greenhouse gas emission

Rising greenhouse gas emissions have contributed to unprecedented levels of climate change, while microbial conversion and utilization of CO2 is a practical way to reduce emissions and promote green manufacturing. This article mainly summarizes several natural CO2 pathways that have been discovered, including the Calvin cycle, the reduced tricarboxylic acid (rTCA) cycle, the Wood–Ljungdahl (WL) pathway, the 3-hydroxypropionate/4-hydroxybutyrate (HP/HB) cycle, the dicarboxylate/4-hydroxybutyrate (DC/HB) cycle, the 3-hydroxypropionate (3HP) cycle, the reductive glycine (rGly) pathway, and artificially designed carbon fixation pathways includes the CETCH cycle, the MOG pathway, the acetyl-CoA bicycle, and the POAP cycle. We also discussed applications of different carbon fixation enzymes, notably ribulose-1, 5-diphosphate carboxylase/oxygenase, pyruvate carboxylase, carbonic anhydrase, as well as formate dehydrogenase. This paper further addressed the development of photosynthetic autotrophs, chemergic autotrophs and model bacteria Escherichia coli or yeast produced main products for CO2 fixation through metabolic engineering, such as alcohols, organic acids, fatty acids and lipids, bioplastics, terpenoids, hydrocarbons, and biomass.  Future studies on CO2 microbial conversion should focus on improving the efficiency of carbon fixation enzymes, metabolic modules of the carbon sequestration pathway, and intracellular energy utilization. Coupled microbial and electrochemical methods for CO2 fixation, in addition to biological fixation, show considerable promise. 

Carbon footprint refers to the total amount of greenhouse gas emitted in the atmosphere by an individual or by an organization causing global warming. There are various causes of greenhouse gas emissions and anaesthetic gases are one amongst them. Greenhouse gases warm the earth by absorbing infrared energy and slowing the rate at which the energy escapes into space. Each greenhouse gas has two important properties. One is the amount of infrared energy that a gas can absorb and the other is the lifetime of that gas in the atmosphere. Anaesthesia as a speciality contributes to carbon footprinting in three ways: direct emission, energy use, and operating room wastes and supplies. Direct emission of Waste Anaesthetic Gases (WAG) from anaesthesia workstations can either be scavenged and thrown out into the environment causing a green greenhouse gas effect or can pollute the operating room due to poor scavenging. Various techniques such as reducing direct emissions, energy use optimisation, and waste management have been tried in minimising carbon footprint in anaesthesia practice but providing safety to the patient is considered of utmost importance.