In conclusion, this study showed that anaerobic codigestion
can be a feasible method for the treatment of MSW
with a high content of nutrient-deficient paper combined
with biosolids in proportions reflecting typical U.S. production
rates. An aggressive start-up strategy using a mixture of
two mesophilic inocula was successful for the rapid start-up
of a thermophilic digester. The steady-state performance
compared favorably to results from previous studies. The
aggressive start-up of an anaerobic codigestion system at
mesophilic conditions proved to be more difficult. A more
gradual start-up strategy would have been beneficial to
achieve a rapid steady state.
Our results suggest that the effects of other operational
parameters on performance should be explored. For example,
to accomplish a rapid start-up using a strategy similar
to the one used in this study, inocula obtained from
‘‘unstable’’ digesters may provide better results. Further
research using SSU rRNA based probes for propionatedegrading
syntrophs and SRB and other syntrophic fatty
acid oxidizing bacteria in combination with the use of
probes for methanogenic populations and performance measures
will allow us to further explore the start-up behavior
of codigestion systems.