Circular Fertilizers at a Glance

The challenge? Keeping an overview of a mountain of data compiled by researchers from many different countries.

That’s why the FER-PLAY project was launched in September 2022: to gather all the pieces of information and fuse them into a powerful, clear whole—and then communicate targeted insights to farmers, fertilizer producers, and policymakers.

Brand-new database

To do this, we had to collect as much existing information on circular fertilizers as possible. And that’s a lot, since these fertilizers can come from industrial and domestic wastewater, biowaste, biological by-products, and processed manure or digestate. Production relies on a wide range of processes. In short: a huge number of possibilities—and a real challenge to make it all accessible.

Still, we succeeded in bundling all of that data into a single database. It covers everything from production, distribution, trade, and storage to the latest insights on nutrient content, costs, and even European legislation. Using filters and data groupings, this (free) database lets you efficiently search existing data.

Benefits and bottlenecks

The project had to be not only comprehensive but also informative. We therefore examined the benefits and/or bottlenecks of circular fertilizers compared to non-sustainable alternatives, taking into account social and economic aspects, overarching regulation, and environmental performance. The takeaway: the advantages are numerous when it comes to acidification, eutrophication, land-use impact, and climate change mitigation.

• The social impact of circular fertilizers depends on the production processes and varies by region, with lower impacts in the north. The circular economy fosters integration across sectors and processes. As a result, social risks associated with the extra waste-processing steps of non-sustainable counterparts are reduced.

• Economically, non-sustainable alternatives such as mineral fertilizers still enjoy a market advantage. This largely stems from their established position, production efficiency, automation, and economies of scale. Since circular fertilizers are still produced on a smaller scale (at public wastewater treatment plants, SMEs, etc.), they cannot yet match the volumes of mineral fertilizers.

On top of that, circular fertilizers are still relatively unknown, which sometimes breeds distrust. Questions also remain about where to source them. In any case, their production will need to be scaled up—while keeping a close eye on energy use as a critical factor.

And in Flanders?

Flanders already offers a wide range of circular fertilizers. Due to lower production capacity, finding them can sometimes take a bit of effort, but there are many inspiring examples.

Consider the scrubber effluent (“spuiwater”) from chemical barn air scrubbers—widely available across Flanders and recognized as a mineral fertilizer. It’s ideal for meeting a crop’s sulfur needs and part of its nitrogen needs. Effluent from biological air scrubbers, or digestate and derivatives from plant-based anaerobic digestion, can be applied under the “other fertilizer” category.

Animal-based circular fertilizers are also available:

1. digestate and its fractions (liquid or solid) from a digester that also treats animal manure,

2. pig urine from a separated housing system, and

3. manure-processing effluent.

Ammonium salts from ammonia stripping and mineral concentrates after reverse osmosis are fertilizers that could in future be recognized as RENURE (mineral fertilizer substitutes). Current production capacity is still relatively small.

Phosphorus fertilizers are available too, in the form of struvite—a granule/crystal recovered from waste or process water. And don’t forget compost or “champost” (spent mushroom substrate): soil improvers with high organic matter content.

More info?

Contact Inès Verleden, researcher in energy and circular economy at Inagro (via ines.verleden@inagro.be