The
integrated-multistage process proposed herein is a practical
example of a biorefinery platform in which the organic fraction of
municipal solid waste (OFMSW) is used as a valued source for polyhydroxyalkanoates
(PHA) and biogas production. Technical and economical feasibilities
of this approach have been demonstrated at pilot-scale, providing
a possible upgrade to traditional biowaste management practices, presently
based on anaerobic digestion (AD). A pH-controlled OFMSW fermentation
stage produced a liquid VFA-rich stream with a high VFA/CODSOL ratio (0.90 COD/COD) that was easily used in the following aerobic
stages for biomass and PHA production. The solid fraction was valorized
into biogas through AD, obtaining energy and minimizing secondary
flux waste generation. The reliable biomass enrichment was demonstrated
by a stable feast-famine regime and supported by microbial community
analysis. The selected consortium accumulated PHA up to 55% wt. Compared
to the traditional AD process in an urban scenario of 900000 AE, the
integrated approach for OFMSW valorization is preferable, and it is
characterized by an electrical energy production of 85.7 MWh/d and
1.976 t/d as PHA productivity. The proposed process was also evaluated
as economically sustainable if the PHA is marketed from 0.90 €/kg
as the minimum threshold to a higher market price.
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