Snow and ice on doorsteps, paths and pavements are traditionally tackled using rock salt, but salt can attack surfaces and surrounding vegetation.
Crystal Clear "is a non-corrosive and biodegradable product. It is a tiny frost and ice removing pellet made from urea, which continues working considerably longer than other alternatives and is non-flammable, low in toxicity and easy to use. To achieve maximum protection, should be applied before snow has fallen or surface water has begun to freeze."
(Note: I've not tried this out, but it looks worth investigating.)
http://chemaide.co.uk/product/Crystal_Clear_non_corrosive_de-icer.html
