3rd Swedish Landfill Symposium
Seite 1
Lulea, 1998
s:publikat\Erwin\1998\LuleaManuskript\Text\Lulea99.doc
Biological Reactivity of Residual Wastes in
Dependence on the Duration of Pretreatment
BINNER Erwin, P.E.
ZACH Alexander, P.E.
Universität für Bodenkultur Wien
(University of Agricultural Sciences, Vienna)
IWGA, Department of Waste Management
Nußdorfer Lände 29-31
A - 1190 Vienna
Austria
Tel.: ++43-1/ 318 99 00
e-mail: Erwin Binner <h526a1@edv2.boku.ac.at>
e-mail: Alexander Zach <h526di09@edv2.boku.ac.at>
ABF
BOKU
Nußdorfer Lände 29-31
A-1190 Vienna
Tel: ++43/1-318 99 00
Fax: ++43/1-318 99 00-50
3rd Swedish Landfill Symposium
Abstract:
Seite 2
Lulea, 1998
The Austrian Landfill Ordinance (1996) sets standards for the
waste which is allowed to be landfilled. There are limits for
TOC, Ignition Loss, Calorific Value and many other parameters
describing the potential of harmful substances, but no
parameters checking the biological reactivity of waste.
The experimental determination of gas generating potential is
very well suited for assessing this reactivity because this
experimental method (incubation test developed by ABFBOKU) allows to reproduce a majority of “natural conditions” in
the laboratory. The problem of anaerobic tests is the long test
duration, that is why also aerobe tests were proved.
To reduce gas generating potential to less than 10 %, a Gas
Generation GS90 < 20 Nl/kg DS is to be kept. Our research
showed, that the correlating Respiration Activity AT7 is
between 12 and 15 mg O2/g DS. To clarify the relationship
between GS90 and AT7 some more tests were started in
autumn.
Key Words: Mechanical-Biological
Pretreatment, Residual Waste,
Biological
Reactivity,
Gas
Generating
Potential,
Respiration Activity
1
Introduction
The Austrian Landfill Ordinance (1996) sets standards for the landfill site, for
design and construction of a landfill, the landfill operation and the quality of
waste allowed to be landfilled. Among other demands there are limits for the
amount of the organic content (TOC < 5% or Ignition Loss (IL) < 8%). For
residual waste this limit can only be reached by incineration. The limitation of
organic material in a landfill is to hinder emissions released during the
uncontrolled metabolic processes. However, the TOC content also implies
carbon which is not degradable. That is why TOC is not a suitable parameter to
describe the potential biological reactivity of waste. The Austrian Landfill
Ordinance also allows the disposal of mechanically-biologically pretreated
waste in a so-called „Mass-waste landfill (Massenabfalldeponie)“, if its calorific
value (Ho) is less than 6,000 kJ/kg dry substance. The calorific value describes
the potential amount of energy gained in an incineration process but is not
intended to describe the reactivity.
In Austria as well as in Germany several ideas have been put forward on how
to describe the activity of waste. Gas generating potential, respiration activity
and analysis of material groups („Stoffgruppenanalysen“ according to Van
Soest) are discussed. The experimental determination of gas generating
potential is very well suited for assessing the reactivity of wastes because this
experimental method (incubation test developed by ABF-BOKU) allows to
reproduce a majority of “natural conditions” in a laboratory-scale test. Because
ABF
BOKU
Nußdorfer Lände 29-31
A-1190 Vienna
Tel: ++43/1-318 99 00
Fax: ++43/1-318 99 00-50
3rd Swedish Landfill Symposium
Seite 3
Lulea, 1998
of the very long duration of this tests (an incubation test lasts approx. 3-8
months) alternative methods had to be developed. That is why the Austrian
Ministry of Environment charged the Department of Waste Management (ABFBOKU) of the Universität für Bodenkultur Wien (University of Agricultural
Sciences in Vienna) to undertake practical tests to describe the reactivity of
mechanically-biologically pretreated residual wastes of 4 plants (first results of
this „MBA-study“ were presented in Sardinia 97).
2
Main Results of the MBA-Study
2.1
Test Methods
2.1.1 Gas Generating Potential
The gas generation is determined using incubation tests (BINNER, 1996). In
doing so, a moist fresh sample sieved to  20 mm (or a sample that has been
stabilized by freezing) with approx. 1 kg of dry matter is wetted to water-holding
capacity and then incubated in glass reactors under anaerobic conditions at
40°C. Gas generation is measured by a so-called „Eudimeter“ (Figure 1) and
calculated to normal-conditions (0 °C, 1013 mbar). The concentrations of CH4,
N2, and O2 are analyzed gaschromatographically. The CO2 concentration is
calculated in building the difference between the amount of gas analyzed and
100 Vol%. Even though gas generation is often not yet complete after
240 days, it is still possible to make an adequately accurate assessment after
90 days.
To differentiate the results of this test with those of conventional fermentation
tests (=Gärtest), which work in an aquatic milieu at 35°C, the total amount of
gas generated in the incubation test is designated “GS n“ at time “n”. In the
fermentation test the volume is designated “GBn”.
