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CO2 bioelectromethanosynthesis represents a promising strategy for the capture and utilization of CO2. In such process, the continuous generation of electron (e-) and proton (H+) in anodic oxidation are of prime importance for the efficient cathodic CO2 electroreduction and process stability. Proton transfer, however, is very easy to be hindered due to the fouling of proton exchange membrane (PEM). In this study, an artificial channel in microbial electrolysis cell (MEC) was proposed to strengthen the transport of protons from anodic to cathodic compartment, and H+-rich anolyte was semi-continuously circulated to the cathodic chamber to provide protons for CO2 electroreduction. The results indicated that the daily CH4 yield in cathode with anolyte circulation (18.5 mL/d·L-reactor) was 5.4-fold higher than that without circulation (2.9 mL/d·L-reactor). Meanwhile, efficient anodic biodegradation of organic components was observed with COD, proteins and polysaccharides removal of up to 95.6 ± 1.9%, 96.3 ± 3.7% and 99.1 ± 0.2% respectively, which supplied a continuous e-/H+ donor for CO2 electroconversion. 16S rRNA gene pyrosequencing analysis identified a large number of proteins-utilizing Bacteroidetes (14.11%) and polysaccharides-consuming Thermotogae (18.49%) in anodic biofilm, conductive to the biodegradation of organic components. Moreover, a high abundance of Methanobacterium (81.07%) was detected to prevail in cathodic biofilm, demonstrating the occurrence of highly enhanced CH4 bioelectrosysthesis. The syntrophic and symbiotic relationship was established in the dual-bioelectrode system, creating a beneficial environment and an energy-efficient approach for biowaste refinery and CO2 electromethanosynthesis.

Underlying mechanism of continuous nano zero-valent iron (nZVI) supply in functional microbes enrichment and methane bioconversion of waste activated sludge were investigated in a lab-scale continuous stirred tank reactor (CSTR). Results indicated that methane productivity strongly relied on nZVI dosage (R = 0.998, p (0.05)

Nowadays there is a huge demand for new and sustainable technologies aiming the reduction of the greenhouse gas, in particular carbon dioxide emission. In this work, enzymatically-boosted supported ionic liquid membrane (EB-SILM) was developed to permeate carbon dioxide with improved efficiency. Firstly, the selected biocatalyst, carbonic anhydrase (CA) was prepared and purified from spinach, a cheap plant biomass containing the enzyme of our interest. Afterwards, the CA enzyme preparation was used for SILM fabrication in order to test the properties towards enhanced carbon dioxide permeation over CH 4 , H 2 and N 2 . The results indicate basically that EB-SILMs possess an increased ability to permeate CO 2 in comparison with enzymeless controls and therefore, may be viewed as a promising approach e.g. towards enhanced CO 2 -capture bioprocesses.

Continuous primary energy consumption has motivated the scientists of the world to search for renewable energy sources that could substitute fossil fuels. Microalgae can be an alternative substrate for renewable energy recovery. In this study, biochemical methane potential (BMP) assays were used as a tool to examine the technical potential of methane production from microalgae (MA) through co-digesting with food waste (FW) at different MA: FW ratios on volatile solids (VS). Three mathematical models (i.e. first-order kinetic, modified Gompertz, and Cone models) were also utilized to fit the experimental data, with the purpose of elucidating the biological degradation and principle kinetics of the co-digestion. The results showed that supplementing food waste significantly improved microalgae digestion performance, with the highest methane yield of 639.8 ± 1.3 mL/g VSadded obtained at a MA:FW ratio of 0.2:0.8, which was 4.99-fold increase with respect to that (106.9 ± 3.2 mL/g VSadded) of the microalgae alone. Cone model had the best fitness and reliability to the experimental results and could describe the co-digestion kinetics more reasonably. Parameter analysis and synergistic impact evaluation together revealed that the improvement in methanogenesis potential (fd) caused by the synergy of co-digestion might be the fundamental cause for the upgraded methane production. These results validated the superiority of co-digestion as a step towards maximizing methane production from microalgae, aiding the development of multi-biomass co-disposal and ultimately bioenergy recovery techniques.

