Investigating the Potential Use of End-of-Life Fire Extinguisher Powder as a Soil Amendment in Different Soil Types: A New Approach Following a Circular Economy Model

Abstract

A first attempt to assess the potential alternative use of fire extinguisher filler powder after its exhaustion has been investigated in the present research. The chemical composition of fire extinguisher filler powder, specifically type ABC 40%, consists of monoammonium phosphate and ammonium sulfate. As its nitrogen and phosphorus content is particularly high, the thought of its possible use as a fertilizer and/or a soil amendment is a challenge. For this purpose, a pot experiment was carried out and two leafy vegetables (spinach and lettuce) were used as biomarkers. Two soil samples from rural areas, one acidic (pH = 5.8 ± 0.1) and one alkaline (pH = 8.2 ± 0.7), were selected for the experiments. Filler powder from a used fire extinguisher was added to the soil samples in two levels (1 and 2% v/v). It was found that the addition of fire extinguisher filler powder caused no toxicity to either of the two plants studied. On the contrary, an increase in their above-ground biomass was observed, proportional to the amount of powder added. It was established that in the pots where the powder was added, in both plant species observed, the plant height, root length, and chlorophyll content of leaves increased, the total antioxidant capacity was enhanced, and the concentrations of nitrate and phosphate in the leaves and roots of plants also increased, compared to the soil without the addition of fire extinguisher powder. The early signs appear to be encouraging, as an increase was observed in almost all aspects. The mandatory end of the life cycle of the powder as a fire-extinguishing agent and its disposal is also a challenge in the context of the circular economy, as reducing the energy requirements for fertilizer production is one of the objectives of sustainable development.