As a short-term test, the incubation test (as well as the fermentation test) is
unsuitable, because a test period of 90 days (21 - 28 days) for a landfill’s
receiving inspection must be carried out. Thus, the incubation test has two
areas of application:
 Scientific experimentation
 Initial inspection of materials from mechanical-biological pretreatment
facilities being assessed for the first time and/or control of the results of other
tests (e.g. respiration activity test) in larger intervals
The incubation test has some advantages to the fermentation test. A large
amount of sample (> 1kg DS, wetted to water capacity) and robust test
conditions (short fluctuations of boundary conditions, e.g., thermostat failure
only have a minimal impact on final results) ensure good reproducability of
results. Due to the larger amount of sample gas generation can be measured
more exactly (1 kg DS of a well pretreated waste produces about 10 l gas) than
in the fermentation test (50 g DS of the same waste only produce 0.5 l gas).
ABF
BOKU
Nußdorfer Lände 29-31
A-1190 Vienna
Tel: ++43/1-318 99 00
Fax: ++43/1-318 99 00-50
3rd Swedish Landfill Symposium
Seite 4
Lulea, 1998
Figure 1: Incubation Test Cell (ABF-BOKU)
With the incubation experiment, toxicity is indicated by an extended lag-phase.
Graphical description allows to detect toxic influences (Figure 2). With a test
period of 90 days, however, misinterpretation is possible. Therefore, the
incubation test must be supplemented with other parameters.
ABF
BOKU
Nußdorfer Lände 29-31
A-1190 Vienna
Tel: ++43/1-318 99 00
Fax: ++43/1-318 99 00-50
3rd Swedish Landfill Symposium
Seite 5
Lulea, 1998
Gas Generation after Different Duration of
Mechanical Biological Pretreatm ent
200
GS90 = 57 Nl gas / kg DS
[Nl / kg Dry Substance]
150
toxicity
Allerheiligen 2 (5 weeks)
Siggerwiesen 2 (3 weeks)
Oberpullendorf 2 (20 weeks)
100
Aich Assach 2 (30 weeks)
50
GS90 = 33 Nl gas / kg DS
GS90 = 24 Nl gas / kg DS
GS90 = 14 Nl gas / kg DS
0
0
50
100
150
200
250
300
350
Test Duration [days]
Figure 2:
Gas generation (incubation test) of residual waste after different
mechanical-biological
pretreatment
periods;
the
sample
“Siggerwiesen 2” shows a long lag-phase as a result of toxic effects
2.1.1 Respiration Activity (Sapromat)
Respiration activity, in contrast to the incubation test, does not assess the
potential of a sample, but rather its activity, meaning its momentary oxygen
consumption per unit of time. Processing should be done by sieving a moist
fresh sample to  20 mm. The fraction < 20 mm is wetted to about 50 %. 30 40 g of this wet sample are put into the reaction bottle. Hardly known samples
are tested in triplicates. Well known material is tested only 2 times. If one
repetition differs significantly, stabilized material (frozen) has to be tested again.
After putting sodium-hydroxide into the absorption dish and 30 minutes of
adaptation to 20 °C in the water bath, the reaction bottle is connected with the
oxygen generator and the pressure control gauge. The CO 2 produced by
aerobe microorganisms is absorbed by the sodium hydroxide. The underpressure starts the oxygen generator, which produces O2 until normal pressure
conditions are reached. O2 production is recorded by a computer (Figure 3).
Normally, oxygen consumption remains constant over a period of 7 to 10 days,
following a short lag-phase. Possible toxic impacts can, however, cause errors
in the AT4 value, which could lead to misinterpretation of the results. The
„Siggerwiesen 2“ sample of the MBA-study (Figure 4) shows that after 7 days
this toxic impact does not longer produce false results. The AT10 determination
does not provide enough additional information to justify its application. A test
period of 7 days is sufficient and, therefore, recommended for respiration
activity determination.
ABF
BOKU
Nußdorfer Lände 29-31
A-1190 Vienna
Tel: ++43/1-318 99 00
Fax: ++43/1-318 99 00-50
3rd Swedish Landfill Symposium
Recorder
Figure 3:
Seite 6
Lulea, 1998
Pressure
O
xygen
Control Gauge
Reaction
G
enerator
Bottle
Control Device
Sapromat E
Respiration Activity after Different Duration
of Mechanical Biological Pretreatment
100
Siggerwiesen 2
5 weeks
103
[mg O2/g Dry Substance]
Allerheiligen 2
5 weeks
75
AT 10
AT 7
AT 4
71
Aich Assach 2
34 weeks
Oberpullendorf 2
20 weeks
50
38
30
27
25
15
12
25
20
7,3
3,8
11
0
0
1
2
3
4
5
6
7
8
9
10
Test Duration [days]
Figure 4:
ABF
Respiration activity (Sapromat) of residual wastes after different
mechanical-biological
pretreatment
periods;
the
sample
„Siggerwiesen 2“ shows a long lag-phase as a result of toxic effects
BOKU
Nußdorfer Lände 29-31
A-1190 Vienna
Tel: ++43/1-318 99 00
Fax: ++43/1-318 99 00-50
3rd Swedish Landfill Symposium
2.2
Seite 7
Lulea, 1998
Correlations and Recommended Limits
The MBA-study showed, that the results of respiration activity tests (AT7, testduration 7 days) and gas generation tests (GS90, test-duration 90 days)
correlate significantly (Figure 5). Moreover, both values correlate to a total gas
generating potential, determined over 240 days. As a result of this relationship,
activity judgement of mechanically-biologically pretreated waste can be carried
out in an adequate time (7 days).
