Electroosmotically enhanced drying of biomass

A laboratory system for experimentally characterizing electroosmotic dewatering of biomass has been developed. The system was used to investigate the dewatering at both constant voltage and constant current of two biomass materials, organic humus with peat and composted wastewater sludge (WWS). The moisture content of humus decreased to 22.5% from an initial value of 44.3% wet basis (wb) after 2 h 10 min of electroosmosis at 50 V across a 2.9 cm thick bed, whereas that of sludge decreased to 53.5% from an initial value of 68.4% after 2 h 20 min at 40 V across the bed. The electrical energy required to remove 1 kg of water by constant-voltage electroosmosis of humus varied from 23% to 61%, in the voltage range of 10-50 V, of the thermal energy required to change the same quantity of free water from liquid to vapor state. For WWS, the energy remained constant at a higher value of 88% over the 20-40-V range studied. The flowrate of liquid water out of the bed at constant voltage linearly increased with the applied electric field, and the electrical energy expended in the constant-current dewatering mode was seen to be a quadratic function of time as predicted by classical electrokinetic theory.