Gaseous emissions reduction from aerobic MBT of municipal solid waste

Full text

Gaseous emissions reduction from aerobic MBT of
municipal solid waste
Isabelle Zdanevitch, Pascal Mallard, Olivier Bour, Mark Briand
To cite this version:
Isabelle Zdanevitch, Pascal Mallard, Olivier Bour, Mark Briand. Gaseous emissions reduction
from aerobic MBT of municipal solid waste. KUEHLE-WEIDEMEIER, Matthias. 3. In-
ternational Symposium MBT and MRF ”Mechanical biological waste treatment and material
recovery facilities” (Waste-to-Resources 2009), May 2009, Hanovre, Germany. Cuvier Verlag.
Gottingen, pp.329-340. <ineris-00973342>
HAL Id: ineris-00973342
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Gaseous émissions réduction from aérobic MBT of
municipal solid waste
Isabelle ZDANEVITCHA, Pascal MALLARD8 c, Olivier BOURA, Mark BRIANDD
AINERIS, BP2, 60550 Verneuil en Halatte, France
B Cemagref, 17 Avenue de Cueille, CS 64427, 35044 Rennes Cedex, France
c Université européenne de Bretagne, France
D SMITOM de LAUNAY LANTIC, 22 rue Pasteur, 22680 Etables sur mer, France
Abstract
Surface gaseous émissions, composition of soil gas and VOC concentration were de-
termined on a French MBT plant, where the biodégradation process is aérobic. Meas-
urements were performed on both the composting windrows and on the landfill cell
which receives the sorting rejects. This allowed the comparison of the global méthane
and CO2 gases, as well as the characterization of the dégradation process on the dif-
férent parts of the site. The performance of the sorting chain allow to obtain a high-
grade compost, which can be valorised on agricultural fields, and leads to deposit much
smaller quantities of degradable waste than in a classical landfill site, and to lowering
serîously the génération of méthane. Therefore, landfill gas (LFG) does not need to be
recovered and treated by classical means, e.g. flares.
Keywords:
aérobic MBT, gaseous émissions, landfill
cell,
surface flux, VOC
1 Introduction
Mechànical biological (MBT) treatment of municipal solid waste (MSW) is mainly used
to stabilize the organic matter prior to landfilling. Other processes allow energy recovery
(by collecting biogas generated during anaerobic digestion) and/or return of organic
matter to the
soil.
Différent processes exist. We hâve evaluated the gaseous émissions
of one of the French MBT aérobic plants within two différent studies. The fîrst study
aimed to measure the gaseous émissions during the composting process, and the sec-
ond one focused on the biogas génération from the associated landfill. In order to char-
acterize the gaseous émissions, several direct and indirect measurement methods were
used during two campaigns, respectively on the composting plant, then on the two first
cells of the landfill. Some methods were used on both the composting plant and the
landfill,
allowing the comparison between surface fluxes and biogas composition.

2
Composting process
Municipal solid waste is received in bags from door-to-door collection. The first step is
an aérobic biological pretreatment in two composting drums, where bags are opened
and waste is physically and biologically pre-degraded. The duration of this step is 3 to 4
days,
in order to initiate the dégradation of paper and cardboard. Then, a high grade
sorting process is undertaken, the final séparation being done at a 10 mm mesh. Thus,
the fine and biodégradable fraction of the waste is well separated and goes to the com-
posting
hall,
where it is mixed with screened green waste compost at a 2:1 ratio. Com-
posting of the biodégradable fraction is done in turned windrows, passively
aerated.
The
rejected coarse fraction is landfilled close to the plant.
3
Material and methods
The investigation covered three composting windrows of différent âges and two cells of
the in-site landfill:
- windrow A, situated in an open shelter, was constituted between one and two
weeks prior to the first measuring day, and was turned by an automatic machine
twice a week,
- windrow B, also under the shelter , was constituted between 15 days and one
month before the first measurement, and was also turned twice a weeks
- windrow C, outside the shelter, was at least 2 months old when the measure-
ments started and was not turned,
- cell
1
of the landfill was rehabilitated, It has a
1
m clay cover plus planted
soil;
- cell 2 was full of the composting rejects, but uncovered yet at the time of meas-
urements. Therefore weexpeeted the maximum surface émissions from this
celi.
Gaseous émissions were characterized by différent techniques:
- Three différent devices were used for surface émission measurements on the
composting windrows: two flux chambers (one static, one dynamic) and one tun-
nel;
low concentrations of méthane (CH4), carbon dioxide (CO2), ammonia (NH3)
and nitrous oxide (N2O) were monitored by an FID (Autofim II) specifically for mé-
thane and a photo acoustic analyzer (Innova) for ail thèse gases; higher concen-
trations of CH4 and CO2 were measured with an infrared portable apparatus
(Ecoprobe 5). The static chamber was also used for surface flux measurements
on the cell n° 2 of the landfill,

