Hydrogen fuel production from sugarcane and its byproducts – a critical review

Dark fermentation in mixed cultures has been extensively studied due to its great potential for sustainable hydrogen production from organic wastes. However, microbial composition, substrate competition, and inhibition by fermentation products can affect hydrogen yield and production rates. Lactic acid bacteria have been identified as the key organisms in this process. On one hand, lactic acid bacteria can efficiently compete for carbohydrate rich substrates, producing lactic acid and secreting bacteriocins that inhibit the growth of hydrogen-producing bacteria, thereby decreasing hydrogen production. On the other hand, due to their metabolic capacity and synergistic interactions with certain hydrogen-producing bacteria, they contribute positively in several ways, for example by providing lactic acid as a substrate for hydrogen generation. Analyzing different perspectives about the role of lactic acid bacteria in hydrogen production by dark fermentation, a literature review was done on this topic. This review article shows a comprehensive view to understand better the role of these bacteria and their influence on the process efficiency, either as competitors or as contributors to hydrogen production by dark fermentation.

Hydrogen production by mixed bacteria through dark and photo fermentation

This chapter focuses on the technological background of dark fermentative hydrogen production from lignocellulosic biomass. Firstly, the utilization of biomass with various conversion technologies for biofuel production is described, and specific biological hydrogen production processes are highlighted. Then, the basic principles of dark hydrogen fermentation and the current technology of the process are outlined. Among the different processes for biological hydrogen production, dark fermentation is advantageous because it is relatively inexpensive and it has low energy demands. The influence of the key process parameters on dark fermentative hydrogen production is summarized and, subsequently, the use of lignocellulosic raw materials for hydrogen production is examined in detail. Pretreatment of lignocellulosic biomass is typically required prior to fermentative hydrogen production because most hydrogen-producing microorganisms cannot directly utilize cellulose or hemicellulose as a carbon source to grow and produce hydrogen. In particular, the influence of biomass type and pretreatment method on hydrogen yield and productivity is discussed. Moreover, the potential of the coproducts to be further valorized toward the improvement of the economic profile of the process is explored. Finally, the challenges of dark fermentative hydrogen production from lignocellulosic biomass as well as the major conclusions drawn and the perspectives for further development are discussed.

Technical insights on various routes of hydrogen production from pharmaceutical, hydrothermal, sewage and textile wastewaters: Cost comparison and challenges

A comprehensive review on environmental and economic impacts of hydrogen production from traditional and cleaner resources

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.

The piston reactor is emerging as a simple, inexpensive, and compact technology to carry out chemical reactions. Potential piston reactor advantages include high temperature and pressure conditions at short residence times, large throughput, and fast quenching steps. Published research related to hydrogen production using piston reactors has almost exclusively focused on the POX route for hydrogen production and on exploring reactor performance as opposed to overall process performance in terms of specific production costs and emissions. This study provides a process-level understanding of the techno-economics of hydrogen production using piston reactor technology via the three prominent routes for grey and blue hydrogen production: methane partial oxidation (POX), auto-thermal reforming (ATR), and steam methane reforming (SMR). A piston reactor model is initially used to screen the reactor performance in terms of methane conversion and hydrogen production, revealing underperformance for the SMR route. Next, stand-alone hydrogen production processes embedding the piston reactors for the remaining POX and ATR routes are synthesized and specific production costs and CO2 emissions for ‘grey’ hydrogen production determined. Next, the piston reactor processes are integrated with CO2 capture and compression steps for subsequent sequestration and the impact of such CO2 emission mitigation on ‘blue’ hydrogen production costs is evaluated. The obtained results show that the piston-reactor ATR process significantly outperforms the piston-reactor POX process for both grey and blue hydrogen production. For a 100 TPD plant capacity and a natural gas price of $3.3/GJ, blue hydrogen production costs for the piston reactor-based ATR processes are observed to be 1.6/kg H2, which is competitive with reported blue hydrogen production costs using the conventional SMR route. A sensitivity study reveals that the plant capacity has significant impact while piston reactor useful life had low impact hydrogen production costs.

Improving hydrogen production from cassava starch by combination of dark and photo fermentation

Photofermentative production of hydrogen is a promising and sustainable process; however, it should be coupled to dark fermentation to become cost effective. In order to integrate dark fermentation and photofermentation, the suitability of dark fermenter effluents for the photofermentative hydrogen production must be demonstrated. In this study, thermophilic dark fermenter effluent (DFE) of sugar beet thick juice was used as a substrate in photofermentation process to compare wild-type and uptake hydrogenase-deficient (hup (-)) mutant strains of Rhodobacter capsulatus by means of hydrogen production and biomass growth. The tests were conducted in small-scale (50mL) batch and large-scale (4 L) continuous photobioreactors in indoor conditions under continuous illumination. In small scale batch conditions, maximum cell concentrations were 0.92 gdcw/L c and 1.50 gdcw/L c, hydrogen yields were 34% and 31%, hydrogen productivities were 0.49mmol/(L c·h) and 0.26mmol/(Lc·h), for hup (-) and wild-type cells, respectively. In large-scale continuous conditions, maximum cell concentrations were 1.44 gdcw/L c and 1.87 gdcw/L c, hydrogen yields were 48 and 46%, and hydrogen productivities were 1.01mmol/(L c·h) and 1.05mmol/(L c·h), for hup (-) and wild-type cells, respectively. Our results showed that Rhodobacter capsulatus hup (-) cells reached to a lower maximum cell concentration but their hydrogen yield and productivity were in the same range or superior compared to the wild-type cells in both batch and continuous operating modes. The maximum biomass concentration, yield and productivity of hydrogen were higher in continuous mode compared to the batch mode with both bacterial strains.

