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Various organic wastes can be used as low-cost substrate for fermentative hydrogen production, which significantly reduces the hydrogen production cost. Furthermore, biohydrogen production from organic wastes can achieve dual benefits of clean energy generation and waste management since agricultural and municipal wastes can be disposed at the same...
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... H2SO4 concentration of 0.5% (in P-8/MX-102) [20], [43], [44]. The acidified slurry is stored in a blending tank (P-9/V-101) and then sent for thermal hydrolysis to a plug flow reactor (P-15/PFR-101). ...
... Low temperatures may lead to insufficient disintegration, while too high temperatures can result in excessive degradation of organic matter in biomass, thus reducing the value of biomass as an organic source for fermentation. Too high treatment temperatures may also cause the formation of refractory compounds, which are inhibitory for fermentation [44]. ...
... The neutralized slurry is mixed with a recycled solution (P-23/V-104), which is analyzed later. A custom mixer (P-24 / MX-105) manages the addition of 5% cellulase [44], and the slurry is fed to a set of 6 stirred Table 4 below displays the stoichiometry and assumed conversion of the enzymatic hydrolysis reactions. The resulting hydrolysate slurry contains concentrated sugars and unhydrolyzed solids such as lignin. ...
This is the ReadMe file of a SuperPro Designer example that analyzes the production of green hydrogen via bioconversion pathways and water electrolysis. The bioconversion process utilizes 18 metric tons (MT) per hour of wheat straw as feedstock which is converted into fermentable sugars via thermochemical and enzymatic hydrolysis. Biohydrogen is produced using a combination of sequential dark and photo fermentation and the product is purified using pressure swing adsorption. The process generates 1.1 MT/hour of purified biohydrogen. The electrolytic process utilizes 10 MT/hour of municipal water, which is converted into ultrapure water and then electrolyzed to produce 1.1 MT/hour of purified hydrogen. This example also includes a model for hydrogen liquefaction. The analysis results for all three processes include material and energy balances, equipment sizing, capital, and operating cost estimation. The results indicate that significant government subsidies are necessary for the financial viability of such investments considering the current technologies and market dynamics.
... The purification process of synthesis gas, obtained from steam reforming of natural gas, is a key step and CO2 separation from H2 plays a crucial role [11]. Biogas/biomethane reforming and biomass gasification and pyrolysis can also be a source of hydrogen from industrial or agriculture waste [12][13][14]. For instance, in dark fermentation, different proportions of H2, CO2, and CH4, depending on the microorganisms used, need to be purified. ...
Mixed matrix membranes (MMMs) consisting of a blend of a hydroxypolyamide (HPA) matrix and variable loads of a porous polymer network (PPN) were thermally treated to induce the transformation of HPA to polybenzoxazole (β-TR-PBO). Here, the HPA matrix was a hydroxypolyamide having two hexafluoropropyilidene moieties, 6FCl-APAF, while the PPN was prepared by reacting triptycene (TRP) and trifluoroacetophenone (TFAP) in a superacid solution. The most probable size of the PPN particles was 75 nm with quite large distributions. The resulting membranes were analyzed by SEM and AFM. Up to 30% PPN loads, both SEM and AFM images confirmed quite planar surfaces, at low scale, with limited roughness. Membranes with high hydrogen permeability and good selectivity for the gas pairs H2/CH4 and H2/N2 were obtained. For H2/CO2, selectivity almost vanished after thermal rearrangement. In all cases, their hydrogen permeability increased with increasing loads of PPN until around 30% PPN with ulterior fairly abrupt decreasing of permeability for all gases studied. Thermal rearrangement of the MMMs resulted in higher permeabilities but lower selectivities. For all the membranes and gas pairs studied, the balance of permeability vs. selectivity surpassed the 1991 Robeson’s upper bound, and approached or even exceeded the 2008 line, for MMMs having 30% PPN loads. In all cases, the HPA-MMMs before thermal rearrangement provided good selectivity versus permeability compromise, similar to their thermally rearranged counterparts but in the zone of high selectivity. For H2/CH4, H2/N2, these nonthermally rearranged MMMs approach the 2008 Robeson’s upper bound while H2/CO2 gives selective transport favoring H2 on the 1991 Robeson’s bound. Thus, attending to the energy cost of thermal rearrangement, it could be avoided in some cases especially when high selectivity is the target rather than high permeability.
