ABEN Masters Theses

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Browsing ABEN Masters Theses by Subject "Canola meal as feed."

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    Anaerobic Co-digestion of Dairy Manure with Canola Meal
    (North Dakota State University, 2011) Atandi, Eric Michieka
    There has been an increase of confined animal feeding operations (CAFOs) generating large amounts of manure. When this manure is not handled properly, it generates greenhouse gases (GHGs), odors and water pollution. Anaerobic digestion (AD) is touted as an acceptable approach to address manure management and associated environmental problems. Biogas production from manure alone is limited by low volumes of biogas yield, thus it has a poor economic reputation. Co-digestion of dairy manure with other agricultural wastes has emerged as a promising strategy to enhance the economic viability of AD. Among the agricultural wastes, canola meal (a by-product from extraction of oil from canola seed) was considered as a potential candidate for co-digestion with dairy manure. The purpose of this research was to investigate the suitability and appropriate ratios of canola meal for anaerobic co-digestion with dairy manure. In this study, various proportions of canola meal: dairy manure (100:0, 10:90, 40:60, 20:80, 0:100) by volume-basis were co-digested in 0.5 L batch bioreactors at a temperature of 35±1 °c for 25 d. Two types of canola meal were used in the study; high oil content (HOC) and low oil content (LOC) canola meal with oil contents of 8.0% and 2.5%, respectively. For HOC, the total solids (TS) were high organic loading (HOL, 7.5±2% TS) and low organic loading (LOL, 4.5±2% TS). LOC trials were done at HOL only. In addition, the pretreatment of the canola meal with caustic solution and digestion at high temperature (60±2°C) were evaluated. Results from this study indicated that at HOL, canola meal is not a viable candidate for anaerobic co-digestion with manure as it lowers biogas production. Manure only digestion performed better than bioreactors augmented with canola meal. The specific methane yield was 352 L/kg VS for manure only and 84 L/kg VS for LOC canola meal only digestion. Nonetheless, at LOL, both 10% and 20% HOC canola meal resulted in increased specific methane of 535 L/kg VS and 445 L/kg VS, respectively. This is 78% and 48% higher than 300 L/kg VS obtained in manure only digestion. Hence, canola meal is beneficial in dairy manure co-digestion at LOL. At all organic loading levels, canola meal alone digestion had the lowest cumulative biogas production (0.9 L per 0.35 L bioreactor) and specific methane yield (83 L/kg VS). For HOL, the cumulative biogas yield and specific methane yield decreased as the canola meal ratio increased, while at LOL, the decrease was only noted for bioreactors with 40% canola meal. This is suspected to be caused by elevated levels of total volatile fatty acids (VF As) of more than 4000 mg/L. Two factors are suspected to impact the accumulation of VF As: the ratio of canola-to-manure in the bioreactor and the organic loading or oil content in the canola meal. In future it will be necessary to look into ways of overcoming the inhibition caused by elevated VF As.