It can work on concrete, as long as you add in some soil or some compost donated from someone else’s bin, to get the mixture going.
Gall y bin weithio ar goncrit os rhoddwch chi rywfaint o bridd neu rywfaint o gompost o fin rhywun arall ar y gwaelod er mwyn ysgogi'r cymysgedd i ddechrau gweithio.