RHIGUS (Prin 2022)

The EU Commission has classified phosphate rock (PR) as a critical raw material due to phosphorus (P) importance to guarantee food security in the next years. The first focus in the sustainable management of this resource is the reduction in its losses by dissipation in the supply-demand chain. The results of previous EU projects that involved the RIGHUS partners demonstrate that some biomass wastes, such as animal manure, are very promising in terms of alternative P-sources when their ashes are recovered after thermal valorization (in accord with the EU waste management and energy recovery strategies). 

The project proposes the recovery of P from biomass waste ashes derived from thermal conversion technologies by using two new technologies (thermal and chemical). The first one is based on the thermal reduction of phosphates, generated by suitable biomass waste sources based on a pyrometallurgy technology to obtain a low-energy carbothermic reaction. This process involves only waste raw materials; no mineral resources or fossil fuels are required. This approach makes the process very promising for several reasons:

• less energy use,

• solid state vs liquid state approach (less waste),

• use K(Na)-rich secondary feeds (waste) to directly produce also K(Na)-phosphate,

• use of biocarbon including biochar/hydrochar, to reduce the carbon footprint of the reactions.

The second (chemical) method proposes the ecodesign and synthesis of totally organic nanostructured sorbent materials, made of nanocellulose recovered from biomass waste (such as agricultural waste), for the recovery of phosphates from leaching waters of the chemical process. Different formulations of the same cellulose-based material will be developed for facing three strategic issues: a) the removal of heavy metals from leaching solutions, b) the selective sorption of phosphates for the production of fertilizers, c) the capture of CO2 produced at the end of the previously described thermal treatment.

The residual ash, after P-recovery treatments, will be proposed as a precursor in eco-sustainable materials, thus realizing a completely waste-free process.

The project includes a sustainability evaluation in terms of energy consumption and GHG emissions.

RHIGUS proposed technologies are focused on key sectors of the EU policies: the project shows the possibility of accessing alternative feedstock sources (sustainable biomass), with the consequent reduction of the GHG emissions and waste (such as SS, animal manure) to be landfilled.

The project is realized by two partners.

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

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