I don't think it is a good idea to put them in a recycling bin, because when they need to get sorted they create a big danger to the people working there. Scrapping it? Well the price of stainless steel(has different categories and grades) is between 70p to £1 a Kilo, so in order to collect at least 1Kilo of scrap DE blades you will need to save for years.
I think the safest way to dispose them is the Bio Hazard sharps box, those bright yellow plastic containers used to dispose used needles and syringes etc..
If not save them in a box or tin and dispose it to normal refuse for landfill I guess that is the safest way to dispose them