Methane is gas, liquified methane spills evaporate and go to atmosphere. Not perfect, but no land poisoning either. SpaceX does use hydrazine-related component

Methane is gas, liquified methane spills evaporate and go to atmosphere. Not perfect, but no land poisoning either. SpaceX does use hydrazine-related components in Dragon and Crew Dragon, but they don't launch from Boca Chica (and rather small by mass) - AFAIK Starship is planned to be 100% methane-oxygen vehicle, justification for Mars flight.