The　integration　of　municipal　sludge　with　phase　change　materials　for　composite　energy　storage　material　fabrication　benefits　to　sludge　significant　reduction　and　recycling,　heavy　metal　fixation,　and　minimizing　environmental　pollution.　This　groundbreaking　work　proposed　municipal　sludge-derived　phase-change　composites　utilizing　potassium　nitrate　as　phase　change　material　to　produce　cost-effective,　low-carbon　thermal　energy　storage　materials.　Five　samples　with　varying　mass　fractions　of　municipal　sludge　incineration　ash　and　potassium　nitrate　were　prepared　through　a　cold-compression　&　hot-sintering　process　and　then　thermal　properties,　microscopic　structure,　mechanical　strength,　and　chemical　compatibility　between　components　was　investigated　extensively　to　explore　the　feasibility　of　municipal　sludge　recycling　for　composite　energy　storage　material　fabrication.　The　results　revealed　successful　encapsulation　of　heavy　metals　within　the　phase　change　composites,　and　the　composite　with　a　50:50　ratio　of　ash　to　potassium　nitrate　exhibited　superior　overall　performance,　which　boasts　a　thermal　energy　storage　capacity　of　330.34　J/g　with　temperature　rising　from　100　up　to　380　°C,　a　peak　thermal　conductivity　of　1.04　W/(m·K),　remarkable　mechanical　strength　of　153.78　MPa,　and　excellent　thermal　stability.　In　addition,　the　components　of　the　municipal　sludge　incineration　ash　and　potassium　nitrate　displayed　exceptional　chemical　compatibility.　This　novel　phase　change　composite　holds　significant　potential　for　engineering　application　compared　to　traditional　alternatives.　©　2024　Elsevier　Ltd