Chemical fertilisers are undoubtedly one of the most important and cost-effective tools ever introduced in agriculture. Since their invention in the early 20th century, they have helped farmers increase crop production efficiency per hectare, supporting a growing global population that has tripled since the 1950s. It's not an overstatement to say that this technology has contributed significantly to reducing world hunger. However, while they are generally considered a reliable, efficient, and cost-effective solution, fertiliser use still harms the environment wherever they are applied.
Notably, their overuse often results in excess nutrients remaining unused in the surrounding ecosystem, polluting the soil, air and water. For example, nitrogen runoff can cause uncontrolled algae growth in water bodies, reducing oxygen levels and harming aquatic life. Not to mention that, generally speaking, these pollutants can be rather challenging to detect—as they are spread across broad areas.
As the agricultural sector increasingly shifts toward sustainable practices, farmers and national authorities have been looking for more eco-friendly options—and one of the most promising ones at the moment is bio-based fertilisers. Under the current EU Fertilising Products Regulation (FPR 2019/1009), this category includes fertilisers containing organic carbon and nutrients of biological origin—although specific inorganic components are still permitted. The potential of these fertilisers to revolutionise farming is significant, as they can be produced through a circular approach, recycling chemicals released into the environment from human activities.
Despite this promise, bio-based fertilisers still face obstacles to widespread use, primarily because their variability in sources and production methods makes them more expensive than traditional mineral fertilisers. Scientists working in this field are quite upfront about the issue. "Traditional inorganic fertilisers are more cost-competitive than bio-fertilisers for now. There's no way around it," says Francisco Corona Encinas, a chemical engineer with a background in nutrient recovery at Fundación CARTIF. "But in the coming years, we expect these technologies to reach the same maturity level as traditional synthetic fertilisers."
Fundación CARTIF, an R&D institution in Valladolid, northwest Spain, is working on bio-fertilisers through an EU-funded consortium, WALNUT—for which Encinas serves as technical coordinator.
"We've tested various technologies at the lab scale, and now we are pushing the most promising ones into the field," he notes, referring to WALNUT's ongoing pilot projects in Spain, Belgium, Hungary, and Cyprus. "What we need is first to establish an optimal process. [...] Classic synthetic fertilisers may have the advantage of economies of scale for now, but they are also highly energy-intensive," he adds. "And with rising energy costs and the increasing scarcity of mineral nutrients, like inorganic nitrogen and phosphate, the price gap will likely narrow over time."
Spain is at the centre of these efforts, with WALNUT currently running two pilot studies there—one in Zamora, central Spain, and another in Ourense, northwest. The Zamora pilot employs a technology developed by CARTIF, currently being tested at a wastewater treatment plant by the French multinational Veolia. This process uses microalgae to recover nutrients from food industry wastewater.
In Galicia, CETAQUA, a research institution focused on the sustainability and efficiency of the water cycle, is developing and testing a different technology for urban wastewater, which has distinct characteristics from industrial discharges. This process relies on more chemical and physical methods to recover nutrients.
But despite the promise of these technologies, experts warn of regulatory challenges. Although bio-fertilisers have been highlighted in several EU funding programmes, no clear regulatory framework defines them—something that in the past has led to scientific and legal confusion. "Legislation for bio-based products, especially those derived from waste, is quite complex," explains Fernando Burgoa Francisco, a sustainability analyst at CARTIF.
"Laws such as the Fertilising Products Regulation and the Wastewater Treatment Directive often overlap, making it difficult to determine which law applies." Many of these regulations, Burgoa adds, are outdated and fail to account for recent technological advancements in nutrient recovery. Much like the cost issue, the lack of a clear regulatory framework prevents bio-fertilisers from competing on equal terms with traditional solutions. "One of our main objectives in WALNUT is to develop a standardised glossary of terms to support the European Commission regarding bio and organic fertilisers," says Burgoa.
"Given the diverse range of products, technologies, and definitions currently in use," Encinas echoes, "achieving consensus and harmonisation on these terms is essential." Both experts believe that these efforts will pave the way for a unified directive or legislation on bio-fertilisers in the coming years. Some signs already point to that; two years ago, the European Commission issued its first resolution on the new fertiliser regulation, which included updated terms and legislation that reflect current needs.
"We believe this field is in the early stages of achieving a cohesive legal framework for bio-fertilisers and related topics," concludes Burgoa. "And it's just a matter of time before this tech becomes a viable, competitive alternative to traditional fertilisers."
Contacts:
Project coordinator:
Francisco Corona Encinas, PhD FUNDACIÓN CARTIF - fraenc@cartif.es
Communication Manager:
Francesco Agresta, ICONS - info@walnutproject.eu
Project website: https://walnutproject.eu/
LinkedIn: WALNUT
Twitter: @walnut_project
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