Recycled nutrients for NPK production

GLOBAL STEWARDSHIP

Recycled nutrients for NPK production

Two EU projects are developing and bringing to market a new generation of fertilizers derived from bio-wastes, as Fertiberia’s Maria Cinta Cazador Ruiz explains.

Bio-waste streams are a potentially valuable resource – one that is under-utilised at present.

Turning currently discarded bio-wastes into products with value – so called valorisation – has obvious attractions. It meets EU waste management policy objectives, for example. And, by eliminating waste and maintaining materials in economic circulation, this approach is also in keeping with circular economy principles.

Mineral fertilizers feed the world and play a vitally important role in supplying nutrients to crops globally. But their production relies heavily on finite resources. The European fertilizer industry is particularly dependent on imports of primary raw materials. This exposes EU fertilizer producers to security of supply risks and price volatility.

Equally, there is a common misconception that all bio-wastes – regardless of their origin and composition – can become effective fertilizers. This is simply untrue. Crucially, bio-wastes must be free of potential harmful compounds if they are to be transformed into effective plant nutrients. To increase crop yields, they must also contain nutrients in plant-available form.

Spain’s Fertiberia has been at the vanguard in developing bio-wastes for use in fertilizer production – as an effective alternative to conventional mineral raw materials.

The NewFert project

Society is facing a ‘resource crunch’ due to a combination of water, food and minerals scarcity and increasing waste generation. These problems will only get worse in future as the global population continues to rise. Waste generation is in fact one of the world’s most alarming environmental problems: the EU alone produces more than 2.5 billion tonnes of waste annually.

The recent EU-funded NewFert project specifically addresses Europe’s enormous waste management challenge. Its purpose was to develop nutrient recovery processes capable of transforming bio-wastes into high-quality and valuable fertilizer products.

NewFert’s full project title is ‘Nutrient Recovery from Bio-based Waste for Fertiliser Production’. The overall aim was to develop new value chains from solid and liquid waste residues. More specifically, the project attempted to manufacture a new generation of fertilizers using ashes from waste incineration and livestock effluents, among others.

NewFert’s main focus was developing new bio-refining technologies capable of increasing nutrient recovery from waste – and creating a technically feasible and cost-effective industrial nutrient recycling scheme. Mitigating the environmental and socio-economic impact of conventional fertilizer production – by replacing non-renewable/fossil-derived raw materials with bio-based nutrient sources – was an equally important project objective.

The NewFert consortium was led by Fertiberia and comprised of five other partners, each possessing different but complementary areas of expertise:

• University of Leon (Spain)
• Drage & Mate International (Spain)
• Proman Management (Austria)
• Institut National de Recherche en Sciences et Technologies pour L’environnement (France)
• Kompententzzentrum Wasser Berlin Gemeinnutzige (Germany).

These organisations cover the whole value chain of nutrient recovery, including bio-based industries, SMEs, research & technology companies and academia. The project’s delivery plan was divided into eight different work packages.

From bio-waste to promising nutrients

An EU bio-waste screening and mapping exercise was initially carried out as part of the project.

Fertiberia developed a specific tool for assessing the potential suitability of biowastes for processing into fertilizing products. This was based on a list of bio-waste requirement criteria. A number of parameters (physico-chemical characteristics, supply, logistics, safety aspects, etc.) were determined for each bio-waste selected.

Around 30 percent of the 50 bio-based materials identified were found to comply with the required criteria.

Piloting nutrient recovery processes

Three novel nutrient recovery processes were developed and validated at pilot plant scale as part of the project:

1. Phosphorus recovery from ashes. This process extracted phosphorus present in ashes sourced from agro-food industry and waste water treatment plants and converted this into plant-available form (Figure 1). The ashes were firstly chemically treated by acid leaching and then neutralised. Phosphate salts were finally produced using a thermally-efficient reactor.

2. Phosphorus and nitrogen recovery from pig slurry. Nitrogen and phosphorus present in pig farm slurry were extracted and crystallised as struvite using biological acidification.

3. Nitrogen recovery and organic matter removal from pig slurry. In this synergistic process, nitrogen from pig slurry was recovered via bio-electrochemical systems (BES), while, simultaneously, microorganisms were used to reduce the organic matter content of the biowaste stream (Figure 2).

Fig. 1: The DMPhos phosphorus recovery process

Fig. 2: Nitrogen recovery and organic matter removal by a combined biological acidification and BES process

Fig. 3: Agronomic results obtained using bio-based NPK fertilizers (NF01, NF04, NF24, NF41 and NF42) vs no fertilization (C-) and standard NPK fertilization (C+)

A new family of bio-based NPK fertilizers

The project included technological validation at pilot plant scale. This successfully incorporated the most promising bio-based materials into a fertilizer production value chain. The following results were achieved:

• Development of a new family of NPK fertilizers
• 15 percent of the nutrient content of these NPK products was derived from bio-based materials
• 100 percent of their nutrient content is plant-available
• More than 80 percent of their nutrient content is water-soluble
• At least 10 percent of the combined nitrogen (N) and phosphorus (P2 O5 ) content is from bio-based materials.

The agronomic performance of all of the bio-based NPK fertilizer formulations was validated using greenhouse trials to determine crop yields. In most cases, the crop response was found to be identical to that obtained with the conventional NPK equivalent (Figure 3). These results generally demonstrated the agronomic suitability of NPK fertilizers that partially incorporate bio-based nutrients.

Next steps: the B-Ferst project

Building on the positive results of the NewFert project, a new project B-Ferst was launched in May 2019. (Its full project title is ‘Bio-based fertilising products as the best practice for agriculture management sustainability’.)

The new project’s main aim is to validate and implement NewFert’s bio-refining technologies at demonstration scale. Eight new bio-based fertilizers will be produced at this industrial scale. These will incorporate recovered nutrients from bio-wastes, specialised organic matter, biostimulants and coating agents.

B-Ferst will demonstrate how the production of these products can be integrated into both farm and fertilizer industry value chains. New logistics models and satellite technologies will be demonstrated by conducting three agronomic field trial campaigns at five separate European sites.

The successful implementation of these technologies at industrial scale could significantly reduce the use of non-renewable raw materials by fertilizer producers. That would contribute greatly to the necessary shift by the fertilizer industry to processes based on circular economy principles and ‘green’ production technology.

Further information

The NewFert project (www.newfert.org) and The B-Ferst project (www.bferst.eu) both received funding from the Biobased Industries Joint Undertaking, part of the EU’s Horizon H2020 research and innovation programme (grant agreements nº 668128 and nº 837583, respectively).