IJCA - Volume I - Flipbook - Page 16
16
The International Journal of Conformity Assessment
concentrations were checked daily with a minimum
time interval of six hours after the first week for
the remainder of the test. The percentage of
biodegradability was obtained by determining the
percentage of carbon in the test sample that was
converted into CO2 during the duration of the test,
and the evolved carbon dioxide was determined
by titration. The carbon dioxide that evolved
was absorbed by standardized 0.025 N barium
hydroxide and the amount of CO2 was determined
by titrating manually with 0.5 N hydrochloric acid
using a phenolphthalein indicator. The carbon
dioxide produced in each vessel reacted with
barium hydroxide and was precipitated as barium
carbonate. The amount of carbon dioxide produced
was determined by titrating the remaining barium
hydroxide with 0.05 N hydrochloric acid to a
phenolphthalein end point. Data obtained from
the titration was used to calculate the amount of
CO2 produced and percentage biodegradability
(Table 1 and Figure 2). The plateau for percentage
biodegradability (93%) was obtained for the sample
after 42 days.
Table 1. Percentage of Aerobic Biodegradation of positive
control and test samples.
% BIODEGRADATION
Day
Positive
control
Specimen
sample1
Specimen
sample2
Specimen
sample 3
0
0
0
0
0
3
4.45
3.27
3.19
3.21
7
9.88
8.58
8.64
8.68
9
17.11
14.23
14.09
14.13
12
25.23
22.88
22.76
22.93
15
36.11
32.14
31.89
32.03
18
45.88
41.15
40.96
40.85
21
54.23
52.71
51.96
51.82
24
62.12
60.74
59.41
59.12
27
73.88
71.06
70.69
70.96
30
81.75
77.84
76.52
77.89
33
88.82
84.55
83.51
83.96
36
93.23
90.15
90.01
89.95
39
95.56
92.21
91.65
91.68
42
96.11
93.47
92.85
93.01
45
96.23
93.56
92.85
92.99
48
96.27
93.61
93.02
93.45
Mean
93.36
Standard deviation
0.3051
RSD
0.3268
2022 | Volume 1, Issue 1
were gradually biodegraded. The reference sample
was degraded 95.38% while the specimen sample
showed 92.73% degradation after 48 days (Table 2,
Table 3, and Figure 3).
Table 2. Volume of biogas of positive control and test samples.
Volume of Biogas (ml)
Day
Figure 2. Percentage biodegradation of specimen samples and
controlled sample under aerobic composting
Anaerobic Biodegradability
The ASTM D5511 standard test method for
determining anaerobic biodegradation of plastic
materials under high-solids anaerobic-digestion
conditions considering gas evolution was employed
for the determination of anaerobic biodegradability
in the present study. The prepared inoculum was
subjected to a short post-fermentation of seven
days. The pH of inoculum was 7.6, Kjeldahl nitrogen
was 1 g/kg, and the volatile fatty acids content was
less than 1 g/kg.
The test material was exposed to a methanogen
inoculum derived from anaerobic digesters
operating at 52±2°C. The test method was designed
to yield the percentage of carbon in the test material
and its rate of conversion to evolved carbon dioxide
and methane (biogas). As these bacteria began
to utilize the carbon in the test samples, they
generated carbonaceous gas such as CH4 and CO2.
These gases were measured, and the results were
carefully recorded. If the positive control (cellulose)
continues to exhibit bio degradation, then the test
is considered valid and the inoculum is considered
alive. When the test is run to satisfaction, final gas
readings are recorded and the incubation vessels are
emptied and the samples are cleaned and weighed;
the percentage of biodegradation of the samples is
determined based on the conversion of carbon from
the test material to carbon in the gaseous phase
(CH4 and CO2). After 48 days of incubation under
dry (52±2°C), anaerobic-controlled composting
conditions using test method ASTM D5511, the
reference (positive control) and polymer sample
Positive
control
Specimen
sample 1
Specimen
sample 2
Specimen
sample 3
17
Table 3. Percentage biodegradability of specimen sample with
respect to positive control cellulose.
Inoculum
control
Group
% Biodegradation
Specimen
sample 1
Specimen
sample 2
Weight (g)
250
10.0068
10.0126
Total volume (ml)
1556
8857
8782.67
Methane (CH4) (%)
13.7
59.8
56.4
213.17
5296.49
4953.43
0
0
0
0
0
3
883
846
816
823
Volume of methane
(CH4)(ml)
7
2216
2107
2095
2075
Weight of CH4(g)
0.15
3.78
3.54
9
3012
2876
2835
2901
12
4186
3773
3756
3792
Carbon dioxide
(CO2) (%)
19.8
38.3
40.2
15
4988
4736
4710
4756
18
5626
5447
5412
5462
Volume of carbon
dioxide (CO2)(ml)
308.09
3392.23
3530.63
21
6316
6107
6098
6123
24
7283
6942
6901
6952
Weight of carbon
dioxide (CO2)(g)
0.61
6.66
6.94
27
7838
7667
7702
7652
30
8218
8081
8106
8025
Total weight of
carbon (g)
0.27
4.24
4.12
33
8536
8387
8356
8364
36
8683
8464
8412
8436
Theoretical weight
of carbon(g)
4.443
4.445
39
8698
8589
8526
8571
42
8786
8654
8654
8671
Biodegradation
0.9538
0.9273
45
8842
8723
8712
8706
Biodegradation (%)
95.38
92.73
48
8857
8786
8779
8783
Mean
8782.67
Standard deviation
3.5119
RSD
0.0399
Compostability
At the end of the composting test, the entire
contents of the bin were sieved through a mesh the
size of 10 mm. The overall compost quality was
determined by the analyses performed on the
