A solid soil improver from slurry

Dung beetles: the experts in poo

If there is one species that desserves the title “experts in poo” it ‘s the dung beetle. His whole existence depends on the excrements of others. He feeds on poo and lays its eggs in it. Some species turn poo into perfectly round balls before digging them in to the soil. The dung ball must be perfect, neither to dry nor to wet. Within the ball conditions are perfect for hatching eggs. The larva doesn’t need to look for food. It’s literally surrounded by it.

Thanks to this form of soil injection, soil fertility is promoted. The dung ball doesn’t only provide food for the larva, but also for earthworms, bacteria and other soil-dwelling microorganisms. Subsequently plants can use the growth promoting nutrients that become available. Furthermore the digging activities of the beetles improve the structure of the soil, which lead to better water retaining and drainage qualities.

Soil injections of slurry

In the late 1980’s, the Dutch manure policy was changed drastically in order to reduce the emission of ammonia. Since 1994, above ground spreading of slurry isn’t allowed on agricultural soil or on pasture areas. Farmers are required to use soil injection. Unfortunately this form of slurry application has never been thoroughly investigated regarding its effect on the soil structure, soil life and biodiversity. The consistence of slurry is inevitably very different from the manure that the dung beetles transport in to the soil. Because of soil health considerations, a growing group of famers would like to have an alternative method of manure application, of course without increasing the emission of ammonia

Lessons from the dung beetle

Within the scope of a SNN VIA project, Bioclear earth and Cow House International research the possibilities to develop a system for drying slurry through composting, transforming it into a form of solid soil improver. This process will also include the extraction of nitrogen from the manure to produce a replacement for artificial fertilizer. In doing so we create an alternative for soil injection and we close the nitrogen cycle at farm level, which will lead to less or even no additional need for the use of artificial fertilizer. The goal of this project is to create a design for an installation prototype.

The advantages of dried manure are:

  • The stable humus structure of dried manure stimulates soil life, promotes a good soil structure, binds moisture and prevents the leaching of nutrients;
  • Closing of the nitrogen cycle is sustainable and cost effective;
  • Lower emission of ammonia;
  • By processing the manure aerobically, methane emission can be prevented;
  • Lower spreading and transport costs, due to volume reduction;
  • A longer period of manure spreading in accordance with Dutch legislation for solid dung.


This innovation project is made possible thanks to the European Regional Development Fund (EFRO) and the Netherland Cooperation Association (SNN).

Would you like to know more about this project, please contact Jeroen Tideman.

Jeroen Tideman
Senior consultant bio-energy