Aarhus Universitets segl



Inspired by advances in military vehicles, researchers will improve the design of machines that can harvest grass from wet meadows. If successful, this will provide access to considerably more biomass for energy throughout most of the world.

Biomass is by far the largest sustainable energy source available. Today it mainly comes from forest wood, organic waste and agricultural products such as straw. Large amounts of biomass from wet natural areas such as meadows can be better utilised than is the case at present. However, more knowledge is required about production conditions, plant growth, nutrient absorption and greenhouse gas emission, as well as new harvesting technology.

Researchers will take a closer look at new methods to harvest, store and pretreat wet biomasses, refine it to biogas, and optimise the whole process from meadow to processing plant – and they are already well on the way.

Wet areas are a challenge for tool carriers
Until now, meadow grass has been a difficult biomass fuel because the grassy areas have a high water level and are thereby relatively inaccessible to traditional tool carriers at most times of the year.

“Today you destroy the grass and soil conditions if you burden the ground with large machines, and this means we have poor access to harvesting crops in the meadows and using them for energy purposes,” says Professor (Docent) Ole Balling.

His activities include participation in the NATO Advanced Vehicle Technology Panel and modelling the mobility of military vehicles inspired him to come up with the idea of designing harvesters for the vulnerable meadows with rough terrain and high water levels.

He is now taking part in the university’s biomass research activities and applying his knowledge. Together with his team, he will develop new harvesting technology that is adapted to the specific soil conditions in meadows.

The aim is to be able to harvest at the same time as protecting and maintaining the natural quality of the meadows by preventing them from becoming overgrown with scrub.

Mathematical models of the earth voltage
The engineering challenge is to find the most optimal and gentle interaction between machine and soil, and this is where the Aarhus University researchers have a head start. In recent years, they have actually been working with a special form of modelling that makes it possible to measure the voltage in the soil and thereby the load rate in a considerable number of different harvesting scenarios.

“We use a modelling method that shows how the soil particles interact. This way, we can see what happens when the ground starts to give in. When you’ve got detailed insight into how the ground behaves under different load types, you can develop machines that take this into account,” says Dr Balling.

The researchers can use the mathematical models to identify items such as optimal wheels or belts, steering mechanisms and tyres for the new type of harvester that is expected to be ready in the first model-based prototype during the course of the next couple of years.

In Denmark alone, there are about 200,000 hectares of meadows that can be used for biomass. The researchers’ modelling technology is expected to be used to design harvesters and tool carriers for a considerable number of other lowland areas all over the world.

PHOTO TOP: In the future, the water level will rise in many parts of the world, and more knowledge about options for cultivating and harvesting in wetlands is therefore a matter of urgency. Researchers will design harvesters that can carry grass from wet and delicate meadows without destroying the soil. This requires extremely detailed knowledge about the way particles in the soil behave under different types of load, and mathematical modelling therefore plays a key role in the design process. (Photo: Colourbox)