Advantages of solar greenhouse biodrying through the lens of heat balance analysis and simulation comparison under tropical climate conditions

• A novel model for heat balance in solar greenhouse biodrying was introduced. • 66 % of the heat input to the waste pile came from bio-heat, 7 % from solar radiation. • The greenhouse system reduced convective and radiative heat losses during biodrying. • Latent heat of evaporation in solar greenhouse biodrying exceeded outdoor biodrying. The high moisture content of municipal solid waste (MSW) reduces the efficiency of mechanical separation and thermal conversion processes. Biodrying, which involves the water evaporation from MSW through heat generated by microbial activity, offers an alternative approach for MSW pre-treatment method. The biodried waste can be used for refuse-derived fuel (RDF) production, contributing to efficient waste management practices. This study aimed to investigate the heat balance of the pilot-scale solar greenhouse biodrying system to better understand its thermal behavior and to demonstrate the advantages of combining a greenhouse system with biodrying, through comparative simulations under greenhouse and non-greenhouse conditions. This pioneering study proposed the new heat balance model for the solar greenhouse biodrying system, improving the accuracy of waste temperature predictions compared to conventional batch biodrying models and extending the modeling scope to include headspace temperature. Results showed that the heat inputs to the waste were metabolic heat (66 %), enthalpy of inlet air (27 %), and solar radiation (7 %). During daytime, latent heat of evaporation reached 2996 MJ, over 18 % higher than nighttime levels (2449 MJ). The greenhouse application in the biodrying process offers several advantages, including increased heat input through solar radiation for enhanced evaporation during daytime, faster moisture reduction (achieving <30 % within 7 days), reduced heat loss from wind-driven convection and thermal radiation to the surroundings, and protection from rainwater intrusion, which helps maintain RDF quality with higher heating content. These results support the integration of solar greenhouse biodrying in waste management strategies, particularly in tropical regions.