Is There a Life Form That Doesn't Use Chemotherapy?

We're assuming that life elsewhere uses chemistry and can give off waste gases. We would perhaps disappointingly not have any idea what kind of life was making those gases. For more than 60 years the UK's Ministry of Defence had a special desk to collect reports of UFO sightings from members of the public. The vast majority of UFO sightings that have been investigated have turned out to be ordinary things like birds, meteors or Chinese lanterns but despite that people still believe we've made first contact with extraterrestrials.