environmental 同environmentally???

you can actually take them as the same expression.
for both expressions, environmental(or environmentally) is to further describe the nature of the word "friendly".
For example, you can say, "This new plastic bag given by the PKshop is environmentally friendly" or "This new plastic bag given by the PKshop is environmental-friendly". They are just the same, and both are grammatically correct.
So it's just up to you to use either one of them.
One thing you should be aware though, is that without the hyphen( - ), environmental friendly is simply ungrammatical. Be sure u have the hyphen if you are trying to use the expression.

2007-12-07 17:37:27 補充：
for environmental, it must be followed by a nounbut for envrionmentally, it must NOT followed by a noun, instead it should be followed by an adjective or a verb...

2007-12-07 17:38:12 補充：
and of course, for environmental, it must NOT be followed by an adjective or verb,,,,

Having individual meaning
environmental
adj.
周围的, 环境的
n.
环境论

must combine with other words
environmentally sound technology
合乎环境要求的工艺

一個係名詞,一個係形容詞,其實係冇咩唔同!!