Electroosmotically enhanced drying of biomass

A laboratory system for experimentally characterizing the electroosmotic dewatering of biomass has been developed. The system was used to investigate dewatering at both constant-voltage and constant-current of two biomass materials: organic humus with peat; and composted wastewater sludge. The moisture content of humus decreased to 22.5% from an initial value of 44.3% wb after 2 h 10 min of electroosmosis at 50 V across a 2.9 cm thick bed, whereas that of sludge decreased to 54.5% 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 V-50 V, of the thermal energy required to change same quantity of free-water from liquid to vapor state. For wastewater sludge, the energy remained constant at a higher value of 88% over the 20 V-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 the classical electrokinetic theory