Relationship betw een Gas Generation (GS90) and
Respiration Activity (AT7)
Respiration Activity (AT7) [mg O2/g DS]
100
toxicity !
75
(
r = 0,962
y = 0.380x + 6.744
)
50
25
14,3
0
20
0
50
100
150
200
250
Gas Generation (GS90) [Nl/kg DS]
Figure 5:
Relationship between Gas Generation GS90 (incubation test) and
Respiration Activity AT7 (Sapromat) of mechanically-biologically
pretreated residual wastes. The correlation line is calculated with 7
samples of the MBA-study (the toxic sample is eliminated).
Based on existing results, as well as on the assumption of a gas generating
potential of 200 Nl/kg DS (EHRIG, 1991; LEIKAM and STEGMANN, 1995) for
untreated residual solid waste, a factor GS 90/GS240 = 0,9 for untreated and 0,8
for well treated waste and a degradation loss during biological treatment of
about 25 % (wet substance), we recommended a limit value for mechanicallybiologically pretreated residual waste of Gas Generation GS90 < 20 Nl/kg DS.
This results in a decrease of the potential volume of landfill gas released
compared to “untreated waste” of more than 90%. From the correlation
between GS90 and AT7 and a GS90 < 20 Nl/kg DS, a value for Respiration
Activity AT7 < 15 mg O2/g DS is obtained.
To verify the results of the MBA-study (they are based on only 8 samples) and
in order to check the influence of the duration of the biological pretreatment on
the reactivity of residual waste, some more research was done during the last
year.
ABF
BOKU
Nußdorfer Lände 29-31
A-1190 Vienna
Tel: ++43/1-318 99 00
Fax: ++43/1-318 99 00-50
3rd Swedish Landfill Symposium
Seite 8
3
Further Investigations
3.1
Materials
Lulea, 1998
To check the influence of the duration of biological pretreatment, residual solid
waste was accompanied through the mechanical-biological pretreatment plant
of Oberpullendorf (10 weeks composted in forced aerated windrows which were
turned weekly, 12 weeks cured in aerated static piles). The input (after 36 hours
in a DANO-drum) and samples after 2, 5, 7, 9, 15 and 22 weeks of biological
treatment were tested (Figure 6). Samples were sieved to 20 mm. Only the
fraction < 20 mm (between 85 % and 97 %) was used for analysis (also for IL,
TOC, Ho).
Gas Generation after Different Duration of
Biological Treatm ent (Forced Aerated W indrow s)
[Nl / kg Dry Substance]
300
250
GS90 = 210 Nl gas / kg DS
200
GS90 = 184 Nl gas / kg DS
GS90 = 34 Nl gas / kg DS (toxicity)
GS90 cor. = 189 Nl gas / kg DS
Output
DANO-Drum
GS90 = 90 Nl gas / kg DS (toxicity)
GS90 cor. = 105 Nl / kg DS
GS90 = 141 Nl gas / kg DS
2 weeks
150
5 weeks
7 weeks
GS90 = 99 Nl gas / kg DS
GS90 = 85 Nl gas / kg DS
100
9 weeks
15 weeks
50
22weeks
0
0
50
100
150
200
250
300
350
400
Test Duration [days]
Figure 6:
Gas generation (incubation test) of residual wastes after different
duration of biological pretreatment (0, 2, 5, 7, 9, 15 and 22 weeks in
forced aerated windrows, turned weekly)
The results indicate, that the biological process didn’t work well. Gas generation
decreased very slowly with the duration of biological treatment and the reactivity of the 22 weeks treated material was much higher (GS 90 = 85 Nl/kg DS)
than the reactivity of the samples taken for the MBA-study (GS90 = 14 Nl/kg
DS). We assume, that the aeration system of the indoor windrow didn’t work
properly. Additional samples taken at other plants, which were also part of our
investigations (Figure 7 and Figure 8), showed a much higher degradation rate
during the first weeks of treatment. This demonstrates, that the first weeks of
biological treatment are very important for the quality of the output of a MBA. If
there is a lack of oxygen in this phase, even a very long duration of curing
afterwards does not catch up the delay in quality.
ABF
BOKU
Nußdorfer Lände 29-31
A-1190 Vienna
Tel: ++43/1-318 99 00
Fax: ++43/1-318 99 00-50
3rd Swedish Landfill Symposium
Seite 9
Lulea, 1998
The failures in the composting process were also shown in the results of
respiration activity tests. Except the samples with long lag-phases (toxic effects)
in the incubation tests, the AT7 was lower than expected (Figure 12).
