Using urine in production was actually quite common for many centuries. It was used as a bleaching agent in the linnen industry. The local population of the industrial towns would collect their pee in jars, this also earned them the nick name of 'kruikenzeikers' or 'jar pissers' in towns like Tilburg, the Netherlands.
If urine was used in the production / blueing process, I'm pretty confident that the town of Berlin would produce it in sufficient quantities, especially when being paid for
