Sludge Treatment Plant (STP) in Surabaya produces solid waste in the form of sludge. STP in Surabaya provides for Solid Separation Chamber (SSC), equalization unit, Oxidation Ditch (OD), final clarifier, distribution unit, polishing pond, sludge Drying Area (DA), Sludge Drying Bed (SDB), and reservoirs. Sludge waste generation is usually collected in DA and SDB units. This sludge is usually reprocessed for the recycling process, one of which has been developed is waste to energy with a thermochemical process. The difference between these two units is that DA is sludge from preliminary treatment while SDB is sludge from secondary treatment, usually producing microbial biomass. This study aimed to evaluate the sludge produced by the two processing units as solid fuel. The water content of the DA sample is lower because the DA unit has mechanical processing, which separates solids from water. The results of the proximate test resulted in a significant difference between the SDB and DA units. The caloric value, water, ash, and fixed carbon values are significant (<0.05), while the volatile values differ for DA and SBD units. This shows that different treatment is needed for each unit to be appropriately processed as fuel.