Hans Friedmann

Dr. Hans Friedmann

dedicates his professional activities to the further development of the biogas technology since 1984 both nationally and internationally. Besides the consultation work and the realization of bioenergy projects he participated in many years of association work in the creation of political and legal framework conditions for the biogas production in Germany. Strongly increased requirements for efficiency and flexibility of the plants set new standards for the biogas technology today and are motivation for Dr. Friedmann to support an active knowledge exchange in practice. Within the international activities the processing of residues of the sugar industry became a focus. Moreover Hans Friedmann operates since 2001 biogas plants with a capacity of up to 5 MW with BKW Biokraftwerke Fürstenwalde GmbH founded by him.

Mechanical Decomposition of Substrates for Increase of the Biogas Yield

Besides encymes the mechanical decomposition of substrates is most widespread. We as biogas plant operators use mechanical decomposition of substrates as long as we operate plants. In case of liquid manure animals…

About the Sense of Decomposition Procedures


Many „new“ procedures to increase the biogas yield from the substrates are developed and propagated particularly in economically difficult times. The best known techniques at the market are

  • use of enzymes for decomposition…

Sense and Necessity of the Micronutrient Addition

Micronutrients or trace elements (these are mostly heavy metals) are needed in all biogas plants. The micronutrients are the central atoms in the enzymes which must be produced by the methane bacteria…

Acidification of the Digester

At the operation of biogas plants acidification of the digester is one of the most expensive problems. When the digester biology is acidotic, it can possibly last months, till the plant has…

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

The analysis of the micronutrient concentrations in the digester supplies no usable information about the level of supply of the digester biology. These costs can be saved. The use of individual mixtures makes no sense, as the level of supply cannot be sensefully detected. A safe micronutrient supply of the digester biology is only possible by the correct addition of a defined product adjusted to the growth of the bacteria population.

My Story With the Use of Micronutrients in Biogas Plants

We develop and pursue the use of micronutrients or essential trace elements since over 25 years. The experience shows, that micronutrients as Acinor 1000 lead to an improvement of the process stability in all plant types, also with the use of liquid manure. High loading rates are only feasible with the addition of micronutrients.

Selfheating and Cooling of Digesters

When I started constructing and commissioning the first high-loaded biogas digesters (digester load 8-10 kg oDM/cbm/d) in 2005, an unexpected phenomenon appeared – the digesters warmed up by themselves in summer without activated heating. The real problem was the too fast increase of temperature, leading to a breakdown of the biology. In a few weeks the planned digester temperature of 39 °C increased to 43 °C, and the digester biology suddenly became unstable.

The Influence of Temperature on the Biogas Production

The still common understanding assumes the existence of a mesophilic (35 – 40 °C) as well as a thermophilic (50 – 55 °C) temperature range for the biogas production. More stable biological…