IMPROVING ALFALFA AND OTHER FORAGE CROPS FOR BIOENERGY, LIVESTOCK PRODUCTION, AND ENVIRONMENTAL PROTECTION
Location: Plant Science Research
Title: Variation Due to Growth Environment in Alfalfa Yield, Cellulosic Ethanol Traits, and Paper Pulp Characteristics
| Rock, Katie - |
| Thelemann, Ryan - |
| Jung, Hans Joachim |
| Tschirner, Ulrike - |
| Sheaffer, Craig - |
| Johnson, Gregg - |
Submitted to: BioEnergy Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 14, 2009
Publication Date: September 1, 2009
Citation: Rock, K.P., Thelemann, R.T., Jung, H.G., Tschirner, U.W., Sheaffer, C.C., Johnson, G.A. 2009. Variation due to growth environment in alfalfa yield, cellulosic ethanol traits, and paper pulp characteristics. BioEnergy Research. 2(3):79-89.
Interpretive Summary: Alfalfa has been proposed as a biomass crop because of its high yield potential, perennial nature, a value-added leaf meal co-product for livestock feeding, and ability to fix nitrogen from the air as a fertilizer for itself and subsequent corn crops. Although alfalfa is adapted to many regions, it does grow better under some environmental conditions than others. And alfalfa must be harvested multiple times per year, creating more environmental variation. A study was conducted to determine if growth environment (landscape characteristics, season of harvest, and yearly weather fluctuations) influenced the quality of alfalfa stems for use as a cellulosic ethanol feedstock or for making paper pulp. Small but significant differences were detected for most traits important to ethanol and paper bioproducts due to season of harvest and yearly weather patterns. However, characteristics of the landscape where the alfalfa was grown (steepness of slope, slope orientation to the sun, etc.) had no measurable impacts on quality traits. The greatest impact of growth environment was on yield rather than stem quality, a fact that is important to a biomass system's performance. These results indicate that cellulosic ethanol and paper pulp bioproduct producers must be prepared to deal with feedstock quality variation when using alfalfa stems as the biomass resource. We expect that this conclusion about growth environment impacts on biomass quality will be true of most, if not all, biomass crops.
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 also subjected to dilute acid pre-treatment, 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 to 3,265 kg ha-1) and 2006 (1,610 to 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 ranged from 440 to 531 g kg-1 DM while lignin ranged from 113 to 161 g kg-1 DM. Release of cell wall sugars by the conversion test ranged widely (419 to 962 g kg-1 DM). Fiber traits were similarly variable with length ranging from 1.24 to 1.59 mm and fines content varying from 15.2 to 21.9%. Utilizing alfalfa biomass for cellulosic ethanol and paper pulp production will involve dealing with significant feedstock quality variation due to growth environment.