Is it permissible to sell donkey dung, knowing it is impure, for use in manufacturing red bricks?

Selling the droppings of animals whose meat is not permissible to eat, such as donkeys, is not allowed according to the majority of jurists, while the Hanafis permitted its sale. As for the droppings of animals whose meat is permissible to eat, it is pure and its sale is permissible. It is permissible to utilize impure droppings for fertilizing land and making bricks. The ruling of impurity is removed by transformation (istihalah) or by encasing it.