UMD Theses and Dissertations

Permanent URI for this collectionhttp://hdl.handle.net/1903/3

New submissions to the thesis/dissertation collections are added automatically as they are received from the Graduate School. Currently, the Graduate School deposits all theses and dissertations from a given semester after the official graduation date. This means that there may be up to a 4 month delay in the appearance of a given thesis/dissertation in DRUM.

More information is available at Theses and Dissertations at University of Maryland Libraries.

Browse

Filters

2009 - 200912020 - 20241

Settings

Subject: search.filters.subject.Bioenergy

Search Results

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    GENERATING BIOENERGY AND HIGH-VALUE PRODUCTS FROM HIGH SALINITY FOOD WASTE
    (2024) McCoy, Emily Lim; Lansing, Stephanie; Environmental Science and Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Bioenergy generation and volatile fatty acids (VFAs) production from household food waste and high salinity food processing waste were explored using anaerobic digestion and dark fermentation processes, respectively. This study tested adding value to three organic waste streams: household food waste, high salinity food processing waste (composed of glycerin sludge from biodiesel production), and residual solids from VFAs separation after dark fermentation of food waste. The investigations were conducted using batch and semi-continuous systems in mesophilic conditions (35°C). Methane (CH4) potential tests were conducted to determine the bioenergy production of food waste and residual solids, including the addition of dark fermentation gas at four ratios of hydrogen (H2) to carbon dioxide (CO2) (1:1, 1:2, 1:3, 1:5) into the liquid portion of the reactor to enhance CH4 production and three inoculum to substrate ratios (1.5:1, 2:1, 4:1). Additionally, a semi-continuous dark fermentation study was used to determine the VFA production from household food waste and high salinity food processing waste combinations over 62 days. The anaerobic digestion of residual solids from VFAs separation had similar bioenergy potential as household food waste when normalized by volatile solids (VS) added (492 ± 11 mL CH4/g VS and 470 ± 11 mL CH4/g VS, respectively). Dark fermentation gas added into the liquid portion of the reactor during anaerobic digestion decreased CH4 yields, especially at low H2:CO2 ratios, suggesting that only dark fermentation reactors that produce high H2:CO2 ratios should have the gas sparged into anaerobic digestion systems. When the residual solids from dark fermentation were fermented at three inoculum to substrate ratios (1.5:1, 2:1, 4:1), the lowest inoculum to substrate ratio (1.5:1) had the highest VFAs concentration (28.05 ± 0.89 g/L) after nine days of fermentation, which showed that residual solids can be fermented with low inoculum levels, allowing more room for substrate fermentation. Additionally, the mono- and co-fermentation of household food waste and high salinity food processing waste showed that the high salinity waste improved VFA production due to the high pH (9 – 10) and high organic loading (6.3 – 17.8 g VS/L-day), even with high salinity levels (21.4 – 85.6 g/L Na) in this waste. There was significantly higher VFA production in high salinity food processing waste (36.04 ± 0.54 g/L) compared to household food waste (9.29 ± 1.01 g/L). The maximum VFA concentration (36.04 ± 0.54 g/L) was achieved after 51 days of high salinity food processing waste semi-continuous fermentation. The findings in this study can be used to improve operations of anaerobic digestion and dark fermentation systems by using residual solids for bioenergy generation or VFA production. The testing of mono- and co-fermentation of household food waste and high salinity food processing waste showed high VFA production in fermenting high salinity food processing waste. This work showed the valorization of three organic waste streams through bioconversion to both bioenergy and high-value products (VFAs), which redirected these waste products from municipal solids landfills and into resources, thereby reducing CH4 released into the atmosphere from landfills and reducing global warming potential.
  • Thumbnail Image
    Item
    SPATIAL AND SEASONAL DISTRIBUTION OF CARBON DIOXIDE EMISSIONS FROM FOSSIL-FUEL COMBUSTION; GLOBAL, REGIONAL, AND NATIONAL POTENTIAL FOR SUSTAINABLE BIOENERGY FROM RESIDUE BIOMASS AND MUNICIPAL SOLID WASTE
    (2009) Gregg, Jay Sterling; Dubayah, Ralph; Geography; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Combustion of fossil fuels releases carbon dioxide (CO2) into the atmosphere, and has led to an increase in the atmospheric concentration of CO2. CO2 is a greenhouse gas, and the increase in concentration leads to an increase in global temperatures and global climatic change. Fossil-fuel consumption, along with cement production, is responsible for 80% of anthropogenic carbon emissions and consumption of fossil fuels continues to increase. Despite its importance to the global climate and the global carbon cycle, data for fossil fuel CO2 emissions are traditionally maintained only on national levels and annual time steps. A method is developed to improve the spatiotemporal resolution to the leading energy consuming countries of the world. The method uses energy consumption datasets as well as other ancillary datasets to apportion national annual emissions totals into sub-national and monthly emissions datasets by fuel type. Emissions patterns are highly variable both temporally and spatially by fuel type, and detailed information on the distribution of emissions improves our understanding of the global carbon cycle and leads to better understanding of the spatial and seasonal distribution of the drivers of global change.
    In the endeavor to develop alternatives to fossil fuels, advanced biomass energy has garnered much attention because of its renewable nature and its potential to approach carbon-neutrality. As co-products, agricultural and forestry residues as well as municipal solid waste (MSW) are potential low-cost and sustainable biomass feedstocks for energy production. The role of residue biomass within the future global energy portfolio is projected and quantified under the context of environmental and economic sustainability. The potential for residue biomass is projected for the next century under a reference (business-as-usual) scenario and a scenario that includes a hypothetical climate policy that limits carbon emissions. While residue biomass alone cannot replace fossil fuels, a substantial amount of energy potentially could come from this resource, particularly in a global economic market under a climate policy that caps CO2 emissions from fossil fuels.