Paper pulpmill sludge utilization: techno-economic potential for fuel ethanol, methane and scp production

Various processes have been developed or proposed for converting cellulosic residues from pulp and paper mills into products which can be used for fuel or food. Among the promising practical possibilities are processes for ethanol, methane and microbial protein production by fermentation technology. Given the current Canadian financial climate and product demand, the results of techno-economic sensitivity analyses of these three process options indicate that microbial protein production for animal food applications is the most attractive followed by methane then ethanol, the last being quite uneconomical at present. Ironically, research emphasis seems to be placed in the reverse order. It is evident that the relevant costs of upstream and downstream processing in the various process proposals have not been adequately addressed. Case studies of several scenarios illustrate the problems.