Recycled fertilizers from sanitation systems are as effective as conventional fertilizers, study finds

Recycled fertilizers from sanitation systems are as effective as conventional fertilizers, study finds

Report

by Melanie Neugart, Institute for Social-Ecological Research

Report

edited by Sadie Harley, reviewed by Alexander Pol

Report

Phosphorus, nitrogen and potassium, for example, are indispensable for agricultural crop production.

Report

However, natural reserves are limited, vary greatly in regional availability or are very energy-intensive to extract.

Report

Resource-oriented sanitation systems (ROS) offer a sustainable solution for managing these raw materials: they collect nutrient-rich material streams from human excreta separately and, as far as possible, undiluted with water.

Report

After targeted treatment, the plant nutrients they contain can be made available for agricultural use again.

Report

A research team has studied this treatment process, compiling extensive international data on various ROS-based recycled fertilizers for the first time in a recent study.

Report

For 13 types of recycled fertilizers, sufficient data were available to characterize their properties in detail.

Report

The study is published in the journal Frontiers in Environmental Science.

Report

Many can be classified into known categories of mineral, organic or organic-mineral fertilizers in terms of nutrient composition and function.

Report

The results show that the recycled products are just as effective agronomically as conventional fertilizers.

Report

"Our findings provide an important scientific basis for their application, as they show that recycled fertilizers derived from separately collected material streams are not second-class fertilizers," says Martina Winker of the Institute for Social-Ecological Research (ISOE), a co-author of the study.

Report

"For the study, we compiled more than 450 data sets from over 200 sources across 32 countries and analyzed them at the product level.

Report

Our findings on individual fertilizer products show that nutrient recycling from human waste has long been a scientific topic at the international level," says Ariane Krause of the Network for Sustainable Sanitation (NetSan), also a co-author of the study.

Report

"Until now, however, there has been no comprehensive overview of the wide variety of products, processes and application conditions.

Report

Nutrient content depends on raw materials and processing

Report

The nutrients contained in a ROS-based fertilizer—as well as their form and concentration—depend largely on the raw material and the specific processing method.

Report

The picture is more nuanced when it comes to potential contaminants.

Report

Overall, the heavy metal concentrations examined were predominantly low and comparable to those in established fertilizers.

Report

The feedstock and treatment conditions are particularly critical for hygiene safety.

Report

In contrast, the data on organic contaminants such as pharmaceutical residues or PFAS are still incomplete and do not yet allow for a comparably comprehensive assessment across all product groups.

Report

No systematic yield disadvantage compared to mineral fertilization

Report

The fertilizing effect was determined for the study using a quantitative meta-analysis of 134 data sets from 68 sources, including 31 crop species as well as field, pot and hydroponic trials.

Report

Across the recycled fertilizers examined, no systematic yield disadvantage was observed compared to mineral fertilizers; yields were generally significantly higher than in unfertilized control treatments.

Report