Spanish slugs overrunning Estonia almost no use for compost or biogas
A surge of invasive Spanish slugs is overwhelming Estonia, creating headaches for residents and officials struggling to dispose of them.
Gardeners are racing to remove the pests from yards, while waste management companies face uncertainty over how to handle the dead slugs.
The Environmental Board recommends burying them or composting in gardens, but digging holes for hundreds of slugs a day is impractical, and piling them in a corner of one's yard can quickly become a messy problem.
Some residents toss slugs in household trash, others in bio- or garden waste bins. Some of the slugs from Tallinn and Harju County reach the EKT Ecobio biogas plant, where they can be turned into gas for buses or liquid fertilizer.
But development manager Kalle Grents said Spanish slugs aren't ideal for energy production.
"We'll allow slug eggs and young slugs which are destroyed at 40–60 degrees Celsius into the biogas plant," Grents said. "Our process guarantees 70 degrees."
However, he noted that the slugs are mostly water and protein, so they produce little gas. Carbohydrates, fats and sugars are what feed the biogas-producing bacteria.
Waste management company Ragn-Sells, which composts yard and kitchen waste, faces similar challenges. CEO Kai Realo said the issue isn't whether slugs and their eggs die in compost heat, but whether compost should contain so much animal product.
Compost is plant-based by design, and the Estonian University of Life Sciences (EMÜ) warned that slug-heavy compost may not meet quality standards.
"If the waste contains a critical mass of slugs and we don't know what they were fed before they were stuck in the compost pile, it can't be considered normal compost," Realo explained, adding that at that point it's already considered contaminated.
She suggested officials have clear guidelines for handling Spanish slugs in place by next spring, noting that a key question is how dead slugs should be disposed of.
"Do we send them for biogas, bury them in landfills — or just toss them in yard waste and see what happens with the compost?" she asked. "We believe that approach is irresponsible."
At residents' request, Saku Waste Station added a dedicated container from AS Vireen for Spanish slug disposal this summer.
Kerli Laur, who has led anti-slug efforts for six years, said separate collection is convenient in theory, but it's often still easier for people to simply toss dead slugs into their household biowaste.
However, when pickups are infrequent, this can mean major odor problems — especially when people are picking up hundreds of slugs a night.
"Do you really want that thing sitting outside your house for a week or two?" she asked.
The Environmental Board is planning a formal action plan ahead of next slug season.
Eike Tammekänd, head of the board's Nature Conservation Bureau, said officials will consult waste management companies and local governments on the best options for biogas production and composting.
One guideline is already set: only dead slugs should go into waste.
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Editor: Mari Peegel, Aili Vahtla
