(WO9858070-A1)      Process for recovering biogas comprises biologically treating a fermentation medium in a reactor (2). The fermentation medium is fed through a zone (5) supplied with a medium containing an electron acceptor especially a oxygen-containing gas (mixture) e.g. air and/or nitrate and/or nitrite. The contact time between the acceptor-containing medium and the fermentation medium is such that H2S formation is suppressed in the fermentation medium and no H2S is present in the biogas.    An apparatus for carrying out the process is also claimed.    USE -   Process is used for recovering biogas from eg. sewage sludge and liquid manure.    ADVANTAGE -   The biogas is free from H2S.    (EP988392-A1)      Process for recovering biogas comprises biologically treating a fermentation medium in a reactor (2). The fermentation medium is fed through a zone (5) supplied with a medium containing an electron acceptor especially a oxygen-containing gas (mixture) e.g. air and/or nitrate and/or nitrite. The contact time between the acceptor-containing medium and the fermentation medium is such that H2S formation is suppressed in the fermentation medium and no H2S is present in the biogas.    An apparatus for carrying out the process is also claimed.    USE -   Process is used for recovering biogas from eg. sewage sludge and liquid manure.    ADVANTAGE -   The biogas is free from H2S.    (JP2000157255-A)      Process for recovering biogas comprises biologically treating a fermentation medium in a reactor (2). The fermentation medium is fed through a zone (5) supplied with a medium containing an electron acceptor especially a oxygen-containing gas (mixture) e.g. air and/or nitrate and/or nitrite. The contact time between the acceptor-containing medium and the fermentation medium is such that H2S formation is suppressed in the fermentation medium and no H2S is present in the biogas.    An apparatus for carrying out the process is also claimed.    USE -   Process is used for recovering biogas from eg. sewage sludge and liquid manure.    ADVANTAGE -   The biogas is free from H2S.    (CN1260838-A)      Process for recovering biogas comprises biologically treating a fermentation medium in a reactor (2). The fermentation medium is fed through a zone (5) supplied with a medium containing an electron acceptor especially a oxygen-containing gas (mixture) e.g. air and/or nitrate and/or nitrite. The contact time between the acceptor-containing medium and the fermentation medium is such that H2S formation is suppressed in the fermentation medium and no H2S is present in the biogas.    An apparatus for carrying out the process is also claimed.    USE -   Process is used for recovering biogas from eg. sewage sludge and liquid manure.    ADVANTAGE -   The biogas is free from H2S.    (KR2001013857-A)      Process for recovering biogas comprises biologically treating a fermentation medium in a reactor (2). The fermentation medium is fed through a zone (5) supplied with a medium containing an electron acceptor especially a oxygen-containing gas (mixture) e.g. air and/or nitrate and/or nitrite. The contact time between the acceptor-containing medium and the fermentation medium is such that H2S formation is suppressed in the fermentation medium and no H2S is present in the biogas.    An apparatus for carrying out the process is also claimed.    USE -   Process is used for recovering biogas from eg. sewage sludge and liquid manure.    ADVANTAGE -   The biogas is free from H2S.