Oxygen is removed from a gas feed such as a landfill gas, a digester gas or an industrial CO.sub.2 off-gas by removing sulfur-containing compounds and siloxanes from the feed gas, heating the feed gas, injecting one or more reactants for oxygen conversion into the heated feed gas, carrying out a selective catalytic oxygen conversion in at least onesuitable reactor and cleaning the resulting oxygen-depleted gas. The reactants to be injected comprise one or more of H.sub.2, CO, ammonia, urea, methanol, ethanol and dimethylether (DME).

A method for the purification of a raw gas stream by selective catalytic oxidation, in which organic and inorganic sulfur compounds, halogenated and non-halogenated volatile organic compounds are selectively oxidized without substantially oxidizing the lower hydrocarbons and the sulfur containing compounds present in the gas to sulfur trioxide and excess of oxygen is removed by oxidation of lower alcohols, ethers or hydrogen added to the raw gas stream upstream the catalytic oxidation.

A fiber reactor system includes a fiber slurry tank configured for receiving fiber feed containing cellulose and hemicellulose for forming a fiber slurry, which is mixed with evaporator condensate. The fiber slurry is mixed with steam vapors for sterilizing. A fiber reactor system is configured for receiving ruled fiber and mixing with microorganisms. The scrubber water is fed the top of a scrubber to capture ethanol and an ethanol-laden fiber stream is sent to a low-ethanol beer stripping system.

Multiple risers are provided to perform different steps in a biogas water wash process. The risers may include absorption risers, flashing risers, and stripping risers. In each riser, the inlets to provide fluids to the riser and outlets to remove fluids from the risers are provided at one end of the riser. Each riser may then be located substantially below grade such that the end with the inlets and outlets is accessible at or just above the ground level. The risers within each step of the water wash process may be connected in series, parallel, or a combination thereof. The risers may also be constructed of a polyethylene material to reduce cost and weight of the water wash system.

The application relates to an anaerobic digestion system for production of biogas with a reduced hydrogen sulphide content. The system comprises an airtight reactor vessel comprising: sludge comprising a surface layer and a volume underneath the surface layer comprising bio-matter and micro-organisms that are able to anaerobically digest the bio-matter, thereby producing biogas comprising hydrogen sulphide, a headspace above the surface layer of the sludge into which biogas migrates out of the sludge, a spraying system for spraying an aqueous nitrate containing solution in the headspace using a carrier gas stream to form a nitrate containing interphase layer between the surface layer of the sludge and the headspace, with the proviso that the reactor vessel does not comprise a membrane or fabric positioned in the headspace.

Anaerobic digestion apparatus comprises a first chamber for retaining organic matter before and/or during anaerobic digestion and a second chamber for retaining organic matter during anaerobic digestion. The anaerobic digestion apparatus is configured to refrigerate or heat the first chamber to suppress methanogenesis in the first chamber. The anaerobic digestion apparatus comprises a controller programmed to regulate the anaerobic digestion process and to thereby reduce system perturbations. The flow of organic matter to the second chamber where methanogenesis is regulated. There is disclosed an inoculum for anaerobic digestion comprising Acetobacterium woodii and Methanosaeta concilii.

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.

Methods and systems for capture of CO.sub.2 from a hydrated gaseous stream are described. Systems can be utilized for direct air capture of CO.sub.2 and incorporate a low energy temperature-vacuum swing adsorption (TVSA) process. A TVSA process can include a multi-step CO.sub.2 capture bed regeneration process that includes depressurization of the bed, heating of the bed, venting and purging of the bed, and cooling of the bed. Multiple beds can be cycled between CO.sub.2 capture and regeneration, during which captured CO.sub.2 is recovered. Off-gas from a CO.sub.2 capture bed can be used in regenerating a parallel bed for increased efficiency.

Multiple risers are provided to perform different steps in a biogas water wash process. The risers may include absorption risers, flashing risers, and stripping risers. In each riser, the inlets to provide fluids to the riser and outlets to remove fluids from the risers are provided at one end of the riser. Each riser may then be located substantially below grade such that the end with the inlets and outlets is accessible at or just above the ground level. The risers within each step of the water wash process may be connected in series, parallel, or a combination thereof. The risers may also be constructed of a polyethylene material to reduce cost and weight of the water wash system.

The disclosure provides for the integration of a gas fermentation process with a gasification process whereby tail gas from the gas fermentation process is recycled to a dryer of the gasification process. The tail gas from the gas fermentation process is utilized to generate heat which in turn is used to dry feedstock to the gasification process. The heat is typically used to heat a drying gas, such as air, which is then directly or indirectly contacted with the gasification feedstock to dry the gasification feedstock. Dried gasification feedstock provides improved yield and improved quality of syngas as compared to gasification feedstock that is not dried.