Sulfate radicals are well-known for their strong oxidation potential (2.60 V), their high reaction rate (106–109 M/s) and longer life span (t1/2 = 30–40 μs). Owing to the revealed impact it is accomplished by oxidizing, many pesticides, dye, and heavy organic substances such as waste activated sludge (WAS) in a very short time duration. In this review, current research exploration, novel encounters, long pathway of sulfate radicals travelling in environmental management and commercial implementation prominence to persulfate oxidation process are abridged and revealed. A broad evaluation analysis intended in this review established its mesmerizing ascendancies over the conventional persulfate oxidation process with respect to rapid, more efficient, broad pH range and outstanding reaction. Regardless of the abundant improvement attained earlier, there are still several challenges for persulfate activation through transition metals such as heavy metal deposit, metal leaching, removal of sulfate, reusability, etc. To tackle the overhead complications, a novel scenario catalyst with a non-radical pathway, i.e. carbon-grounded catalyst (activated carbon, graphene oxide, biochar, etc.) is under extensive trials. The challenge and practical problems faced in the course of sulfate radical usage are deliberated and the upcoming need for a study to promote full-scale implementations of those approaches are proposed.

highlights � Zero valent scrap iron (ZVSI) was used to stimulate the anaerobic digestion of sludge. � The highest methane yield was 174.9 ± 1.5 mL/g VSSfed with ZVSI 1.0 g/g VSS, increasing by 38.3%. � ZVSI enhanced the methanogenesis via acting as electron donors and creating favorable environment. � Responsible mechanisms for enhancing methane formation in the presence of ZVSI were proposed. graphical a bstract abstract The use potential of zero valent scrap iron (ZVSI) for promoting anaerobic production of waste activated sludge (WAS) was assessed. The results indicated that the presence of ZVSI effectively enhanced WAS methane production. Methane yield reached the maximum of 174.9 ± 1.5 mL/g VSSfed with addition of 1.0 g-ZVSI/g VSS, increasing by 38.3%. The corresponding values for sludge hydrolysis (%H), acidogenesis (%A), and methanogenesis rate (%M) increased into 52.6 ± 0.4%, 44.5 ± 2.9% and 40.8 ± 0.3%, respectively, versus 45.2 ± 0.5%, 40.9 ± 2.0% and 29.5 ± 0.2% in the test without ZVSI. Further investigations confirmed that ZVSI could offer electrons (H2/(H)), promote H2 consumption and afford beneficial pH environment for WAS digestion, which stimulated the metabolisms of critical microbes involved in the process and, subsequently accelerated the hydrolysis-acidification-methanation steps of WAS. As a result of this, methane production was upgraded. The superior ability of ZVSI to serve as a source of electron donors will open a new door for WAS treatment. Moreover, ZVSI is less expensive, and convenient to use, providing a cost-efficient alternative for simultaneous energy recovery along with waste iron scrap conservation.

The activated sludge process of wastewater leads to the production of a substantial amount of excess activated sludge. The increasing interest of Fe(II)-mediated persulfate ( S 2 O 8 2 - ) oxidation in improving sludge dewatering highlights a need to understand their environmental impacts on subsequent treatment, but the potential effects on sludge anaerobic digestion remains unknown. In this study, the response of waste activated sludge anaerobic digestion to a shock load of Fe ( II ) / S 2 O 8 2 - oxidation were investigated. It was observed that total suspended solids (TSS) and volatile suspended solids (VSS) removals were considerably lowered when Fe(II) and S 2 O 8 2 - dosages were greater than 0.8 and 1.0 mmol/g VSS, respectively, while 34.6–60.5% drop in hydrogen sulfide (H 2 S) took place. Degradation of extracellular polymeric substances (EPS) of sludge induced by Fe ( II ) / S 2 O 8 2 - oxidation resulted in their deteriorating protective role on the microorganisms, which may cause the inhibitory effects on the microbial activity, and subsequently reduce digestion efficiency and H 2 S generation. Then, sludge dewaterability during digestion process was investigated. It was found that dewaterability of sludge, firstly improved by Fe ( II ) S 2 O 8 2 - pretreatment, was gradually worsened during subsequent digestion because of slightly increased EPS. The visualization of EPS with three-dimensional excitation–emission matrix (3D-EEM) fluorescence spectroscopy further revealed that the discernable rise in tyrosine and tryptophan protein-like substances together contributed to poorer dewaterability.