Can the biological stage of a mechanical–biological treatment plant that is designed for mixed municipal solid waste be successfully utilized for effective composting of selectively collected biowaste?

•In full-scale mechanical–biological treatment (MBT) plant compost was produced.•Production of compost, not stabilizate, contributes to increasing recycling rates.•Biowaste compost from MBT plant rich in nutrients (N, P, K, Mg, Ca)•During biowaste composting most intensive humification proceeded during 120 days.•Production of compost from biowaste in accordance with a circular economy.