Processes, systems, and associated control methodologies are disclosed that control the flow of biogas during the biogas cleanup process to create a more consistent flow of biogas through the digester, while also optimizing the output and efficiency of the overall renewable natural gas facility. In representative embodiments, a biogas buffer storage system may be used during the cleanup process to control the pressure and flow rate of biogas. The biogas buffer storage system may monitor and control the biogas flow rate to either bring down or increase the digester pressure, thereby maintaining a normalized biogas flow rate.

The present invention relates to a biomimetic-hybrid solvent system for simultaneous capture of H.sub.2S and CO.sub.2 from any gaseous composition. The present invention also relates to a process for upgradation of biogas to bio CNG by removing gaseous contaminants, including microbial removal of H.sub.2S, to obtained purified CO.sub.2. The biomimetic-hybrid solvent system contains three components selected from tertiary amine compounds, a functional colloidal fluid, and an enzyme mimic.

Processes, systems, and associated control methodologies are disclosed that control the flow of biogas during the biogas cleanup process to create a more consistent flow of biogas through the digester, while also optimizing the output and efficiency of the overall renewable natural gas facility. In representative embodiments, a biogas buffer storage system may be used during the cleanup process to control the pressure and flow rate of biogas. The biogas buffer storage system may monitor and control the biogas flow rate to either bring down or increase the digester pressure, thereby maintaining a normalized biogas flow rate.

This nitrogen recovery method is for causing nitrifying bacteria to decompose an ammonia component in an ammonia-containing gas, and recovering a nitrogen component contained in ammonia as an ammonia gas decomposition product, involving: supplying circulating water to a microorganism decomposition tank retaining a nitrifying bacterium carrier carrying nitrifying bacteria to maintain the carrier wet; passing ammonia-containing gas through the carrier in the wet state in an oxygen-containing atmosphere; dissolving an ammonia component in the ammonia-containing gas in the circulating water, together with an ammonia gas decomposition product produced by the nitrifying bacteria, to continue decomposing the ammonia-containing gas while the decomposition product is accumulated in the circulating water; and collecting all or a portion of the circulating water to recover the ammonia gas decomposition product, when the concentration of nitrate ion as an ammonia decomposition product in the circulating water reaches a predetermined concentration of 5000 mg/L or more.

An integrated process and system for the production of at least one gas fermentation product from a gaseous stream has been developed. The disclosure provides improved carbon utilization through both the recycle of a bioreactor tail gas via various different flow schemes and the employment of a CO.sub.2 to CO conversion system such as a reverse water gas shift unit. Recycling of the bioreactor tail gas and employment of a CO.sub.2 to CO conversion process provides for favourable H.sub.2:CO molar ratios of the feed to the gas fermentation bioreactor(s) for enhanced production of fermentation products. Bypass embodiments provide for optimal sizing of the reverse water gas shift unit to minimize cost.

The disclosure is directed to a process and an apparatus for providing a feedstock. A gaseous feed stream comprising at least one hydrocarbon is passed to a reforming unit followed by a water gas shift reaction zone to provide a first gaseous stream comprising H.sub.2, CO, and CO.sub.2. The first gaseous stream is fed a hydrogen separation zone to separate it into a hydrogen enriched stream and a second gaseous stream comprising CO, CO.sub.2 and H.sub.2. The second gaseous stream is fed to a CO.sub.2 to CO conversion system to produce a third gaseous stream comprising H.sub.2 and CO having a H.sub.2:CO molar ratio of less than 5:1. The third gaseous stream is fed as the feedstock for a gas fermentation unit to have increased stability and product selectivity.

A biogas upgrading system can include a multiple stage membrane system that is configured to remove oxygen so that the biogas is upgraded to have a higher concentration of methane, a pre-selected oxygen (O.sub.2) concentration (e.g. less than or equal to 0.2 mol %, etc.), and a pre-selected carbon dioxide (CO.sub.2) concentration (e.g. less than or equal to 5 mol %, etc.). The membrane system can be configured to reject O.sub.2 by utilizing a low CO.sub.2/O.sub.2 selectivity that is within a pre-determined range (e.g. less than 5 or less than 4.5). In some embodiments, the upgraded biogas that is output from the system can be entirely made up of methane, carbon dioxide, and oxygen. In other embodiments, the biogas can be almost entirely composed of these components along with a small amount of nitrogen and a trace amount (e.g. less than or equal to 0.2%-0.1%, etc.) of other components.

An anaerobic digestion device based on self-sustained air flotation includes an anaerobic digestion tank unit, a self-sustained air flotation screening unit and a biogas measurement and collection unit. The self-sustained air flotation screening unit includes an air flotation screening part, a material sedimentation part, a reflux part and a three-phase separation part connected sequentially from bottom to top. A digested material in the anaerobic digestion tank unit is pumped into the air flotation screening part, overflows into the material sedimentation part, and then is raised to the reflux part. Gas passing through the three-phase separation part and gas produced in the anaerobic digestion tank unit enter the biogas measurement and collection unit to be measured and collected.

The invention essentially concerns a method for storing a biogas in a tank, said method comprising the following steps:

direct contacting of the biogas with a hydrocarbon of the C.sub.3 to C.sub.7 family under conditions allowing at least partial liquefaction of the biogas to obtain a biogas-hydrocarbon mixture that is at least partly liquid, and

storing (S260) the biogas-hydrocarbon mixture in the tank.

Several embodiments of the invention relate generally to a system and methods for the treatment of gaseous emissions comprising methane and one or more non-methane compounds that can influence the metabolism of methane-oxidizing microorganisms. In several embodiments, there is provided a system and methods for the treatment of methane emissions through the use of methanotrophic microorganisms to generate functionally consistent and harvestable products. Certain embodiments of the invention are particularly advantageous because they reduce environmentally-destructive methane emissions and produce harvestable end-products.