Submitted to: Biomass and Bioenergy
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 5, 2014
Publication Date: March 31, 2014
Citation: Lamb, J.F., Jung, H.G., Riday, H. 2014. Growth environment, harvest management and germplasm impacts on potential ethanol and crude protein yield in alfalfa. Biomass and Bioenergy. 63:114-125. Interpretive Summary: Alfalfa has the potential to be a significant contributor to America's renewable energy future. In an alfalfa biomass energy production system, alfalfa forage would be separated into stems and leaves. The stems would be processed to produce liquid fuel (ethanol), and the leaves would be sold separately as a livestock feed. One of the advantages of alfalfa over other crops to produce biomass energy is this potential for a secondary income selling the leaves as an animal feed. Therefore, maximizing the concentrations and yields of leaf protein and stem cell wall sugars (used to produce ethanol) are equally important for the profitability of an alfalfa biofuel production system. Our goals were to evaluate total leaf crude protein and potential ethanol yields of four alfalfas, two commercial high-quality hay-type alfalfas and two new, non-lodging, large-stemmed biomass energy types grown in two locations (MN and WI) for 2 years. In each growing season we harvested both types of alfalfa at two different maturity stages, early bud (4 cuts per season) and late flower (3 cuts per season) to see if either one of these cutting management strategies could improve leaf crude protein and potential ethanol yields. At both locations, potential ethanol yield was greater at late flower compared to early bud, while leaf crude protein yields were similar between the two cutting management schemes. The two non-lodging biomass alfalfas had greater potential ethanol yield compared to the high forage quality cultivars at WI, but no differences between the alfalfa types were found for ethanol yield at MN. At WI, no difference were found between the alfalfa types for leaf crude protein yield, but the high-quality cultivars had greater leaf crude protein yield than the non-lodging types at MN. Late flower cutting management improved total potential ethanol yield, differences between the alfalfa types were identified for leaf crude protein and potential ethanol yields, but differences found between the two alfalfa types were not consistent between the MN and WI locations.
Technical Abstract: An alfalfa (Medicago sativa L) biomass energy production system would produce two products. Leaves would be separated from stems to produce a high protein feed for livestock and stems would be processed to produce ethanol. Therefore, maximum yields of both leaves and stems are essential for profitability of this biomass production system. Our objective was to evaluate the impact of growth environment (locations, years, and plant density) and harvest maturity stage (early bud (4 cuts) and late flower (3 cuts)) on leaf crude protein and potential ethanol yields for four alfalfa germplasms, two with high forage quality and two non-lodging biomass types. Potential ethanol yield was greater at late flower compared to early bud, while leaf crude protein concentration was similar at the two harvest maturity stages at both locations. Leaf crude protein yield was greater at MN compared to WI. The two non-lodging biomass germplasms had greater potential ethanol yield compared to the high forage quality cultivars at WI, but no differences among the alfalfa germplasms were found for ethanol yield at MN. In WI, no difference were found among the germplasms for leaf crude protein yield, but the high-quality cultivars had greater leaf crude protein yield than the non-lodging germplasms at MN. Germplasm differences were identified for leaf crude protein and potential ethanol yields, total potential ethanol yield was improved by cutting at a later maturity stage, but environmental influences had the greatest impact on these to alfalfa biomass energy products.