As said before (Figure 2) short biological pretreatment often shows long lagphases. To prevent misinterpretation we corrected the GS90 by calculating and
eliminating the lag-phase.
Other samples of residual waste, treated biologically by a simple windrow
system (naturally aerated, turned weekly) after very intensive mechanical
manipulation, were analyzed after 0, 4 and 9 weeks of treatment (Figure 7).
The tested fraction were sieved < 20 mm (0 and 4 weeks of treatment) and
< 10 mm (9 weeks of treatment), respectively.
Gas Generation after Different Duration of
Treatm ent (W indrow Com posting)
150
GS90 = 129 Nl gas / kg DS
[Nl / kg Dry Substance]
raw material
100
GS90 = 57 Nl gas / kg DS
4 weeks of biological treatment
50
GS90 = 10 Nl gas / kg DS
9 weeks of biological treatment
0
0
50
100
150
200
250
Test Duration (Days)
Figure 7:
Gas generation (incubation test) of very well mechanically
pretreated residual waste after 0, 4 and 9 weeks of biological
pretreatment by windrow composting.
Additionally, a large amount of sample (residual waste) was taken from the
facility of Siggerwiesen and treated biologically in laboratory test cells (100 l).
The output of a DANO-drum (< 100 mm) was ground wet to a particle size
< 20 mm before biological treatment. Samples were taken after 0 and 8 weeks
of biological treatment (Figure 8). Because of the optimized treatment
conditions (high aeration rates by controlling the CO2-content in the exhausted
air, optimizing of water content and homogenity by turning the material every
week) the recommended limit value of the respiration activity
(AT7 < 15 mg O2/g DS) was reached already after 7 weeks.
Finally, mechanically-biologically pretreated waste of the facilities Allerheiligen
(18 weeks biological treatment, sieved < 12 mm), Oberpullendorf (5 weeks
ABF
BOKU
Nußdorfer Lände 29-31
A-1190 Vienna
Tel: ++43/1-318 99 00
Fax: ++43/1-318 99 00-50
3rd Swedish Landfill Symposium
Seite 10
Lulea, 1998
biological treatment, sieved < 20 mm) and Zell am See (13 weeks biological
treatment, sieved < 20 mm) were tested.
Gas Generation after Different Duration of
Biological Treatm ent (Laboratory Test)
[Nl / kg Dry Substance]
200
150
GS90 = 36 Nl gas / kg DS
GS90 cor. = 91 Nl gas / kg DS
100
Output DANO-Drum
50
8 weeks
GS90 = 16 Nl gas / kg DS
0
0
50
100
150
200
250
300
350
Test Duration [days]
Figure 8:
3.2
Gas Generation (incubation test) of residual wastes after 8 weeks
of biological treatment in laboratory test reactors
Results Concerning the Duration of the Incubation Test
As already mentioned, gas generation often is not yet completed even after a
test duration of 240 days. However, our research showed, that well pretreated
waste produces 95 to 100 % of its gas generating potential within 240 days.
The amount of gas generated within 90 days is between 80 and 95 % of the
volume produced in 240 days (Table 1). Short pretreated materials show
quantities higher than 90 %, toxic impacts excepted. With longer pretreatment
periods, the amounts obtained are about 85 % - 90 %. A shorter (60-day)
experimental period leads to considerably lower findings (65 –90 %), and for a
30-day period, findings are only between 23 and 75 %.
The Germans propose a test duration for the fermentation test until gas
generation decreases to less than 1 % of the total amount already produced.
The incubation test reaches this point in 29 to 77 days (toxic impacts excepted).
At that moment total gas generation, however, is only between 35 % and 88 %
of the amount produced within 240 days. Therefore we prefer a test-duration of
90 days.
ABF
BOKU
Nußdorfer Lände 29-31
A-1190 Vienna
Tel: ++43/1-318 99 00
Fax: ++43/1-318 99 00-50
3rd Swedish Landfill Symposium
Seite 11
Lulea, 1998
Duration GS30 GS45 GS60 GS75 GS90 GS240 GSPot
Total
of PreTest
treatment
Duration
Sample
[weeks]
[%240] [%240] [%240] [%240] [%240] [%240] [%240]
[days]
SAB 3-01)
0
7
11
16
19
22
100
118
260
SAB 3-8
8
32
44
52
59
64
100
n.e.
220
SAB 1-3
3
23
45
69
84
91
100
100
335
SAB 2-31)
3
4
6
10
19
34
100
109
355
MV 1-5
5
49
73
83
89
92
100
101
310
MV 2-5
5
76
83
85
86
88
100
100
260
MV 3-18
18
75
83
87
89
90
100
103
95
AA 1-20
20
65
74
79
83
86
100
106
311
AA 1-34
34
68
76
81
84
87
100
104
240
OP 6-01)
0
5
7
8
10
13
100
112
345
OP 6-2
2
14
43
69
88
93
100
101
190
OP 6-51)
5
16
23
32
43
56
100
103
310
OP 6-7
7
53
83
92
95
96
100
101
176
OP 6-9
9
44
67
82
89
92
100
101
155
OP 6-15
15
33
51
66
81
89
100
101
200
OP 6-22
22
40
60
76
85
90
100
101
190
OP 1-20
20
67
76
81
84
86
100
100
320
OP 2-20
20
70
77
82
85
88
100
100
230
OP 7-5
5
47
76
88
93
96
100
101
150
KOM 1-0
0
13
35
62
80
89
100
101
195
KOM 1-4
4
59
75
82
85
88
100
n.e.