- Composition of the soil gas (CH4, CO2) was assessed by the use of a probe and
the portable analyzer Ecoprobe 5; thèse measurements were performed on both
the windrows (where
"soil"
means compost) and the landfill
cell,
- Concentrations of trace gases (VOC) were established on some samples taken
on the static chamber, also on the windrows and the landfill cell surface.
Due to the relatively high porosity of the material compared to the soil which are usually
scanned with the static chamber, there were some différences between the fluxes de-
termined with the static chamber and the dynamic one on the compost windrows (fluxes
measured with the static chamber being the lowest). Results of the comparison of the
techniques will be published elsewhere (report: MALLARD ET AL, 2008). The flux meas-
ured with the static chamber represents more or less the gaseous flux emitted by the
surface of the windrows in a total absence of convective gas flows. Nevertheless, due to
the short measurement time, a large number of local fluxes can be determined with this
method,
allowing the interpolation and cartography of the surface émissions.
3.1 Surface fluxes measurements
Measurements of méthane and carbon dioxide surface fluxes were performed with a
patented static chamber (see Figure 1). Monitoring of the gas concentration increases in
the ehamber was done in parallel with a flame ionization detector (FID) for low concen-
trations of méthane (down to 1-2 pprrïv), and a CH4/CO2 infra-red analyzer (Ecoprobe 5)
for lârger concentrations (up to 100 % v/v). Interpolation of thèse points gives access to
the cartography of global émissions and to the mean surface fluxes. Méthane and CO2
fluxes were calculated for windrows of différent âges, and for the landfill
cell,
allowing
the comparison of émissions between the composting process and the landfill.
FID
Chamber
Soil
Figure 1 : apparatus for gaseous surface émissions (static chamber)

3.2 Composition of bîogas
Composition of the biogas was determined at 1 meter depth with a soil gas probe and
the Ecoprobe 5 analyzer. The analyzer also comprises an electrochemical cell to meas-
ure oxygen concentrations in the soil gas.
Photo 1 : CH4 and CO2 measurements on soil gas (Ecoprobe 5)
3.3 Trace VOC émission
Some VOC samples were taken on the flux chamber for identification and quantification,
following US-EPA TO15 and TO17 air toxic methods. Sampling was done using the fol-
lowing methods:
- on the windrowà, sampling was performed by pumping 1 liter of chamber air on
3-zones adsorbent tubes ("Air Toxics" type) at 100rnl/min, thus the sampling time
is 10 minutes. On some points, during the time period of air sampling, the com-
bustible gases (méthane + trace VOC) concentration increase was monitored by
the FID, which allowed an estimation of the VOC fluxes, using the hypothesis
that VOC concentrations follow the global combustible gas monitored by the FID,
- on the landfill
cell,
air from the chamber was sampled by diffusion in an emptied
steel canister. This method theoretically gives access do compounds of low mo-
lecular weight which are not stable on solid adsorbents, such as vinyl chloride.
Analysis was done by preconcentration on Perkin Elmer ATD400 or Turbomatrix (with
the thermodesorption of the adsorbent tubes), gas chromatography and mass spec-
trometry. This method allows the identification of VOC, and the quantification down to
3 for the most usual compounds, by using standard gas mixtures of aromatic and
Waste-to-Resources 2009 III International Symposium MBT & MRF waste-to-resources.com wasteconsult.de

