Abstract
Molasses is a highly dense and refined byproduct produced in the sugarcane industry, and it contains high amounts of degradable compounds. Through bioconversion, these compounds can be transformed into renewable products. However, the involved biological process is negatively influenced by the high chemical oxygen demand (COD) of molasses and ion concentration. The co-digestion of molasses with rice-alcohol wastewater (RAW) was compared with its mono-digestion at an increasing organic loading rate (OLR). Both processes were assessed by detecting the COD removal rate, the methane contents of biogas, and the structure and composition of microbial communities at different stages. Results showed that the co-digestion is stable up to a maximum OLR of 16 g COD L−1 d−1, whereas after the acclimatization phase, the mono-digestion process was disturbed two times, which occurred at a maximum OLR of 9 and 10 g COD L−1 d−1. The volatile fatty acids (VFAs) observed were 2059.66 mg/L and 1896.9 mg/L, which in mono-digestion causes the inhibition at maximum OLRs. In the co-digestion process, the concomitant COD removal rates and methane content recorded was 90.72 ± 0.63% 64.47% ± 0.59% correspondingly. While in the mono-digestion process, high COD removal rate and methane contents observed were 89.29 ± 0.094% and 61.37 ± 1.06% respectively. From the analysis of microbial communities, it has been observed that both the bacterial and archaeal communities respond differently at unlike stages. However, in both processes, Propionibacteriaceae was the most abundant family in the bacterial communities, whereas Methanosaetaceae was abundant in the archaeal communities. From the current study, it has been concluded that that rice-alcohol wastewater could be a good co-substrate for the anaerobic digestion of molasses in terms of COD removal rate and methane contents production, that could integrate molasses into progressive biogas production with high OLR.
Highlights
Side streams produced in huge quantities in agro-industrial processes contain high organic compounds of low value, and these streams are an attractive feedstock to be used in bio-refineries.The highly biodegradable substances present in these streams can be converted into chemicals of interest [1,2]
Molasses is a byproduct of the sugarcane industry and is among the attractive sources for biogas production due to its high organic fraction
We investigated the digestion of molasses utilizing both mono-digestion and co-digestion processes
Summary
Side streams produced in huge quantities in agro-industrial processes contain high organic compounds of low value, and these streams are an attractive feedstock to be used in bio-refineries. The high organic fraction of molasses is attributed to its high sucrose content, and sucrose can be used as a substrate in bio-refineries and is possibly involved in several microbial pathways [2] Biofuels, such as ethanol, hydrogen, and methane, are well-known products of molasses digestion. Keeping in view the afore-mentioned importance of molasses and its anaerobic fermentation, this study was conducted for the first time to evaluate the anaerobic co-digestion of molasses with rice-alcohol wastewater and to compare with the mono-digestion of molasses in addition to an analysis of microbial composition The efficiency of both processes was assessed in terms of COD removal rate and percent methane contents of biogas produced. VFAs were monitored periodically, which could cause negative effects on the digestion process, while high throughput sequencing was applied to identify and characterize the Archaeal and bacterial communities in different phases of the process
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
