Assertion: natural gas's propane | /r/HasProperty | eco-friendly
Facets:
value: after combustion
type: TEMPORAL
Source sentences:
text: Propane is eco-friendly before and after combustion, which means that propane and natural gas are both environmentally safe.
text: You could state that propane is the more eco-friendly option, but reality displays there is little difference on their environmental effects, since both are eco-friendly fuels.