The document summarizes a study that compared the biogas production of anaerobic co-digestion of binary and trinary mixtures of organic waste substrates. Batch tests and semi-continuous reactor tests showed that a trinary mixture of organic fraction of municipal solid waste, thickened waste activated sludge, and primary sludge produced 25-135% more biogas than expected from individual substrates. Cumulative methane yield was also higher for the trinary mixtures compared to corresponding binary mixtures. Results from reactors with hydraulic retention times of 15, 10, and 7 days supported the batch test results, showing enhanced biogas production from the trinary mixture over binary mixtures.

1. Enhanced biogas production by anaerobic co-digestion from
a trinary mix substrate over a binary mix substrate
Efath Ara
Majid Sartaj
Kevin Kennedy
Civil Engineering, University of Ottawa, Canada
M Sartaj, Civil Engineering, University of Ottawa, 161 Louis-Pasteur, Ottawa, ON, K1N 6N5,
Canada. Email: msartajatyahoo.com
Abstract
The synergetic enhancement of mesophilic anaerobic co-digestion of trinary and binary mix of
organic fraction of municipal
solid waste (OFMSW) + primary sludge (PS) + thickened waste activated sludge (TWAS) as
substrates was investigated through
batch biological methane potential (BMP) and semi-continuous flow reactor tests. Cumulative biogas
yield (CBY) yield for the
binary mix of OFMSW:TWAS was 555, 580, and 660 mL/g volatile solids (VS)added for an
OFMSW:TWAS ratio of 25:75, 50:50, and 75:25, respectively, which was 48, 78.5, and 140% higher
than the calculated
expected biogas (CEB) yield from the corresponding individual substrates. The trinary mixture of
OFMSW:TWAS:PS at ratios of
25:37.5:375.5, 50:25:25 and 75:12.5:12.5 was able to produce 680, 710 and 780 mL/g VSadded,
respectively, which was 25.5, 62.0 and 135.6% more biogas than the calculated expected biogas
yield from the corresponding
individual substrates. Cumulative methane yield (CMY) of trinary mixtures was also higher than the
corresponding binary mixtures
(20, 27, and 12 % increase for OFMSW:TWAS:PS at a ratio of 25:37.5:37.5, 50:25:25, and
75:12.5:12.5 compared to the binary
mix of OFMSW:TWAS at a ratio of 25:75, 50:50, and 75:25, respectively). Methane content of the
biogas varied from 54 to 57%.
The results from semi-continuous flow anaerobic reactors under hydraulic retention times (HRT) of
15, 10 and 7 days supported
the results of batch biological methane potential tests. The results were conclusive that

2. enhancement in biogas production
was noticeably higher from the co-digestion of trinary mix of organic fraction of municipal solid
waste+ thickened waste activated
sludge + primary sludge than the binary mix organic fraction of municipal solid waste+thickened
waste activated sludge or
thickened waste activated sludge+primary sludge with concomitant improvements in VS removal
and biodegradability for tri-digestion
of organic fraction of municipal solid waste, thickened waste activated sludge and primary sludge.
Article Notes
Funding This work was supported by funding received from Ontario Ministry of Economic
Development and Innovation - Ontario Research
Fund Research Excellence (grant number ORF_RE02-007).
Declaration of conflicting interests The authors declare that there is no conflict of interest.