life cycle assessment of phosphorus sources from phosphate ore and urban sinks:sewage sludge and mswincineration fly ash

urban sinks accumulate phosphorus and other elements and may serve as sources of secondaryraw materials. this paper evaluates phosphorus sources based on their environmental impact. in a life cycleassessment (lca) the conventional production was used as a yardstick against which tomeasure the performanceof two recycling options: spreading of sewage sludge and phosphorus recovery from municipal solid wasteincineration fly ash (mswa). when compared as three gate-to-gate processes, the sludge spreading had thelowest potential environmental impact, except in the impact categories eco- and human toxicity. in the future, thesludge spreading could potentially outperform the conventional process also with regard to toxicity, provided itshg and cu content can be reduced. phosphorus extracted from the mswa had the highest impact, except inrelation to eutrophication. the benefits of avoiding the conventional production were greater than the sludgerecycling impacts for all categories except toxicity. when conventional production is substituted by the mswarecycling, the eutrophication and land-use impacts are avoided, while the impacts in other categories areconsiderable. the development needs identified for this method include substitution of hcl, reduced waterconsumption, and reduction of the product’smetal content. solutions to all of these challenges have been proposedand are currently being tested.