Regarding SMP, the increase of PLF percentage as co-substrate
leads to 1.5, 2.5 and 3 times higher values, respectively for phases
II, III and IV, than for single substrate (phase I). Although the
highest SMP was achieved in phase IV (472.0 ± 1.3 mL g1 VS), considering
GPR, biogas quality and MPR trend along the trial phases,
the overall performance was optimized in phase III. Furthermore,
digestate’s pH profile along the trial phases showed a decreasing
tendency: 8.60 ± 0.15 (phase I), 7.31 ± 0.21 (phase II), 7.03 ± 0.20
(phase III) and 6.44 ± 0.38 (phase IV), indicating that under the
conditions used in phase IV acidification will take place leading
to reactor failure. On the contrary, for phase III, the alkaline components
of LCM enhanced the buffer capacity and stability of the
anaerobic system. Furthermore, addition of LCM increased the total
organic nitrogen in the system, resulting in higher concentration of
ammonia that may have neutralized the formed VFA avoiding acidification.
Therefore, we considered phase III to be the best one
because it clearly illustrated the synergetic effect of both
substrates