Biochar for horticultural rooting media improvement: Evaluation of Biochar from gasification and slow pyrolysis

Chris Blok*, Caroline van der Salm, Jantineke Hofland-Zijlstra, Marta Streminska, Barbara Eveleens-Clark, Inge Regelink, Lydia Fryda, Rianne Visser

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

29 Citations (Scopus)

Abstract

Peat is used as rooting medium in greenhouse horticulture. Biochar is a sustainable alternative for the use of peat, which will reduce peat derived carbon dioxide emissions. Biochar in potting soil mixtures allegedly increases water storage, nutrient supply, microbial life and disease suppression but this depends on feedstock and the production process. The aim of this paper is to find combinations of feedstock and production circumstances which will deliver biochars with value for the horticultural end user. Low-temperature (600 °C-750 °C) gasification was used for combined energy and biochar generation. Biochars produced were screened in laboratory tests and selected biochars were used in plant experiments. Tests included dry bulk density, total pore space, specific surface area, phytotoxicity, pH, EC, moisture characteristics and microbial stability. We conclude that biochars from nutrient-rich feedstocks are too saline and too alkaline to be applied in horticultural rooting media. Biochars from less nutrient-rich feedstocks can be conveniently neutralized by mixing with acid peat. The influence of production parameters on specific surface area, pH, total pore space and toxicity is discussed. Biochar mildly improved the survival of beneficial micro-organisms in a mix with peat. Overall, wood biochar can replace at least 20% v/v of peat in potting soils without affecting plant growth.

Original languageEnglish
Article number6
JournalAgronomy
Volume7
Issue number1
DOIs
Publication statusPublished - 2017

Keywords

  • Alkalinity
  • Biochar
  • Degradability
  • Gasification
  • pH
  • Phytotoxicity
  • Pyrolysis
  • Salinity
  • Stability

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