
Don't know about card transactions. Anything under say $100 I do in cash. My ATM card is just that. Bigger transactions go on either the DR or CR cards.
I don't get the bit about carbon footprints. The shop is next door and I'm going there (on foot) with coins on me, or without.
A more persuasive (IMHO) long-term saving scheme, is to live like you never get a pay-rise. Save/invest the increment from any you do get. That can really add up over the years.