Nowadays, the production of new materials is closely related to the reverse logistics, considered one of most important instruments for applying shared responsibility for the products lifecycle. Reverse logistics is an instrument of economic and social development characterized by a set of actions, procedures and means to enable the collection and restitution of solid waste to the business sector, for reuse, in its cycle or in other cycles productive, or other environmentally appropriate final destination , the reverse logistic is perfectly applied in the agriculture context. An application of this concept is to provide novel processes for the synthesis of different calcium and / or potassium phosphates from any source of calcium carbonate (CaCO3), making it a soil conditioner. Among sources, eggshells are important wastes of food industries and excellent CaCO3 sources (more specifically calcite) , with monobasic potassium dihydrogen phosphate. Everyday millions of tons of eggshells are produced as biowaste around the world, disposed in landfills with no pretreatment and producing odors due to microbial growth.