this capacitor will used to actuate a latching solenoid valve by discharging it through the coil.
But i fear that the Zero Hz ESR may be well high and poorly toleranced from part to part (or batch to batch?)
There you are, the frequency when discharging is not zero. Don't confuse its state before discharging with the discharge itself.
A solenoid has an inductance, and as such the current through it will start at zero and rise more or less linearly when a square voltage is applied to it.
So, the current drawn will be triangular, or rather sawtooth, -shaped. A triangle-wave has certain frequency components, definitely not zero.
I think steve mixed up the ESR/frequency relationship, I've always measured (and seen in datasheets) an increase in ESR with a decrease in frequency.
The ESR has a loose tolerance to begin with and is not to be relied upon to remain very stable. It varies with temperature & age as well as several other parameters.
If for some reason you need a well-defined ESR then I suggest you get the lowest-ESR cap possible, and then add a real resistor in series with this.
Organic Semiconductor caps have an ultra-low ESR, and the Nichicon HZ series have the lowest ESR of the standard electrolytics.