Freshwater salmon farming in Chile generates approximately 522,180 tonnes per year of sludge—comprising fish feces and uneaten feed—which is currently disposed of in disused industrial landfills. Simultaneously, the national seaweed processing industry produces an estimated 15,000 tonnes of annual waste, commonly referred to as brozas. Additionally, thousands of tonnes of seaweed (e.g., arribazones, sargassum) accumulate along Chile’s coastlines due to recurring storm surges—a phenomenon increasingly linked to climate change.
In parallel, the forestry, fruit, and broader agricultural sectors are facing a surge in the costs of fertilizers and soil amendments, which rose by over 130% as of 2023. Vast areas of land now require remediation following forest fires and prolonged droughts. In response, a methodology has been developed to formulate a soil amendment for use in agricultural and forestry contexts. This amendment is derived from fish-farm sludge, vegetative waste (brushwood), and stranded macroalgae (Figure 1). The process involves the chemical, physical, and microbiological characterization of the raw materials; preparation for pelleting; and microbiological analyses and soil metabarcording both prior to and following field trials.
Currently, field trials are being conducted on industrial species in the Araucanía region, specifically targeting post-fire and eroded soils (Figure 2). The performance of the developed amendments is evaluated against various conventional fertilizers—including earthworm humus, triple superphosphate, and poultry manure—while unfertilized topsoil serves as a control (Figure 2). Preliminary results indicate that the amendments enhance plant growth and development by 30% to 130%.
Financial support: This study is a collaboration funded by several partner companies: Ingeniería Sustentable Faro Verde, Algas Bucalemu, Salmonífera Dalcahue, and Gromor SpA. Additional funding was received from the ANID’s FONDEF IDeA Project ID25I10044, Universidad Católica de Temuco and Unidad de Desarrollo Tecnológico de la Universidad de Concepción. The authors express their gratitude to all funding sources.