Abstract
Direct addition of sulfur-reducing agents during anaerobic digestion (AD) is very effective in controlling hydrogen sulfide (H2S) content in biogas, although one major problem is the high operational cost due to the large amount of chemicals used. The objective of this study was to remove H2S using a waste mill scale (MS) as a sulfur-reducing agent. To evaluate its feasibility, MS was added to AD fed with food waste (FW) at concentrations between 0 and 160 g MS/kg total chemical oxygen demand (TCOD) during the batch test, and the experimental results were compared to those of the batch test with the addition of iron chloride (FeCl3). Both FeCl3 and MS played an important role as electro-conductive materials in improving methane productivity by promoting direct interspecies electron transfer. An increase in H2S removal efficiency was observed with increases in both materials. In total, 30%, 60%, and 90% of H2S production based on the maximum sulfur in the form of H2S (control) was 3.7, 9.4, and 23.8 g FeCl3/kg TCOD and 13.3, 34.1, and 86.2 g MS/kg TCOD, respectively. This finding indicates that MS can be used as a sulfur-reducing agent substitute for H2S removal in AD fed with FW.
Highlights
Sustainable organic waste management has become one of the greatest challenges worldwide
The sample in the presence of 11 g FeCl3 /kg chemical oxygen demand (COD) showed a CH4 yield of 258 ± 4 mL CH4 /g COD and a CH4 production rate of 23.1 ± 1.1 mL CH4 /d, and the sample added with 44 g FeCl3 /kg COD resulted in a CH4 yield of 332 ± 2 mL
The results showed that mill scale (MS) positively affected the Anaerobic digestion (AD) process
Summary
Sustainable organic waste management has become one of the greatest challenges worldwide. Anaerobic digestion (AD) is recognized as a well-established technology for the treatment of a wide range of organic matter (such as food waste, sewage sludge, agricultural residues, and livestock manure) and for the production of biogas, which has been utilized for a combination of heat and electricity generation [1,2,3,4]. The use of biogas is moving toward new applications, such as vehicle fuels and injection into the natural gas grid. To utilize it widely, biogas purity is critical, which can often compromise its true economic potential [5]. Common H2 S removal technologies include physicochemical approaches either during digestion or from crude biogas [5,10,11,12,13]
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