Lots of questions here!
Most UK and US runway deicers are based on potassium acetate. Glycols are also used but they are not as enviromentally friendly. Potassium formate deicers are used mainly in Europe. All must meet stringent requirements of AMS 1435A test methods - and from 1 December REACH regulations in Europe.
Sodium formate based solid deicers meeting AMS1431B are available from some larger suppliers. Useful for use on aprons, walkways, steps etc. Some operators use a mix of solid granules and liquid on the runways - particularly when conditions are very icy.
Main UK suppliers are Brotherton Esseco and Omex. Esseco, Kemira, Addcon and Clariant are main suppliers on the continent.
Most airports have substantial stock tanks - Manchester has over 500 tonnes, for example. However, some have very small stocks and order only when desparate. They rely on the suppliers to work miracles when half the roads are closed.