The global push toward circular economies is transforming how cities handle what was once considered waste—municipal sewage sludge. A new review in *South Sustainability* (published as *Sostenibilidad del Sur* in Spanish) by lead author Isabel Milagros Gavilan-Figari of the Centro de Innovación Productiva y Transferencia Tecnológica Agroindustrial Ica in Peru offers a timely roadmap for turning sludge into a resource while balancing environmental, health, and economic goals.
Gavilan-Figari and her team argue that there is no one-size-fits-all solution. “The most suitable sludge management pathway depends on local conditions,” she notes, “including treatment infrastructure, regulatory frameworks, and even climate.” This means cities must weigh options like agricultural reuse, energy recovery, or construction material production—not just for sustainability, but for commercial viability.
For the energy sector, the findings are particularly compelling. Sludge-to-energy pathways, such as anaerobic digestion or biofuel production, are gaining traction as alternatives to landfilling or incineration. But as the review highlights, these methods require pre-treatment, strict process control, and reliable monitoring to be both efficient and safe. “Resource recovery can reduce environmental burdens and generate value,” Gavilan-Figari explains, “but only if implemented with robust infrastructure and oversight.”
The study also underscores the tension between public health and profit. While land application of biosolids can enrich soils, it demands careful management of contaminants like heavy metals and pathogens. “Agricultural reuse improves soil fertility,” she says, “but without proper safeguards, it risks harming ecosystems and communities.”
What emerges is a call for integrated decision-making—one that considers life-cycle impacts, regulatory constraints, and social equity. For industries eyeing sludge as a feedstock, this means future investments must align with local realities, not just global trends.
As cities worldwide grapple with aging infrastructure and tightening regulations, Gavilan-Figari’s work suggests a shift is underway: sludge is no longer just a disposal problem, but a strategic opportunity. The question now is which cities—and which industries—will seize it first.