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Title: Economic and Environmental Assessment of Switchgrass Production on High-Fertility Soil and an Assessment of Anaerobic Digests as an Intermediate Market for Switchgrass

Technical Report ·
DOI:https://doi.org/10.2172/1126616· OSTI ID:1126616

This project had two parts. Part 1 was an economic and environmental assessment of switchgrass production on high-fertility soil, and included an assessment of the effects of field irrigation with treated municipal wastewater (Studies A,C, and E in Final Agreement). Part 2 was an assessment of methods to enhance anaerobic digestion of switchgrass, and included evaluation of several other potential biomass feedstocks (Studies B and D in Final Agreement). Results from Part 1 demonstrated that switchgrass does not compete economically against a corn and soybean rotation on highly productive soils. All four varieties of switchgrass lost money while corn and soybeans were profitable in all four years of this study. Breakeven prices for the four switchgrass varieties were calculated using production costs. The installation of a center pivot irrigation system had minimal impact on crop production and corn and soybean production remained profitable in the year the irrigator was installed. Because of drought and delays in installing the wastewater treatment plant, the irrigation system was not used until year 4 of this study. Therefore, longer term studies evaluating multiple year studies on the impact of irrigation on switchgrass are warranted. Results from irrigating with treated municipal wastewater showed no negative impact on soil quality. Results from Part 2 demonstrated that anaerobic digestion (AD) of switchgrass could be significantly enhanced using low heat (100oC) and mild caustic pretreatment without fine-grinding. Heat for pretreatment could be available from biogas-based combined heat and power (CHP) systems. In bench-top digesters simulating municipal wastewater treatment AD, methane production of coarse-ground switchgrass increased over 20-fold with pretreatment compared to untreated switchgrass. Bench-top studies simulating dairy-based AD also found high specific methane yield, but even untreated switchgrass digested reasonably well, indicating the value of AD micro-organisms acclimated to lignocellulosic feedstock. Similar results were found for corn stover. However, oak and maple leaves – representing common urban yard waste – were more resistant to digestion even with pretreatment. More pretreatment research is required before yard waste could become a significant feedstock for the low/medium-solids digesters common to municipal wastewater or livestock operations.

Research Organization:
Illinois State University (ISU), Normal, IL (United States)
Sponsoring Organization:
USDOE Office of Energy Efficiency and Renewable Energy (EERE), Sustainable Transportation Office. Bioenergy Technologies Office
DOE Contract Number:
FG36-08GO88039
OSTI ID:
1126616
Report Number(s):
DE-FG36-08GO88039
Country of Publication:
United States
Language:
English