In this chapter, we propose creating macroporous ceramics with ultra-high porosities of 80-99% by using the novel green manufacturing technique of gelation freezing in which the main waste material is water and in which the pores originate from ice crystals formed in the raw powder dispersed in the gel body during freezing. A macroporous monolith with a very high porosity of 80-99. vol% and a wide pore size ranging from 10-300. -m with interconnected pores can be fabricated by this green method. This gelation freezing technique allows macroporous engineering ceramics to be produced for several diverse applications by permitting varied and tailored architectures of porosity, pore size, pore orientation, and interconnectivity to be produced by careful control of the freezing conditions.