Analysis of the Supply with Micronutrients in Biogas Plants – Expensive and Useless?

In the biogas branch a new business segment developed in the previous years: the biological support of plants and the analysis of digester contents for essential trace elements or micronutrients. As these analysis are quite expensive, it is worth to question their sense.

Meanwhile, the benefit of using micronutrients is widely undisputed. However, there is a whole series of business models and many different products on the market. Some manufacturers offer individual adapted micronutrient products, based on
an analysis of the micronutrients supply of the digester biology.

The micronutrients or essential trace elements are needed in an extremely small amount for the formation of encymes, the biocatalysts of the bacteria. Therefore these trace elements have to be available in a form, in which the bacteria can „see“ them. So the micronutrients have to be bioavailable. If the micronutrients are bonded, for example as a sulfid, the bacteria cannot use them.

In the eighties the necessary concentrations of essential trace elements were already detected, when developing nutrient media for methane bacteria. Thereby it was found, that the minimum concentrations are extremely low, so low, that these concentrations even with most modern measuring technology cannot be detected, also not yet today.

However, the decisive problem with the analysis of the supply with micronutrients lies therein, that until now no functioning process exists, which enables to measure the actually bioavailable part of trace elements. Even when, for example in the analysis, a good supply with for example nickel is measured, that does not mean, that thereof is enough visible for the bacteria.

An analysis of the trace elements in the digester contents can find out at the best case, if a trace element is not available at all or only lies below the detection limit. However, with the conventional trace element analysis can be detected in no case, if the digester biology is undersupplied or not. Hence these analysis are not necessary.

In practise never can be predicted, which quantity of trace elements is added with the substrate. Even less it can be predicted, how bioavailable these trace elements, brought in with the substrate, are. Both will fluctuate almost daily. With an individual mixture the situation of the digester on the day of the analysis is shown in the best case.

A further problem of individual mixtures lies in the declaration of the products. For each individual mixture an own new safety data sheet must be created. An expenditure which makes the products very expensive. According to my conviction the use of individual mixtures therefore makes no sense.

A predictable and secured supply of the digester biology with micronutrients is only ensured when a defined and high quality product is daily dosed in the correct way. Composition and dosing have to be adjusted to the growth of the bacteria population in the digester. It must be dosed as much as the bacteria need for their growth.

This also means that the micronutrients, added uncontrolled with the substrate, have to be ignored in the consideration. Hence an overdosing cannot arise, as the necessary concentrations lie several orders of magnitude under the toxic concentrations. When using a high quality and excellent bioavailable product as Acinor 1000, the added quantity of active ingredients is also as low, that the increase of the heavy metal concentrations in the end product is negligible low.