Static and dynamic respirometric indexes – Italian
research and studies
1Adani
F., 1Ubbiali C., 1Tambone F., 1Scaglia B., 2Centemero M and 1Genevini P.L.
1Dipartimeno
di Produzione Vegetale – Università degli Studi di Milano, Via Celoria 2,
20133, Milano, Italy
2 Scuola Agraria del Parco di Monza, Viale Cavriga 5, Monza, Italy
Web site:
http://users.unimi.it/~ricicla/ricicla.htm
Respirometric methods are used for biological stability
determination
CO2 production : these methods are inexpensive, but do not differentiate between
anaerobic and aerobic CO2, moreover the degree of oxidation of the organic matter
affects O2 uptake per mole of the CO2 produced (e.g. SOLVITA)
O2 uptake: is preferred for respirometric purpose.
Adani and Tambone, (1998) suggested the following classification:
STATIC METHODS:
- Solid state (e.g. sapromat, The U.S. Composting Council
methods; ASTM, 1992; DSOUR)
- Liquid state (e.g. SOUR)
DYNAMIC METHODS:
- adiabatic (DiProVe)
- pre-set temperature (ASTM, 1996)
Respirometric methods:
O2 uptake
Dynamic method
Static method: solid state
Static methods
Solid state (DSOUR)
êsystematic errors due to the impossibility to measure biomass free air space (Es. UNI
10780 method);
ê passive oxygen diffusion
caused undersize of the respirometric activity;
Liquid state (SOUR)
êlow amount of sample;
ê measure made in different condition respect solid state fermentation);
ê methods is influenced by water soluble fraction
Dynamic method
DiProVe method (Adani 1993)
American Standard Testing Material method (ASTM, 1996)
Negative aspects:
more time for analysis respect SOUR (2 days) but similar to DSOUR;
higher price respect other methods
Positive aspects:
No limits to oxygen diffusion into the biomass (aeration)
higher amount of sample used (from some grams to 50 kg);
determination does not requires the calculation of free air space;
Analytical condition similar to the full scale process
Measure made under adiabatic condition such as in a full scale process (temperature
as additional parameters)
What is it biological stability in Italy ?
Current opinion: biological activity measured by dynamic
respiration index below 1000 mg O2 kg VS-1 h-1
such as suggested also by 2nd Draft of Biological treatment
of Biowaste of EC.
This mean, from a practical point of view to
incentive door to door separate collection or
to treat biologically MSW for 10-30 days
under optimal condition !!!!!!!
6000
BT-1
BT-2
-1
-1
DRI (mg O2 kg VS h )
5000
BT-3
BS-1
4000
BS-2
BS-3
3000
2000
1000
0
Inizio p rocesso
M età p rocesso
process
Fine Processo
15-20 (d)
Putrescible reduction assuming 1000 as stability index
70-80 % on a relative basis and of about 90 % of an absolute basis !!!!!
RW from
door to door
collection
Waste from
road
container
Go
de
C.
ga
S.
U
m
be
rt
o
M
ist
o
Sp
in
ea
Ro
vi
go
Ze
vi
o
B.
Po
le
sin
e
Ve
ro
na
Vi
go
da
rz
er
e
Vi
lla
no
va
C.
S.
M
ar
t in
V.
o
de
lC
on
te
-1
-1
DRI (mg O2 kg VS h )
1600
1400
1200
1000*
1000
800
600
400
200
0
Matrix
RW from
double road
container
OM content in the residual waste in Provincia di Milano (Italy)(Favoino, 2001)
A lb a ira t e
A lb ia t e
A re s e
B ia s s o n o
B ru g h e rio
B u c c in a s c o
C a s ta no P .
C in is e llo B .
C o lo g n o M .
C o rb e t t a
D e s io
La in a t e
M e le g n a n o
M is in t o
M o nza
N o v a te M .
P a d e rn o D .
R o s a te
T re z z o s / A
T ru c a z z a n o
Va re d o
Villa s a n t a
Vim e rc a t e
0%
10%
20%
Fonte: Provincia di Milano 1998
30%
40%
50%
60%
OM in residual waste vs DRI
(Collaboration with Environmental National Agency)
DRI vs Organic fraction
R 2 = 0.92, p< 0.01
90
80
Organic fraction (%)
70
60
50
40
30
2020
10
0
0
1000
2000
DRI (mg O
2
kg VS
-1
4000
h -1 )
6000
Therefore we fixed biological stability indicating a
number and a method
Nevertheless many other methods are proposed in the
literature
Therefore it could be useful to give corresponding
value for biological stability indication
Comparison tests between different methods; we
tested
- Dynamic Respiration Index (DiProVe methods, Scaglia et al., 2000) (used in Italy)
- SOUR (Stentiford and Lasaridi, 1998) (used in UK)
- SRI (DiProVe methods; Scaglia et al., 2000) (used in Italy, USA)
- Sapromat (Binner and Zach, 1998) (used in Germany, Austria)
- Solvita (by Woods end® Research, Mt vernon, Me –USA) (used in USA)
National Environmental Agency in collaboration with
University of Milano and University of Padova
18 organic matrices of different origin and characteristics
- 3 MBT processes (15-20 days) (BT) [beginning (b), meddle (m) and end (e)]
- 3 biostabiliztion-biodrying processes (12 days) (BS) [beginning (b) end (e)]
- 3 sample from RDF production (Ø < 20 mm) (BT)
Volatile solid contents, respirometric indeces, DOC, hydrophilic-DOC and hydrophobic-DOC,
determined for organic matrices studied (from Adani et al., 2002 and Cossu et al., 2001)
Respiration index (mg O2 ⋅ kg SV-1 ⋅ h-1)
Dissolved Organic Carbon fractions
VS
g kg-1
DRI
SRI
SOUR
SAPROMAT
Hydrophilic
DOCg kgVS-1
Hydrophobic
DOCg kgVS-1
DOC
g kgVS-1
BT-1-I
510 ± 11.3
4,126
1.182
16,446
98,300
33.3
8.8
4.21
BT-1-m
397 ± 1.5
2,529
532
10,850
52,700
13.9
25.5
3.94
BT-1-f
400 ± 19.4
780
366
7,117
50,100
10
5
1.50
BT-2-I
687 ± 4.4
5,148
1.326
14,997
104,500
38.6
17.3
5.59
BT-2-m
628 ± 6.7
1,300
654
12,413
84,300
29.9
55.5
8.54
BT-2-f
625 ± 15.9
985
502
8,308
72,200
25.4
36.1
6.15
BT-3-I
781 ± 10.3
3,255
529
18,980
78,800
134.9
39.1
14.40
BT-3-m
612 ± 16
2,349
595
n.d.
