رسائل ماجيستير
English
2022
Enhancing methane production by adding conductive materials in anaerobic digester
Md. Abdullah Al-Mamun, Talal Etri, Zahra Khasib Mohammed Al-Hasaniyah
كلية الهندسة-جامعة السلطان قابوس · عمان
Organic waste generation and the depletion of energy resources have become pressing issues that must be addressed. In this regard, adopting waste-to-energy technologies is critical for managing organic waste and producing renewable energy. Anaerobic digestion (AD) is among the most widely used technologies, offering dual benefits: waste treatment and alternative energy generation. It has been commonly applied to treat various types of organic waste, such as agricultural residues, livestock manure, and wastewater sludge.
However, AD technology faces several limitations, including low biodegradation efficiency, specific temperature requirements, and the need for special gas handling. Recent research has mainly focused on enhancing biogas production and improving biodegradation efficiency. Several studies have demonstrated that incorporating conductive additives into the AD matrix can enhance both biodegradation and biogas production performance. The type of conductive additive used significantly affects the efficiency of the AD process.
Therefore, this study aims to:
(i) synthesize a novel conductive composite additive made of granular activated carbon (GAC) coated with nano zero-valent iron (nZVI) via the co-precipitation method;
(ii) characterize the surface morphology and electrical conductivity of the synthesized materials; and
(iii) evaluate the effects of adding these conductive materials on biogas production and biodegradation efficiency in AD systems.
To achieve this, thermophilic anaerobic digestion (TAD) was operated under three different conditions:
Addition of GAC/nZVI to the TAD matrix during co-digestion of cow manure with food waste (ground rice and bread);
Addition of GAC/nZVI to the TAD matrix during mono-digestion of cow manure;
A control TAD reactor without GAC/nZVI additives, used for co-digestion.
Biogas production increased 11-fold in the reactor using GAC/nZVI compared to the control TAD without additives. Additionally, the methane content (%) in the biogas increased 20.7-fold compared to the control reactor. This enhancement is attributed to the conductive additives, which facilitated electron transfer between microorganisms, thereby improving microbial communication and growth.
However, the addition of conductive materials in the TAD matrix did not enhance methane production during mono-digestion with cow manure alone. This is likely due to the significantly lower levels of biodegradable nutrients in cow manure, which are essential for acetogenic and methanogenic microbes.
The findings demonstrate that incorporating GAC/nZVI conductive materials into the TAD matrix significantly improves methane production, COD removal, and pH stabilization during co-digestion of cow manure with food waste.