New formula unlocks hidden energy value in trash
Researchers have developed a predictive model that accurately calculates the recoverable energy content in municipal solid waste based on its chemical composition. The breakthrough could help waste-to-energy facilities and recyclers optimize operations and identify which waste streams deliver the most economic value.
Originaltitel: Estimating the specific chemical exergy of municipal solid waste
Forskare vid Högskolan i Borås har utvecklat en prediktionsmodell för att beräkna den specifika kemiska exergin i kommunalt avfall — en parameter som är avgörande för att värdera avfallsomvandlingen till energi. Modellen bygger på elementarsammansättningen (kol, väte, syre, kväve, svavel, klor) och använder statistisk analys av 56 avfallsfraktioner samt validering på 30 ytterligare prover. Forskarna analyserade även entropi för 117 organiska ämnen och bedömde bidraget från oorganisk materia. Resultaten visar att värmevärdet dominerar över entropins inverkan när man skattar avfallsexergin. Modellen korrelerar väl med uppmätta värden och är jämförbar med tidigare modeller. För energi- och avfallshanteringsbranschen möjliggör detta mer exakt dimensionering av förbränningsanläggningar och värmeåtervinningssystem, vilket förbättrar ekonomin i avfallsvärmekonvertering och bidrar till effektivare resursåtervinning.
<p>A new model for predicting the specific chemical exergy of municipal solid waste (MSW) is presented; the model is based on the content of carbon, hydrogen, oxygen, nitrogen, sulfur, and chlorine on a dry ash-free basis (daf). The proposed model was obtained from estimations of the higher heating value (HHV) and standard entropy of MSW using statistical analysis. The ultimate analysis of 56 different parts of MSW was used for the derivation of the HHV expression. In addition, 30 extra parts were used for validation. One hundred and seventeen relevant organic substances that represented the main constituents in MSW were used for derivation of the standard entropy of solid waste. The substances were divided into different waste fractions, and the standard entropies of each waste fraction and for the complete mixture were calculated. The specific chemical exergy of inorganic matter in the waste was also investigated by considering the inorganic compounds in the ash. However, as a result of the extremely low value calculated, the exergy of inorganic matter was ignored. The results obtained from the HHV model show a good correlation with the measured values and are comparable with other recent and previous models. The correlation of the standard entropy of the complete waste mixture is less accurate than the correlations of each individual waste fraction. However, the correlations give similar results for the specific chemical exergy, indicating that HHV has a greater impact when estimating the specific exergy of solid waste than entropy.</p>