Effects of Metals from Flue Gas on Microalgae Biofuels and Co-products: Sustainability and Scalability

Utah State University, Logan UT

Investigators

Abstract

CBET - 1335550 Jason Quinn Utah State University The production of alternative transportation fuels is imperative to meeting current energy demands without contributing to global climate change. Microalgae are considered a promising feedstock, but require specific resources (e.g. water and concentrated carbon dioxide) that are either difficult to provide in high purity and concentration or that compete with other essential activities such as food production. A variety of microalgae feasibility assessments have been performed that assume the seamless integration of waste carbon dioxide sources, such as coal fired power plant flue gas, with microalgae cultivation. The utilization of flue gas as a source for carbon dioxide in the cultivation phase of microalgae represents an environmentally favorable process step for the production of biofuels from microalgae. The burning of coal generates a carbon dioxide rich stream ideal for integration with microalgae, but also contains trace amounts of a variety of heavy metals such as arsenic, cadmium, cobalt, chromium, copper, mercury, manganese, nickel, lead, antimony, selenium, tin, tellurium, titanium, vanadium, and zinc. The integration of flue gases as a nutrient source in microalgae cultivation will ultimately introduce these heavy metals into the growth media where they can be absorbed and potentially concentrated by the microalgae. The fate of heavy metals and their effect on microalgal cultivation and the characteristics of end products from the use of flue gas as the carbon source will be quantified by this study. Understanding the effect and fate of heavy metals in the microalgae-to-biofuels process will enable higher resolution environmental assessments. The study will investigate 1) the effects of the presence of heavy metals in growth media on microalgae growth and lipid content and the effects on the quality of biodiesel produced, 2) the effects of heavy metals on downstream processing of the lipid extracted algae via fermentation for production of acetone, butanol and ethanol and methane production from anaerobic digestion, and 3) the sustainability and scalability of the microalgae to biofuels process integrated with flue gas. Accomplishment of these tasks will facilitate the evaluation of the effects of heavy metals found in flue gas on microalgae cultivation and resulting products. This study will investigate potential processes where heavy metal buildup could occur and quantify the amounts involved. Systems models will be informed by the experimental data for scalability and environmental impact assessments. This project will provide new insights into the environmental impacts of integrating microalgae cultivation with carbon dioxide derived from industrial point sources such as coal power plant flue gas. The integration of flue gas with microalgae cultivation will inevitably introduce heavy metals into the growth media that can be absorbed and concentrated. This study will evaluate the end fate of heavy metals present in microalgae growth media and investigate the effects on growth, fuel properties and co-products from the microalgae to biofuels process. The information learned from the experimental work will be integrated into a modeling effort to directly assess the large-scale environmental implications of integrating carbon rich flue gas with microalgae cultivation.