Char　reactivity　usually　determines　the　overall　efficiency　of　the　entire　gasification　process,　while　the　presence　of　the　alkali　and　alkaline　earth　metals　(AAEMs)　has　a　catalytic　effect　on　char　gasification.　In　this　study,　the　influence　of　inherent　AAEMs　in　the　gasification　behaviour　of　char　was　investigated.　The　char　sample　was　prepared　through　the　pyrolysis　of　solid　digestate　derived　from　anaerobic　co-digestion　of　silage　and　dairy　cattle　slurry.　The　raw　char　and　HCl-washed　char　were　characterized　by　elemental　analyzer,　ICP-OES,　SEM　and　XRD　to　explore　their　structural　changes.　HCl-char　loses　weight　in　the　temperature　range　of　440–620　°C,　and　the　weight　loss　percentage　is　significantly　higher　than　that　of　char.　Ash　content　of　char　is　reduced　by　half　after　a　pickling　process.　AAEMs　are　largely　removed　after　char　acid　pickling,　resulting　in　an　increase　in　activation　energy　of　the　gasification　reaction　and　a　decrease　in　gasification　reactivity,　resulting　in　the　gasification　reaction　time　of　HCl-char　longer　than　char.　Water-soluble　AAEM　and　ion-exchange　AAEM　affect　the　evolution　of　carbon　structure,　which　directly　lead　to　char　reactivity　during　the　gasification　reaction.　As　the　carbon　is　consumed,　the　carbon　microcrystalline　structure　of　the　residual　carbon　tends　to　be　ordered,　resulting　in　fewer　active　free　carbon　sites　for　the　gasification　reaction.　Kinetic　analysis　showed　that　the　loss　and　deactivation　of　AAEMs　after　char　acid　washing　increased　the　average　activation　energy　Ea　by　115.76　KJ/mol　compared　with　the　original　char.　©　2022　Elsevier　Ltd