Volunteer is similar to Voluntary. Voluntary is the opposite of Automatic. Automatic is similar to Smart. 
Sustainable is derived from Sustain. Sustain is a synonym of Maintain. Maintain is a synonym of Adopt. 
Volunteer <--SimilarTo--> Voluntary <--Antonym--> Automatic <--SimilarTo--> Smart 
Sustainable --DerivedFrom--> Sustain <--Synonym--> Maintain <--Synonym--> Adopt 