'We boost the soil'

Circular soil improvers

To reach their full potential, trees and plants need good growing space, with healthy soil. Van Berkel makes natural soil conditioners from recycled green waste streams and offers a solution for roots under pavement.

Van Berkel Biomass and Soil Products, one of the four divisions of the Van Berkel Group, processes green residual streams with composting processes into soil improvers. "This is how we close the chain: we return green residual streams to public spaces as high-quality soil improvers," says Berend Aelbers, soil improvers consultant at Van Berkel. "Especially in cities, the importance of good soil for trees is great."

Healthy soil

Soil health is indicated by several parameters, Aelbers explains. "A few crucial parameters are organic matter content and pH. The amount of organic matter is important for water balance and nutrient retention in the soil. The pH value says something about the availability of nutrients for the plants and trees. There are also specific nutrients, such as nitrogen, phosphorus and potassium, which must be at the right level. Using the parameters, we can analyze the existing soil. In this way we can give project-specific advice on the application of the best suited soil improver. In practice, for example, it is not always necessary to remove large quantities of soil, because upgrading the existing soil is often a very good option and in this way we give the soil a boost." 

Trees in the city

A good growing site has soil with a healthy composition and is well designed. Aelbers: "Everyone agrees on the importance of trees in urban areas. They reduce heat stress, absorb rain peaks, provide shade, convert CO2 into oxygen, contribute to people's well-being with their appearance and increase the economic value of the built environment. But trees start contributing significantly only after 20 years or so, only then is the crown so large that the tree can provide major benefits. To grow well, the tree must have a good growing site, with plenty of room for the roots. In a city, paving is often close to the tree. This can lead to root pressure: trees want to survive and are looking for moisture and nutrients to do so. We have therefore developed a product that provides growth space under the paving and less root pressure: tree granulate."

Growth space under pavement

"Tree granulate consists of rock and nutrients. The rock forms a skeleton, which is so load-bearing that the pavement can rest on it and (heavy) traffic can drive over it. It is fairly coarse rock, so there are hollow spaces between the stones. In those hollow spaces is nutrient soil. Roots can grow between the rock. This makes it a nice natural solution." For under sidewalks, there is tree sand. "Less bearing capacity is needed there, so sand suffices. This tree sand contains organic matter and nutrients. With this you have the bearing capacity and ease of processing of crusher sand, and also the nutrition for the trees. So there is also growth space for trees under the sidewalk."

Years of experience

"No one will deny the importance of trees, but how to provide growing sites where trees can really grow big so they can contribute optimally, that's what we specialize in," Aelbers concludes. "We think along and can provide customized solutions, because of our experience and knowledge. We have been making soil improvers from green waste streams for years. Van Berkel already specialized in circular processes before circularity became a social issue. We have never done anything else."