A combined plant for cryogenic separation and liquefaction of methane and carbon dioxide in a biogas stream, including a mixing means, a compressor, a first exchanger, a distillation column, a second exchanger, a separating means, an expanding means, and a separator vessel. Wherein, the mixing means is configured such that the recycle gas is the overhead vapour stream, and the first exchanger and the expanding means are combined.

A combined plant for cryogenic separation and liquefaction of methane and carbon dioxide in a biogas stream, including a mixing means, a compressor, a first exchanger, a distillation column, a second exchanger, a separating means, an expanding means, and a separator vessel. Wherein, the mixing means is configured such that the recycle gas is the overhead vapour stream, and the first exchanger and the expanding means are combined.

A combined plant for cryogenic separation and liquefaction of methane and carbon dioxide in a biogas stream, including a mixing means, a compressor, a first exchanger, a distillation column, a second exchanger, a separating means, an expanding means, and a separator vessel. Wherein, the mixing means is configured such that the recycle gas is the overhead vapour stream, and the first exchanger and the expanding means are combined.

A combined plant for cryogenic separation and liquefaction of methane and carbon dioxide in a biogas stream, including a mixing means, a compressor, a first exchanger, a distillation column, a second exchanger, a separating means, an expanding means, and a separator vessel. Wherein, the mixing means is configured such that the recycle gas is the overhead vapour stream, and the first exchanger and the expanding means are combined.

Process for producing biomethane from a biogas stream including methane, carbon dioxide and at least one impurity chosen from ammonia, volatile organic compounds, water, sulfur-based impurities (H.sub.2S) and siloxanes. A biogas stream is dried, the at least one impurity is at least partially removed by solidification and removal of the impurity. The methane and the carbon dioxide contained in the biogas obtained from the second step are separated so as to produce a biomethane stream and a CO.sub.2 stream.

The present invention relates to processes for producing industrial products such as hydrocarbon products from non-polar lipids in a vegetative plant part. Preferred industrial products include alkyl esters which may be blended with petroleum based fuels.

A gas processing system for recovering methane gas from a landfill includes a high pressure main absorber plus a relatively low pressure one. The low pressure absorber receives a gas stream from an equally low pressure flash tank. This low pressure gas stream consists mostly of carbon dioxide and methane. The methane would normally be lost due to the high cost of recompressing the carbon dioxide, but by running this mixture of carbon dioxide and methane through the low pressure absorber with a slip stream of cold absorbent, a large portion of the carbon dioxide can be removed with negligible methane losses. The remaining methane can be recycled through the high pressure main absorber without having to recompress the removed portion of carbon dioxide.

A biogas-utilizing methanation system includes: a solid oxide fuel cell using a to-be-treated gas as a fuel gas; a hydrogen production device capable of producing hydrogen by using power of a renewable energy power generation device; and a methanation device capable of methanating carbon dioxide in the system with the hydrogen produced by the hydrogen production device. The carbon dioxide in the system can be stored in a storage device on the basis of the supply amount of the to-be-treated gas or the power of the renewable energy power generation device.

A method for conversion of food waste to biofuel can include a first fermentation in which food waste is converted C.sub.2-C.sub.4 short-chain carboxylic acids, and a second fermentation in which the C.sub.2-C.sub.4 short-chain carboxylic acid are elongated into C.sub.5-C.sub.8 medium-chain carboxylic acids. Medium-chain carboxylic acids can undergo hydrogenation-dehydration of the medium-chain carboxylic acids into C.sub.5-C.sub.8 linear olefins. The C.sub.5-C.sub.8 linear olefins are then oligomerized to a C.sub.10-C.sub.25 mixture comprising olefins, paraffin, cycloparaffins, and aromatics through dimerization; and saturated to C.sub.10-C.sub.25 mixture by hydrogenation to produce the biofuel.

A fuel production plant includes an electrolysis apparatus; an ethanol generation apparatus that decomposes sugars to generate ethanol and carbon dioxide; and a hydrocarbon generation apparatus that generates hydrocarbons by reacting carbon dioxide with hydrogen. The fuel production plant further includes a hydrogen supply part that supplies hydrogen generated in the electrolysis apparatus to the hydrocarbon generation apparatus by coupling the electrolysis apparatus to the hydrocarbon generation apparatus, an oxygen supply part that supplies oxygen generated in the electrolysis apparatus to the ethanol generation apparatus by coupling the electrolysis apparatus to the ethanol generation apparatus, and a carbon dioxide supply part that supplies carbon dioxide generated in the ethanol generation apparatus to the hydrocarbon generation apparatus by coupling the ethanol generation apparatus to the hydrocarbon generation apparatus.