Life Cycle Assessment of Phosphorus Sources from Phosphate ore and urban sinks:Sewage Sludge and MSW Incineration fly ash

Urban sinks accumulate phosphorus and other elements and may serve as sources of secondary raw materials. This paper evaluates phosphorus sources based on their environmental impact. In a life cycle assessment (LCA) the conventional production was used as a yardstick against which to measure the performance of two recycling options: spreading of sewage sludge and phosphorus recovery from municipal solid waste incineration fly ash (MSWA). When compared as three gate-to-gate processes, the sludge spreading had the lowest potential environmental impact, except in the impact categories eco- and human toxicity. In the future, the sludge spreading could potentially outperform the conventional process also with regard to toxicity, provided its Hg and Cu content can be reduced. Phosphorus extracted from the MSWA had the highest impact, except in relation to eutrophication. The benefits of avoiding the conventional production were greater than the sludge recycling impacts for all categories except toxicity. When conventional production is substituted by the MSWA recycling, the eutrophication and land-use impacts are avoided, while the impacts in other categories are considerable. The development needs identified for this method include substitution of HCl, reduced water consumption, and reduction of the product's metal content. Solutions to all of these challenges have been proposed and are currently being tested.