He studied chemistry in Dortmund from 1988 to 1993. Kahl worked at the Leibniz Institute for Analytical Sciences and obtained his doctorate at the University of Dortmund. He habilitated at the University of Kassel in 2007. Kahl taught and researched at the Max Planck Institute for Chemical Ecology in Jena, at the Universities of Kassel and Copenhagen and was a guest lecturer at the Universities of Barcelona, Sao Paulo and Warsaw.

In his new role, he also coordinates the Organic Food System Program, a core initiative of the United Nations 10-Year Framework of Programmes on Sustainable Consumption and Production Patterns.