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? In the following sentence:


  我们每个人都是世界公民，千万不应该有低碳生活与己无关的想法，即别人都过“低碳生活”，我自己过“高碳生活”也无妨。


无妨 means "might as well", "there is no harm", or "no matter". 

However, it then makes no sense, since the meaning would become something like the following:


  Every person is the world citizen, so should never have the idea that low-carbon life is irrelevant with yourself. That is, others make a low-carbon life while I make a high-carbon life is also no harm (无妨).


This does not make sense, as 无妨 seems to be positive connotation for the sentence 我自己过“高碳生活”, which is incompatible with the author's point of view, which proposes the low-carbon life.

So what is the meaning of 无妨 here? Is my understanding here correct in the first place?
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.