chlorinated compounds. On the landfill cell 2, toxic compounds: BTEX and chlorinated
solvents, were specifically searched. On the windrows, the analysis purpose was différ-
ent: identification of the major VOC by the mass detector, and quantification of the most
abundant ones.
4 Results
4.1 Surface émissions of CH4 and CO2: comparîson between the
windrows and the landfill cell
The first finding is that méthane émissions from the open cell of the landfill are very low:
see Figure 2. It cornes from the fact that a large part of the organic matter is diverted
from the waste to the composting process. Waste which is landfilled contains mostly
materials such as plastics, foams... which are not easily biodegraded.
90
70
10
15 20 25 30 35 40 45 50
25
Landfili ceii
2
Figure 2 : Interpolated méthane émissions on landfill cell 2, ml/m2/min
Méthane émissions from the three composting windrows are very différent, as shown on
Figure 3, due to the "âge" of the material - e.g. the stabilization of the organic matter.
Méthane émission increases with the âge of the windrow, but also when the windrow is
not turned (windrow C). Furthermore, méthane émissions are higher at the top of the
windrow, which is natural, as température - measured in the same time with an infra-
red caméra - and gas fluxes are known to be higher at tops.

m
60 J
56-
50
45-
40-
36
30
26I
20
15I
10
8
20
Flux,
mUmZtmm
m
45
40
35-
30-
25-
20-
15
roi
-BD
V
|30
20
I:
024Ôm
Q 2 4 8 m
WifidrowA Windrow B Windrow C
Figure 3 : Interpolated méthane émissions on windrows, mL/m2/min
Meanwhile, CO2 émissions are more stable, indicating the constancy of the aérobic de-
gradation.
Therefore, the interpolations of CO2 fluxes on the différent parts of the site
are not detailed hère.
The major finding is the comparison of the surface émissions between the composting
plant and the landfill cell measured with the static chamber. Results are given in the
Table 1.

Table 1 :
CH4
and
CO2
fluxes on
composting windrows
and the landfill cell
Age of
the
windrow/storage
Interpolated surface area, m2
MeanCH4flux,
L-h"1-m"2
Mean CO2 flux, L-rf1-m'2
Total CH4 flux on each part, m3/h
Total CO2 flux on each part, m3/h
Composting plant : windrows
A
2 weeks
368
0,08
6,4
0.029
2.36
B
1 month
293
0,60
8,3
0.176
2.43
C*
2-3 months
382
1,1
6,0
0.42
2.29
Landfill,
cell
2 : waste
refuse
< 2 years
2760
0,25**
2,3
0.69
8.65
*
maturation
step,
not
turned;
**
méthane
is
partially oxidized through
the surface layer
Mean carbon dioxide fluxes are quite similar on each windrow, whatever their âge.
Mean émissions from the landfill are a little smaller, indicating that aérobic dégradation
process is less important in the landfill
cell.
Méthane émissions vary more, from a small value on the younger windrow (2 weeks) to
a higher one on the older windrow. This latter value is mainly due to a singular point
which shows a high méthane flux on this windrow (7.3 L*h'1im"2). In comparison, mean
méthane émission is smaller on the landfill, than on two of the 3 windrows, due to low
organic content of waste and partial oxidation in the cell cover (results will be published
elsewhere : BOUR
ET
AL, 2009). Landfilling of the rejected fraction from composting,
which contains a small proportion of organic matter and is partially stabilized, leads to
small méthane émissions, which do not need to be recovered. A simple oxidizing cover
could be sufficiént to manage this residual émission, with spécial care on rainwater
management.
Because ôf the surface area involved, both méthane and CO2 émissions are compara-
ble with the sum of the émissions of the windrows. This shows that in the case of MBT
prior to landfilling of municipal waste, it is important to take into account both the émis-
sions of the landfill site and of the MBT plant, particularly in this case where the com-
posting material is rather fine and thus poorly aerated, leading to significant émission
rates of méthane.
4.2 Gas composition
in
the compost
As for the surface fluxes, windrows of différent âges and the landfill cell n° 2 were
stud-
ied.
Méthane and CO2 concentrations at 1 m depth are given by the Ecoprobe 5. The
repartition in composition for both the windrows and the landfill cell are given in figures 4
and 5 under box-plot graphs.

