The degradation of the water quality of the Baltic Sea is an ongoing problem, despite investments in measures to reduce external inputs of pollutants and nutrients from both diffuse and point sources. Excessive inputs of nutrients coming from the surrounding land are among the primary causes of the eutrophication of the Baltic. Diffuse sources, most originating from agricultural activities, are two dominant riverine pollution pathways for both nitrogen and phosphorus. Recently, there has been growing attention paid to the reuse of carbon, nitrogen and phosphorus from agricultural waste streams. However, no comprehensive and systematic assessment of ecotechnologies focusing on recovery or reuse of these substances in the agricultural sector is available.

The protocol involves searching for both academic and grey literature. English-language searches to be performed in four bibliographic databases and search platforms, and Google Scholar. Furthermore, searches of 38 specialist websites are to be performed in English, Finnish, Polish and Swedish. The searches are restricted to the period 2013 to 2017. Eligibility screening is to be conducted at two levels: title and abstract (screened concurrently for efficiency) and full text. Metadata to be extracted from eligible studies includes bibliographic details, study location, ecotechnology name and description, type of outcome (i.e. recovered or reused carbon and/or nutrients), type of ecotechnology in terms of recovery source, and type of reuse (in terms of the end-product).

Findings are to presented in narrative form and in a searchable, geographically explicit database, visualized in an evidence atlas (an interactive geographical information system). Knowledge gaps and knowledge clusters in the evidence base are to be identified and described.