Synergistic Use of Peat and Charred Material in Growing Media – An Option to Reduce the Pressure on Peatlands?

Abstract

Peat is used as a high quality substrate for growing media in horticulture. However, unsustainable peat extraction damages peatland ecosystems, which disappeared to a large extent in Central and South Europe. Furthermore, disturbed peatlands are becoming a source of greenhouse gases due to drainage and excavation. This study is the result of a workshop within the EU COST Action TD1107 (Biochar as option for sustainable resource management), held in Tartu (Estonia) in 2015. The view of stakeholders were consulted on new biochar-based growing media and to what extent peat may be replaced in growing media by new compounds like carbonaceous materials from thermochemical conversion. First positive results from laboratory and greenhouse experiments have been reported with biochar content in growing media ranging up to 50%. Various companies have already started to use biochar as an additive in their growing media formulations. Biochar might play a more important role in replacing peat in growing media, when biochar is available, meets the quality requirements, and their use is economically feasible.

Increasing Sustainability of Growing Media Constituents and Stand-Alone Substrates in Soilless Culture Systems

“…Biochar and HTC char have physical and chemical properties that are variable, depending on the raw material used and the carbonization technique. Usually, the electrical conductivity (EC) and pH values are similarly low in peat and HTC and are slightly increased in biochar [25].…”

“…Several studies reported that biochar in potting media results in the same ornamental plant growth as in peat-based standard substrates [65,145,146]. According to Kern et al [25], char materials must not necessarily remain on the level of a minor ingredient, but have the potential to be used as major constituents. Furthermore, since they are characterized by a high porosity and a high water-holding capacity, these materials may also be usable as a substitute for constituents, which are already established in the growing media market, but which have a limited supply [25,147,148].…”

“…The water-saturated and oxygen-free conditions prevent peat from fully decomposing. Peatlands are a habitat with special ecological value with the most important long-term carbon sinks and one of the most effective eco-systems in the terrestrial biosphere, providing different environmental services, such as biodiversity, carbon (C) storage, regulation of the local water quality, and local hydrology conditions, including flood protection [23][24][25]. Covering only about 3% of Earth's land area, they may store 21% [26] to 33% [27] of the total world's terrestrial organic carbon.…”

Substitution of peat moss with softwood biochar for soil-free marigold growth

“…Biochar (BC) has been recently proposed as a strong candidate to substitute for peat because of its high porosity, low density and high cation-exchange capacity (Steiner and Harttung, 2014;Vaughn et al, 2015;Kern et al, 2017). Biochar is a carbon (C)-rich material produced by pyrolysis of biomass and has been a major subject of study as a soil amendment in the last decade (Lehmann and Joseph, 2015).…”

Representativeness of European Biochar Research: Part I – Field Experiments

“…The reason for such a spread is probably the higher economical return that is expected per tonne of added (rather expensive) biochar from arable crops than from pastures/ forests. For the same reason, biochar use may well become widespread first as a growing medium constituent in highvalue crops (see Kern et al 2017, this issue) than as a fieldscale soil amendment material.…”