Er, no, I mean you can't have more than one (distinct) live blockchain standard; eg if you have Bitcoin and Litecoin, one of them must be using less than 50% of the available hashing capacity (because otherwise it would add up to >100%), and therefore not be secure[0].

Good point about some power use having beneficial side effects (heating) in addition to the actual work though.

0: because if it ever actually needed the security - was more valuable to attack than the majority chain - then the miners on the majority chain would have a economic incentive to attack the minority chain and gain more from attacking than they lost from undefended attacks on the majority chain.

Obviously it's possible to have two blockchains in practice, just like it's possible to have two internets in practice, but there's a constant pressure to drain applications from the minority (quasi-)singleton into the majority singleton until the minority goes defunct from lack of use.