In order to investigate the impacts of partial aeration in anaerobic bio-gasification, a laboratory scale bioreactor (5.5 L working volume) was operated for more than 120 days duration at 35 o C under the organic loading rate of 0.33 kg COD/m 3 .d and hydraulic retention time of 33 days. Different oxygenation conditions, 0, 2.5, 5.0 and 10.1 % (as % of feed COD) induced by daily air injection after daily feeding, were tested during the course of the experiment. Oxygenation, under these operating conditions, reduced the methane generation with only a trifling effect on biogas generation. The accumulation of volatile fatty acids is extensively reduced by oxygen introduction, significantly improving the digester stability. Reduction of soluble COD and VFAs at increasing aeration level, decrease of CH 4 /CO 2 ratio with increased aeration, and immediate increase of CH 4 content upon reducing the aeration level at the end of the experimental duration, points out that the observed digester behaviour can be explained considering the substrate consumption by aerobic respiration activity of facultative biomass present in the reactor. Partially aerated anaerobic digestion can be a useful and a stable process for enhanced waste treatment and resource recovery.

An experimental study was carried out to understand the possible impacts of limited aeration in an anaerobic bio-gasification process. A number of anaerobic bioreactors were operated at 35 o C, both under semi-continuous and batch feed modes, with different oxygenation loads. Two series of batch experiments clearly indicated an increasing methane yield in the range of oxygenation loads of 0-16 % (% O 2 of COD input). In the semi continuous feed mode, four completely mixed bioreactors operated under oxygenation levels of 0, 1.3, 2.6 and 3.9 % produced biogas at approximately equal level and constant rates. The methane generation rate at the low oxygenation level of 1.3 % was higher than the strict anaerobic condition, while higher oxygenation levels induced increasingly negative impact on methane production. Accumulation of volatile fatty acids at the start up of the continuous feed reactors was lower for the aerated than the strict anaerobic reactor. The positive effect of oxygen on methane production has a much larger range in the batch feed mode compared to the semi-continuous feed mode. This suggests that methane production can be optimized by some limited aeration in the first of two or more stages of anaerobic digestion.

Biogas upgrading to biomethane with microbial electrosynthesis (MES) is receiving much attention due to increasing biomethane demands and surplus renewable energy. Research has demonstrated the feasibility of MES to increase methane yield by reducing CO2 in anaerobic digestion (AD). Such CO2 reduction occurs at the cathode and requires the supply of both protons and electrons. The most studied sources of protons and electrons are oxidation of organic substances and water, generated at the anode. These anodic reactions, however, also imply the production of CO2 and O2, respectively, both with negative implications for the AD process. A source of protons and electrons without CO2 and O2 as by-products would be beneficial for MES-enhanced biomethane production. This opinion article discusses the possibility of ammonium to serve as a sustainable proton and electron source.

A growing awareness of global climate change has led to an increased interest in investigating renewable energy sources, such as the anaerobic digestion of biomass. This process utilizes a wide range of microbial communities to degrade biodegradable material in feedstock through a complex series of biochemical interactions. Anaerobic digestion exhibits nonlinear dynamics due to the complex and interacting biochemical processes involved. Due to its dynamic and nonlinear behavior, uncertain feedstock quality, and sensitivity to the process’s environmental conditions, anaerobic digestion is highly susceptible to instabilities. Therefore, in order to model and operate a biogas production unit effectively, it is necessary to understand which parameters are most influential on the model outputs. This also reduces the amount of estimation required. Through a scoping review, the present study analyzes the studies on the application of sensitivity analysis in anaerobic digestion modeling. Both local and global sensitivity analysis approaches were carried out using different mathematical models. The results indicate that anaerobic digestion model no.1 (ADM1) was the most commonly used model for analyzing sensitivity. Both local and global sensitivity analyses are widely employed to investigate the influence of key model parameters such as kinetic, stoichiometric, and mass transfer parameters on model outputs such as biogas production, methane concentration, pH, or economic viability of the plant.

High-rise glazing systems are among the most important components affecting energy efficiency. Through the lens of Life Cycle Assessment, glass has always been an unlikely material for large buildings due to its considerable energy consumption throughout the pre-use and post-use phases. Moreover, the use of high-tech materials has a negative impact on the environment. Therefore, the present study aims to assess a comparative life cycle of four different glazing system technologies (BIPV, smart glass, low-E, and double glazing) representing the most used commercial high potential glazing systems. The next step has been optimized for the Leadenhall iconic tower as the case study. In this analysis, energy simulation is combined with life cycle assessment to investigate the environmental impacts. ZEB-COM tool, Rhino®, and Grasshopper® have been used to calculate emissions, 3D modeling, and energy modeling, respectively. The results reveal that BIPV achieved 37% of total energy-saving and stood first. A hybrid solution (two glazing systems) has been proposed to eliminate negative aspects and increase livability. Although it can generate almost 30% less energy than the complete BIPV installation, with a specific design by the authors, it can cover aesthetic concerns in this system and compensates for 27% of the total energy demand of the Leadenhall project.

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