Fertilizer International 526 May-Jun 2025
2 May 2025
PuraLoop – a circular solution that delivers for crops
COMMERCIAL PHOSPHORUS RECOVERY
PuraLoop – a circular solution that delivers for crops
ICL has introduced PuraLoop, a new phosphate fertilizer created from recycled phosphorus. This innovative product ‘closes the loop’ by transforming previously discarded waste into a valuable agricultural resource. ICL’s Patricia Imas and Lucas van der Saag highlight its environmental, economic and agronomic benefits.
Background
Phosphorus is an essential nutrient for plant growth, playing a pivotal role in energy transfer, photosynthesis, and nutrient transport. But transforming phosphate rock, a non-renewable resource, into fertilizer is energy-intensive and requires the large-scale consumption of water and basic chemicals. The production process also generates huge volumes of phosphogypsum waste which require long-term storage and management.
Interest in the recovery and reuse of phosphorus – as a more sustainable alternative to primary phosphate rock mining – has grown in recent years, particularly in Europe. This is being driven by several factors:
• Currently, the EU has access to one phosphate resource only – Yara’s Siilinjarvi phosphate mine in Finland – and consequently the region is import-reliant for phosphate rock.
• The EU also added phosphorus to its critical minerals list in 2023 to highlight its strategic importance and the need for supply security.
• The gradual introduction of cadmium limits under the EU’s Fertilising Products Regulation (FPR), which entered into force in 2022, also excludes phosphate rock imports from certain countries.
In response, ICL has developed an innovative process known as PuraLoop to transform sewage sludge ash (SSA) into an efficient phosphate fertilizer and effective crop nutrient source.
The company has been operating a first-of-its-kind phosphate recycling unit at its Amsterdam fertilizer (Amfert) production site in the Netherlands for the last five years (Fertilizer International 494, p27). This novel unit allows ICL to incorporate recovered phosphorus from secondary sources and reuse this in the industrial-scale production of phosphate-based fertilizers.
The unit, which uses high volume alternative sources of phosphorus such as sewage sludge ash (SSA), was formally opened in March 2019 (see photo). It is helping the company to ‘close the loop’ and develop a portfolio of fertilizers based on recycled phosphorus, as ICL’s Lucas van der Saag explained to delegates at last year’s CRU Phosphates conference in Warsaw.
“The idea at ICL, with our current process, is to use this sewage sludge ash as basis for the production of fertilizer,” said van der Saag. “We believe that sewage sludge ash, as a raw material, has a huge potential for phosphate recovery.”
About 32% of sewage sludge from Europe’s wastewater treatment plants ends up being incinerated to create SSA currently. This one source alone could provide around 6% of Europe’s phosphate fertilizer demand, according to estimates.
“If we look towards the future, if all of Europe’s sewage sludge was incinerated and reused, we could go up to around 20% [of demand],” said van der Saag. “So there is great potential in using sewage sludge ash to replace phosphate ore in Europe.”
Currently, within the EU, around 34% of sewage sludge is directly used in agriculture with (as already stated) a further 32% being incinerated as SSA, while the remainder either goes to landfill (12%), composting (12%) or other uses (10%). Applying sewage sludge directly to soils is not ideal and carries risks, as it can contain undesirable and potentially hazardous soil contaminants such as drugs.
SSA is produced from the combustion of dewatered sewage sludge in an incinerator. Beneficially, the resulting incinerated ash is free from organic contaminants and enriched in phosphorus (10-13%), containing the equivalent of around four million tonnes of P globally, with Europe contributing around 0.3 million tonnes of P to this total.
In theory, although farmers could spread SSA directly on their fields, its phosphorus content is not much use as it is largely unavailable to crops. The heavy metal content of SSA also means it does not comply with EU regulatory limits (Table 1).
The PuraLoop process
By recovering and reusing phosphorus on a commercial scale (Figure 1), ICL’s PuraLoop process benefits Europe in several ways, as Lucas van der Saag explains:
“One is that we can turn waste into a product of agronomic and economic value. We can also reduce our dependency for critical raw materials on outside sources and, finally, we can have a leadership role in environmental and technological innovations for food and fertilizer production.”
In the PuraLoop process, SSA is firstly mixed with sulphuric acid or phosphoric acid in an acidulation step. The run-of-pile (ROP) material is then granulated to produce the fertilizer end-product. In 2023, test runs with this SSA-based process met all the necessary EU regulatory requirements to produce single superphosphate (SSP) and triple superphosphate (TSP). This included legal stipulations such as the FPR D1 conformity audit and full REACH registration.
The advantages of using SSA as a fertilizer production raw material, according to van der Saag, is that it eliminates odour (compared to the processing of phosphate rock) and is essentially cadmium- and fluorine-free. Agronomic trials have also shown very good results, he added.
A full-scale industrial PuraLoop installation is now up and running at ICL’s Amfert production site at the port of Amsterdam. This is capable of producing two products – the phosphate fertilizer PuraLoop 0-38-0 and NPK fertilizer PuraLoop 5-5-22. ICL manufactured 1,000 tonnes of PuraLoop 0-38-0, known as PuraLoop 38, during successful production runs at the end of 2023. Production of PuraLoop 38 was 6,000 tonnes in 2024 and is expected to reach 15,000 tonnes in 2025. ICL is also planning to expand the PuraLoop product range by introducing SSA-based PK products this year.
