The methanol in windshield wiper fluid is sometimes referred to as wood alcohol because it used to be produced from the destructive distillation of wood.
Methanol (wood alcohol) appears in many industrial products, like formaldehyde and fuel, that are cheaper and stronger than ethanol (the alcohol you drink); it's also really toxic.
They wanted the byproducts coming from the wood as it was being converted to charcoal, byproducts such as wood alcohol, tar, calcium acetate and other wood oils.