Seven years after its adoption, and nearly four years after it entered into application, the EU Fertilising Products Regulation (FPR) offers a quiet lesson in how EU regulatory design actually works. The lesson is not about fertilisers alone. It concerns what happens when a harmonised EU framework is placed alongside mature national systems, with producers free to choose between them.
That choice is known, in the language of EU product law, as optional harmonisation. Under the FPR, producers can CE-mark their product and place it on the internal market under EU rules, or they can continue to follow national legislation. Recital 5 of Regulation (EU) 2019/1009 makes this design choice explicit: unlike most Union product harmonisation measures, the FPR does not prevent non-harmonised fertilising products from being placed on the internal market under national law [1]. Compliance with harmonised rules therefore remains optional.
The underlying logic is rooted in the EU’s “New Approach” to technical harmonisation, where optional harmonisation was historically used in sectors characterised by very local markets, leaving manufacturers to choose between harmonised Community rules (with free movement) or national legislation (without that guarantee) [2]. For fertilising products, this design choice reflected the reality that many Member States had well-established national rules, particularly for organic and circular products, and that a hard shift to EU-only rules risked disrupting functioning national markets.
A natural experiment across 27 markets
Four years in, the effects of this design choice are starting to come into view. Where the FPR builds on existing harmonisation, as with conventional inorganic fertilisers already governed by Regulation (EC) 2003/2003 since 2003 [3], the transition to the EU route is well established. Where the FPR extends harmonisation to product categories previously governed only by national legislation, including organic fertilisers, soil improvers, growing media, plant biostimulants, and fertilising product blends [1], uptake has been slow. Bio-based fertilising products, despite their theoretical potential for nutrient recycling, seldom replace mineral fertilisers in practice [5].
The pattern reflects regulatory design interacting with market structure rather than regulatory failure. Producers choose the harmonised route when it offers clear advantages over the national alternative. When the harmonised route is less complete, more costly, or harder to navigate than the national one, producers tend to stay where they are. This is easy to overlook in the assumption that harmonisation follows automatically from the adoption of a harmonised regulation.
Why uptake stalls for circular products
The slow uptake of the FPR in circular and bio-based product categories is not principally a story about the regulation itself. It reflects deeper structural features of the sector.
First, the regulatory framework still tends to favour synthetic fertilisers. Supportive policies, effective contaminant management, and interdisciplinary approaches are needed to unlock the benefits of nutrient recycling [4]. Kvakkestad and colleagues [5], in a qualitative study of Norwegian farmers, suppliers, and civil society representatives, document precisely this dynamic: different regulatory barriers affect suppliers’ capacity to produce bio-based fertiliser products, and economic challenges remain a crucial constraint on both supply and demand even where technical solutions exist.
Second, the framework itself is still being completed. The FPR relies heavily on delegated acts to define Component Material Categories (CMCs), end-of-waste criteria, and technical standards. Several of these remain incomplete for circular and recovered product categories. The framework is mid-build, and producers facing that uncertainty often prefer to keep operating under the national rules they already know. The European Commission’s Joint Research Centre has long documented this challenge, noting that the lack of harmonisation across Member States creates legal uncertainty for waste management decisions, affecting both producers and users of recycled materials [6].
Third, national systems in this sector are not placeholders waiting to be replaced. Many Member States have decades of regulatory practice in circular product categories, often embedded in functioning markets. When the harmonised route appears more demanding than the national one, for little additional commercial benefit, producers understandably defer.
Optionality is not a neutral choice
These three factors mean that optionality, as a regulatory design, is more than a technical detail. It is a substantive policy instrument with three consequences.
It protects continuity for SMEs and niche producers during a long transition, which is a real benefit in a sector where small producers would struggle with a sudden shift to harmonised conformity assessment requirements. It sustains regulatory islands that raise the transaction costs of scaling EU-wide, since cross-border producers must manage multiple regulatory systems simultaneously, which erodes the single-market gains that harmonisation is supposed to deliver. And it shifts the burden of harmonisation from the legislator to the market, which matters most for the longer-term trajectory of the FPR.
If optionality is preserved indefinitely, the success of harmonisation depends on whether the EU route becomes demonstrably simpler, cheaper, and more complete than the national alternatives, and also on whether the supporting infrastructure of notified bodies, harmonised standards, and established testing routes is built alongside it. Without both the regulatory and infrastructural conditions in place, migration tends to stall regardless of how well the rules are written.
