Abstract
The co-production of biohydrogen and methane from the organic fraction of municipal solid waste was investigated using a two-stage AD system, composed of a pilot scale dark fermenter (DF) and a continuous methanogenic biofilm reactor. From the DF process, a biohydrogen yield of 41.7 (± 2.3) ml H₂/gVSadded was achieved. The liquid DF effluent (DFE) was rich in short chain volatile fatty acids, i.e. mainly acetic and butyric acid. The DFE was valorized by producing methane in the methanogenic biofilm reactor. Two methanogenic biofilm reactors were used to assess the biotic and abiotic role of the DFE on the performance of the reactors. Regardless of the different DFE feeding (i.e. biotic and abiotic), similar and stable operational performance of the two methanogenic biofilm reactors were observed with a respective methane yield and COD removal efficiency of 280-300 ml CH₄/gCODremoved and 80-90 %. Both methanogenic biofilm reactors showed significant resistance towards organic shock loads and recovered faster after reactor disturbance. The total estimated energy recovered in the form of hydrogen and methane gas was, respectively, 28 % and 72 %, of the initial COD.
Highlights
The global increase in fuel prices coupled to the depletion of fossil fuel reserves are creating an energy crisis, which is one of the biggest challenges of the 21st century (Raheem et al, 2016)
This study focused on the co-production of biohydrogen and methane from OFMSW using a two-stage anaerobic digestion (AD) system, comprised of a batch pilot scale dark fermentation processes (DF) and a continuous methanogenic biofilm reactor
After finalizing the start-up process within 25 days, i.e., reaching the desired organic loading rate (OLR) (9.0 gCOD/L.day) by achieving a satisfying chemical oxygen demand (COD) removal efficiency (≥ 80%) and stable methane production rate, the two reactors were fed the different DF effluent (DFE): Rabiotic was fed with the abiotic DFE, while Rbiotic was fed with the biotic DFE
Summary
The global increase in fuel prices coupled to the depletion of fossil fuel reserves are creating an energy crisis, which is one of the biggest challenges of the 21st century (Raheem et al, 2016). As an alternative strategy to exploit most of the energy content of organic substrates, coupling the DF process (producing biohydrogen) with the anaerobic digestion (AD) process (producing methane) has recently received a renewed attention by many researchers (Cavinato et al, 2012; Monlau et al, 2015; Yeshanew et al, 2016c) Such a coupled system creates a wider scope in developing a sustainable approach by producing a highly valued gaseous fuel: biohythane (Capson-Tojo et al, 2016; Cavinato et al, 2016). The microbial communities in the two methanogenic biofilm reactors were characterized as well
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