| dc.description.abstract | Abstract
Methane and carbon dioxide are two of the most significant greenhouse gases, responsible for global warming. A primary source of these emissions is the improper disposal of organic waste, including food waste and fish sludge. Developing sustainable strategies for managing such waste streams is crucial to human beings. This thesis studies two projects for the valorization of food waste and fish sludge. The first project investigates the anaerobic digestion of fish sludge and food waste under mesophilic conditions, aiming to maximize biogas production. The second project aims to construct and test the bench-scale circulation coculture biofilm photobioreactor (CCBP) to convert biogas produced from the first project into microbial biomass, which can be subsequently converted into an aquafeed.
In Chapter 1, the need for conducting this project and the purpose of the research are investigated by treating waste and converting it into value-added materials, such as methane and nutrient-rich compounds, to utilize this biogas in the CCBP, which is equipped with a conveyor belt and membrane to grow single-cell protein for fishmeal. These justifications were based on the fundamentals and need to build and develop the proposed waste2feed biotechnology.
In chapter 2, the co-digestion of the fish sludge and food waste is examined. The effect of the ratio of food waste and fish sludge on the methane and biogas volume production is studied. The results show that food waste was responsible for increasing the percentage of the solid content and contributing more carbon content to the process. Eventually, the increase in food waste can lead to a rise in methane and biogas production. The analysis of the Chemical Oxygen Demand (COD)
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reveals that the COD of the food waste and fish sludge decreases after the anaerobic digestion process. Therefore, the co-digestion of fish sludge and food waste not only improves anaerobic digestion but also enhances waste management by reducing the COD of the two waste streams. In the previous chapter, the co-digestion of fish sludge and food waste was studied. The effect of the ratio of food waste and fish sludge on the methane and biogas volume production is investigated. The results show that food waste was responsible for increasing the percentage of the solid content and contributing more carbon to the system. Consequently, as the food waste portion increases, the amount of methane and gas also increases. The analysis of the Chemical Oxygen Demand (COD) reveals that the COD of the food waste and fish sludge decreases after the anaerobic digestion process. The co-digestion of fish sludge and food waste not only improves anaerobic digestion but also enhances waste management by reducing the COD of the two waste streams.
In Chapter 3, the construction and development of the CCBP are discussed. The main components, necessary items, and sensors were designed and customized using design software such as Fusion 360 and manufactured in the maker space at Auburn University. Our challenge is to maintain the temperature and utilize intelligent monitoring by leveraging Arduino sensors. This challenge was addressed by using the BMP280 Arduino sensor, coil heating, and specialized insulation. Different candidates for conveyor belts were tested using methanotrophs in this chapter as well. The results showed that all the tested materials had the potential to be used as a conveyor belt, as there was no significant inhibition from them. The need for producing fish meal out of fish sludge is discussed in this chapter, too. The CSTR configuration, using a Bioflo bioreactor, was employed to convert the 10% anaerobic digestion (AD) effluent from Chapter 2 into single-cell protein. All parameters, including the growth rate and biomass concentration during the process, as well as the amounts of protein and lipid, are studied in this chapter.
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In Chapter 4, the conclusion of the chapters above is discussed. The co-digestion of food waste and fish sludge resulted in a synergistic effect that can improve biogas and methane yield. The COD removal parameters indicated that this system could help convert organic matter into inorganic matter. The effluent coming from the codigestion was diluted 10 times and used in the coculture of methanotrophs and microalgae to produce fish meal. The results for this coculture showed that not only was the growth rate high, but also the protein and lipid content of the biomass made this product a good candidate for the fish meal. Since these results come from laboratory scales. The real application requires some modifications and improvements, such as scaling up the process and conducting more analyses of the liquid and gas to understand better and monitor the process. For the future, the CCBP and co-digestion of fish sludge and food waste should be integrated as a single process, not only to remove organic matter from food waste and fish sludge but also to produce single-cell protein for the fish. | en_US |
