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Variation due to Growth Environment in Alfalfa Yield, Cellulosic Ethanol Traits, and Paper Pulp Characteristics Katie Petersen Rock & Ryan T. Thelemann & Hans-Joachim G. Jung & Ulrike W. Tschirner & Craig C. Sheaffer & Gregg A. Johnson

Published online: 30 July 2009 # US Government 2009

Abstract Alfalfa (Medicago sativa L.) is a promising bioenergy and bioproduct feedstock because of its high yield, N-fixation capacity, potential for planting in rotation with corn (Zea mays L.), and valuable protein co-product (leaf meal). Our objective was to examine the effect of growth environment on biomass yield, cellulosic ethanol traits, and paper pulp fiber characteristics of alfalfa stems. Landscape position (summit and mild slope), season of harvest (four harvests per season), and multiple years (2005 and 2006) provided environmental variation. Alfalfa stem samples were analyzed for cell wall carbohydrate and lignin concentration. Stems were subjected to dilute acid pretreatment, enzymatic saccharification, and pulping processes to measure relevant cellulosic ethanol and paper production traits. Landscape position was not a significant source of variation for yield or any biomass quality trait. Yields varied among harvests in 2005 (1,410– 3,265 kg ha−1) and 2006 (1,610–3,795 kg ha−1). All cell wall, conversion test, and paper production traits exhibited year by harvest interactions with no clear pattern. Total carbohydrates and lignin ranged from 440 to 531 gkg−1 K. P. Rock : R. T. Thelemann : C. C. Sheaffer : G. A. Johnson Department of Agronomy and Plant Genetics, University of Minnesota, USDA-ARS, 411 Borlaug Hall, 1991 Upper Buford Circle, St. Paul, MN 55108, USA H.-J. G. Jung (*) Plant Science Research Unit, USDA-ARS, St. Paul, MN 55108, USA e-mail: [email protected] U. W. Tschirner Department of Bioproducts and Biosystems Engineering, University of Minnesota, St. Paul, MN 55108, USA

DM and from 113 to 161 gkg-1 DM, respectively. Release of cell wall sugars by the conversion test ranged widely (419 to 962 gkg−1 DM). Fiber traits were similarly variable with length and fine content ranging from 1.24 to 1.59 mm and from 15.2% to 21.9%, respectively. Utilizing alfalfa biomass for cellulosic ethanol and paper pulp production will involve dealing with significant feedstock quality variation due to growth environment. Keywords Alfalfa . Cellulosic ethanol . Environment . Paper pulp fiber . Yield

Introduction Alfalfa (Medicago sativa L.) has considerable potential as a feedstock for bio-based fuels, industrial materials, and paper products [35, 37, 44]. It has been proposed that alfalfa herbage can be separated into a stem fraction for conversion to bioenergy and a leaf fraction for use as a protein feed for livestock [13, 15, 20]. Saruul et al. [47] showed that poly-β-hydroxybutyrate, a biodegradable plastic, can be produced from alfalfa leaves with the use of transgenic technology. Alfalfa is the fourth most widely grown crop in the USA with 3.4 million hectares harvested in 2008 [60]. The perennial growth habit an