GeoHumat Plus ®


How GeoHumat Plus ® works in biogas plants and digestates

By Matthias Neumann MSc

Gelistet in der Betriebsmittelliste für den ökologischen Landbau in Deutschland.

What is GeoHumat Plus ® and how does it work in biogas plant digesters?

The active constituents of GeoHumat Plus ® are formed from a unique mixture of humic substances.

Some of the humic substances in our additive have very different molecular weights, which usually means they are of different sizes. The molecular weight and microstructure of the molecules generally determine whether and how humic substances interact with their environment.

The characteristic mixture of different humic substances confers particularly high bioactivity on GeoHumat Plus ®. This activity develops from the moment they are placed in the digester.

Here these humic substances (mainly humic acids) form special compounds with the nutrients in the substrate. The most important types of compounds are chelate complexes.

Using a process called chelatisation, humic substances envelop e.g. trace elements and thus protect them from undesirable secondary reactions that could reduce the availability of nutritional elements for the useful microorganisms in the digester. Despite these strong chemical bonds, the nutrients remain available for micro-biological processes. High bioavailability of nutritional elements increases the enzyme activity of living organisms and leads, in the case of methanogenic archaea in the digester, to increased gas production and better conversion of the substrate. Microorganisms can also use the humic acids themselves as electron acceptors for their metabolism.

Extensive scientific analyses have shown that fluctuations in the efficiency of biogas plants can now be traced back to an imbalance of various nutritional elements much more often than was previously thought. A high concentration of nutrients, even if they are trace elements, can interfere with microbial degradation of the biomass. Humic substances can counteract these imbalances through this process of chelatisation and reduce the reactivity of the chelatised elements. In this way GeoHumat Plus ® not only reduces the harmfulness of excessive concentrations of certain trace elements but also the harmful effects of primary toxic heavy metals, which are not used by the target organisms as coenzymes. GeoHumat Plus® acts as a buffer in the digester, compensating for fluctuations in the milieu.

A stable milieu is one of the most important pre-requirements for better process stability and consistently high biogas production and substrate utilisation. Humic substances can benefit a multitude of microorganisms, but here the main focus is on the very special and extremely desirable effects they help to create in the digester: the interactions between humic substances and methanogenic archaea (methane-producing organisms). Taking a closer look at the natural living environments of methanogenic archaea, it can be seen that humic substances are almost always present in these habitats. It stands to reason that these impressive living organisms are not only able to exist in high concentrations of humic substances, but have also developed strategies over the course of evolution to use humic substances catalytically to the benefit of their metabolism.

The effects of GeoHumat Plus ® on the digestate

Some groups of organisms certainly have the ability to metabolise, i.e. break down, humic substances. However, their stability can still be considered very high. One of the reasons for this, is that humic substances are already breakdown products, having arisen from the incomplete mineralisation of complex carbon compounds. Due to this stability, humic substances from GeoHumat Plus ® are found in the digestate and are then ideally spread with the many other growth-promoting substances in the digestate as fertiliser on agricultural land.

At this point, however, it should be emphasised that direct treatment of the digestate with our product GeoHumat ® develops the effects described below with greater intensity due to a higher dosage and different composition.

The effects humic substances produce in soils are very similar to those in the aqueous milieu of the digester. They form chelate complexes in the soil, thus increasing the availability of nutrients such as trace elements. Some nutrients often form compounds particularly quickly in agricultural soils and are therefore difficult to use by plants. Phosphorus is one of these substances. Much of the phosphates in soils is in the form of aluminium, calcium or magnesium phosphate, which makes them unavailable in their immediate state to plants. Because humic substances form complexes with aluminium, calcium and magnesium ions, phosphorus has difficulty reacting with these ions, which means phosphorus is present in the form of phosphates that can be taken up more easily by plants.

Furthermore, this complex-forming process by humic substances reduces the harmfulness of toxic heavy metals. Other harmful substances, such as aluminium ions found particularly in acid soils, are chelatised by humic substances. Plant species that are exposed to high aluminium ion concentrations in nature create much of their own humic or other substances with a similar function so as to protect themselves from the growth-inhibiting effects of aluminium. Unfortunately, the crops we grow are not capable of doing this. GeoHumat Plus offers a natural way to reduce the potential damaging effects on plant growth from aluminium and other inhibitors.