103
KOM 1-9
9
52
63
71
76
80
100
n.e.
110
ZS 1-13
13
61
75
81
85
88
100
100
180
1)
toxic effects (low pH-values)
n.e. = not estimable
Table 1:
ABF
Gas generation after different test durations compared to the gas
generation in 240 days (amounts italics are estimated). The 8
samples of the MBA-study are written in bold stylus.
BOKU
Nußdorfer Lände 29-31
A-1190 Vienna
Tel: ++43/1-318 99 00
Fax: ++43/1-318 99 00-50
3rd Swedish Landfill Symposium
3.3
Seite 12
Lulea, 1998
Results of Chemical and Biological Analysis
Sample
Duration Ignition Organ. Calorific
of PreLoss Carbon Value
treatm.
IL
TOC
Ho
[weeks]
[%DS]
[%DS]
[kJ/kgDS]
Respiration
Activity
AT4
AT7
Gas
Generat.
GS90
[mgO2/gDS] [mgO2/gDS]
[Nl/kg DS]
SAB 3-0 <100
0
55.7
34.8
12,400
53
71
361)/91
SAB 3-8 <100
8
36.3
23.5
7,500
5.1
7.1
16.1
SAB 1-3 <100
3
59.5
35.2
14,200
47
73
168
SAB2-3 <100
3
59.1
35.5
13,800
30
71
571)/113
MV 1-5
<80
5
51.0
33.3
13,200
20
35
92
MV 2-5
<80
5
35.7
23.0
8,000
15
27
33
MV 3-18 <12
18
33.1
17.6
6,700
12.6
20
35
AA 1-20 <60
20
38.1
19.8
7,100
15.0
24
31
AA 1-34 <60
34
35.0
19.3
6,400
12.0
20
23.7
OP 6-0
<20
0
63.6
35.6
13,300
32
75
341)/189
OP 6-2
<20
2
59.1
33.4
11,900
55
89
210
OP 6-5
<20
5
50.8
27.2
9,900
28
44
901)/103
OP 6-7
<20
7
53.8
30.5
10,600
25
41
184
OP 6-9
<20
9
49.0
26.5
9,900
23
39
141
OP 6-15 <20
15
44.4
24.2
8,400
13.6
22
99
OP 6-22 <20
22
41.3
21.0
8,200
14.1
24
85
OP 1-20 <25
20
32.2
18.8
6,000
2.5
5.5
16.1
OP 2-20 <25
20
32.3
18.2
6,200
3.8
7.3
13.6
<20
5
44.1
27.0
n.a.
32
44
114
KOM 1-0 <20
0
33.3
20.6
6,500
17.0
53
116
KOM 1-4 <20
4
28.5
n.a.
n.a.
22
31
56
KOM 1-9 <10
9
22.0
10.4
3,800
4.7
7.4
10.4
13
33.3
20.1
8,500
6.7
11.6
24.2
OP 7-5
ZS 1-13
<20
1)
toxic effects (low pH-values); the 2nd value is corrected by eliminating
the lag-phase
n.a. = not analyzed
Table 2:
ABF
Ignition Loss, TOC, Calorific Value, Respiration Activity (AT 4 and
AT7) and Gas Generation (GS90) of residual wastes after different
mechanical-biological pretreatment. The 8 samples of the MBAstudy are written in bold stylus.
BOKU
Nußdorfer Lände 29-31
A-1190 Vienna
Tel: ++43/1-318 99 00
Fax: ++43/1-318 99 00-50
3rd Swedish Landfill Symposium
Seite 13
Lulea, 1998
3.4 Comparison of Incubation Test and Fermentation Test, Effects of
Inoculation
Gas Generation in Incubation Test and
Ferm entation Test (w ithout Inoculation)
150
[Nl / kg Dry Substance]
GS90 = 129 Nl gas / kg DS
GB42 = 91 Nl gas / kg DS
100
Incubation Test
(raw material)
Fermentation Test
(raw material)
Incubation Test
(9 weeks biol. treatment)
50
GS90 = 10 Nl gas / kg DS
Fermentation Test
(9 weeks biol. treatment)
GB42 = 3,2 Nl gas / kg DS
0
0
50
100
150
200
250
Test Duration (Days)
Figure 9:
Comparison of incubation test and fermentation test (without
inoculation)
Figure 9 compares gas generation of untreated residual waste (with very
intensive mechanical pretreatment, IL = 33.3 % DS) and 9 weeks biologically
treated waste (naturally aerated windrow composting) tested by the incubation
test and the fermentation test. Both tests were done without inoculation.
