Biochar as rooting medium

Published on
January 10, 2017

Biochar is a side-product of the production of bio-fuels and bio-plastics from organic residual materials. There is interest to use biochar as a rooting medium for horticultural purposes. In cooperation the Energy Centre for The Netherlands (ECN) and the business unit Greenhouse Horticulture of Wageningen University & Research did research on a large number of differently produced biochars.

Biochar as part of a rooting medium could contribute to the
partial replacement of peat and lower the related release of carbon dioxide into the atmosphere. It may also be possible to use specific biochar qualities to carry micro-organisms to make plants less susceptible for certain pathogens.

Up to now the production of biochar was organised without considering the end use of biochar. In cooperation the Energy Centre for The Netherlands (ECN) and Wageningen UR Greenhouse Horticulture did research on a large number of differently produced  biochars. The results:

  1. Avoid feed stock materials which will only result in biochar with a too high salinity or a too high alkalinity (pH-buffer). Methods to test feedstocks prior to production have been developed.
  2. Choose process settings and an oven construction which will lead to desirable biochars including the eventual particle size, degradability, internal surface area and prevention of condensation of tocix hydrocarbons. Rules for proper process organisation have been developed.
  3. Measuring methods of direct relevance for the end user and of direct relevance for potting soil producers in horticulture. These methods allow users for example to directly assess how much nitrogen may be fixated, and how much acid material needs to be added to deliver a neutral mix of proper pH.

By combining production and user knowledge it is possible to use biochar safely in horticulture. It is also possible to define –beforehand- how a biochar should look which will be used to carry micro-organisms.

The same approach as mentioned above -but with adapted methods-, can be used to produce biochars for other applications such as bulbs
(water storage); tree crops (mycorrhizas); and soil improvement (nutrient

This research was funded with a TO2 grant by the ministry of economic affairs.