Calcium chloride works best for deicing (down to -25 °F) and it releases heat as it dissolves. So, using less means having fewer problems. In terms of usage rates, calcium chloride is less toxic or corrosive than sodium, potassium, or magnesium chloride.
- Sodium chloride only works down to +20 °F
- Potassium chloride only works down to +25 °F
- Magnesium chloride only works down to 0 °F
Potassium chloride is not commonly used for deicing because it has relatively low melt volume capability. And Magnesium chloride contains about 55% water, so you actually have to use about twice the amount of it!
But ALL chloride materials will have (pound for pound) about same level with corrosiveness... so the more you use, the more corrosion and toxicity you get.
Calcium and/or magnesium acetate is essentially non corrosive (it has about the same corrosiveness as tap water). Acetates (same ingredient as hand warmers) work okay for deicing (+20 °F is about the same as sodium chloride) but they aren't quite as effective as chlorides. The upshot is that acetates are way less toxic than chlorides. The biggest downside is the cost. So acetates are usually mixed with chlorides to offset costs.
Urea is also sometimes used, because (like calcium chloride) it also releases heat as it melts and it is lower in toxicity to plants and wildlife than chlorides. The downside is that it doesn't work as well (only down to +25 °F).
Also, cat litter (and/or sand or any other gritty) deserves an honorable mention. It's not the best in the world, but it can help by absorbing heat from the sun and adding some grit for stepping on (making the road less slippery). It's common road treatment in my area to mix sand and grit with salt.
And so with that in mind, a mixture would probably be in your best interest. I can't really advise you without knowing a little more about your weather conditions, but for example, I might recommend the following mixture:
- 100 parts sand
- 50 parts urea
- 50 parts calcium/magnesium acetate
- 50 parts cacium chloride
Also, as more of a footnote, carbon black has been used in experiments and found to work. The black color absorbs sun rays and warms the snow.
Cons: Of course it would only work during the day and the water would re-freeze at night; it will not work if it snows after treatment (snow covering the black); having black stuff everywhere; solar powered.
Pros: It does work (if it's applied to the top of snow); carbon black has no toxicity or corrosiveness; and a little bit will go a long way, so it is very cost effective; solar powered.