HydroFoam

Etiology and counter strategies for foam formation in biogas plants (HydroFoam)

Topic

In order to integrate biogas production and utilisation into the renewable energies system, the conditions providing demand driven biogas production are crucial. Flexible biogas production is attained by using easy degradable substrates - in the renewable biomass sector these are sugar beet and grain meal. However, previous studies showed that these substrates can destabilize the biogas process under certain circumstances: the digestate may become over-acidified or a strong foam layer may develop. Even today, without widespread flexibilization due to utilisation of easily degradable substrates, numerous plant operators already report foam occurrences. Thus, biogas plant operators face problems that are well known in the waste treatment sector: damaged plant components, clogged gas lines, economic losses due to biogas leakage due to the overpressure in the system, overtime of personnel, cleaning and repair costs, as well as environmental damage due to leakage of methane and digestate.

Goals

The primary goal of the project is to enable the flexibilization of biogas production through a stable biogas production process. To this end, the project team will investigate the process of foam formation during the fermentation of easy-degradable substrates in detail as well as develop practically applicable corrective measures and evaluate their cost-effectiveness. At the end of the project, a guideline with recommendations for stable plant operation during the application of easily degradable substrates will be developed. The project will focus exclusively on agricultural biogas plants.
The core of the project will be experiments with spatially separated hydrolysis process on a pilot plant scale. Using a correlation analysis, the project team will identify the most important factors that play a role in foam formation. Based on these results, measures to prevent or control foam will be developed. These measures will be assessed for their economic efficiency and acceptance by plant operators.

Project tasks of the State Institute

The project team will explore various aspects of the hydrolysis of easy degradable substrates such as sugar beet or cereal meal and investigate the process engineering, physicochemical and microbiological components. In order to tackle the research topic as comprehensively as possible, expertise from different fields will be brought together - foam formation in biotechnological processes (UFZ-UBZ), two-phase fermentation (University of Hohenheim), microbiology of the biogas process (UFZ-UMB), and economic analysis and acceptance research in the field of renewable energies (Nürtingen-Geislingen University of Applied Sciences).

The State Institute will be responsible for the following project tasks:

• Conducting parallel experiments in two-stage and single-stage pilot biogas plant with simultaneous measurement of the foaming potential of the digestate using a bubble test.
• Optimization of the process duration and process parameters of the hydrolysis stage in two-stage system.
• Verification of the results obtained in high-load operation mode.