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Case study: Resolve foam formation in biogas plant by enzyme application


Biogas AG “Vorharz” eG Silstedt
Plant power capacity: 780 kW
Date: June/2016
Plant engineer: Various
Substrate: Corn silage, solid cow dung

Application design
Biogas AG “Vorharz” eG had a major foam formation problem in fermenters, secondary fermenters and the fermentation residue store. Some critical lines were blocked and had to be flushed clear. It was necessary to use huge quantities of vegetable oil in order to prevent major damage or a disaster. These issues were resolved by the use of a special enzyme.

The results
- It was possible to contain and stem the occurrence of foam by the addition of a special enzyme
- The use of massive quantities of vegetable oil could be replaced by the cost-effective addition of the enzyme
- Gas production has increased by around 2% on a monthly average
- It was possible to save 0.5 to 1 ton of corn silage as a substrate over the long-term

The benefits of a special enzyme
- No longer necessary to use large volumes of oil
- Less agitation
- Clear gas lines
- Higher gas yields
- Improved process stability

The customer’s opinion
This special enzyme guarantees the constant and continuous operation of the biogas plant - and it was even possible to reduce the use of corn silage.


Power capacity: 780 kW
Plant engineer: Various
Number of reactors: 3
1. Fermenter (2,150m³)
2. Fermenter (2,150m³)
3. Secondary fermenter (3,400m³)
Process type: Continuous dry fermentation
Digester load (fermenter): 3.7 kg oTS/m³ x day
Dwell time (fermenter): 35 days
Temperature: Mesophilic
Substrate: Corn silage, solid cow dung, process water

Process and application details
Build-up of the required enzyme concentration in the fermenter over a period of 7 days, then addition of a standard dose of special enzyme. Significantly greater flexibility of plant operation. The effects could be visually observed and technically quantified immediately.

After a successful trial phase, the biogas plant is continuing to use the enzyme preparation in its ongoing operation. It was possible to replace the huge volumes of vegetable oil by the targeted use of the specific enzyme product. At an application rate of approximately 1.5 kg of enzyme product, a more cost-effective and efficient solution to the foam problem could be found.


Figure 1 - No Enzymes


Figure 2 - Day 1 (enzyme application initiated 16 hours prior to photo)


Figure 3 - Day 4

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