Some variations provide a process for producing mixed alcohols, comprising: purifying a biogas feedstock to generate a renewable natural gas stream comprising methane; introducing the renewable natural gas stream into a methane-to-syngas unit operated at effective conditions to convert the methane to a first syngas stream containing at least H.sub.2, CO, and CO.sub.2; purifying the first syngas stream, including separating the CO.sub.2 from the first syngas stream, and optionally separating some of the H.sub.2 from the first syngas stream, thereby generating a clean syngas stream; introducing the clean syngas stream into a mixed-alcohol reactor operated at effective alcohol synthesis conditions with an alcohol-synthesis catalyst, thereby generating mixed alcohols; and purifying the mixed alcohols to generate a mixed-alcohol product. The mixed-alcohol product may be blended with a hydrocarbon fuel, such as gasoline, to produce a blended fuel. The blended fuel has significantly lower carbon intensity than the base hydrocarbon fuel.

A system for a carbon neutral cycle of gas production may include a molten salt reactor configured to generate zero carbon dioxide (CO.sub.2) emissions electricity. The system may include a desalination unit configured to receive the zero-CO.sub.2 emissions electricity from the molten salt reactor and produce a desalinated water. The system may include an electrolysis unit configured to be powered by the zero-CO2 emissions electricity generated by the molten salt reactor and generate hydrogen (H.sub.2) and oxygen (O.sub.2) from the desalinated water. The system may include an oxy-combustion unit configured to receive and combust a hydrocarbon fuel with the O.sub.2 from the electrolysis unit to produce electricity and CO.sub.2. The system may include a CO.sub.2 capture system adapted to capture the CO.sub.2 produced by the oxy-combustion unit and a catalytic hydrogenation unit configured to receive and convert H.sub.2 from the electrolysis unit and CO.sub.2 from the CO.sub.2 capture system to produce the hydrocarbon fuel.

The disclosure relates to methods of capturing carbon by microbial fermentation of a gaseous substrate comprising CO into one or more first products which, in turn, may be incorporated into an article of manufacture or one or more second products. Further, the disclosure relates to improving carbon capture and/or efficiency.

Systems and methods for sequestering carbon, evolving hydrogen gas, producing iron oxide as magnetite, and producing magnesium carbonate as magnesite through sequential carbonation and serpentinization/hydration reactions involving processed olivine- and/or pyroxene-rich ores, as typically found in mafic and ultramafic igneous rock. Precious or scarce metals, such nickel, cobalt, chromium, rare earth elements, and others, may be concentrated in the remaining ore to facilitate their recovery from any gangue material.

Methods and systems for gas separation of syngas applying differences in water solubilities of syngas components, the method including producing a product gas comprising hydrogen and carbon dioxide from a hydrocarbon fuel source; separating hydrogen from the product gas to create a hydrogen product stream and a byproduct stream by solubilizing components in water that are more soluble in water than hydrogen; injecting the byproduct stream into a reservoir containing mafic rock; and allowing components of the byproduct stream to react in situ with components of the mafic rock to precipitate and store components of the byproduct stream in the reservoir.

A process for the manufacture of a useful product from synthesis gas having a desired hydrogen to carbon monoxide molar ratio comprises gasifying a first carbonaceous feedstock comprising waste materials and/or biomass in a gasification zone to produce a first synthesis gas; optionally partially oxidising the first synthesis gas in a partial oxidation zone to generate oxidised synthesis gas; reforming a second carbonaceous feedstock to produce a second synthesis gas, the second synthesis gas having a different hydrogen to carbon ratio from that of the first raw synthesis gas; combining at least a portion of the first synthesis gas and at least a portion of the second synthesis gas in an amount to achieve the desired hydrogen to carbon molar ratio and to generate a combined synthesis gas and subjecting at least part of the combined synthesis gas to a conversion process effective to produce the useful product.

The invention relates to a method for separating gases which comprises: a first step in which a gas fuel stream comprising combustible substances that produce gas products when oxidised, and an oxygen-rich inlet stream are passed through at least two modules of oxygen-separating ceramic membranes, such that the two streams come into contact through the membranes and exchange heat; a second step of selective diffusion of oxygen from the oxygen-rich stream to the fuel stream, such that the outlet streams from the membrane modules are an oxygen-depleted or completely oxygen-free stream and a partially or completely oxidised stream; and a third step of recovery of at least two separate outlet streams of at least two gases selected from oxygen, nitrogen, carbon dioxide and hydrogen.

Methods and systems for producing hydrogen substantially without greenhouse gas emissions, one method including producing a product gas comprising hydrogen and carbon dioxide from a hydrocarbon fuel source; separating hydrogen from the product gas to create a hydrogen product stream and a byproduct stream; injecting the byproduct stream into a reservoir containing mafic rock; and allowing components of the byproduct stream to react in situ with components of the mafic rock to precipitate and store components of the byproduct stream in the reservoir.

A process and/or system for producing fuel that includes providing biogas, removing carbon dioxide from the biogas, transporting the upgraded biogas to a hydrogen plant; providing the transported upgraded biogas and fossil-based natural gas as feedstock for hydrogen production. The carbon intensity of the fuel is less than 11 gCO.sub.2-eq/MJ, at least in part because carbon dioxide removed from the biogas and carbon dioxide from hydrogen production is captured and stored.

The present disclosure provides a method for reducing the carbon intensity of hydrogen by replacing, at a hydrogen production facility, a fraction of a non-renewable gaseous feedstock with a biomethane feedstock, wherein the non-renewable gaseous feedstock replaced is (a) a feedstock fed to methane reforming and/or (b) a feedstock used to generate heat for the reforming in the hydrogen production, and wherein the fraction of the non-renewable gaseous feedstock replaced by the biomethane feedstock is less than 50% and is at least r defined by Equation A herein. The disclosed process for reducing the carbon intensity of hydrogen is designed to reduce greenhouse gas (GHG) emissions and mitigate climate change. The biomethane feedstock in some examples has a carbon intensity (CI) value within a range that is between 15 g CO.sub.2 eq/MJ and −500 g CO.sub.2 eq/MJ.