Humic substances in the soil allow it to retain more moisture. This happens through their numerous polar, i.e. hydrophilic functional groups, which favour the formation of a hydration shell around the macromolecules, some of which are quite large. Many years of research have also shown lower nitrate contents in plants that grow on soils treated with humic substances. Two other positive aspects are the higher quality of the harvested plants and reduced soil depletion. The ability of living organisms to resist various forms of stress can be clearly improved if they are exposed at the same time to humic substances. It is not always clear that the higher stress resistance can be traced back exclusively to improved bioavailability of nutrients and the buffer function in high concentrations of harmful substances. Some humic substances in GeoHumat Plus ® cannot behave as effective complex-formers because of their small size and coordination sites. Instead, they interact among other things directly with membrane structures of living organisms, for which this represents a form of stress. At this point, it must be said that this stress is only slight. For humic substances to act as true inhibitors it requires unnaturally high concentrations. The affected organisms react to the stress by high regulation of certain genes, the translation products of which can reduce sensitivity to heat, for example.

These reactions to low-intensity stress influences are mostly non-specific and thus increase the general resistance of the affected organisms. A comparable phenomenon in our everyday life is the effect time-limited cold stimuli have on the human body. It also provokes some slight oxidative stress, which can increase the resistance of an individual long after the stimuli have ended. Humic substances also have a positive effect on the breakdown of crop residues and the formation of humus. It was not clear for a long time how humic substances were able to produce this effect. It was eventually shown that the dark colour of humic substances causes the soil to warm to some extent and more quickly convert the not yet decomposed material. However, this effect is much stronger following direct treatment of the stubble with GeoHumat ®. Humic substances stimulate the growth of actinomyces to further increase mineralisation. Actinomyces are some of the most important decomposers of dead, cellulose-rich plant material.

In summary, it can be said that humic substances have important and diverse effects on digester and soil biology. The low dose required to produce an effect is remarkable. There is increasing evidence in the literature that some groups of substances, even if they are at the limit of detectability in terms of concentration, play key roles in the important microbiological material cycles of our environment. These effects have been reflected in the high operational efficiency of GeoHumat Plus ® in all laboratory tests and practical applications to date.

  Bacteria after 30 days

GeoHumat Plus ® has a positive effect on methane producers (methanogenic archaea). In the 30-day test, these are shown to more than double in quantity (115% growth) with GeoHumat Plus ®!

And there is still more:

The rod-shaped methane producers increase by 140%!

This results in two crucial advantages in practice:

First, the rod-shaped archaea are the most resistant of the methane producers and can best cope with operational fluctuations in the process.
Second, many rod-shaped methane producers are hydrogenotrophs, i.e. they bond with free hydrogen and react with readily available CO2 to create methane. If more free hydrogen is consumed by the methanogens, there remains less to produce H2S!

  Benefit from a more stable process and better gas quality with GeoHumat Plus ®! 

Test report from the University of Rostock

The report from the University of Rostock shows you the experiments confirming higher humic substance concentrations.

Lufa Test 2019

The aim of the Lufa Test was to discover how much gas can be obtained from a digester with a retention period of 120 days.

Batch Test Gollipp

The Gollipp Test involved a 4.5 MW gas processing plant operated by E.ON.

MTE Service Batch Test

The MTE Service Batch Test shows you the final digestate from a dry fermentation plant. The test sought to investigate balanced viscosity.

MTE Service Batch Test
(2nd test series)

Microbial investigation with and without GeoHumat Plus

Advanced maize straw digestion project in cooperation with WABIO®

MTE Service Gas Yield and Reference Digestion Tests

Influence of the process additive GeoVita on the qualitative and quantitative biogas yield and on viscosity

Increasing nitrogen binding and methane bacteria

  We sell GeoHumat Plus ® in 3 sizes  

Canister (20 litre)

IBC (300 litre)

IBC (1000 litre)