Date of Award

5-2026

Document Type

Thesis

Degree Name

Master of Science

Department

Chemical Engineering

Abstract

Anaerobic digestion (AD) is a widely adopted waste‑management technology and a key process for renewable energy production in the form of biogas. Manures, such as goat manure (GM), often exhibit low carbon‑to‑nitrogen (C/N) ratios, which may limit biogas recovery. This study evaluated and optimized the anaerobic co‑digestion of GM with rice husk (RH) and rice straw (RS) across varying substrate proportions (0–100% GM). Goat manure was collected from the International Goat Research Center at Prairie View A&M University (PVAMU), while RH and RS were obtained from Gulf Pacific Co. (Houston, TX), and the inoculum was sourced from the PVAMU wastewater treatment plant. The measured C/N ratios of RH, RS, and GM were 107.3, 45.1, and 21.3, respectively. Triplicate batch assays were conducted in 250 mL serum bottles at an organic loading rate of 10% (total solids basis), an inoculum‑to‑substrate ratio of 2:1, and a temperature of 36 ± 1 °C over 65 days. Daily biogas production was measured using the liquid displacement method, converted to standard temperature and pressure (STP), and

expressed as mL g⁻¹ VS. Process performance was evaluated using biomethane potential (BMP), theoretical methane yield (TMY), biodegradability (BD), and the synergistic effect index (SEI). In the serum bottle experiments, the highest biogas yields were observed for 100% GM, 90% GM + 10% RH, and 30% GM + 70% RH, yielding 245.1, 233.6, and 232.5 mL g⁻¹ VS, respectively. In 2 L bioreactor experiments conducted over 85 days, biogas yields of 342.13 mL g⁻¹ VS and 327.4 mL g⁻¹ VS were obtained for 100% GM and 90% GM + 10% RH, respectively, while 50% GM + 50% RS yielded 276.4 mL g⁻¹ VS. The experimental biogas production data were well described using both modified Gompertz and first‑order kinetic modeling approaches. Life cycle assessment (LCA) results indicate that while GM monodigestion achieved the highest biogas yield, GM + RH exhibited comparable environmental impacts with the added benefit of diverting rice husk from disposal or open burning. In contrast, GM + RS exhibited higher impact potential. Overall, co‑digestion with RH or RS did not enhance anaerobic digestion performance relative to GM monodigestion under the conditions investigated.

Index Terms—Anaerobic digestion (AD); biomethane potential (BMP); biogas production; carbon-to-nitrogen ratio (C/N ratio); co-digestion; goat manure (GM); life cycle assessment (LCA); lignocellulosic residues; rice husk (RH); rice straw (RS).

Committee Chair/Advisor

Raghava Kommalapati

Committee Member

Sheena Reeves

Committee Member

Ripendra Awal

Committee Member

Hongbo Du

Publisher

Prairie View A&M University

Rights

© 2021 Prairie View A & M University

Creative Commons License
This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.

Date of Digitization

6/15/2026

Contributing Institution

John B Coleman Library

City of Publication

Prairie View

MIME Type

Application/PDF

Download


Share

COinS