Title : From mine waste to root zone: Smectite-rich marl ceramics as self-regulating emitters for coupled water and nutrient delivery in arid agriculture
Abstract:
Water scarcity and nutrient loss jointly limit agriculture across Morocco's arid and semi-arid belt. Conventional irrigation applies water in pulses that far exceed instantaneous root demand: much is lost to evaporation and deep percolation, while the soluble fertilizers carried with it are leached below the rhizosphere before roots can intercept them. This calls for continuous delivery driven by soil demand rather than pump schedules. This project addresses that need with sub-surface porous ceramic emitters manufactured entirely from phosphate mine waste. The “Gantour Benguerir” basin, is mined open-pit: reaching marls beds 20.5 m thick in total requires stripping 69m of overburden, so that at 30% ratios, Benguerir alone produces over 10 million tons of waste annually, dominated by smectite-rich marls, stored in surface piles that immobilize land, emit dust, and impose perpetual transport, stabilization and monitoring costs while generating no value.
We characterized these marls and identified smectite clays and dolomite as the functional phases, dolomite decomposition acting as the principal source of microporosity on firing. Pellet formulation, shaping and sintering at 1050 °C were optimized through a design-of-experiments approach using an organic waste as pore former. The optimized ceramics reached an average water absorption of 64% while retaining a compressive strength of 106.58 MPa, well above the loading imposed by a sub-surface soil environment. Desorption remained markedly slow, confirming the self-regulating release sought for fertigation. A plant irrigation and fertigation test bench has been established with the UM6P Experimental Farm, and emitter geometry is now being modelled as parallel cylindrical elements with a flared outlet to suppress clogging.
This establishes that a mining liability can be converted, at low cost, into a durable emitter combining high water uptake with slow controlled release turning phosphate waste into an instrument of water conservation.
Keywords: sustainable materials - Waste Valorization – Water Use Efficiency - Circular Mining
