Does peroxide do the same job?
They have similar uses but have gained popularity for roof cleaning. Less likely to cause a break down in the tar from the granules.
Does it damage plants/lawns?
Yes, it can, always water plants and lawns down.
Is it as cost effective?
I have found a multitude of products with different prices. It is more costly than SH. Although someone may have a better hook up than I do.
The most popular and most expensive would be Oxi-clean
from my understanding, all it is is oxygenated bleach. Some one please correct me if im wrong!
Hope that helps!!