<p>The landfilled easily degradable (LED) group is a lignocellulosic material from landfilled municipal solid waste (MSW). This group was studied for its contamination potential in a composting system for subsequent application in the soil of degraded areas in Campinas city, Brazil, promoting a circular economy. Therefore, the physicochemical characteristics of leachates produced on a laboratory scale were evaluated by obtaining water and acid extracts, according to Brazilian and international methods. The first extracts would simulate leachates generated by rainwater and irrigation system of the composting process with neutral pH, while the second, with acidic pH. The water extracts indicated BOD concentrations higher than those permitted in Brazilian river waters for drinking water supply, colour and hardness values not permitted for drinking water and high potential to raise the salinity levels of water bodies and surrounding soil. The acid extracts presented much higher BOD, COD, AOV and alkalinity values than those obtained by the water extracts, which were considered unsuitable for the analysis of these variables in a composting process. Therefore, the composting system for the LED group should consist of a leachate drainage and treatment system and a liner system to avoid the contamination of water bodies, soil and groundwater.</p>