Autogenerative high-pressure digestion

Individual species of microorganism have different optimal conditions in which they grow and replicate most rapidly.{{Citation needed|date=August 2024|reason=Claim must be sourced}}There is a specificrange around that optimum in which a specie is able to survive. Libretexts Biology 17.2: Factors that Influence Bacterial Growth https://bio.libretexts.org/Bookshelves/Microbiology/Microbiology_(Kaiser)/Unit_7%3A_Microbial_Genetics_and_Microbial_Metabolism/17%3A_Bacterial_Growth_and_Energy_Production/17.2%3A_Factors_that_Influence_Bacterial_Growth Factors such as the pH, temperature, Libretexts Biology 8.3: The Effects of pH and Temperature on Microbial Growth https://bio.libretexts.org/Courses/Manchester_Community_College_(MCC)/Remix_of_Openstax%3AMicrobiology_by_Parker_Schneegurt_et_al/08%3A_Microbial_Growth/8.03%3A_The_Effects_of_pH_on_Microbial_Growth osmotic pressure (often caused by salinity) all contribute to the optimal condition of all microorganisms. For example, in terms of pressure, some species are able to survive in extremophile conditions such as extreme radiation, temperature, salinity or pressure. Piezophile microorganisms have their optimal growth condition at a pressure equal to or above 10 megapascals (99 atm; 1,500 psi).{{Citation needed|date=August 2024|reason=All claims must be verified}} Kanekar, P.P., Kanekar, S.P. (2022). Piezophilic or Barophilic Microorganisms. In: Diversity and Biotechnology of Extremophilic Microorganisms from India. Microorganisms for Sustainability. Springer, Singapore. https://doi.org/10.1007/978-981-19-1573-4_9 Some bacteria and archaea have adapted to life in the deep oceans, where the pressure (Hydrostatic pressure) is much higher than at sea level. For example, the methane-producing archaea species Methanocaldococcus, Methanothermococcus, Methanopyrus and Methanotorris have been found in hydrothermal vents in the ocean floor.{{Cite journal|author = Zeng, X., Alain, K. & Shao, Z. |year= 2021 |title=Microorganisms from deep-sea hydrothermal vents |journal= Marine Life Science & Technology|volume= 3|issue= 2|pages= 204–230|doi=10.1007/s42995-020-00086-4|pmid= 37073341|pmc= 10077256 |bibcode= 2021MLST....3..204Z |url= https://hal.archives-ouvertes.fr/hal-03124399/file/Zeng2021_Article_MicroorganismsFromDeep-seaHydr.pdf }} Research at the University of Groningen (RUG) has shown that the bacterial community is affected by pressure from composition changes.{{Cite journal |vauthors=Zhao J, Li Y, Zhang Z |date=February 2023 |title= Hydraulic retention time and pressure affect anaerobic digestion process treating synthetic glucose wastewater |journal=Bioresource Technology |volume= 370 |article-number=128531 |doi=10.1016/j.biortech.2022.128531|pmid=36574891 |bibcode=2023BiTec.37028531Z |url=https://pure.rug.nl/ws/files/845017954/Hydraulic_retention_time_and_pressure_affect_anaerobic_digestion_process_treating_synthetic_glucose_wastewater_.pdf }} This makes it possible to influence the anaerobic digestion process.File:The Hydrogen Ladder, Version 5.0.jpgA further development of this technique is the addition of hydrogen gas to the reactor. According to Henry's law, this gas also dissolves more at increased pressure.{{Citation needed|date=August 2024}} Henry's Law Constants → hydrogen (H2) https://henrys-law.org/henry/casrn/1333-74-0 The result is that it can be better absorbed by bacteria and archea. In turn, it converts the hydrogen gas with the already dissolved carbon dioxide into additional methane. This combination of techniques was described in detail by Kim et all in 2021,{{Cite journal|author = Sangmi Kim |year= 2021 |title=Production of high-calorific biogas from food waste by integrating two approaches: Autogenerative high-pressure and hydrogen injection |journal= Water Research |volume= 194|issue= |pages= |doi=10.1016/j.watres.2021.116920|pmid= 33609909|bibcode= 2021WatRe.19416920K }} known to be a process called biological methanation. On Michael Liebreich's hydrogen ladder 5.0, this form of biogas upgrading is at step C. The Hydrogen Ladder https://www.smoltek.com/investors/blog/the-hydrogen-ladder/6778/ This is considerably higher than applications as fuel in vehicles. These are spread over steps D to G.{{cite web |date=23 October 2023 |title=Hydrogen Ladder | Seven H2 applications relegated in updated use-case analysis, but three promoted |url=https://www.hydrogeninsight.com/policy/hydrogen-ladder-seven-h2-applications-relegated-in-updated-use-case-analysis-but-three-promoted/2-1-1540086 |archive-url=https://web.archive.org/web/20231107210758/https://www.hydrogeninsight.com/policy/hydrogen-ladder-seven-h2-applications-relegated-in-updated-use-case-analysis-but-three-promoted/2-1-1540086 |archive-date=2023-11-07}}

Although the technique is usually used as a fermentation process for thick liquid flows and solid biomass, it can also be applied as anaerobic Wastewater treatment. In South Korea, they have succeeded in operating a UASB reactor (a form of anaerobic wastewater treatment) at 8 Bar. {{Cite journal|author = Om Prakash |year= 2023 |title=Upflow anaerobic sludge blanket reactor operation under high pressure for energy-rich biogas production |journal= Bioresource Technology |volume= 376|issue= |pages= |doi=10.1016/j.biortech.2023.128897|pmid= 36931446|bibcode= 2023BiTec.37628897P }} A biogas was then created with a methane content of 96.7%. A remarkable finding was that the grains in the sludge that are so similar in characteristic of the UASB technique were well preserved. This was because more Extracellular polymeric substance (EPS) was formed in the biofilm. Microorganisms make these to protect themselves against difficult conditions, in this case the extreme pressure.

• Biogas
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