FAQ –

Frequently asked questions

Some microorganisms can form slimy layers, so-called biofilms, on surfaces. In order to adhere to the surface and settle there, they produce sticky substances that they excrete from their cells and release into the environment. They prefer to do this where favorable growth conditions prevail, e.g. in places with a good supply of nutrients or optimum temperatures. In biogas plants, these are preferably pipes or heating lines. As a result, the pipe flow or heat transfer is impeded and technical faults can occur.

We are regularly confronted with this preconception.
The preferred reference is to a project funded by the Agency for Renewable Resources (FNR), which was completed in 2015. The inferred statements are false and have been clearly refuted by us and our competitors. If you want to know more, please read our summary entitled “Myths and facts about the effectiveness of enzymes in biogas plants”, Enzymes in biogas plants”, which you can find in this Biopract blog post.

Fermenters are generally bioreactors, i.e. containers in which microorganisms, sometimes also cells or plants, are kept under optimal living conditions (temperature, nutrient supply, pH value and others). The process is called fermentation. In biogas plants, the fermenter is the heart of the plant. In the fermenter, usually a container made of concrete, which is insulated and heated, substrate such as maize silage, manure and slurry is gradually broken down into biogas (methane and carbon dioxide) over several stages with constant mixing by microorganisms.

Digestate, also often referred to as fermentation product, is the liquid residue that remains after fermentation of substrates in biogas plants to produce biogas. As the microorganisms cannot convert all the organic matter into biogas during fermentation, a residue of plant components that are difficult to break down, such as lignin, and inorganic compounds remains. The digestate contains valuable ingredients in the form of plant-available nutrients and is therefore used on agricultural land as a fertilizer in arable farming. Due to its fertilizer value, digestate is a valuable material for agriculture and is therefore often referred to as a “digestate”.

Gas expulsion describes the escape of biogas from the liquid. The methane and carbon dioxide produced by microorganisms is dissolved in the liquid up to a limit concentration and escapes from the liquid as a gas when the limit concentration is exceeded. The resulting gas bubbles rise in the liquid. The rate of ascent is influenced by the viscosity of the liquid. The lower the viscosity, the greater the rising speed of the gas bubbles.

Microbial biomass refers to the entirety of all microorganisms. In a biogas plant, it is mainly made up of various bacteria and archaea. The microbial biomass is responsible for all process steps in the plant (hydrolysis, acidogenesis, acetogenesis, methanogenesis). It thus ensures that the substrates are converted into biogas. However, part of the substrate energy is also used for the formation of microbial biomass and is not converted into gas.

The term NA-WA-RO stands for renewable raw materials and examples of these are maize, wheat, rye, grass and sugar beet. In an NA-WA-RO plant, these plant substrates are preferably used for biogas production. The conditions of use are regulated by the Renewable Energy Sources Act (EEG).

Our products have been developed for a very broad pH and temperature spectrum. They therefore function reliably under the usual practical conditions.

In order to ensure trouble-free and economical operation of biogas plants, the fermentation medium, i.e. the mixture of the respective substrates in the fermenter, must remain stirrable. This is necessary for successful microbial decomposition and the release of the biogas produced. Vegetable substrates or residues with a high fiber content (straw, manure) and especially silage with a high content of swellable mucilage (GPS: whole-plant cereal silage, grass silage) not only make it more difficult to mix the ferment content, but also increase the viscosity of the fermentation medium. This results in an increased energy requirement of the fermenter agitators and, in extreme cases, can lead to serious accidents. In practice, this is currently seen as the primary justification for the use of substrate-adapted enzyme preparations.

“The inclined channel or inclined rail is a specially built construction that is used in the Biopract laboratory for the inclined channel or inclined rail test. The inclined channel test was developed internally by Biopract employees to test the change in viscosity / flowability when different enzyme products are added.
Up to six samples can slide or flow in parallel on an inclined channel (see photo). For sample preparation, subsamples are taken from untreated and undiluted fermenter contents and incubated for 72 hours at the respective plant operating temperature with the addition of various enzyme preparations. In addition, one of the samples serves as a control and is incubated without the addition of enzymes. After incubation, the flowability is evaluated in the inclined channel test by placing the control and up to five subsamples in the channels and lowering the inclined channel in a controlled manner. The flow behavior of the samples is documented by video, allowing media and treatments to be directly compared visually and measurably. The test results allow an evaluation of the flowability based on running times, volume ratios, the degree of liquefaction and the change in the water retention capacity of the feed material. By adjusting the channel angle and observation time, it was possible to test both slightly liquid and almost solid fermenter contents. Based on the video, our sales staff can evaluate which enzyme has the best effect on the viscosity of the respective fermenter content and make a product recommendation. Read more about the inclined channel test in our article in the Biogas Journal: “Inclined channel test checks enzyme effect.

The formation of layers in the fermenter is an undesirable phenomenon that is not only caused by the inhomogeneity of the substrates, but above all by the specific density and physical properties of the substrate components. Highly fibrous, woody components (straw, grass) that are light and buoyant due to gas inclusions contribute to the formation of floating layers. Floating layers often occur when high proportions of manure are used, if the components that are difficult to ferment are not sufficiently enzymatically digested and the resulting increased segregation of the substrate input leads to floating of the fiber content. Floating layers or floating covers can reach thicknesses of one to several meters and thus considerably restrict the fermenter’s useful volume.

Sink marks are also the result of segregation of the fermentation material and insufficient fermentation. This can be caused by disturbances in the biological process in the fermenter. An adapted trace element supply and, if necessary, suitable enzyme preparations can help here. Excessive contamination can also lead to sedimentation layers and ultimately soil deposits, which can ultimately lead to a complete fermenter clean-up.

A substrate is generally defined as a material on which organisms such as bacteria, microorganisms or plants live. The organisms decompose the substrate into its individual chemical components and use these as nutrients. This biochemical process is naturally catalyzed, i.e. accelerated, by enzymes. The enzymes are excreted by the organisms. The main substrates used in biogas plants, often also referred to as feedstocks, are plant silage such as maize, grass or sugar beet and farm manure such as dung, liquid manure or dry chicken manure. Emzyme additives can accelerate the natural degradation process, especially of fiber-rich substrates, and thus ensure the economic operation of biogas plants.

Viscosity describes the viscosity of a liquid and the flowability decreases with increasing viscosity.
At a high viscosity, the particles in a liquid are more strongly bound together, which reduces the mobility of the liquid.
Samples from a biogas plant are usually structurally viscous, whereby the viscosity is not a constant, but changes with the shear gradient generated by the agitator.

When selecting the right enzyme product, it depends on the substrates that you use in your system and what you want to achieve with the enzyme. In general, our enzymes are used to prevent and eliminate process faults (e.g. floating layers, increased viscosity, foaming), to maintain stable plant operation and to optimize the efficiency of your plant. Details on our various enzyme products and their areas of application can be found on our website under the Products tab.
Our employees will be happy to provide you with more detailed application recommendations:

Your contact person
Torsten Unmack
+49 (0)30 6670 2058
t.unmack@biopract-abt.de

No, there is no practical evidence of a decrease in the effectiveness of biocatalysts. If you stop using the enzyme, gas formation will return to the normal level before the enzyme is used.