College of Agriculture & Natural Resources
Permanent URI for this communityhttp://hdl.handle.net/1903/1598
The collections in this community comprise faculty research works, as well as graduate theses and dissertations.
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Item Enhanced Biogas Production of Cassava Wastewater Using Zeolite and Biochar Additives and Manure Co-Digestion(MDPI, 2020-01-19) Achi, Chibueze G.; Hassanein, Amro; Lansing, StephanieCurrently, there are challenges with proper disposal of cassava processing wastewater, and a need for sustainable energy in the cassava industry. This study investigated the impact of co-digestion of cassava wastewater (CW) with livestock manure (poultry litter (PL) and dairy manure (DM)), and porous adsorbents (biochar (B-Char) and zeolite (ZEO)) on energy production and treatment efficiency. Batch anaerobic digestion experiments were conducted, with 16 treatments of CW combined with manure and/or porous adsorbents using triplicate reactors for 48 days. The results showed that CW combined with ZEO (3 g/g total solids (TS)) produced the highest cumulative CH4 (653 mL CH4/g VS), while CW:PL (1:1) produced the most CH4 on a mass basis (17.9 mL CH4/g substrate). The largest reduction in lag phase was observed in the mixture containing CW (1:1), PL (1:1), and B-Char (3 g/g TS), yielding 400 mL CH4/g volatile solids (VS) after 15 days of digestion, which was 84.8% of the total cumulative CH4 from the 48-day trial. Co-digesting CW with ZEO, B-Char, or PL provided the necessary buffer needed for digestion of CW, which improved the process stability and resulted in a significant reduction in chemical oxygen demand (COD). Co-digestion could provide a sustainable strategy for treating and valorizing CW. Scale-up calculations showed that a CW input of 1000–2000 L/d co-digested with PL (1:1) could produce 9403 m3 CH4/yr using a 50 m3 digester, equivalent to 373,327 MJ/yr or 24.9 tons of firewood/year. This system would have a profit of $5642/yr and a $47,805 net present value.Item Assessment of Petroleum-Based Plastic and Bioplastics Degradation Using Anaerobic Digestion(MDPI, 2021-12-01) Nachod, Benjamin; Keller, Emily; Hassanein, Amro; Lansing, StephanieBioplastics have emerged as a viable alternative to traditional petroleum-based plastic (PET). Three of the most common bioplastic polymers are polyhydroxybutyrate-valerate (PHBV), polylactide (PLA), and cellulose-based bioplastic (CBB). This study assessed biodegradation through anaerobic digestion (AD) of these three bioplastics and PET digested with food waste (FW) at mesophilic (35 °C) and thermophilic (55 °C) temperatures. The four plastic types were digested with FW in triplicate batch reactors. Additionally, two blank treatments (inoculum-only) and two PHBV treatments (with FW + inoculum and inoculum-only) were digested at 35 and 55 °C. The PHBV treatment without FW at 35 °C (PHBV-35) produced the most methane (CH4) normalized by the volatile solids (VS) of the bioplastics over the 104-day experimental period (271 mL CH4/g VS). Most bioplastics had more CH4 production than PET when normalized by digester volume or gram substrate added, with the PLA-FW-55 (5.80 m3 CH4/m3), PHBV-FW-55 (2.29 m3 CH4/m3), and PHBV-55 (4.05 m3 CH4/m3) having 848,275 and 561%, respectively, more CH4 production than the PET treatment. The scanning electron microscopy (SEM) showed full degradation of PHBV pellets after AD. The results show that when PHBV is used as bioplastic, it can be degraded with energy production through AD.Item EVALUATION OF A METHOD TO MEASURE VOLATILE FATTY ACIDS AND GASES IN VITRO WITH MATHEMATICAL MODELING(2018) Judd, Latisha Marquita; Kohn, Richard A; Animal Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Methane emissions from ruminants have become an issue over the last 50 years. Previous research has shown that methane emissions are stoichiometrically linked with volatile fatty acid (VFA) profiles in ruminant animals. For example, a shift from acetate to propionate may decrease carbon dioxide (CO2) and hydrogen (H2) production, and in turn, decrease conversion of CO2 and H2 to methane. In vitro methods have been developed to measure the digestibility of feeds, but such methods may not accurately estimate methane or volatile fatty acid (VFA) profile. The development of in vitro methods to accurately estimate gas production and VFA profile in rumen fermentation would enable isolation of fermentation effects from various animal interactions. Therefore, the focus of this dissertation was to develop an in vitro method that will have the same VFA and gas profiles as in the rumen. The objectives of this project are: to develop an in vitro technique that mimics an in vivo rumen environment in order to study VFA profiles and gas production during fermentation, to examine and evaluate the efficacy of selected feed additives (e.g. probiotics) on VFA profiles and gas production, and to develop a mechanistic model of the in vitro fermentation system and the effects of feed supplements on the system. The results indicate that gas profile, VFA profile, and gas production were affected by differing in vitro fermentation conditions (buffering capacity, headspace gas composition, acetate concentration). A review of the literature was conducted to establish the effect of probiotics such as lactic acid bacteria on in vitro and in vivo systems. These findings indicated Enterococcus and Lactobacillus species tended to affect ruminal fermentation parameters. Further in vitro analysis of these probiotics indicated these bacteria tended to affect ruminal fermentation, such as gas and VFA production. A developmental mechanistic model was built to predict whether the effect of probiotics was thermodynamically or kinetically limiting. Future studies will further development of this simple model by using published literature for a meta-analysis that may aid in further interpretation of rumen fermentation regarding thermodynamic limits and maximal efficiency of key rumen fermentation reactions.