Effect of fresh bed materials on alkali release and thermogravimetric behavior during straw gasification

•Online alkali measurement during gasification of straw and fresh bed material blends.•The main elements in bed material migrate to the char surface and affect gasification.•Dolomite significantly increases alkali release from straw during gasification.•Si-containing materials reduce gasification reactivity and alkali release.•Alumina reduces char gasification reactivity due to K-Al-Si ternary reactions.