Population growth, changing in diet and lifestyle, modern agriculture and intensive livestock farming are the main drivers responsible for the increase in food production observed in the last 50 years, which reached approximately 24 million tons of food per day worldwide. The associated excessive use of chemical fertilizers in the agricultural sector causes high environmental impacts, such as eutrophication and greenhouse gas emissions, along with the exploitation of soil, water and natural resources. Furthermore, as a results of the agricultural activities, huge amount of waste is generated, with livestock manure as main contributor.
Thus, innovative sustainable solutions are required to reduce the pressure on finite resources, to decrease the amount of chemical input in agriculture, and to promote a more responsible management of waste. In the view of circular economy, re-use and valorisation of agricultural waste are of paramount importance to foster the production of bio-based fertilisers. In addition, waste treatment technologies, such as anaerobic digestion and hydrothermal carbonization, represent a solution to stimulate material and energy recovery.
Nutrients, such as phosphorus, nitrogen and potassium, can be recovered from livestock manure to produce high-quality fertilizer ingredients, as struvite and K-struvite. The purpose of the M.Sc. thesis is to investigate different strategies for nutrient recovery from such secondary source. Experimental activities will be performed at the lab-scale in the view of developing innovative technologies to scale-up in relevant environment in cooperation with industrial stakeholders. A possible recovery route will concern the recovery of nitrogen and phosphorus from the liquid fraction of digestate via selective precipitation, ion exchange or other separation/purification techniques. The recovery will be optimized to maximize the nutrients recovery efficiency and recovered products characteristics, while minimizing the addition of chemicals and the use of energy, to guarantee solution techno-economic feasibility and environmental sustainability.

Reference teacher: Dr. Andrea Turolla – andrea.turolla@polimi.it