Insights on biological hydrogen production routes and potential microorganisms for high hydrogen yield

There are many developments in sustainable hydrogen production, like the increasing usage of electrolysis, which accounts for 5% of the hydrogen produced worldwide, as well as the current research into biological production methods. One of these methods is the usage of microorganisms to produce hydrogen through the biological pathways of dark fermentation. It can use renewable raw materials or biomass, such as municipal waste, liquid manure or sewage water as substrate to produce a hydrogen‐rich gas. Hydrogen generation through dark fermentation is a promising method because the process can be integrated into existing biogas plants to use the existing infrastructure to produce biogas and hydrogen as an additional product. However, modifying the existing biogas plants is not feasible or economical for the operator in every case. This paper reports a site analysis conducted to find the most suitable biogas plants in Germany for integrating dark fermentation and assesses the potential costs of hydrogen production via dark fermentation. The site analysis was based on Marktstammdatenregister, Biogas Datenbank, and the Biogaspartner database.

Isolation and characterization of Enterococcus faecalis isolate VT-H1: A highly efficient hydrogen-producing bacterium from palm oil mill effluent (POME)

Biohydrogen production by dark fermentation of different waste materials is a promising approach to produce bio-energy in terms of renewable energy exploration. This communication has reviewed various influencing factors of dark fermentation process with detailed account of determinants in biohydrogen production. It has also focused on different factors such as improved bacterial strain, reactor design, metabolic engineering and two stage processes to enhance the bioenergy productivity from substrate. The study also suggest that complete utilization of substrates for biological hydrogen production requires the concentrated research and development for efficient functioning of microorganism with integrated application for energy production and bioremediation. Various studies have been taken into account here, to show the comparative efficiency of different substrates and operating conditions with inhibitory factors and pretreatment option for biohydrogen production. The study reveals that an extensive research is needed to observe field efficiency of process using low cost substrates and integration of dark and photo fermentation process. Integrated approach of fermentation process will surely compete with conventional hydrogen process and replace it completely in future.

Numerical investigation of pH control on dark fermentation and hydrogen production in a microbioreactor

Solar water splitting is a promising route for sustainable and scalable hydrogen production from renewable sources: water and sunlight. The hydrogen can be used as a clean fuel for refueling fuel cell electric vehicles with zero emissions. Hydrogen can also serve as a feedstock for the production of drop-in liquid fuels by CO2 hydrogenation, and ammonia via the Haber–Bosch process. The greatest challenges towards viable solar water splitting technology lay in the selection and design of photocatalytic materials and devices that harvest sunlight and split water efficiently and produce hydrogen at a competitive cost. To this end photocatalytic materials that are stable in alkaline or acidic aqueous solutions, absorb visible light, promote water oxidation or reduction reactions and comprise of abundant materials must be employed. Iron oxide (α-Fe2O3, hematite), aka rust, is one of few materials meeting these criteria, but its poor transport properties and fast charge recombination present challenges for efficient charge carrier generation, separation and collection. We explore innovative solutions to these challenges using ultrathin (20-30 nm) films on specular back reflectors. This simple optical cavity design effectively traps the light in otherwise nearly translucent ultrathin films, amplifying the intensity close to the surface wherein photogenerated charge carriers can reach the surface and split water before recombination takes place. This is the enabling key towards the development of high-efficiency iron oxide photoelectrodes whose structure and properties can be tailored by design. However, the design rules for these devices remain elusive because iron oxide behaves differently than conventional semiconductors such as silicon, probably due to the strong correlation between the electrons that give rise to the current and the ions that form the crystalline lattice. Our first goal is to discover the physico-chemical processes that limit the performance of iron oxide photoelectrode and devise design principles that enable overcoming these limitations through material design at the nanoscale that combines iron oxide together with selective underlayers and overlayers that separate positive and negative charge carriers, thereby reducing recombination losses and increasing efficiency. The second goal is to apply these design principles to construct high-efficiency solar water splitting devices. The third and final goal is to invent new device architectures and operation schemes that enable affordable solar hydrogen production in large-scale applications, closing the gap between basic research on lab-scale devices and a new solar energy technology that provides stable power on demand. Figure 1