When it comes to anaerobic digestion plants, the significance of biogas holders cannot be overstated. These essential components, whether fixed, floating, or inflatable, play a pivotal role in maintaining optimal operation. In this article, we delve into the functionality and evolution of biogas holders, with a focus on the widely adopted flexible inflatable membrane covers, given their prevalence in the industry.

Let's look at the different types of covers and their significance:

  1. Fixed Covers: Typically found in older digester designs used in Wastewater Treatment (Sewage) Works, fixed covers necessitate a separate biogas holder. This holder allows gas to flow freely into the gas-holding vessel as pressure in the digester tank rises.
  2. Floating Covers: These covers adjust according to gas and sludge volume, utilising their weight to provide gas pressure. Equipped with a perimeter-rim skirt, they create a seal for gas-to-air, enabling biogas storage. Similar to natural-gas gasometers, their operation relies on the liquid within the tank to seal the perimeter.
  3. Flexible Inflatable Membrane Covers: Widely used in commercial anaerobic digestion plants, these double-skinned covers offer insulation from heat loss. By adjusting air pressure between the two skins, they regulate the amount of biogas stored, balancing demand with production. An air pressure control system maintains pressure balance between the inner and outer membranes.

The History of Biogas Holders:

Traditionally, steel and concrete were the primary materials used for constructing gas storage vessels. These materials were employed in various gas holder designs, such as steel floating dome roofs and bell-over-water types. However, as biogas technology advanced, the need for reliable, low-maintenance gas storage became apparent.

The emergence of double membrane biogas holders in the 1980s revolutionised the industry. Utilising fabrics developed in the architectural sector, these membranes offered superior gas impermeability and durability. The development of dense PVC coatings further enhanced their performance, making them resistant to corrosion and requiring minimal maintenance.

Lifespan and Replacement of Double Membranes

The lifespan of a double membrane system typically ranges from 10 to 20 years, dependent upon various factors including material quality, maintenance protocols, and environmental conditions.  Regular inspections, adherence to manufacturer guidelines, and timely repairs are imperative for prolonging the system's longevity.

Determining when to replace a double membrane involves vigilant inspection and assessment.  Visual checks for damage, monitoring gas leakage, odour detection, pressure testing, consideration of age and usage, and adherence to manufacturer recommendations are all critical factors.  When in doubt, consulting with experts ensures informed decision-making for safety and efficiency.

What to Expect from Circular Renewables

When it comes to biogas roof repair and replacement, Circular Renewables stands out with its specialized expertise and high-quality membranes. Crafted to precise measurements, our membranes guarantee a seamless installation process without any complications. Our dedicated engineers conduct thorough site visits to ensure accurate measurements are taken, making your ordering experience hassle-free. Partnering with top suppliers in Europe, we deliver solutions that combine functionality with design innovation.

Every project is supported by a comprehensive plan, full project management and Health & Safety documentation, certified by our CHAS accreditation, ensuring regulatory compliance.


In conclusion, flexible biogas holders represent the epitome of efficency and reliability in anaerobic digestion plants.  With a keen focus on evolution, durability and meticulous maintenance, these holders pave the way for sustainable biogas production.  Partnering with Circular Renewables ensures a seamless journey towards optimised biogas solutions, fortified by expertise, quality and commitment to excellence.

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