Phosphorus recovery for fertilisers from dairy wastewater – Sustainability assessment at early stages of technology development

Licentiate thesis, 2022

A reduction in the availability of phosphate rock resources for fertiliser production coincides with an increase in phosphorus-rich dairy wastewater in Europe. This confluence of events has led to the development of technologies for phosphorus recovery from dairy wastewater and the use of the products as fertilisers in agriculture. This thesis aims to contribute both to the technical development of this emerging technical system and methodological development of assessing the sustainability of it with regard to (1) the identification and selection of sustainability indicators, and (2) the assessment of life cycle environmental impacts. The thesis describes an approach developed for identifying and selecting sustainability indicators by reviewing scientific documents and interviews as well as an approach employed for performing a meta-analysis of previously published life cycle assessment results to cope with lack of inventory data. The employed method for indicator selection narrows down an initial set of 382 sustainability indicators identified in the literature to 26, which were considered representative and useful for the assessment of the considered innovative conceptual system. The meta-analysis results suggested that the examined phosphorus recovery technologies exhibited a lower global warming potential and cumulative energy demand than those of dairy wastewater treatment processes and that those technologies recovering phosphorus from the liquid phase had lower impacts than those recovering phosphorus from sludge or ash.