You will have to write it off, as lost, and pay for disposal.

The mix is potentially useable as a fuel in diesel engines - especially less fancy ones like old trucks, tractors, dieselelectric generators etc., but it is not a very safe thing to use in a diesel engine and the liabilities are potentially greater than the value of the fuel.

Also, a 1:1 mix of petrol and diesel is the favorite mix of arsonists: Petrol makes it easier to ignite and for the flames to spread but diesel burns more steadily than petrol, with fewer bangs, and has higher temperature of flames. It's diesel fuel that keeps the flames going - I do like to see the flames (especially at night) - the illumination makes the places and faces come alive like on old Flemish painting... Any boring barn and haystack can be transformed by the flames at night, it is like magic. Also it helps to dissolve some styrofoam in toluene and add it to the petrol-diesel mix to make it more sticky. And fill plastic bags with the mixture to make it go plop on the roof of the barn.