Aarhus University Seal / Aarhus Universitets segl


Complete DNA profiles

for biogas bacteria

Many chapters in the story of microbiological evolution still remain to be written. With the help of new technology, researchers have begun the monumental task of mapping microorganisms at DNA level. This will produce new knowledge about ways to optimise biogas production. The photo shows Associate Professor Lars D.M. Ottosen in front of the biogas plant at Aarhus University, Foulum.

New knowledge about microorganisms is set to increase the output from biogas production. Researchers have begun a momentous study of the role of bacteria in the conversion of manure, plant fibres, wastewater sludge and food waste to green energy.

It is possible that neither expensive processing methods nor advanced technology will pave the way for economically viable biogas production. It appears that we can achieve a much greater gas output by closely studying bacteria and fine-tuning the conditions at the biogas plant to create the right environment for the microbiological processes.

“We’d like biogas production to be both energy-efficient and cheap, and this means getting microorganisms to work better. We’d therefore like to acquire new knowledge about the type of bacteria that exists in the biogas reactor and how they behave. It’s essential for us to increase the current level of methane yields in the reactor,” says Associate Professor Lars D. M. Ottosen.

Analytical work of historic proportions
Today, organic waste and residual products are converted into biogas in large tanks mainly based on practical experience with what works. In recent decades, science has been able to describe parts of the microbiological processes that influence biogas production, but this is far from sufficient if we want to optimise the output on the basis of evidence.

Over the coming years, researchers at Aarhus University will therefore map in great detail the complex interplay between the microbial processes involved in biogas production in the hope of making energy production more effective.

The task involves analysing the composition of microorganisms and mapping the genomes of relevant species – something that was impossible only a few years ago. Today, Aarhus University has access to new DNA sequencing technology, and the researchers can use specialised equipment to extract an individual bacterium from the mass and study its entire genome.

“It will require extremely detailed knowledge of the microbiological processes that take place in the biogas plants if we’re to become better at controlling these processes. This is where the technological development can help us. In principle, we can currently identify a complete DNA profile for each and every microorganism and thereby describe their specific properties and how they work in the methane-producing food chain. We can also test how they react when we feed them different types of substrates or use different pre-treatment methods,” says Associate Professor Ottosen.

Good and bad microorganisms
The researchers aim to optimise the conditions for the bacteria in biogas plants, and the research project therefore includes comprehensive analyses of the composition of the microbial community under different operating conditions. Initial results are promising and make it possible to begin identifying indicator organisms for good and bad biogas production.

“We can conclude that some biogas plants perform better than others. We just don’t know what the exact reasons are, and we need to get much better at troubleshooting to ensure a reliable and high level of gas production,” says Associate Professor Ottosen.

According to the associate professor, it is currently more or less coincidental that some biogas plants end up with a better composition of microorganisms than others and thus a higher methane yield.

Once the researchers have a comprehensive understanding of the microbial processes, they can begin much more targeted work on process control at biogas plants, including temperature regulation, addition of nutrients and groups of bacteria.