Biological waste processing

Maribor is at the heart of Europe’s economy, but it depends heavily on outside resources to meet its demand for raw materials, energy, water, and food, and to manage its space, waste and emissions. Slovenia’s self-sufficiency is low, fertile soil is disappearing, and food quality is declining, while young people often lack knowledge about, and motivation for, healthy eating.

Maribor does not want any more landfill sites. Instead, it is aiming to use the waste produced by its residents as an input material for making new products.

The main objective of the project is to use the city’s waste as a resource for producing and adding value to new products and food, applying an innovative process for producing soil, and subsequently to improve local self-sufficiency and lower the region’s carbon footprint.

The URBAN SOIL 4 FOOD project starts by addressing the challenge of how to turn the city’s organic and mineral waste into fine soil, for use in food production, parks and construction. The project’s partners will develop safe and certified soil, and produce electricity as a by-product; this will be achieved using a combination of fermentation, pyrolysis, and homogenisation technologies.

The project encompasses four main inter-connected circles, with two overarching investments: the establishment of a pilot system for urban soil production, and the creation of four urban gardens (using the urban soil produced).

The material circle will analyse the material flows of the city’s waste with a view to producing urban soil. As part of the food circle, some currently unused municipality land will be turned into urban community gardens, where food will be grown – and the circle completed by creating an urban food label. The open innovation circle comprises establishing an agricultural and food lab for developing and testing innovative pilot concepts, such as urban flowers for urban bees, micro urban gardening and urban soil rehabilitation, while simultaneously supporting innovative start-ups working in the field of the circular economy. The knowledge circle will encompass sharing the knowledge gained from the project with other cities in Slovenia and in the EU, as well as the development of certificates and patents in order to promote urban soil technology internationally.

In the URBAN SOIL 4 FOOD pilot project, we will process small quantities of organic waste, primarily wood and trimmings.Cutting-edge technology will be used to process up to 500 kg of organic waste a year, producing soil that will be used in Maribor’s greenhouses, urban gardens, and green spaces.

The main technological processes to take place:

  • dry fermentation, which will be undertaken in a tank with negative pressure to prevent odour emissions;
  • composting using a system which is usually used by large hotels to process large quantities of kitchen waste, and which has filters preventing odour emissions; and the mixing of compost i.e. soil, altering the ratios between materials to produce as fertile a soil as possible.


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