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Extent of Pyrolysis Impacts on Fast Pyrolysis Biochar Properties
Author(s) -
Brewer Catherine E.,
Hu YanYan,
SchmidtRohr Klaus,
Loynachan Thomas E.,
Laird David A.,
Brown Robert C.
Publication year - 2012
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.2134/jeq2011.0118
Subject(s) - biochar , corn stover , pyrolysis , nutrient , soil water , environmental chemistry , chemistry , biomass (ecology) , stover , microorganism , agronomy , environmental science , soil science , biology , bacteria , crop , food science , organic chemistry , genetics , fermentation
A potential concern about the use of fast pyrolysis rather than slow pyrolysis biochars as soil amendments is that they may contain high levels of bioavailable C due to short particle residence times in the reactors, which could reduce the stability of biochar C and cause nutrient immobilization in soils. To investigate this concern, three corn ( Zea mays L.) stover fast pyrolysis biochars prepared using different reactor conditions were chemically and physically characterized to determine their extent of pyrolysis. These biochars were also incubated in soil to assess their impact on soil CO 2 emissions, nutrient availability, microorganism population growth, and water retention capacity. Elemental analysis and quantitative solid‐state 13 C nuclear magnetic resonance spectroscopy showed variation in O functional groups (associated primarily with carbohydrates) and aromatic C, which could be used to define extent of pyrolysis. A 24‐wk incubation performed using a sandy soil amended with 0.5 wt% of corn stover biochar showed a small but significant decrease in soil CO 2 emissions and a decrease in the bacteria:fungi ratios with extent of pyrolysis. Relative to the control soil, biochar‐amended soils had small increases in CO 2 emissions and extractable nutrients, but similar microorganism populations, extractable NO 3 levels, and water retention capacities. Corn stover amendments, by contrast, significantly increased soil CO 2 emissions and microbial populations, and reduced extractable NO 3 . These results indicate that C in fast pyrolysis biochar is stable in soil environments and will not appreciably contribute to nutrient immobilization.