Promoting Interspecies Electron Transfer with Biochar

TLDR

Biochar is a charcoal‑like product from incomplete combustion of organic materials, increasingly used as a soil amendment to improve fertility. The study examined whether biochar could promote direct interspecies electron transfer (DIET) similarly to granular activated carbon. Although 1000 times less conductive than GAC, the biochars stimulated DIET in Geobacter and Methanosarcina co‑cultures using ethanol, with cells attached but not in close contact, indicating electron conduction through biochar and implying that biochar amendments could enhance anaerobic methane production from organic wastes.

Abstract

Biochar, a charcoal-like product of the incomplete combustion of organic materials, is an increasingly popular soil amendment designed to improve soil fertility. We investigated the possibility that biochar could promote direct interspecies electron transfer (DIET) in a manner similar to that previously reported for granular activated carbon (GAC). Although the biochars investigated were 1000 times less conductive than GAC, they stimulated DIET in co-cultures of Geobacter metallireducens with Geobacter sulfurreducens or Methanosarcina barkeri in which ethanol was the electron donor. Cells were attached to the biochar, yet not in close contact, suggesting that electrons were likely conducted through the biochar, rather than biological electrical connections. The finding that biochar can stimulate DIET may be an important consideration when amending soils with biochar and can help explain why biochar may enhance methane production from organic wastes under anaerobic conditions.