A method for extracting ethane from a stream of initial natural gas, comprising the following steps: - cooling the stream of initial natural gas in at least one first upstream heat exchanger, to form a stream of cooled natural gas; - separating the stream of cooled natural gas into a liquid flow and a gas flow; - expanding the liquid flow and introducing at least one stream originating from the liquid flow into a methane and C2+ hydrocarbon separation column at a first level; - forming a turbine feed stream from the gas flow; - expanding the turbine feed stream in a dynamic expansion turbine and introducing the expanded stream originating from the dynamic expansion turbine into the separation column at a second level, - recovering and compressing at least a part of a head stream originating from the separation column to form a stream of compressed purified natural gas; - liquefying the stream of compressed purified natural gas in a liquefier to form a stream of pressurized liquefied natural gas; - flash expanding the stream of pressurized liquefied natural gas and recovering the expanded liquefied natural gas in storage; - recovering at least one flow of flash gas (126; 162) originating from the expansion of the stream of pressurized liquefied natural gas; - compressing the or each flow of flash gas (126; 162), characterized by the following steps: - introduction of a bottom stream rich in C2+ hydrocarbons recovered from the separation column into a fractionation column, and recovering a flow of ethane from the fractionation column; - separating the flow of compressed flash gas (132; 164) into a fuel stream and a recycle stream; - at least partially cooling and expanding the recycle stream, then introducing the cooled and expanded recycle stream at a head stage of the separation column. - cooling the stream of initial natural gas in at least one first upstream heat exchanger, to form a stream of cooled natural gas; - separating the stream of cooled natural gas into a liquid flow and a gas flow; - expanding the liquid flow and introducing at least one stream originating from the liquid flow into a methane and C2+ hydrocarbon separation column at a first level; - forming a turbine feed stream from the gas flow; - expanding the turbine feed stream in a dynamic expansion turbine and introducing the expanded stream originating from the dynamic expansion turbine into the separation column at a second level, - recovering and compressing at least a part of a head stream originating from the separation column to form a stream of compressed purified natural gas; - liquefying the stream of compressed purified natural gas in a liquefier to form a stream of pressurized liquefied natural gas; - flash expanding the stream of pressurized liquefied natural gas and recovering the expanded liquefied natural gas in storage; - recovering at least one flow of flash gas (126; 162) originating from the expansion of the stream of pressurized liquefied natural gas; - compressing the or each flow of flash gas (126; 162), characterized by the following steps: - introduction of a bottom stream rich in C2+ hydrocarbons recovered from the separation column into a fractionation column, and recovering a flow of ethane from the fractionation column; - separating the flow of compressed flash gas (132; 164) into a fuel stream and a recycle stream; - at least partially cooling and expanding the recycle stream, then introducing the cooled and expanded recycle stream at a head stage of the separation column.