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Ultrasonic Pretreatment for Anaerobic Digestion: a Study on Feedstock, Methane Yield, and Energy Balance

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Title: Ultrasonic Pretreatment for Anaerobic Digestion: a Study on Feedstock, Methane Yield, and Energy Balance
Author: Moisan, Maxime
Department: School of Engineering
Program: Engineering
Advisor: Dutta, Animesh
Abstract: The research represents a first approach to measure the utilization potential of ultrasonic pretreatment on six different substrates: fat, oil and grease (FOG), paper sludge, ground switch grass, ground hay, ground wheat straw, and cut wheat straw. Several laboratories techniques were applied to determine the influence of ultrasonication on biogas production and yield, biogas quality, and digestibility ratio. With the data, mathematical definitions of Net Energy Balance and Net Economy Balance were computed to draw a first justification or rejection of the use of this pretreatment technology for the specific substrates. Ultrasonic pretreatment has a significant effect on biogas production and yield as well as digestibility ratio (p-value < 0.0001) from the early stages of digestion until as far as 50 days of digestion. Ultrasonication and macro particle size management did not influence significantly the methane (CH4) content in the biogas (p-value = 0.1793). Also, the impact of ultrasonication on the substrate varies between all studied feedstock. Most of the ultrasonicated digestion cases studied provided a negative Net Energy and Economic Balance except for FOG where a certain window of utilization was found. In the context of an ultrasonication process retrofit upgrade, the technology looks to be more useful for substrates that are hard to digest when the retention time is, unfortunately, longer than common retention time. In the context of a new facility, a design that includes an understood ultrasonication technology has yet a small potential success depending on several variables. The ultrasonication technology for anaerobic digestion is hard to recommend due to its energy consumption that, in many cases, overshadows the energy surplus derived from its use.
URI: http://hdl.handle.net/10214/5091
Date: 2012-12
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http://creativecommons.org/licenses/by-nc-nd/2.5/ca/ Except where otherwise noted, this item's license is described as http://creativecommons.org/licenses/by-nc-nd/2.5/ca/