The broader lesson for EU regulatory design
The FPR is a useful case because the pattern it illustrates is not only sectoral. The gap between formal harmonisation and effective harmonisation is a well-established theme in EU implementation scholarship. Versluis [7], in an influential study of the Safety Data Sheets Directive, showed that even when Member States formally transpose EU directives correctly, the “law in the books” does not automatically become the “law in action.” Practical implementation is shaped by national administrative structures, enforcement capacity, and the incentives facing the regulated.
The OECD [8] makes the same point in broader terms. A rule will only ever be as effective in achieving impact as its implementation on the ground, no matter how well designed it is. Once in force, the effectiveness of a law or regulation depends on the ability of governments to foster compliance and drive behavioural change.
For the FPR, the implication is direct. Harmonisation is not achieved by writing a harmonised regulation. It is achieved when the harmonised regulation becomes the rational default, the point at which the “law in the books” and the “law in action” converge for the actors the regulation is designed to govern.
What this means for the evaluation and beyond
The FPR is currently under evaluation, with a report due to the European Commission by July 2026 under Article 49 of Regulation (EU) 2019/1009 [1]. That evaluation is doing the detailed work of assessing uptake across Product Function Categories, the progress of delegated acts, the functioning of the internal market, and coherence with adjacent EU legislation that the Article requires. Sitting alongside that work, a broader question arises about how the EU approaches regulatory design in sectors where harmonisation is genuinely new, where national systems are mature, and where the circular economy transition requires the harmonised route to become the attractive route. In such sectors, optionality is a bridge rather than a destination. The question is how the bridge is built, and how long it takes before the harmonised side becomes the side most producers choose to stand on.
Circular nutrient recovery is too important to be left as a second option.
References
[1] European Parliament and Council, “Regulation (EU) 2019/1009 of 5 June 2019 laying down rules on the making available on the market of EU fertilising products and amending Regulations (EC) No 1069/2009 and (EC) No 1107/2009 and repealing Regulation (EC) No 2003/2003,” Official Journal of the European Union, L 170, pp. 1–114, Jun. 25, 2019. [Online]. Available: https://eur-lex.europa.eu/eli/reg/2019/1009/oj
[2] European Committee for Standardization (CEN) and European Committee for Electrotechnical Standardization (CENELEC), Guidance Document on the ‘New Approach’ and the ‘Global Approach’. Brussels, Belgium: CEN/CENELEC, 1999. [Online]. Available: https://boss.cen.eu/reference-material/guidancedoc/pages/newapproach
[3] European Parliament and Council, “Regulation (EC) No 2003/2003 of 13 October 2003 relating to fertilisers,” Official Journal of the European Union, L 304, pp. 1–194, Nov. 21, 2003. [Online]. Available: https://eur-lex.europa.eu/legal-content/EN/TXT/?uri=CELEX:32003R2003
[4] C. M. Cordeiro and E. Sindhøj, “Situating the discourse of recycled nutrient fertilizers in circular economy principles for sustainable agriculture,” Frontiers in Sustainability, vol. 5, art. 1465752, Nov. 2024, doi: 10.3389/frsus.2024.1465752.
[5] V. Kvakkestad, E. Brod, B. E. Flø, O. Hanserud, and H. Helgesen, “Circulation of nutrients through bio-based fertilizer products: perspectives from farmers, suppliers, and civil society,” Frontiers in Sustainable Food Systems, vol. 7, art. 1239353, Oct. 2023, doi: 10.3389/fsufs.2023.1239353.
[6] H. Saveyn and P. Eder, End-of-Waste Criteria for Biodegradable Waste Subjected to Biological Treatment (Compost and Digestate): Technical Proposals, European Commission Joint Research Centre, JRC Scientific and Policy Reports, EUR 26425 EN, 2014, doi: 10.2791/6295. [Online]. Available: https://publications.jrc.ec.europa.eu/repository/handle/JRC87124
[7] E. Versluis, “Even rules, uneven practices: opening the ‘black box’ of EU law in action,” West European Politics, vol. 30, no. 1, pp. 50–67, Jan. 2007, doi: 10.1080/01402380601019647.
[8] Organisation for Economic Co-operation and Development (OECD), Better Regulation Practices across the European Union 2025. Paris, France: OECD Publishing, 2025, doi: 10.1787/6f007516-en.