Apparatus for a plant for the management of gases produced in a decentralized way, in particular renewable gases, said plant comprising a first higher pressure network and a second lower pressure network, said apparatus: - is configured to be connected upstream with said second lower pressure network and downstream with said first higher pressure network, - is configured to re-inject the gas from and/or circulating in said second lower pressure network to said first higher pressure network, - comprises a compression unit connected to a control unit, the latter being configured so that, on the basis of the measurements of the gas pressure and/or flow rate made upstream of said compression unit, correspondingly controls the activation/deactivation of said compression unit and/or the modulation of its flow rate, and characterized in that it comprises: - a measuring module configured to measure the amount of gas which, through the apparatus, passes from the second network at a lower pressure to the first at a higher pressure network, said measuring module being connected with said control unit to send to the latter data representative of the measurements carried out by said measuring module, a purification module for removing from the gas from the second lower pressure network the substances and/or compounds not accepted by the first higher pressure network, said purification module is provided at the inlet of said apparatus and is positioned upstream of the remaining modules within said apparatus, so as to remove from the gas entering into said apparatus the substances and compounds that could damage the appliances and/or instruments provided in said re-injection apparatus. - is configured to be connected upstream with said second lower pressure network and downstream with said first higher pressure network, - is configured to re-inject the gas from and/or circulating in said second lower pressure network to said first higher pressure network, - comprises a compression unit connected to a control unit, the latter being configured so that, on the basis of the measurements of the gas pressure and/or flow rate made upstream of said compression unit, correspondingly controls the activation/deactivation of said compression unit and/or the modulation of its flow rate, and characterized in that it comprises: - a measuring module configured to measure the amount of gas which, through the apparatus, passes from the second network at a lower pressure to the first at a higher pressure network, said measuring module being connected with said control unit to send to the latter data representative of the measurements carried out by said measuring module, - a measuring module configured to measure the amount of gas which, through the apparatus, passes from the second network at a lower pressure to the first at a higher pressure network, said measuring module being connected with said control unit to send to the latter data representative of the measurements carried out by said measuring module, a purification module for removing from the gas from the second lower pressure network the substances and/or compounds not accepted by the first higher pressure network, said purification module is provided at the inlet of said apparatus and is positioned upstream of the remaining modules within said apparatus, so as to remove from the gas entering into said apparatus the substances and compounds that could damage the appliances and/or instruments provided in said re-injection apparatus.