Biogas blending into the gas grid of a small municipality for the decarbonization of the heating sector

Thepracticeofblendingbiogasintothegasnetwork,especiallyatthedistributionlevel,offerstheopportunityto usebiogasasasubstituteoffossilgas.The‘greening’ofthegasnetworkthroughbiogasblendingwouldindeed takeadvantageoftherobustnessandextensivenessofanalreadyexistingenergyinfrastructure.Asteadystate and multi-component thermal-fluid-dynamic model of the gas network is applied to a portion of the Italian distributionnetwork.Thereceivingpotentialcapacityoftheexistinginfrastructureisassessedwithrespectto biogasinjection.Fluid-dynamicaspectsofthispracticeareconsideredandcommented.Themaximumallowable percentage ofinjectable biogas(purifiedfrom sulphurcompounds,O2 andsiloxanesbut notupgradedto biomethanebyremovingCO2)iscalculatedonanodalbasis,referringtotheactualgasnetworkconfiguration,and in agreement with the quality constraints set by the current regulation (UNI/TR 11537:2016). A major hypothesishasbeenassumedinthiswork:gasqualityrequirementsareenforcedonthenetworkasawhole(i.e., after blending the injected gas into grid) rather than at the injection point, which is instead the current prescriptionofmostoftheEUcountries.Byexploitingthequality-trackingfeatureofthemodel,theconstrainton the quality assessment at the injection point is thus relaxed and its effect on the grid gas quality has been quantified.Resultsfromthecasestudyshowshowbiogasblendingintothegasgridmayleadtoareductionon thefossilnaturalgasdependenceofupto4.7%.