The lag-phase of untreated waste in the incubation test (35 days) is much
longer than in the fermentation test (14 days). On the other hand in the
incubation test the total amount of gas generated is higher. The well treated
sample produces in the fermentation test only one third compared to the
incubation test. There the fermentation test shows no positive effect neither on
the lag-phase nor on the gas generation rate.
In Figure 10 gas generation of untreated residual waste and 8 weeks
biologically treated waste (treated in laboratory test cells) analyzed by
incubation test and fermentation test is shown. Fermentation tests were done
with and without inoculation.
Inoculation has no important effect on the lag-phase and the gas generation
rate. But the fermentation test of untreated waste shows a very short lag-phase
and a much higher gas generation rate in comparison to the incubation test.
Toxic effects (acidification) are „diluted“ because of the aquatic milieu. Even the
total gas amount seems to be higher in the fermentation test (the incubation
test is still running). Well treated waste doesn’t show effects like these. There,
on the contrary, the total gas amount is lower in the fermentation test.
ABF
BOKU
Nußdorfer Lände 29-31
A-1190 Vienna
Tel: ++43/1-318 99 00
Fax: ++43/1-318 99 00-50
3rd Swedish Landfill Symposium
Seite 14
Lulea, 1998
Gas Generation in Incubation Test and
Fermentation Test
300
Incubation Test (DANOOutput not inoculated)
GB42 = 176/177 Nl gas / kg DS
[Nl / kg Dry Substance]
250
Fermentation Test (DANOOutput, not inoculated)
GS90 = 36 Nl gas / kg DS
GS90 cor. = 91 Nl gas / kg DS
200
Fermentation Test (DANOOutput, inoculated)
150
Incubation Test
(8 weeks, not inoculated)
100
GB42 = 7/6 Nl gas / kg DS
50
Fermentation Test
(8 week, not inoculated)
GS90 = 16 Nl gas / kg DS
Fermentation Test
(8 week, inoculated)
0
0
50
100
150
200
250
300
350
Test Duration [days]
Figure 10: Comparison of incubation test (without
fermentation test (with and without inoculation)
inoculation)
and
Figure 11 shows the effects of adding inoculum to a 5 week biologically treated
residual waste in the incubation test. Inoculation forces gas generation, but the
total amount of gas seems to be higher without inoculation.
The fermentation test is as fast as the incubation test. Inoculation reduces the
lag-phase from 14 days to 5 days (in both tests). As gas generation rates are
nearly the same as without inoculation, the duration of the test decreases only
from 90 days (not inoculated) to about 50 days (inoculated).
With the reservation, that all the tests are done with copretreated solid wastes
(residual waste + sewage sludge), our first tests (3 samples) indicate, that
inoculation reduces the lag-phase. The GS90 amount can be generated in 60 to
80 days. But the effects of inoculation are too less to justify the larger effort.
Drying the material (for stabilisation) before wetting it to water capacity, shows
negative effects; gas generation rates are lower.
ABF
BOKU
Nußdorfer Lände 29-31
A-1190 Vienna
Tel: ++43/1-318 99 00
Fax: ++43/1-318 99 00-50
3rd Swedish Landfill Symposium
Seite 15
Lulea, 1998
Gas Generation in Incubation Test and
Ferm entation Test (5 w eeks biological treatm ent)
[Nl / kg Dry Substance]
200
150
GB42 = 112 Nl gas / kg DS GS90 = 114 Nl gas / kg DS
Incubation Test (not inoculated)
100
Fermentation Test (not inoculated)
GB42 = 80 Nl gas / kg DS GS90 = 107 Nl gas / kg DS
Incubation Test (inoculated)
50
Fermentation Test (inoculated)
0
0
50
100
150
200
250
300
350
Test Duration [days]
Figure 11: Comparison of incubation test and fermentation test (with and
without inoculation)
3.5
Correlations
3.5.1 Correlations between Gas Generation (GS90) and Respiration
Activity (AT7)
Relationship betw een Gas Generation (GS90) and
Respiration Activity (AT7)
Respiration Activity (AT7) [mg O2/g DS]
100
7 samples of the MBA-project: r = 0.962
y = 0.380x + 6.744
toxic effects (corrected)
75
Siggerwiesen
Allerheiligen
Aich Assach
50
Oberpullendorf
Oberpullendorf (<20 mm)
oxygen starvation
25
Frojach Katsch <20 mm
very well mechanical treatment
12 bis 15
Zell am See
0
0
20
50
100
150
200
250
Gas Generation (GS90) [Nl / kg DS]
Figure 12: Relationship between Gas Generation GS90 (incubation test) and
Respiration Activity AT7 (Sapromat) of mechanically-biologically
pretreated residual waste.
ABF
BOKU
Nußdorfer Lände 29-31
A-1190 Vienna
Tel: ++43/1-318 99 00
Fax: ++43/1-318 99 00-50
3rd Swedish Landfill Symposium
Seite 16
Lulea, 1998
The new results (15 samples) underline the results of the first 8 samples of the
MBA-study. The dark correlation line (Figure 12) is the one from the MBA-study
(r = 0.962). The dotted line includes all samples (r = 0.848). Gas generation of
the „toxic“ samples is corrected by eliminating the lag-phase. Samples with
oxygen starvation during the biological pretreatment show lower results of
respiration activity than expected. That indicates, that it is important to do
anaerobic tests and aerobic tests in combination.
