Title: Sewage sludge and municipal waste: potential sources of phosphorus for land restoration
Abstract
Waste disposal is one of the environmental challenges facing city authorities. Waste contains nutrients and organic matter required for plant growth that can, in many cases, be recovered and put to use. Quantifying the amount of waste generated and nutrients that can be recovered from it is important. Further, cost of applying the waste on land should be evaluated in order to make wise investment decisions. Globally much of the waste generated is disposed without resource recovery. Therefore, the objectives of this study were to 1) quantify the amount waste generated in the Reykjavík capital area in Iceland, 2) determine the quantity of phosphorus contained in waste and 3) evaluate the cost of transporting the waste to nearby restoration sites and spreading it on the field. Operational data were collected from operators of wastewater and municipal waste treatment in the capital area. The capital area generated 722 tons/year of sewage sludge, 98,890 tons/year of solid waste and 82 million m3/year of wastewater in 2015. Wastewater treatment and municipal waste contributed 68% and 32% phosphorus, respectively. Phosphorus disposed in waste was 435% higher than the phosphorus used by the Soil Conservation Service in 2015. If all this phosphorus were recovered, it would most likely meet all the phosphorus requirements for land restoration in Iceland. The cost of utilizing phosphorus from waste is higher than using inorganic fertilizers. However, for highly degraded soils, such as those with an erosion scale of 3-5, application of waste would quicken soil recovery as it is rich in organic matter and nutrients. Further, utilizing waste reduces environmental pollution and conserves the non-renewable phosphorus reserves. The study recommends that waste be utilized in restoration as a means of recovering and reusing phosphorus. Legislation should be put in place to encourage waste utilization in land restoration.