A pure and practical phosphate fertilizer
Unlike unprocessed sewage sludge ash, PuraLoop 38 complies with European regulations governing the reuse of waste materials in fertilizer. This includes REACH registration with the European Chemicals Agency (ECHA). Overall, PuraLoop 38 is a safe product that meets stringent European standards for agricultural use, with a heavy metal content below EU regulatory limits (Table 1).
PuraLoop 38 is offered to the market as compact, free-flowing granules. These are easy to apply as their highly consistent and dust-free nature ensure uniform spreading in the field. The product is suitable for direct application in fields, orchards and crop plantations. It can also be bulk blended with other fertilizers. ICL recommends incorporating PuraLoop 38 directly into the soil for optimal results.
The phosphorus present in PuraLoop 38 is in phosphate form (38% P2O5 total) and is therefore available for plant take up. One of the standout features of the product is its double-action formulation:
• Plants get an initial boost from its water-soluble phosphate content (20% P2O5)
• The remaining phosphate content is then released by organic acids in the crop’s root zone.
This ensures that around half of the PuraLoop’s phosphorus content is immediately available to plants, providing an initial nutrient supply. The remaining phosphorus is then root-activated, offering prolonged and gradual availability throughout the growing season while reducing soil fixation, leaching and runoff.
This dual-release mechanism enhances phosphorus use efficiency by ensuring plants can access P over an extended period to support crop growth and productivity.
In addition to phosphorus, PuraLoop also contains other essential nutrients such as potassium (K), magnesium (Mg), calcium (Ca), and sulphur (S) – as shown in Table 2 – along with small amounts of micronutrients. This broad nutrient profile supports balanced crop fertilization and overall plant growth.
Proven agronomic performance
ICL has conducted pot and field trials in Israel and Europe to validate the agronomic effectiveness of PuraLoop 38. These have included:
• Cabbage – 2022 pot trial, ICL R&D North, Israel, in a low phosphorus, sandy soil.
• Maize – 2022 pot trial, Landlab, Italy, in a low phosphorus, sandy soil.
• Pepper – 2022 pot trial, Landlab, Italy, in a low phosphorus, sandy soil.
• Rye grass – 2023 pot trial, Weihenstephan Triesdorf University, Germany, in a slightly acid silty loam and slightly alkaline sandy loam.
• Maize – 2023 pot trial, Weihenstephan Triesdorf University, Germany, in a slightly acid silty loam and slightly alkaline sandy loam.
• Winter flax – 2024 field trial, University of Agriculture, Krakow, Poland, on a neutral silty loam.
• Rapeseed – 2024 field trial, France, on an alkaline clay loam.
All of these trials have consistently demonstrated that PuraLoop performs on a par with traditional phosphorus fertilizers like TSP – in terms of phosphorus availability, and crop growth and yield responses. Example results for the 2024 French rapeseed field trial are shown in Figure 2.
“PuraLoop underscores ICL’s commitment to sustainability and innovation. Its market entry is a significant step towards making agriculture part of the circular economy.
The main agronomic conclusions to date are:
• For all trials, control treatments had significantly poorer development, showing that soils were responsive to P fertilization.
• For all trials, PuraLoop matched the performance of conventional, fully water-soluble phosphate fertilizers.
• In completed field trials, Puraloop outperformed TSP – with ongoing field trials showing similar positive findings.
• While P uptake from PuraLoop was slightly lower than TSP on higher pH soils, it was sufficient for optimal plant growth. PuraLoop-treated pepper plants, meanwhile, demonstrated a higher P uptake versus TSP.
• Since PuraLoop has a root-activated phosphorus fraction, unlike TSP, residual effects for consecutive growing cycles are expected.
Further agronomic trials are planned in 2025.
Conclusions
PuraLoop underscores ICL’s commitment to sustainability and innovation. Its market entry is a significant step towards making agriculture part of the circular economy.
By closing the loop on phosphorus use, and transforming waste into a resource, this innovative product promotes sustainability and resource efficiency. Its proven agronomic performance, ease of use and circular economy attributes make PuraLoop an ideal choice for farmers looking to enhance crop yields and quality while contributing to a more sustainable future.
The environmental benefits are significant. In particular, by incorporating recycled phosphorus, PuraLoop helps reduce the environmental impacts of fertilizer production. Its substitution for conventional phosphate fertilizers conserves phosphate ore reserves and reduces the greenhouse gas emissions associated with the mining and processing of phosphate rock. Phosphorus reuse also helps to create a more circular economy and sustainable waste management system by diverting waste from landfill.
By offering farmers an affordable, cost-effective alternative to traditional phosphate fertilizers, PuraLoop has economic merits too. In the long term, greater use of products based on recycled phosphorus should also help stabilise fertilizer price volatility by reducing market dependency on fluctuating phosphate rock prices.
