A Review of Biohydrogen Productions from Lignocellulosic Precursor via Dark Fermentation: Perspective on Hydrolysate Composition and Electron-Equivalent Balance

Abstract

This paper reviews the current technological development of bio-hydrogen (BioH2) generation, focusing on using lignocellulosic feedstock via dark fermentation (DF). Using the collected reference reports as the training data set, supervised machine learning via the constructed artificial neuron networks (ANNs) imbedded with feed backward propagation and one cross-out validation approach was deployed to establish correlations between the carbon sources (glucose and xylose) together with the inhibitors (acetate and other inhibitors, such as furfural and aromatic compounds), hydrogen yield (HY), and hydrogen evolution rate (HER) from reported works. Through the statistical analysis, the concentrations variations of glucose (F-value = 0.0027) and acetate (F-value = 0.0028) were found to be statistically significant among the investigated parameters to HY and HER. Manipulating the ratio of glucose to acetate at an optimal range (approximate in 14:1) will effectively improve the BioH2 generation (HY and HER) regardless of microbial strains inoculated. Comparative studies were also carried out on the evolutions of electron equivalent balances using lignocellulosic biomass as substrates for BioH2 production across different reported works. The larger electron sinks in the acetate is found to be appreciably related to the higher HY and HER. To maintain a relative higher level of the BioH2 production, the biosynthesis needs to be kept over 30% in batch cultivation, while the biosynthesis can be kept at a low level (2%) in the continuous operation among the investigated reports. Among available solutions for the enhancement of BioH2 production, the selection of microbial strains with higher capacity in hydrogen productions is still one of the most phenomenal approaches in enhancing BioH2 production. Other process intensifications using continuous operation compounded with synergistic chemical additions could deliver additional enhancement for BioH2 productions during dark fermentation.

Kinetic Study of Product Distribution Using Various Data-Driven and Statistical Models for Fischer–Tropsch Synthesis

“…In statistics, response surface methodology explores the relationships between several explanatory variables and one or more response variables. 43,44 The main idea of RSM is to use a sequence of designed experiments to obtain an optimal response. In addition, it can also be used to directly correlate the influential operational parameters with responses using the most widely deployed second-degree polynomial expressions to find out the offset, linear, quadratic, and interactive terms as follows…”

“…In statistics, response surface methodology explores the relationships between several explanatory variables and one or more response variables. , The main idea of RSM is to use a sequence of designed experiments to obtain an optimal response. In addition, it can also be used to directly correlate the influential operational parameters with responses using the most widely deployed second-degree polynomial expressions to find out the offset, linear, quadratic, and interactive terms as follows where Y i is the responded value (in this work, there are 36 different responses including X CO , S CH4 , r CO , S CO2 , S C2–C4 , r P n , r O n with n ≤ 15), X i X j is the binary parameter of the investigated operational parameters ( T , P , GHSV, and SR), and b 0 , b i , and b ii ( b ij ) are coefficients from the polynomial expression.…”

A New Perspective for Climate Change Mitigation—Introducing Carbon-Negative Hydrogen Production from Biomass with Carbon Capture and Storage (HyBECCS)

“…Sugars and starchy products are particularly suitable feedstocks for dark fermentation [48]. However, with pretreatment, a variety of feedstocks such as food waste, wood, or wastewater can be used for biological hydrogen production [46,49,54,55]. In dark fermentation, the contained glucose is decomposed into hydrogen, carbon dioxide, and the byproducts acetic acid (3), propionic acid (4), or butyric acid (5) [39,48,49,56,57].…”

Efficient Extraction of Fermentation Inhibitors by Means of Green Hydrophobic Deep Eutectic Solvents

“…The generation of hydrogen, optimization of the process, and purification of the gaseous products [ 1 , 2 , 3 ] are considered to be some of the key research directions for second-generation biofuels [ 4 , 5 , 6 , 7 ]. The most abundant fraction of lignocellulosic biomass, i.e., sugar polymers, are the source of the sole carbon source in the fermentation processes.…”

“…Consequently, the liquid phase composition is affected by this process and therefore the management of the pre- and post-fermentation broth becomes an important direction of research [ 5 , 7 ]. There are a number of reports [ 1 , 3 , 5 , 12 ] on chemical compounds formed in the liquid phase during the biomass pretreatment or after dark fermentation. Some of them may affect the efficiency of fermentation [ 5 ].…”