From 1990 to 1992, he then trained as a senior building inspector for landscape management in the Ministry of the Environment of the State of Rhineland-Palatinate [de].

From 1992 to 1995, he again attended the University of Kassel, graduating with a degree in landscape ecology.

[1] He has been a member of the Kusel district council since 1996 and was the parliamentary group spokesman for Alliance 90/The Greens until 2021.

He was chairman of the Committee on Economic Affairs, Climate Protection, Energy and Regional Planning, a member of the Committee on Environment, Forestry, Agriculture, Food and Viticulture, and the specialist policy spokesman for the environment and nature conservation, construction/housing and regional planning for the Green parliamentary group.

On 27 October 2022, Hartenfels resigned from the Alliance 90/The Greens party and at the same time left the parliamentary group.