KombiWirt

Joint project: Combined fermentation of pre-treated nitrogen-containing farm manure; sub-project 1: Semi-technical trials, balancing and evaluation

On 1 November 2023, BIORESTEC launched a new research project called ‘KombiWirt’ in collaboration with the Institute for Urban Water Management and Waste Technology (ISAH) at Leibniz University Hannover. The aim of the project is to demonstrate the increased economic efficiency of manure fermentation through a pre-treatment chain.

The fermentation of farm manure and fibre-rich residues can make a valuable contribution to environmental protection and the energy transition. Even in the current geopolitical situation, which has reignited the ‘fuel or food’ debate, biogas production from agricultural by-products should not be generally dismissed. Currently, the use of these substrates is significantly below their total potential, as overall economic efficiency is rarely achieved. This is mainly due to the comparatively low specific methane yields of the aforementioned input materials and also to the fact that technical innovations are awaiting funding. 

The aim of the new approach is to increase the economic efficiency of the entire process chain for the fermentation of farm manure and fibre-rich residues so that the utilisation of residues for the provision of renewable energy can be implemented across the board. To this end, a new approach to substrate preparation is being investigated.

As part of the proposed process, treatment steps for fractional evaporation and ammonia pickling in combination with the subsequent fermentation of farm manure are to be quantitatively investigated in a newly interconnected process chain. The investigation will take place on a laboratory and pilot plant scale. The data obtained will be used to determine the practical feasibility, taking into account the parameters of economic efficiency and sustainability.

Targeted advantages of the proposed substrate treatment approach:

• Reduction of greenhouse gas potential through reduction of methane and nitrous oxide emissions
• Increase in methane yield from raw manure
• Increase in methane yield from the separated solid phase and fibre-rich farm manure through aqueous ammonia soaking (AAS)
• Hygienisation of farm manure through thermal treatment
• Control of nitrogen concentration during the fermentation process
• Significant improvement in plant productivity and overall economic efficiency