This variable is a constant between both types of brakes. How is this relevant when comparing brakes? They both need it, one puts energy into a battery, the other one just heats up air due to the friction created by the system.

It's relevant to the question of whether regenerative braking produces dust from tire wear.

As compared to just straight braking — hence it’s irrelevant

The whole thread started with this message:

> Regenerative brakes rely on friction just like any other. Pollution is a given.

The article is about pollution from tires. Regenerative breaking can't cheat the laws of physics. That force has to be applied to the road through tires, just like any other form of wheel braking. And tires have significantly more mass to shed over their lives than brake pads.