I have a very frugal friend who does not waste anything. He conserves paper, energy, electricity, fuel and does not throw very much away. He is very careful with his money also, and is prudent. If he does not need something, he recycles it so it can be used by someone else. He is very conscientious about everything he does.

He is a conservationist when it comes to paper.

Positive: My friend uses the least amount of paper he can get by. He's a tree hugger! Negative: My friend uses the least amount of paper he can get by. He's a cheapskie! Not exactly an adjective in the above examples.... Positive: "tree hugging", "nature loving", "environment friendly" etc Negative: miserly, stingy, whacko, etc Also you can also use the neutral "greenpeace" for either situation. "Greenpeace whacko", "Greenpeace lover".

Are you looking for a word that is positive or negative? The connotation you want to use to describe you friend can change the word you need to use. Connotation is the feeling a sentence gives off.