Date of Award

January 2019

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Earth System Science & Policy

First Advisor

Soizik Laguette

Abstract

The US government has mandated the annual usage of 61 GL of cellulosic biofuel by 2022. Cellulosic residues from annual crops, such as corn (Zea mays L.) and wheat (Triticum aestivum L. ssp. aestivum) represent a potential source of cellulosic biomass. Another source is the production of cellulosic bioenergy crops. Switchgrass (Panicum virgatum L.) was identified as a model biomass crop by the US Department of Energy in 1992, features the most advanced agronomic development among herbaceous perennial bioenergy feedstock candidates, and is widely adapted across North America. In three interconnected studies considering a 99-county area of the eastern Dakotas and western Minnesota, this dissertation characterizes the existing resource base of corn and wheat cellulosic biomass, estimates the biomass prices necessary for switchgrass to be competitive with collection of existing corn and wheat biomass, and estimates the necessary incentives for switchgrass to supplant sufficient corn or wheat area to offset recent grassland-to-cropland conversions observed within the study region. An improved parameterization of upland switchgrass ecotypes for the ALMANAC (Agricultural Land Management Alternative with Numerical Assessment Criteria) model was shown to predict multiyear-average yields with an RMSE of 1.95 Mg ha-1 and PBIAS of 7.2%. Using moderate-resolution regional inputs, ALMANAC estimated county-scale multiyear-average corn yields with an RMSE of 0.71 Mg ha-1 and PBIAS of 1.9%, and corresponding wheat yields with an RMSE of 0.28 Mg ha-1 and PBIAS of 2.8%. Corn and wheat can supply up to 16.48 Tg of biomass annually within estimated biorefinery collection areas, at a biomass price of $60 Mg-1 or less. Switchgrass would require biomass prices of $60 to $180 Mg-1 to supplant corn or wheat production, dependent on establishment and production cost assumptions. Annual payments of $120 to $290 million would encourage sufficient switchgrass production to offset recent grassland-to-cropland conversions in the study region, and can be strategically directed to maximize the environmental benefits of switchgrass production.

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