... The objective of the pre-treatment is to destroy the lignin seal protecting the cellulose molecules and aid in their release into solution followed by destruction of the crystalline arrangement of the cellulose molecules and depolymerisation to enhance enzymatic digestibility and acidogenic fermentation into bio-hydrogen [25,29e36]. Several technologies, classified into physical, physico-chemical, chemical and biological, have been investigated with the aim to increase the bio-hydrogen yield from lignocellulosic i n t e r n a t i o n a l j o u r n a l o f h y d r o g e n e n e r g y 4 4 ( 2 0 1 9 ) 1 7 3 4 6 e1 7 3 6 2 biomass and in-depth assessment of these techniques has been provided in previous review articles [17,33,35]. Among the various techniques studied for substrates pre-treatment prior to dark fermentative bio-hydrogen production, it has been reported that acid and thermal pre-treatments are often the most effective pre-treatment technologies [33]. ...
This study provided an estimate of the potential of bio-hydrogen production from dark fermentation of crop residues on a worldwide scale. The different crop residues reviewed included sugarcane tops, leaves and bagasse, corn straw, corn cob and corn stover, wheat straw, rice straw and husk, soybean straw, oil palm trunk and empty fruit bunch, sugar beet pulp, cassava residue, barley straw and sweet sorghum bagasse. Among these crop residues, wheat and rice straws are produced in the highest amount although sugarcane dominates crop production on a worldwide scale. Based on the bio-hydrogen yields reported in literature, estimated worldwide bio-hydrogen potential is highest for untreated rice straw at 58,002 Mm3/year followed by untreated wheat straw at 34,680 Mm3/year. This corresponds to a bio-energy potential of 623 PJ/year and 373 PJ/year for raw rice straw and wheat straw respectively while pre-treatment of the crop residues significantly increases the bio-hydrogen and bio-energy potential. While dark fermentation of crop residues offers a huge bio-energy potential, the process suffers from several constraints that hinder its implementation. As such, coupling of the dark fermentation process with the anaerobic digestion process as a two-stage process seems the most economically viable option for large-scale implementation.
Significant efforts are being made to produce biofuels to replace fossil fuels and address the issues caused by global climate change. Due to its potential better conversion efficiency to
useable power, decreased emission of pollutants, and high energy density, H2 is one of the prospective options that are seen as a desirable future clean energy carrier. Although there are numerous technologies available for producing H2, this review concentrates on fermentative H2 production techniques, their drawbacks, and current developments. While being a promising method, fermentative strategies still have several drawbacks, including low H2 production yields. Many approaches have been used to address these issues; among them, the field of metabolic pathway engineering has made enormous strides. To improve
H2 generation, this paper reviewed and discussed several metabolic pathways and modified strains. As well as the challenges involved in H2 scale-up from a laboratory setting to a
commercial scale.
This study explored alcohol production from volatile fatty acids (VFAs) in single-chambered microbial electrosynthesis systems (MES) under continuous pH control (≤pH 5.5) for methanogen inhibition. MES with 2 g-COD/l VFA could produce highest current of 5.3 mA followed by 3.6 mA in 6 g-COD/l and 0.44 mA in 8 g-COD/l, implying active bioelectrochemical reactions of microorganisms on the electrodes. Ethanol, methanol and propanol were detected as fermented bio-alcohols without methane production, and ethanol was the main product with a cumulative recovery of 7.14 mM in 2 g-COD/l, 13.6 mM in 6 g-COD/l and 17.9 mM in 8 g-COD/l. Maximum bio-alcohol yield of 0.71 g-CODAlcohols/g-CODVFAs with a recovery efficiency of 35% was obtained from MES under 2.0 g-COD/l, followed by 6 and 8 g-COD/l. The results demonstrate that pH adjustment method is an effective strategy to suppress methanogens for improved bioelectrochemical performance of alcohol production from VFAs in MES.
Rapid industrialization and urbanization are mainly responsible for the energy crisis, environmental pollution and climate change. In addition, depletion of the fossil fuels is a major concern now. To confront these problems, it is essential to produce energy from sustainable and renewable energy sources. Hydrogen is widely considered as a clean and efficient energy carrier for the future because it does not produce carbon-based emission and has the highest energy density among any other known fuels. Due to the environmental and socioeconomic limitation associated with conventional processes for the hydrogen production, new approaches of producing hydrogen from biological sources have been greatly encouraged. From the perspective of sustainability, microalgae offer a promising source and have several advantages for the biohydrogen production. Microalgae are characterized as high rate of cell growth with superior photosynthetic efficiency and can be grown in brackish or wastewater on non-arable land. In recent years, biohydrogen production from microalgae via photolysis or being used as substrate in dark fermentation is gaining considerable interest. The present chapter describes the different methods involved in hydrogen production from microalgae. Suitability of the microalgae as a feedstock for the dark fermentation is discussed. This review also includes the challenges faced in hydrogen production from microalgae as well as the genetic and metabolic engineering approaches for the enhancement of biohydrogen production.
