Types and classification of research papers

 
Egestabase Research distinguishes four types of research papers that can be explored separately from one another:

  • Pathwayinvestigate selected aspects of specific circular nutrient solutions
  • Reviewreview various aspects of a broader range of circular nutrient solutions
  • Evaluationevaluate circular nutrient solution in a specific context (e.g. region or city)
  • Conceptdescribe selected conceptual aspects of circular nutrient solutions

The classification of research papers depends on the type of paper:

Framework

Recirculation Pathway

 
To categorize various approaches to the recovery of nutrients from human excreta and domestic wastewater, we chose five dimensions that together constitute a recirculation pathway. The recirculation pathway begins with an organic residue that is being managed – i.e., source stream (e.g., urine, domestic wastewater, sewage sludge ash). Following the collection and transportation of a given source stream, one or several recovery technologies (e.g., precipitation, leaching followed by precipitation) may be applied to recover nutrients. Recovery results in a recovered fertilizer product (e.g., struvite) that that can be reused back in agriculture and food production (e.g., as fertilizer, animal feed, or raw material for protein production). Nutrient recirculation as a whole may target one or several critical plant nutrients (e.g., nitrogen, phosphorus, potassium, etc.).

In summary, the recirculation pathway thus specifies which nutrients are being recovered, from what, how, in what form, and for what purpose:

Recirculation Pathways
In each recirculation pathway dimensions, categories are defined across three hierarchy levels so that the data can be navigated at different aggregation levels. The actual categories can be explored by using the respective buttons (i.e. source, technology, product, reuse, target) at the top of the page.

Research Domain

 
To categorize the focus of a given research paper, we distinguished six research domains that are delineated as follows:

  • SOURphysico-chemical characteristics of source streams in terms of composition, contamination levels, etc.
  • COLLcollection of source streams in terms of required appliances (e.g. toilet), piping, etc.
  • TECHdevelopment of recovery technology in terms of recovery efficiency, fate of contaminants, etc.
  • PRODphysico-chemical characteristics of recovered products in terms of composition, contamination levels, etc.
  • AGRIuse of recovered products in agriculture in terms of agronomic value, health risks, environmental pollution, etc.
  • USERuser acceptance of source streams, collection systems, recovery technologies, recovered products, or their reuse in agriculture

Research Domains

Research Cluster

 
Taken together, the combination of a given recirculation pathway and a given research domain constitute a research cluster.

Note that not all recirculation pathway dimensions are fully specified for all research domains:

Table Framework

L2 or L3 indicate specification up to level 2 or level 3.
() indicates that the given dimension is specified up to this level for some but not all research papers.
NA indicates that this dimension was not specified at all for this dimension.