Abstract
The effects of organic loading rates (OLRs) on fermentative productions of hydrogen and ethanol were investigated in a continuous stirred tank reactor (CSTR) with attached sludge using molasses as substrate. The CSTR reactor with attached sludge was operated under different OLRs, ranging from 8 to 24 kg/m3·d. The H2 and ethanol production rate essentially increased with increasing OLR. The highest H2 production rate (10.74 mmol/h·L) and ethanol production rate (11.72 mmol/h·L) were obtained both operating at OLR = 24 kg/m3·d. Linear regression results show that ethanol production rate (y) and H2 production rate (x) were proportionately correlated and can be expressed as y = 1.5365x − 5.054 (r2 = 0.9751). The best energy generation rate was 19.08 kJ/h·L, which occurred at OLR = 24 kg/m3·d. In addition, the hydrogen yield was affected by the presence of ethanol and acetic acid in the liquid phase, and the maximum hydrogen production rate occurred while the ratio of ethanol to acetic acid was close to 1.
Highlights
The negative impacts on the global environment due to the intensive use of fossil fuels need to be reduced and reversed by replacing them gradually with sustainable and carbonneutral energy carriers [1]
Volatile fatty acids (VFAs) and ethanol in the fermentation solution were analyzed by gas chromatography (Model GC-112, Shanghai Analytical Apparatus Corporation, China) with a hydrogen flame ionization detector and a stainless steel column (2 m × 5 mm) packed with support (GDX103, 60/80 mesh, Shanghai Maikun Chemical Co., Ltd)
The H2 and ethanol production rate in continuous stirred tank reactor (CSTR) essentially increased with increasing organic loading rates (OLRs)
Summary
The negative impacts on the global environment due to the intensive use of fossil fuels need to be reduced and reversed by replacing them gradually with sustainable and carbonneutral energy carriers [1]. Ethanol can be supplemented to gasoline as a fuel for transportation and can be used as a substrate for biodiesel production. At this moment, bioenergy technology focuses heavily on converting biomass feedstock to bioethanol and/or biodiesel [2]. Hydrogen is considered as a clean energy carrier for the future due to its high conversion, recyclability, and nonpolluting nature [4]. The use of organic waste reduces waste disposal problems [5, 6]. In addition to H2 production, anaerobic fermentation produces a significant amount of alcohols (such as ethanol) [7]
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