In 2022, ComPeat competed in the Circular Challenge. They worked with a plant called water pennywort, the residual stream of the Noorderzijlvest Water Board. The team created a new type of potting soil, derived from water pennywort compost. This is a sustainable alternative to the potting soil that is currently sold in garden centers, which often contains peat.

Team ComPeat won the silver medal during the Circular Challenge in March 2022, working with water pennywort, the residual stream of the Noorderzijlvest Water Board. Although this invasive plant has a tremendously disruptive impact on the Dutch ecosystem, team ComPeat determined that it had at least one good property: water pennywort compost contains much more nitrogen and phosphorus than conventional compost. The presence of these nutrients inspired the team to create a new type of potting soil from water pennywort compost. This is a sustainable alternative to the potting soil that is currently sold in garden centers, which often contains peat. Peat extraction worldwide is thought to account for an estimated 5% of annual CO2 emissions. “You just want to work in your garden, you don’t want to be responsible for such substantial CO2 emissions”, says the ComPeat team. ComPeat’s potting soil contains 25% water pennywort compost. The remaining 75% consists of compost from other indigenous plants. The Noorderzijlvest Water Board made available 400 tons of water pennywort, with which the team wants to produce 520,000 litres of potting soil.

After the Circular Challenge, Compeat continued to develop its idea for sustainable potting soil but to date the product has yet to be launched.