2.3.3 Balloon-Type Digester

Left Cross-Section View of Balloon-Type Digesters (FAO, 1996), Right: Installed Balloon Type Digester (Energypedia, 2010)

A balloon biogas digester is a weather-resistant plastic or rubber bag with a long shape. It serves the dual purpose of functioning as a digester and a biogas holder, storing the gas in the balloon’s upper portion. The inlet and outlet connections are directly attached to the balloon’s surface. This digester effectively prevents short-circuiting, allowing the digestate to flow through the reactor in a plug-flow manner.

To increase gas pressure, weight must be placed on the top of the balloon. Notably, balloon-type biogas solution offers a cost-effective approach and is suitable for areas with high groundwater tables or rocky ground because of shallow below-ground installation. To enhance longevity and reduce vulnerability to mechanical damage, it is advisable to consider utilising UV-resistant and reinforced plastic balloons. These reinforced balloons have the potential to last up to 10 years, providing a more durable and reliable solution.

The table highlights the pros and cons of balloon-type digesters.

Easy to understand and operateRelative short lifespan
Prefabricated and low-costSusceptibility to mechanical damage
Increased digester temperature in a warm climateSusceptibility to temperature fluctuations
Easy to transport and installSpecial knowledge and expertise might be required to repair a balloon digester
Uncomplicated emptying and maintenanceLow gas pressure requires extra weight or a gas pump
Suitable for areas with high groundwater tables and/or rocky groundRequires space
The system is moveable, especially suitable in the context where permanent construction is not permitted 
Adopted from: (Vögeli Y., 2014), (GTZ )
Pros & Cons of Balloon Type Digesters

For further information, please click on the Materials tab at the top of the page.

Further reading:

  • Low-Cost Polyethylene Tube Digesters (Link)