Regressions Statistics
Observations
Correlation Coefficient (r)
Intersection with y-axis
Slope
GS90 - AT7
23
0.848
7.658
0.338
GS90 - AT7
9 (GS90 < 50)
0.906
-4.086
0.812
Discussing the samples with low reactivity (GS90 < 50 Nl/kg TS) indicates, that
the correlation line might turn a little (Figure 12, r = 0,906). The Respiration
Activity (AT7) correlating to the GS90 = 20 Nl/kg DS (reduction of gas generating
potential > 90 %) in that case is about 12 (instead of 15) mg O2/g DS. In
September we started new test-series with very well pretreated wastes to clarify
the correlation.
3.5.2 Correlations between Gas Generation and Ignition Loss
Discussing the MBA-study we were very astonished, to find significant
correlations between Gas Generation and Ignition Loss. The correlation
coefficient was r = 0.982. The new samples indicate, that there are significant
correlations for the samples of the same pretreatment plant, but not so
significant correlations for samples of different plants (Figure 13). Although the
correlation coefficient is 0.844, the samples of the pretreatment plant Frojach
Katsch indicate, that Ignition Loss (and TOC) alone are not suitable parameters
for describing the reactivity of waste. The efficient mechanical pretreatment
decreases the Ignition Loss to 33.3 % without any biological treatment.
Regressions Statistics
Observations
Correlation Coefficient (r)
Intersection with y-axis
Slope
ABF
BOKU
GS90 - IL
23
0.844
29.583
0.158
Nußdorfer Lände 29-31
A-1190 Vienna
Tel: ++43/1-318 99 00
Fax: ++43/1-318 99 00-50
3rd Swedish Landfill Symposium
Seite 17
Lulea, 1998
Relationship betw een Gas generation (GS90) and
Ignition Loss
75
toxic effects (corrected)
Ignition Loss [% DS]
( )
50
Siggerwiesen
Allerheiligen
Aich Assach
Oberpullendorf
25
Oberpullendorf (<20 mm)
oxygen starvation
Frojach Katsch <20 mm
very well mechanical treatment
Zell am See
0
0
50
100
150
200
250
Gas Generation (GS90) [Nl / kg DS]
Figure 13: Relationship between Gas Generation GS90 (incubation test) and
Ignition Loss (IL) of mechanically-biologically pretreated waste
3.5.3 Correlations between Gas Generation and Calorific Value
Basically, Calorific Values show the same tendencies as Ignition Loss Values.
Figure 14 presents the relationship between Gas Generation (GS 90) and
Calorific Value.
Relationship betw een Gas generation (GS90) and
Calorific Value
15.000
Calorific Value [kJ/kg DS]
12.500
Siggerwiesen
10.000
Allerheiligen
Allerheiligen (<12 mm)
7.500
Aich Assach
Oberpullendorf
5.000
Oberpullendorf (<20 mm)
oxygen starvation
2.500
Frojach Katsch <20 mm
very well mechanical treatment
Zell am See
0
0
50
100
150
200
250
Gas Generation (GS90) [Nl / kg DS]
Figure 14: Relationship between Gas Generation GS90 (incubation test) and
Calorific Value (Ho) of mechanically-biologically pretreated waste
ABF
BOKU
Nußdorfer Lände 29-31
A-1190 Vienna
Tel: ++43/1-318 99 00
Fax: ++43/1-318 99 00-50
3rd Swedish Landfill Symposium
Seite 18
Lulea, 1998
3.5.4 Correlations between Ignition Loss and Calorific Value
Another, especially for Austria, important relationship, is the one between
Ignition Loss and Calorific Value. Sample imhomogenity and small amounts of
sample for analysis make it difficult to find out the „true“ Calorific Value.
However, a high correlation between Calorific Value and Ignition Loss could be
obtained. Therefore it might be a more suitable way for describing the potential
energy of mechanically-biologically pretreated waste by analyzing the Ignition
Loss. The MBA-study showed a correlation coefficient of about 0.979. The new
samples back up this result. The correlation coefficient of 21 samples was
r = 0.950. The Ignition Loss corresponding to a Calorific Value of 6,000 kJ/kg
DS, calculated by using the relationship of this research, is 30.6 % DS.
IL - Ho
21
0.950
-1389
241.312
Regressions Statistics
Observations
Correlation Coefficient (r)
Intersection with y-axis
Slope
Relationship betw een Ignition Loss and
Calorific Value
Siggerwiesen
Allerheiligen
15.000
Aich Assach
Oberpullendorf
Calorific Value [kJ/kg DS]
12.500
Oberpullendorf (<20 mm)
oxygen starvation
10.000
Frojach Katsch <20 mm
very well mechanical treatment
outside analysis
( )
Zell am See
7.500
( )
30,6
5.000
2.500
0
0
10
20
30
40
50
60
Ignition Loss [% DS]
Figure 15: Relationship between Ignition Loss (IL) and Calorific Value (H o) of
mechanically biologically pretreated residual waste
ABF
BOKU
Nußdorfer Lände 29-31
A-1190 Vienna
Tel: ++43/1-318 99 00
Fax: ++43/1-318 99 00-50
3rd Swedish Landfill Symposium
4
Seite 19
Lulea, 1998
Conclusions
The main results of the MBA-study (8 samples) were backed up by further
additional 15 samples of mechanically-biologically pretreated residual waste:
 The amount of gas, generated in the incubation test in 90 days (GS90), is
about 80 % to 90 % of the gas generating potential of well pretreated
residual waste.
