I've noticed that in some words the schwa sounds more like an 'e' and not 'ə', for exmaple: environment(.mənt), is with a schwa, but sounds like 'e'. Also in a word like 'substance'(.stəns) doesn't sound like it has a schwa but it has.
Many unstressed vowels are quite flexible in their pronunciation. If the word is spoken slowly and carefully, the unstressed vowels are formed carefully, and often are close to their written vowel. If "Environment" is spoken slowly, the last part may be said as /ment/ if spoken at normal speed, the unstressed vowel is reduced to a schwa or even lost completely, resulting in a syllabic /n/.
Dictionaries usually show only the normal pronunciation.