Soil Carbon Dynamics of Transition to Pacific Northwest Cellulosic Ethanol Feedstock Production

Document Type

Article

Journal/Book Title/Conference

Soil Science Society of America Journal

Volume

79

Issue

1

Publisher

Soil Science Society of America

Publication Date

1-13-2015

First Page

272

Last Page

281

Abstract

Cellulosic ethanol commercialization promises to produce energy from agricultural biomass. Available biomass depends on plant net primary productivity (NPP) and crop type, which maintain total soil organic carbon (TOC). Effect of crop-type, residue removal, and NPP on ethanol yield and TOC levels were assessed by means of a three-pool C model derived from long-term soil incubation, acid hydrolysis, and curve fitting of a nonlinear regression model. A 2-yr field study consisting of three input regimes (Low, Medium, or High NPP), three crops [corn (Zea mays L.), wheat (Triticum aestivum, L.), and switchgrass (SG, Panicum virgatumL., cv. Blackwell)], and two harvest levels [residue removed (R) or residue not removed (NR)] was conducted near Prosser, WA, USA. After 2 yr, ethanol yield of all crops were similar under Low NPP while ethanol yield of SG under Medium and High NPP was significantly greater than that of corn or wheat under the same NPP. Switchgrass significantly contributed to active [mean residence time (MRT) < 7 d] and resistant (MRT > 500 yr) soil C pools. Other crops had net zero or significantly reduced C pools. During a transition to cellulosic energy production, SG will contribute to soil C maintenance across a range of potential net productivity.

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