Biochar And The Biomass Recycling Industry

Biocycle
BioCycle August 2011, Vol. 52, No. 8, p. 50
Jim Grob, Art Donnelly, Gloria Flora and Thomas Miles

To realize its full potential as a tool for carbon cycle management and to sustainably increase soil productivity, biochar should be tested in combination with other organic waste streams.

BIOCHAR, the high carbon content remains of organic biomass heated in the absence of oxygen, has been a topic of intense interest and growing experimentation in the past five years. The rediscovery of terra preta (or black earth) soils in the Amazon has sparked the imagination and curiosity of researchers around the world. These “human-built” soils are dark, productive deposits — a composite of charcoal (biochar), pottery shards and organic matter such as plant material, animal feces and fish and animal bones. Significantly, these soils are several thousand years old, yet continue to maintain high plant productivity and high soil carbon content despite existing in a region well known for low soil productivity and rapid organic matter decomposition. Charcoal presence is not unique to the tropics. U.S. farmland soils can vary in charcoal content from 10 to 35 percent of the total organic carbon (TOC), with charcoal-enriched areas in regions with a wildfire-dependent ecology (Skemstad et al., 2002).

Much of the published terra preta research to date has focused solely on the biochar component. A full picture of “biochar-only” effects is yet to be fully understood. Most of the best-documented studies have used a single addition of biochar, which is intensively measured over a number of years, but data to date suggest a wide range of outcomes. Biochar additions have been seen to be positive, neutral and even negative. This wide range in outcomes may be due to differences in the specific biochar used, time since addition, the crop species tested and the particular starting soil properties/deficiencies.

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