Abstract
Nitrogen-based fertilisers are pivotal for global food security, yet their production is a notable source of greenhouse gas emissions. Urea, a vital fertiliser with significant market presence—19% in Europe and 33% globally—is produced through an energy-demanding process reliant on fossil fuels. This study introduces a ’Green’ Urea plant concept, aimed for implementation in Ravenna, Italy, harnessing exclusively renewable energy sources to foster agricultural sustainability. With a production capacity of 1,300 tonnes per day, this facility neighbours Italy’s first carbon capture and storage (CCS) facility at Ravenna. The core of the proposed methodology is the synthesis of green ammonia. Seawater Reverse Osmosis-Polymer Electrolyte Membrane Electrolysis (SWRO-PEM) and Pressure Swing Adsorption (PSA) yield the necessary hydrogen and nitrogen feedstocks. An enhanced Haber-Bosch process utilising a Ru-based catalyst, facilitating lower operational conditions (500◦C and 100 bar) for the aforementioned reagents. Urea synthesis integrates CO2 captured both from the adjacent Ravenna CCS and Direct Air Capture (DAC) systems, culminating in a closed-loop operation. Simulation of the PSA, Haber-Bosch, and Urea processes is conducted via Aspen Hysys, complemented by a GUROBI Python-based linear cost minimisation model to calculate the optimal mix of wind and solar energy, ensuring year-round production congruent with real-world climate patterns. Energy storage and discharge is modelled to minimise excess energy loss. Moreover, utility costs are optimised through Heat Exchanger Network integration and a cost minimisation model implemented in GAMS Studio. An environmental assessment, using OpenLCA, contrasts the ’Green’ plant’s footprint with traditional urea manufacturing, examining economic, environmental, and thermodynamic Key Performance Indicators (KPIs). The integrated modelling and KPI analysis provide evidence to suggest that the proposed plant’s fiscal viability, environmental footprint, and N2 conversion present a viable