Marco Zevenhoven has 34 years of working experience at RHP, the knowledge centre for substrates. RHP also manages and develops the quality mark RHP for raw materials and growing media for professional horticulture. The RHP quality mark is all about safety and quality and is considered the world’s most stringent quality standard for the growing media industry. For years Marco has been technical advisor for producers of growing media and suppliers of raw materials. He knows the products and processes in the entire chain of the growing media industry. He has visited hundreds of locations all over the world. He coordinates various international product groups that are active within RHP. And he is partly responsible for the requirements that RHP sets for the products. Marco also plays a role in the raw materials transition. Due to the increasing use of renewable raw materials, the properties of growing media will change significantly in the coming years. RHP is working on extensive research into the properties of (new) raw materials and their interactions in growing media.