantees effective digester cleaning, ensuring enhanced biogas production while minimising operational disruptions.

Work With
Circular Renewables

Call us 01405 947123