Methane production from rendering waste covered anaerobic digester: Greenhouse gas reduction and energy production

Authors: Lovanh, Nanh; Loughrin, John; RUIZ-AGUILAR, GRACIELA - University Of Guanajuato; Sistani, Karamat

Submitted to: Energies
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/26/2023
Publication Date: 11/29/2023
Citation: Lovanh, N.C., Loughrin, J.H., Ruiz-Aguilar, G., Sistani, K.R. 2023. Methane production from rendering waste covered anaerobic digester: Greenhouse gas reduction and energy production. Energies. 16. Article 7844. https://doi.org/10.3390/en16237844.
DOI: https://doi.org/10.3390/en16237844

Interpretive Summary: Livestock wastes can serve as the feedstock for biogas production (mainly methane) that could be used as alternative energy source. The green energy derived from animal wastes is considered to be carbon neutral and offsetting those generated from fossil fuels. In this study, an evaluation of methane production from anaerobic digesters utilizing different livestock residues (e.g., poultry rendering wastewater and dairy manure) was carried out along with actual large-scale covered poultry rendering wastewater lagoon. The results show that covered poultry rendering wastewater lagoons could be quite beneficial to reducing air pollution such as greenhouse gases and odors, biomass, and, at the same time, obtain renewable bioenergy for on-farm use. Due to the constraint on physical size (volume) and the high throughput of wastewater influent, the hydraulic residence time (HRT) was reduced below the ideal HRT for effective anaerobic digestion system. However, biogas production was still very high, but incomplete digestion of organic materials persisted. This is evident in the high concentrations of long chain fatty acids in the effluent. Furthermore, due to the nature of the system being subjected to natural environmental conditions, biogas productions fluctuated quite a bit due to seasonal environmental conditions, namely temperatures.

Technical Abstract: Livestock wastes can serve as the feedstock for biogas production (mainly methane) that could be used as an alternative energy source. The green energy derived from animal wastes is considered to be carbon neutral and offsetting the emissions generated from fossil fuels. In this study, an evaluation of methane production from anaerobic digesters utilizing different livestock residues (e.g., poultry rendering wastewater and dairy manure) was carried out. An anaerobic continuous flow system (15 million gallons, polyethylene-covered) subjected to natural conditions (i.e., high flowrate, seasonal temperatures, etc.) containing poultry rendering wastewater was set up to evaluate methane potential and energy production. A parallel pilot-scale plug-flow anaerobic digestion system (9 m3) was also set up to test different feedstocks and operating parameters. Biogas production was sampled and monitored by gas chromatography over several months of operation. The results showed that methane production increased as the temperature increased as well as depending on the type of feedstock utilized. The covered rendering wastewater lagoon achieved an upward of 80% (v/v) methane production. The rates of methane production were 0.0478 g per g of COD for the poultry rendering wastewater and 0.0141 g per g of COD for dairy manure as feedstock. Hence, a poultry processing plant with a rendering wastewater flow rate of about 4.5 million liters per day has the potential to capture about two million kilograms of methane for energy production per year from a waste retention pond, potentially reducing global warming potential by about 50,000 tons of CO2 equivalent annually.