The Slag in Zurich’s Trash Bags

Zurich’s state apparatus has run into a rather unglamourous bottleneck. It is neither a sudden financial deficit nor an infrastructure breakdown, but the quiet daily habits of the canton’s pet felines. Officials at the administrative offices for waste and the environment are now nudging pet owners to abandon traditional mineral cat litter in favour of plant-based alternatives.

The rationale behind this official request is purely logistical. Traditional cat litter consists primarily of bentonite, a clay mineral extracted internationally, dried through energy-intensive processes, and sold in heavy bags. When discarded, Swiss hygiene regulations strictly mandate that used litter must enter the municipal household waste stream to prevent the spread of potential pathogens. It ends up in waste incineration facilities, where it reveals its fundamental flaw: bentonite does not burn.

What remains after the incineration process is an unyielding mineral slag that must be deposited in specialized landfills. According to the 2022 national garbage bag study, bentonite litter accounts for 4.4 percent of the weight of an average household trash bag. In the Canton of Zurich alone, the Office for Waste, Water, Energy and Air estimates that mineral litter generates up to ten percent of all incineration slag. That equates to roughly 9,000 tons of inert waste every year—a volume requiring 450 truckloads to haul away to increasingly scarce landfill capacity.

Here, Swiss administrative reality encounters its own procedural weight. Opening new landfill sites or extending existing facilities involves planning and approval procedures so cumbersome that expanding capacity takes years. Rather than streamlining the bureaucracy required to build waste infrastructure, authorities prefer to manage consumer behaviour.

The proposed alternative relies on market-available organic alternatives made from wood chips, cellulose, or agricultural residues. These plant-based products absorb liquid effectively, clump as needed, and, crucially, burn almost completely during incineration. Instead of clogging specialized landfills with thousands of tons of residue, organic litter converts directly into electricity and district heating. It is a neat, rational solution to a self-inflicted logistical nuisance—provided cat owners actually decide to change their habits.

Written by Martina Kirchner martina.kirchner@alpineweekly.com