Abstract
In the context of hydrogen production from biomass or organic waste with dark fermentation, this study analysed 55 studies (339 experiments) in the literature looking for the effect of operating parameters on the process performance of dark fermentation. The effect of substrate concentration, pH, temperature, and residence time on hydrogen yield, productivity, and content in the biogas was analysed. In addition, a linear regression model was developed to also account for the effect of nature and pretreatment of the substrate, inhibition of methanogenesis, and continuous or batch operating mode. The analysis showed that the hydrogen yield was mainly affected by pH and residence time, with the highest yields obtained for low pH and short residence time. High hydrogen productivity was favoured by high feed concentration, short residence time, and low pH. More modest was the effect on the hydrogen content. The mean values of hydrogen yield, productivity, and content were, respectively, 6.49% COD COD−1, 135 mg L−1 d−1, 51% v/v, while 10% of the considered experiments obtained yield, productivity, and content of or higher than 15.55% COD COD−1, 305.16 mg L−1 d−1, 64% v/v. Overall, this study provides insight into how to select the optimum operating conditions to obtain the desired hydrogen production.
Highlights
Anaerobic digestion (AD) is an established process used across the world for the conversion of biomass and organic waste into methane, a renewable energy vector [1–3]
While the use of AD to produce methane is an established commercial process, to the best of our knowledge, there are, to date, no full-scale processes in which AD, called dark fermentation (DF) in this case, is used for the primary purpose to produce the intermediates of the process, i.e., hydrogen and short-chain organic acids (SCOAs)
A large volume of literature is being published on the use of DF for hydrogen production
Summary
Anaerobic digestion (AD) is an established process used across the world for the conversion of biomass and organic waste into methane, a renewable energy vector [1–3]. While the use of AD to produce methane is an established commercial process, to the best of our knowledge, there are, to date, no full-scale processes in which AD, called dark fermentation (DF) in this case, is used for the primary purpose to produce the intermediates of the process, i.e., hydrogen and short-chain organic acids (SCOAs). This is despite the large volume of recent research, at lab or pilot scale, on DF to produce these intermediates [4]. The intermediates produced in the second step can be more economically valuable than the end product methane [5]
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