Comparative study on the performance of iron-amended cassava pulp feed bio-methanation in CSTRs

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Htay Aung Pyae
Win Win Aye
Chatpet Yossapol
Somchai Dararatana


In recent years, the advances in the biogas related technology and plant design open new possibilities in biogas production from various biomasses other than activated waste sludge from a waste water treatment plant. Although, the anaerobic digestion (AD) process offers sustainable and environmental friendly energy to curb heavy reliance on fossil fuels to a certain extent, the low methane (CH4) content of biogas remains as a challenge. Using selected pieces of scrap iron with the properties of zero valent iron (ZVI), this paper attempts to enhance the biomethane content of biogas in terms of quality and quantity. The characteristics of scrap iron were verified using XPS and SEM. The optimum iron level was observed at 20 g/L where COD removal reached 95%. This represents a 20% enhancement over than that a of control reactor with 75% removal.  Bio‑methane production could further be improved using iron with superior characteristics (particularly zero valent iron, ZVI). Nevertheless, by means of the current iron amendments in cassava pulp feed CSTRs with an optimum organic loading rate (OLR) of 3.25 g VSS L‑1 day-1, methane was enriched from 50% to 75% with 10% to 35% additional gas yield over that of the control reactor. VFA/TA levels are a critical control factor. Inhibition starts when iron addition exceeds 20 g/L. The outcome of iron addition is seen immediately, making the process easier to control with better stability during digestion. The presence of iron cut the frequency of re-buffering and thus reduced chemical consumption for pH control and provided for a longer buffer resistance period. Iron amendment during anaerobic digestion of cassava pulp was shown to promote higher levels of bio-methane production.


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Pyae, H. A., Aye, W. W., Yossapol, C., & Dararatana, S. (2019). Comparative study on the performance of iron-amended cassava pulp feed bio-methanation in CSTRs. Engineering and Applied Science Research, 46(3), 219-226. Retrieved from


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