DEEP PURPLE develops fertilizer from bio-waste

EU-funded project, DEEP PURPLE, has developed a fertilizer created from bio-waste and waste water, which releases nutrients slowly to the soil, in order to make it more effective.

In 2019 a collaborative effort from partners across Europe created a multi-biorefinery platform, which valorises the organic fraction of municipal bio-waste as well as domestic waste water. Bio-waste and wastewater hold great potential as a source of renewable energy and recycled materials. Waste water contains valuable components such as cellulose and nutrients that can be used as feedstock for many breakthrough applications. This way, resources are reused and not wasted, all in the spirit of a more sustainable and circular economy. Such innovations are desperately needed, as currently 75% of the up to 138 million t of urban bio-waste are incinerated and landfilled in the EU with huge ecological and economical costs.

Sample of the slow-release bio-fertilizer

At the core of the endeavour to produce this slow-release bio-fertilizer was the biomass platform with the first photobioreactor biorefinery of its kind built at the Linares wastewater treatment plant in Linares, Jaén, Spain. The plant is operated by Aqualia and owned by the Linares Council and utilises microscopic power houses, called purple phototrophic bacteria (PPB), which turn sunlight and organics from the waste streams into an enriched biomass, containing valuable nutrients suitable for further processing. In an initial phase, the steps of pre-treatment, conversion, and downstream processes were optimised and upscaled. In a second phase, the demo sites were designed, launched, and monitored in order to demonstrate the photo-biorefinery multi-platform approach at a demo-scale. In the third and last phase of the project, the bio-based products were validated at an industrial scale and trialled in the field.

Photobioreactors at Linares WWTP

The slow-release bio-fertilizer development was spearheaded by AII-RG (Roullier) in their plant in Saint-Malo, France. The special biodegradable coating for delaying the release of the nutrients included polyhydroxyalkanoates (PHA) and cellulose nanofibers (CNF) which were derived from the biomass and cellulose platforms. Partners ACTIVATEC and ITENE played key roles in extracting PHA and developing the coating, and AII-RG successfully produced and tested the slow-release bio-fertilizer at an industrial pilot plant and later at a demo level, with plans to expand its implementation to various locations in Europe. The result is an eco-friendly and agronomically focused fertilizer dedicated to organic farming.

Overview of the multiplatform approach

Other high value bio-products created through this multi-platform photo-biorefinery approach are bio-polyesters and bio-film for packaging, composites for self-healing concrete and ectoine for cosmetics production.