The presented paper deals with the testing of a possibility to reduce emissions of undesirable greenhouse gases (CH4, CO2; NOx) and their mixture (biogas) during the storage of digestate using applications of secondary plant metabolites (tannins). The experiment was conducted in laboratory conditions in which the digestate was placed in fermentation chambers. Prior to the fermentation process, preparations were applied to the digestate, which contained tannins: Tanenol Antibotrytis (TA), Tanenol Clar (TC) and Tanenol Rouge (TR) in three concentrations (0.5, 1.0 and 2.0% w/w). The application of these preparations demonstrably affected the production of biogas and the contents of CH4, CO2 and N therein. The application of TR preparation in the concentration of 1.0% and 2.0% significantly reduced the production of biogas as compared with all variants. The preparation further inhibited the process of CH4 development. In contrast, the other preparations with the content of different kinds of TA and TC increased the production of biogas (on average by 15%), CH4 (on average by 7%) and CO2 (on average by 12%) as compared with the control variant and TR variant. These two variants reduced the concentration of N in biogas on average by 38%. Thus, the tested Tanenol tannin preparations can be used in different concentrations either to control emissions of greenhouse gases during the storage of digestate or, in case of increased production of CO2 for its reuse in order to increase methane yields in the process of anaerobic fermentation.
The respiratory activity of microorganisms in sewage sludge is affected by several physicochemical factors, and a considerable amount of information concerning the influence of individual factors has been recorded. However, very little is known about their effects in combination. In the recent past, the concentration of chlorides entering wastewater has increased greatly and the major source is sodium chloride, which is used in large quantities to de‐ice roads in winter. In this article, the effects of various concentrations of sodium chloride at different temperatures on the respiratory activity of the microorganisms have been examined. It is found that low temperature (6°C) and high concentrations of NaCl (1 M) had drastic effects on the metabolism of the microorganisms in activated sludge; the acclimation phase of activated sludge is 117 h. Not only is their respiratory activity strongly depressed but also the length of their acclimation period is greatly magnified.
Employing deep reservoirs as UGS (underground gas storage) has a long history across continents. In 2018, 689 underground gas reservoirs with a total volume of 417 bcm were in operation worldwide. It is known that many microbial processes take place in the deep underground, even under the conditions of underground gas reservoirs. In this review, we focus mainly on methanogenesis and discuss related topics such as optimal environmental conditions, description of different types of UGS and microbial communities inhabiting these environments. We elucidate the potential of UGS as natural bioreactors for non-fossil methane production in the context of Power to Methane technology and the extension/expansion of the low-carbon economy. The role of carbon-neutral methane in the energy mix is likely to play a significant role in the coming decades. The safe production, transportation and storage of methane are well managed as well the existing infrastructure has been in place for a long time without problems. We also have experience in the long-term operation of underground gas storage systems. Methane technology thus appears to be a very promising approach and, together with the functioning UGS infrastructure, could be an important step towards the potential use of biomethanation in underground gas storage facilities as a way to reduce greenhouse gas emissions in the future.
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