- They are used to backfill underground stopes and drifts at two Sandfire MATSA mines in Almonaster la Real.
Magnon, together with Sandfire MATSA, is leading from its renewable energy complex in Huelva a pioneering circular-economy initiative in Spain.
In late 2025, the two companies launched a project that will make it possible to reuse biomass fly ash as a partial substitute for cement in the backfilling of mining stopes and drifts. This is an unprecedented advance in Spain’s mining sector, strengthening both companies’ commitment to industrial innovation, efficiency, and the circular economy.
In this context, Magnon has begun managing, for this purpose, the ash generated at one of the facility’s three plants, Huelva 50 MW.
This ash is being recovered as a byproduct and progressively incorporated into the paste that Sandfire MATSA uses to backfill underground stopes and drifts. The use is being implemented at two of its mining operations, Aguas Teñidas and Magdalena, located in Almonaster la Real.
Innovative process
The initiative consists of progressively incorporating fly ash generated in renewable biomass power production as a cementitious material in manufacturing the paste used to backfill underground stopes and drifts. This ash has been designated by the Andalusian Regional Government’s Ministry of Sustainability, Environment, and the Blue Economy as a byproduct, suitable for this specific use at these two mines.
Improved strength and durability
Tests carried out by the Sandfire MATSA team and verified by independent laboratories with recognized national and international prestige in the construction field show that the paste resulting from the mixture of cement and biomass fly ash maintains—and even improves—its strength and durability and therefore performs better over time, providing greater long-term safety.
