Waste cooking oil – An extremely harmful or highly useful waste?
Within the framework of the European ECOLE project (Interreg Alpine Space), partners from Italy, Germany, Austria, Slovenia and France are exploring ways to strengthen the circular economy in industrial zones. The Regional development agency of the Ljubljana urban region (RRA LUR) has focused on Industrial Zone Zalog, connecting two major companies with the local community. The key link? Waste cooking oil. This valuable waste can be converted into biodiesel, soaps, lubricants, paints, varnishes, or even scented candles, yet a systematic collection system is still lacking. RRA LUR is preparing expert groundwork for a pilot project to establish a collection system in Zalog.
From Industrial zones to Eco-Industrial parks
Experience from project partners and in-depth analyses of the circular economy show that industrial zones can more easily integrate circular processes and transition into Eco-industrial parks if they have a dedicated management entity. This entity fosters service optimization and strives toward the common goal of reducing the carbon footprint. Such optimization is achieved through industrial symbiosis, where companies exchange resources—including logistics services and energy solutions such as the reuse of waste heat. A great example of this is Atlantis water park in Ljubljana, Slovenia, where company BTC utilizes waste heat from the nearby Aquafil factory, a circular economy company that produces ecological or “eternal” nylon from discarded nylon. In Slovenia, a fully circular management model has yet to be established.
Waste cooking oil as an opportunity
RRA LUR emphasizes that the circular economy in industrial zones is not only about optimizing production processes but also about involving the community in sustainable solutions. In the Industrial Zone Zalog, a specific circular potential has been identified between businesses and the local community: household waste cooking oil. This waste material is highly valuable, particularly for biodiesel production, yet a systematic collection system is not yet available in Ljubljana. The Polje District community has expressed strong support for such an initiative. Since two key companies operate in the zone—JP VOKA SNAGA, the official collector of household waste oil in Ljubljana and ten surrounding municipalities, and KOTO, which processes the oil into biodiesel—RRA LUR is developing expert groundwork for a pilot project to collect waste cooking oil from households in Zalog. The goal is to establish a foundation for testing collection models, which, following a strategic decision by the official municipal waste management company, could be implemented systematically in Zalog.
The first step – raising awareness
While capacities and strategic solutions for the systematic collection of used oil are being developed, it is crucial that residents recognize the importance of proper oil disposal. To this end, on February 18, 2025, RRA LUR, in collaboration with the Polje District community, organized an engaging awareness workshop in Zalog. Participants were introduced to the harmful consequences of improper oil disposal, which can extend as far as groundwater contamination:
- Clogging of pipes and sewers – Oil accumulates on pipe walls, reducing flow capacity and causing blockages, which can lead to water overflows and high cleaning costs. Fat deposits also adhere to mechanical equipment in wastewater treatment plants, promoting the growth of filamentous bacteria that disrupt the cleaning process.
- Water pollution – Oil floating on the water’s surface prevents oxygen transfer, endangering aquatic organisms.
- Groundwater contamination – Disposing of oil in compost prevents natural decomposition and microbial activity. Over time, it seeps underground, polluting groundwater.
- Attracting rodents – In the sewer system, oil serves as a food source for rats, improving their survival conditions.
Participants also learned about the process of converting waste cooking oil into biodiesel. Current legislation requires at least 7% biodiesel to be blended into diesel fuel, meaning that, with proper disposal, individuals can contribute to this sustainable fuel source. To do so, simply let the oil cool after use, pour it into any empty plastic bottle, and drop it off at one of the designated collection points:
- At KOTO in the Industrial Zone Zalog, used cooking oil can be handed over at the security gate. According to Peter Jenko, this collection point was set up to make it easier for Zalog residents and others to dispose of their oil.
- At JP VOKA SNAGA’s collection centers on Barje or Povšetova Street in Ljubljana, or at their mobile hazardous waste collection unit (schedule available on their website).
Waste cooking oil as a raw material for candles
The engaging awareness workshop was led by Bogdan Dobnik from the company BOLJE, which, in addition to using waste cooking oil for biodiesel, has developed a particularly creative solution—turning it into scented candles under the brand name Oilright. The workshop concluded with a fun and simple candle-making activity.
Project ECOLE: A Network of Eco-Industrial Zones for Strengthening Smart and Circular Economy in Alpine Regions is co-financed by the European Union under the Interreg Alpine Space program. The views and opinions expressed in this document are solely those of RRA LUR and do not necessarily reflect the views of the European Union or the program’s managing authority.
