What does 无妨 mean in 即别人都过“低碳生活”，我自己过“高碳生活”也无妨?
What you post under Philipp's answer is correct, which I have upvoted it. 

即 here indeed means 'that is'. 

So 低碳生活与己无关的 想法:  the notion of excluding ourselves from the concept "low-carbon life"; 

即： that is (the notion[想法] is);   

别人都过“低碳生活”，我自己过“高碳生活”也无妨。: Since other people live a low-carbon life (already), it's ok/not a big deal for me to live a high-carbon life. (apparently this is a selfish notion, which the author is trying to persuade people not to have.)

无妨 means there is no harm. I interpret 无妨 here as ok/not a big deal according to the context.