RHIGUS (Prin 2022)

RHIGUS is a PRIN 2022 research project coordinated by the University of Brescia in collaboration with the Politecnico di Milano, bringing together expertise in environmental engineering, materials science, chemistry and sustainability assessment to develop next-generation technologies for phosphorus recovery.

Elza Bontempi (PI, UNIBS) and Carlo Punta. Carlo is responsible for the POLITECNICO DI MILANO unit.

♻️ Turning Waste into a Strategic Resource

Phosphorus is one of the essential elements for life. 🌱 Every day it supports food production, agriculture, advanced materials, batteries and numerous industrial processes. Yet Europe depends heavily on imported phosphate rock, a resource classified by the European Union as a Critical Raw Material because of its strategic importance and limited availability. At the same time, millions of tonnes of biomass residues are generated every year from wastewater treatment and livestock farming, and much of the valuable phosphorus they contain is still lost.

RHIGUS was created to change this perspective. Rather than considering these materials as waste, the project views them as an untapped resource. By developing innovative recovery technologies, RHIGUS aims to transform biomass residues into a new sustainable source of high-grade phosphorus, reducing the need for mining while contributing to a cleaner and more circular economy.

🌍 From a Linear to a Circular Economy

Nature does not produce waste: every resource becomes the starting point for a new cycle. RHIGUS follows the same principle.

Instead of extracting new raw materials from mines, the project recovers phosphorus already present in sewage sludge ash, poultry manure ash and other biomass residues. These materials are rich in phosphorus but are often disposed of or underutilized. Recovering this critical element means reducing landfill disposal, limiting environmental pollution, decreasing greenhouse gas emissions and creating new value from existing resources.

The project therefore contributes to one of the major challenges identified by the European Green Deal: making critical raw materials available through circular and sustainable strategies rather than increasing extraction.

⚗️ Two Innovative Technologies, One Common Goal

RHIGUS combines two complementary approaches.

The first is an advanced chemical process based on bio-derived nanostructured materials obtained from renewable cellulose. These innovative adsorbents selectively capture phosphorus while simultaneously removing contaminants from process waters. Their design follows eco-design principles, ensuring that sustainability is considered from the very beginning of material development.

The second approach is an innovative microwave-assisted thermal technology. Unlike conventional high-temperature processes, this method substantially reduces energy consumption while recovering high-purity phosphorus from biomass ash. The technology is based on a patented microwave-assisted carbothermic process that minimizes the use of fossil resources and maximizes resource efficiency.

🔄 Nothing is Wasted

One of the distinctive features of RHIGUS is its zero-waste philosophy.

The recovered phosphorus can be reused in agriculture and industry, while the remaining mineral residues are not discarded. Instead, they are investigated as secondary raw materials for sustainable construction products, contributing to the development of low-impact building materials.

In RHIGUS, every output of the process becomes the input for a new application, extending the life cycle of resources and reducing environmental impact.

💡 Why RHIGUS is Different

Many existing technologies focus only on recovering phosphorus. RHIGUS goes further by integrating scientific innovation, environmental sustainability and circular economy principles into a single strategy.

The project develops technologies that:

⚡ reduce energy consumption through microwave-assisted processing;

♻️ recover phosphorus exclusively from waste-derived materials;

🌱 replace virgin raw materials with secondary resources;

🏗️ reuse residual materials instead of producing new waste;

📉 reduce greenhouse gas emissions and landfill disposal;

🌍 evaluate environmental performance through dedicated sustainability assessment methods.

This integrated approach makes RHIGUS much more than a phosphorus recovery project: it is a model for future sustainable resource management.

🌾 From Science to Society

Recovering phosphorus is not only a scientific challenge—it is also an investment in food security, environmental protection and industrial competitiveness.

A more efficient phosphorus cycle means producing fertilizers more sustainably, reducing Europe's dependence on imported resources and supporting innovative industrial processes based on recycled materials. At the same time, improved waste management contributes to cleaner water, healthier soils and lower environmental impacts.

The knowledge generated by RHIGUS will also support future policies on waste management, critical raw materials and circular economy, providing scientific evidence for more sustainable resource strategies.

The project implements the following SDGs of the 2030 Agenda for Sustainable Development

Papers published in the frame of the project:

• Exploring the potential of sewage sludge ash for CO2 sequestration and resource recovery

• Enhancing phosphorus recovery from poultry litter ash through microwave-assisted thermochemical treatment for improving its solubility

• Characterization of the ash samples before and after thermal processing aiming phosphorus extraction and residues valorization 

• Dual valorization of sewage sludge ash through phosphorus recovery and wastewater remediation

• Microwave-Assisted Thermochemical Treatment of Sewage Sludge Ash for Enhanced Phosphorus Recovery and Mitigation of Cr(VI) Formation.

See also the newspaper article about the project:

• Eco di Bergamo

• e-cology.it

• BresciaOggi

• BresciaOggi

• ARGAV

• GreenReport

• RivistaNatura