noun-modifying (irregular)
non-fossil
Technical term used in energy and environmental contexts to describe energy sources or fuels that do not come from fossil fuels, such as renewables or nuclear.
A shift to non-fossil energy is urgently needed.
The government is promoting the use of non-fossil fuels.
再生可能エネルギー specifically means 'renewable energy', a subset of non-fossil energy sources. 非化石 is a broader category that can also include nuclear energy.
Compound of 非 (hi, 'non-') + 化石 (kaseki, 'fossil'). A modern technical term formed by prefixation.