Opinion of Advocate General Rantos delivered on 20 May 2021.#Biofa AG v Sikma D. Vertriebs GmbH und Co. KG.#Request for a preliminary ruling from the Oberlandesgericht Köln.#Reference for a preliminary ruling – Regulation (UE) No 528/2012 – Article 3(1)(a) and (c) – Definitions of ‘biocidal product’ and ‘active substance’ – Conditions – Mode of action other than mere physical or mechanical action – Article 9(1)(a) – Approval of an active substance – Scope of approval.#Case C-29/20.