Méthane concentrations in soil gas
60
50
40
g
'"g
30
•E
3
o
u
20
4
as
"S
10
4
WindrowA
Windrow
B
Windrow
C LF
Cell2
Figure
4 :
répartition
of
méthane values
in
soil
gas,
windrows
and
landfill
cell
Méthane concentrations are very low (mostly null) in the younger windrows, A and B.
Windrow C, which is older and not turned (thus having less oxygen available for biode-
gratation processes) contains more méthane: mean concentration is 6.9 % v/v, médian
value is 6.2, The higher concentration measured at 1 m depth on windrow C corre-
sponds to the higher méthane surface flux. The landfill cell has a very différent behavior:
méthane concentrations are very dispersed, from 0 to 50 % v/v, the mean and médian
values are différent.
CO2 concentrations show a différent behavior: most values are very similar for the three
différent windrows, and close to 17 % v/v, which correspond to the consumption of the
atmospheric oxygen in aérobic dégradation. Mean and médian values are also very
close,
which confirms that the dégradation processes are the same within the three
windrows. On the contrary, CO2 concentrations at 1 m depth in the landfill cell are very
similar to the méthane concentrations at the same location, indicating that the soil gas is
a mixture of méthane and CO2 in similar proportions. This is the signature of a typical
biogas emitted by the anaerobic dégradation of municipal waste.
Both méthane and CO2 concentration values inside the landfill cell are much dispersed:
one can imagine that the landfilled waste, which is very heterogeneous, has a variable
amount of residual organic matter.

"5
S?
0}
o
CD
O
c
CM
O
O
CO2 concentrations
in
soil
gas
Windrow A Windrow B Windrow
C
LF Cell2
Figure
5 :
repartition
of
CO2 values
in
soil gas, windrows
and
landfill cell
i
.3 Effect of windrow turning on the gas concentrations
he effect of windrow turning has been assessed by CH4 and CO2 in
1-meter
depth
leasurements repeated within 24 hours after the
turn.
Influence
of
windrow turning
25.0
O
n i,
09:30
11:30 13:30 15:30 17:30 19:30 21:30
23:30
01:30
03:30 05:30 07:30
-1~«~CH4-2 ~»ifc»»CH4-3-CO2-1-CO2-CO2-3
Figure
6 :
effect
of
windrow turning
on CH4 and CO2
concentrations
in the
compost

CO2 and CH4 concentrations are considerably iowered just after turning of the windrow.
However, after 24 hours, thèse concentrations are quite the same as before the turning.
This shows that the available oxygen does not last long inside the windrow. The sub-
strate is relatively fine and homogeneous, it is therefore important to turn regularly the
windrows, which is done at least twice a week on this plant.
Since thèse measurements, improvements hâve been brought to the process. The fol-
lowing changes will be made in the composting process itself. In order to obtain an op-
timum biodégradation, organic matter extracted from the municipal waste will be mixed
with crushed végétal residues, and the process will be operated in closed boxes with
forced aération, in order to keep a higher amount of oxygen within the material, helping
the aérobic biodégradation.
4.4 Surface VOC émissions
4.4.1 Composition
As the analytical procédures for identification were différent between the samples from
the windrows and the landfill
cell,
it is not possible to compare exactly ail the VOC pré-
sent in ail the samples. But tendencies can be established. Major results are given in
Table 2.
Concerning the présence of toxic compounds, the major finding is that trichloroethylene
and tetrachloroethylene were never detected on any of the samples. Benzène and
tolu-
ène are, except in one case, never detected on the samples taken on the windrows,
Meanwhile, they are présent on the two samples taken on the landfill cell 2, but at rather
low concentrations. This isalways the case for MSW landfills Their présence in the
landfill gas shows that, or îhe stored waste probably contains some industria! waste, or
they corne from the dégradation of higher molecular weight compounds. More work
would be needed to clear this point. Nevertheless, the low concentration level indicates
that thèse compounds will not be responsible for a health risk.
There are more VOC, and at larger concentrations, in the gas samples taken on the
windrows that on the landfill
cell.
Several compounds such as the terpenes (a-pinene,
limonene) corne from the green waste which is crushed and mixed to the organic matter
of the municipal waste. The other compounds probably corne from the municipal waste,
and are combined with the organic matter which undergoes composting. A-pinene and
limonene on the landfill cell probably corne from the crushed bark used as a temporary
cover.

