Phasing out peat in growing media - results from Scandinavian studies

Summary

The first part of this report deals with peat as a natural resource in the three Scandinavian countries; Denmark, Norway and Sweden. Mires with peat receive raised awareness today with increased climate change and decreased biodiversity. The authorities and several non-governmental organizations are advocating to reduce the use of peat. Communication is often directed towards private users, who undertake about half of the peat sold for growing media as estimated both by volume and value. Private growers may act as a driver for change to reduce peat use because they can afford to pay more for alternatives than commercial growers, and they can take more risks if growing media do not always perform well. Organic regulations restrict the use of peat to horticulture. Since mineral nitrogen fertilisers may not be applied in organic growing, the development of growing media for the organic sector may increase our knowledge on applicability of organic materials more rich in nutrients than peat e.g. composts.
Scandinavian studies on peat-reduced growing media are plenty but the results are not always translated to or explained in English. Research and industry have cooperated in the attempts to replace peat. Students have done efforts to find solutions and several written works are published.
Wood products, possibly composted, are relevant to replace peat in growing media in Scandinavia where woody material is plenty. Other materials to be applied could be solid digestate from biogas plants, waste from industry and agriculture or residual materials from private gardens and public green areas. Substrates applied in growing media need to be studied both separately and in mixtures. Volume, processing and price are other factors to be considered. Because peat has unique properties as growing media, cultivation of white mosses in “paludi-culture” has received some interest and is briefly described in the report.
The report briefly presents some peat-free products available on the Scandinavian market in 2021. The markets overlap country boarders and change rapidly from year to year.
The report is written with funding from the Horizon 2020 project “Pathways to phase-out contentious inputs from organic agriculture in Europe” (Organic-PLUS), GA774340 (2018-2022), where NORSØK leads a work package on fertilisation, growing media and degradable plastic in organic farming. The purpose of the report is to present in the English an overview of studies conducted in Scandinavia to phase out peat from growing media.