 A test duration as suggested for the fermentation test in Germany (till the
daily gas production is less than 1 % of the total gas amount) only gives
35 % to 88 % of the gas generating potential (in 29 to 77 days)
 A limit value for Gas Generation GS90 < 20 Nl/kg DS reduces the reactivity of
> 90 % compared to untreated residual waste.
 First tests (3 samples) showed, that inoculation reduces the lag-phase. The
GS90 amount can be generated in 60 to 80 days. But the effects of
inoculation are too less to justify the larger effort. (This is sure only for
cocomposting of residual waste and sewage sludge, which is done in almost
all Austrian mechanical-biological pretreatment plants).
 When testing low reactive material, the incubation test produces a higher
total gas amount than the fermentation test. Inoculation does not make the
process faster.
 Testing reactive material - especially not or very short biological treated
material (solid waste + sewage sludge) - in the fermentation test the lagphase can be shortened (toxic effects are „diluted“). Inoculation sometimes
shows similar effects. But nevertheless the duration of the fermentation test
has to be more than 40 days.
 There is a significant correlation between Gas Generation (GS 90) and
Respiration Activity (AT7). The correlation coefficient is r = 0.848. The AT7
correlating to GS90 = 20 Nl/kg DS is about 12 to 15 mg O2/g DS. To clarify
this recommended limit value, further investigation has started in September.
 There are also correlations between Gas Generation and Ignition Loss (TOC
or Calorific Value). The correlation coefficient for GS 90 and IL is r = 0.844.
But the analysis of Ignition Loss cannot replace biological parameters,
because a good mechanical pretreatment might simulate to little reactivity by
analyzing Ignition Loss alone.
 There are significant correlations between Ignition Loss and Calorific Value.
The correlation coefficient is r = 0.950. The Ignition Loss correlating to
6,000 kJ/kg DS is about 30.6 % DS
 Under optimized conditions (laboratory tests) a good stabilisation of residual
waste + sewage sludge is possible within 8 weeks of biological pretreatment.
 The first weeks of biological pretreatment are very important for the quality of
the pretreated waste. If there are failures during the first weeks, even a
treatment duration of 22 weeks is not enough
ABF
BOKU
Nußdorfer Lände 29-31
A-1190 Vienna
Tel: ++43/1-318 99 00
Fax: ++43/1-318 99 00-50
3rd Swedish Landfill Symposium
5
Seite 20
Lulea, 1998
References
BINNER E. (1996) Der Inkubationsversuch - eine Methode zur Beurteilung der
Reaktivität von Abfällen. In: Waste Reports 4/96 pp. 54-62. Lechner P. (eds).
ABF-BOKU, Vienna, A, 1996
BINNER E., LECHNER P., WIDERIN M., ZACH A.: „Laboratory Test Methods
Characterizing the Biological Reactivity of Wastes“ In: Landfill Processes and
Waste Pretreatment, Proceedings of the 6 th International Landfill Symposium,
Volume 1, pp. 485-494, Sardinia 1997
BINNER E., ZACH A., WIDERIN M., LECHNER P.: „Auswahl und
Anwendbarkeit von Parametern zur Charakterisierung der Endprodukte aus
mechanisch-biologischen Restmüllbehandlungsverfahren“, In: Schriftenreihe
des BMUJF Band 9, Vienna 1998 (a short version is published in Waste
Reports 7/98. Lechner P. (eds). ABF-BOKU, Vienna A.)
BGBl. Nr. 164/96: Bundesministerium für Umwelt: Verordnung des
Bundesministers für Umwelt über die Ablagerung von Abfällen (=
Deponieverordnung), 1996
EHRIG, H.J.: Gasprognose bei Restmülldeponien, Trierer Berichte zur
Abfallwirtschaft Band 2 (Deponiegasnutzung), 1991
LEIKAM, K.; STEGMANN R.: Emissionsverhalten von mechanisch-biologisch
vorbehandelten Restabfällen, In: Waste Reports 2/95, pp. 7-23, Lechner P.
(eds). ABF-BOKU, Vienna A., 1995
Van SOEST, P.J.: Use of Detergents in the Analysis of Fibrous Feeds. A rapid
Method for the Determination of Cell-Wall Constituents. J. Assoc. Off. Anal.
Chem. (A.O.A.C.), 50 (1), pp. 50-55, 1963.
ABF
BOKU
Nußdorfer Lände 29-31
A-1190 Vienna
Tel: ++43/1-318 99 00
Fax: ++43/1-318 99 00-50