Table
2 : VOC
composition
of air
samples taken
on the
static flux chamber
Compounds
Ethanol
Pent-1-ene
Pentane
Acétone
Dimethylsulfide
Methyl vinyl cetone
Butan-2-one (MEK)
Butan-2-ol
Benzène
Pentan-2-one
Methyl-3 butanol
n-Heptane
Toluène
Octane
m+p Xylenes
o-Xylene
+ Styrène
a-Pinene
Decane
Limonene
Undecane
Wind.
A, 2
2354
1989
1302
4503
2774
505
1961
Wind.
A, 21
1496
969
481
1158
1000
3
Wind.
B\ 82
356
846
1350
147
124
53
90
289
12266
264
Wind.
C top
1058
569
383
127
30
50
862
Wind.
B,C8
70
1693
1287
6481
5628
283
416
77
51
313
128
2341
Cell2
Can4
32
66
203
33
299
214
1506
50
540
Cell2
Can I
5
15
20
8
14
10
57
46
341
Concentrations
are
given
in
jug/m
4.4.2 Estimation
of
VOC surface fluxes
While
the air was
sampled
on
adsorbent tubes,
the
flammable
gas
concentration
was
monitored
by
the FID
on
some sampling points.
We
used
the
hypothesis that VOC con-
centrations follow the global flammable
gas
concentration
in
order
to
evaluate the VOC
fluxes. Partial results, calculated on one point, are given
in
Table
3.
As
the
measured concentration
of
VOC
in the
static
air
chamber
are low (in the
ng/m3
range),
the
corresponding fluxes
are
nàturally very low. Though thèse fluxes were
not
measured directly, this calculation helps
to
evaluate local
VOC
émissions from
the
composting windrows. This work needs
to be
continued
to get
better précision.

Table
3 :
approximate
VOC
fluxes,
point n° 2 on the
windrow
A
Compound
Ethanol
Acétone
Acétate de methyle
Methyl vinyl cetone
Butan-2-one (MEK)
Butan-2-ol
Acétate d'ethyle
Methyl-3 butanol
Limonene
Flux,
uJ/m2/min
29.4
19.7
5.8
10.7
36.0
21.8
8.4
3.3
8.3
5 Conclusions
The two différent studies on the gaseous émissions of a French MBT plant and the as-
sociated landfill gave the opportunity to compare the relative impacts of the plant and of
the landfill. Due to the fact that a large part of the organic matter is sorted out from the
MSW to undergo composting, the gaseous émissions of the landfill cell are really low-
ered compared to a classical landfill without MBT. In addition, the sorting of the waste is
sufficiently efficient to obtain a high grade compost, which allows its use in amending
agricultural soils.
6 Références
Bour, Zdanevitch, Bri-
and,
Llinas
Mallard,
Zdanevitch,
Pradelle, Frejafon
Acknowledgements
2009 "Estimating méthane émission and oxidation frorn two
tern-
porary covers on landfilling of MBT treated waste". Submit-
ted for présentation to the Sardinia 2009 symposium
2008 « Projet EMISITE: évaluation sur site de différentes métho-
des de mesure des émissions gazeuses
d'une
installation
de compostage » Final report, ADEME ne
0675c0081,
Au-
gust 2008
This work was financed by the French Ministry of Environment and ADEME
Author's address
Dr Isabelle Zdanevitch
INERIS
BP2
F-60550
Verneuil-en-Halatte
Tel:
33+ (0)3 44 55 63 90
E-Mail
:
sabalie.Zdeiievtîcfi@ineri
Web site : www.ineris.fr
@ineris.fr