Raw materials

The core ingredients which are used in the compostproduction are different all over the world. It is depending also on price and availability. This means using straw, a nitrogen source and gypsum. For this Walkro companies use horse manure, straw, broiler manure and gypsum.

Horse manure

Horse manure is straw which already contains some bacterial life. Horse manure is also an easy attainable product in our region and also cheaper then straw. On top of that it also contains some bacterial life by the presence of fertiliser and urine, this bacterial life is being used in the later fermentation process. This is also the largest Ingredient of the product.  Walkro uses horse manure that is being transported from riding schools, stables and run tracks in Holland, Belgium  and Germany. In this region we are able to process a lot of horse manure. In other countries in Europe is less horse manure available so more straw is needed.

The largest part is already added with the horse manure. But we cannot get around the use of fresh straw in the process. This is depending of the availability of horse manure. The straw share in the substrate can vary from 40% in the summer to 0% in the winter. Walkro mainly uses wheatstraw. Worldwide also is been used: rice straw, barley straw, rye-straw and hay in its production. And again it is dependent on availability and price.

Broiler manure

Broiler manure is added as the nitrogen source. Nitrogen is an important parameter for the mushroom. Broiler manure also contains a lot of bacteria which sustain the fermentation in the process. Broiler manure is relatively cheap and easy to attain in the Netherlands. However, this is slowly changing due to the increasing demand of Nitrogen products on the world market. On top of that the competition in manure product processing companies increases. Other nitrogen sources being used in composting all over the world are urea, ammonium sulfate,  cotton seeds, cocos and soyaflour.


Gypsum acts as a stabilizer. It regulates the pH and has a positive influence on the structure of the material.

Process water

At the end process water is added. Process water at Walkro contains fluids that are being gathered on the entire terrain. Think of water that leaks out during the process itself, cleaning water and rain. The spray water that is being used to wash the ammonia containing air is added as well. With this everything is re-cycled at Walkro and nothing is thrown away. The process water is added at phase 1 and is used to get the substrate on the right moisture level and to increase the nitrogen level.