Valorization of wastes from the fertilizer industry: Current status and future trends

Abstract

Based on a systematic literature search (Number of initial publications = 1571; Number of in-depth publications = 97), this paper reviews the different potential applications for phosphogypsum, the main unwanted by-product of the fertilizer industry, providing some insights into the new valorization routes, and critically describing the advantages and drawbacks of each one. Industry and policy makers face the challenge to manage the increasing loads of phosphogypsum generated worldwide, especially on reasons of cost, safety and environmental impact. The recycling of this material could be an environmentally friendly, safe and cost-effective solution for this quandary. Different phosphogypsum valorization routes were developed in the last years in agriculture, building, and environmental and energy sectors, and these topics are described along this review. The first barrier to be overcome is the shift of paradigm needed to consider phosphogypsum not as a waste but as a raw material and the harmonization of classification rules of this material worldwide. Another issue to be faced is the heterogeneity of phosphogypsum reported worldwide, which could make unfeasible certain applications due to chemical and physical differences. On the one hand, while technical and economic constraints are increasingly lifted, many applications of phosphogypsum valorization consume low amounts of waste, and thus cannot satisfy the purpose of mass consumption. In addition, the different valorization routes may cause a secondary pollution which must be evaluated and compared with that caused by traditional disposal options. In order to provide a solution to this waste management, a better social and political awareness is needed. Economic and technical constraints must be lifted by a higher economic investment on research and development. However, site by site studies and assessment of secondary pollution using suitable tools (e.g. life cycle analysis) must be performed in order to assure the success of each valorization route.