55,600
51.2
35.1
8.63
BT-3-f
637 ± 22.3
918
n.d.
13,225
57,000
34.3
23.5
5.78
BS-1-I
875 ± 22.7
1,808
913
5,570
85,500
18.2
54.8
7.30
BS-1-f
863 ± 18.9
692
205
2,935
58,500
11.7
10.3
2.20
BS-2-I
905 ± 34.3
1,746
790
5,698
73,100
40.8
45.3
8.61
BS-2-f
756 ± 41
595
178
2,940
19,400
7.8
10.7
1.85
BS-3-I
732 ± 45.6
1,971
485
4,725
32,200
13.6
4.9
1.85
BS-3-f
779 ± 2.4
582
99
n.d.
15,500
5.1
2.5
0.76
ST-1
449 ± 11.3
2,272
487
10,215
35,100
n.d.
n.d.
n.d.
ST-2
466 ± 24.9
889
294
6,338
27,900
n.d.
n.d.
n.d.
ST-3
445 ± 17.5
1,447
944
8,870
27,900
n.d.
n.d.
n.d.
Sample
Correlation matrix of respirometric determination (DRI,
SRI, SOUR and Sapromat) and dissolved organic carbon
fractions (from Adani et al., 2002 and Cossu et al., 2001)
DRI
SRI
SOUR
SAPROMAT
DOC
DOC
hydrophilic
DRI
1
SRI
0.78
1
SOUR
0.70
0.55
1
SAPROMAT
0.65
0.72
0.57
1
DOC
0.36
0.31
0.60
0.53
1
DOC
hydrophilic
0.46
0.05
0.69
0.42
0.91
1
0.14
0.30
0.14
0.52
0.72
n.s.
†DOC
hydrophobic
†
DOC hydrophilic = (DOC – DOC hydrophilic)
DOC
hydrophobic
1
Biological stability limits corresponding to
DRI = 1000 mg O2 kg VS-1h-1 ,
calculated for different method.
DRI
SRI
SAPROMAT
SOUR
(mg O2 kg VS-1h-1)
(mg O2 kg VS-1h-1)
(mg O2 kg VS-1 96h-1)
(mg O2 kg VS-1h-1)
1000
395
45,393
7,038
BT 409
BS 340
BT 59,570 (?)
BS 41,555 (?)
BT 8,310(?)
BS 3,611(?)
Equation and fit parameters for DRI versus SRI values
45
DRI = 2SRI - 121
R2=0.77 p< 0.01 (Scaglia et al, 2000)
17
DRI=1.6 SRI + 252
R2 =0.54 p< 0.05
(Seccafieno, 2002)
21
DRI=1.63SRI-290
R2=0.99 p< 0.01
(Adani et al., 2001)
† SRIs= static respiration index by sapromat method
Scaglia et al., (2000), found
413
Seccafieno (2002), found
467
Adani et al., (2001) found
435
As correspondig to 1000
Dynamic RI vs Static RI regression for 74 matrix studied
1000
~ 440
SRI =
DRI - 121
2
Regression for SOLVITA versus DRI
SOLVITA-1=0.49+-36.45/x
R2=0.99; p < 0.01
9
SOLVITA (sovlita units)
8
7
For DRI > 200-300 solvita is not able
to discriminate biological stability
6
5
4
3
2
1
0
1000
200
2000
3000
DRI (mg O2 kg VS-1h-1)
4000
5000
Comparison methods: conclusion
Results confirm that static methods give lower value than
dynamic because of the oxygen diffusion limits; anyway a
corresponding value could be proposed above all for stable
samples because with stability, differences became less.
More studied needed
SOUR presents some advantage respect solid state condition but,
it is affected by water soluble fraction content and does not
reflect field condition, contrarily to the dynamic solid state
approach.
More studied needed.
Solvita: it is not useful for stability determination because of low
resolution limits for DRI < 200-300. Anyway it could be used as
method for substrate characterization or for compost that
present high degree of evolution
Biological Stability: limits suggested
Static method (DSOUR)
500 mg kg VS-1 h-1 (e.g.The U.S. Composting Council,1997; Iannotti et al., 1993,
USA)
600 mg kg VS-1 h-1 (e.g.Regione Veneto,I)
5000 mg kg TS-1 96h-1 (Sapromat, German and Austrian indication) (cumulated of 96
h)
10000 mg kg TS-1 96h-1 (2nd Draft Biowaste treatemnt EU)
Dynamic methods (DRI)
1000 mg kg VS-1 h-1 (DiProVe, Regione Lombardia, Italy) (2nd Draft Biowaste
treatemnt EU)
(mean of 24 h);
35000-50.0000 mg kg VS-1 96 h-1 (ASTM, 1996)
Different values are proposed for biological stability; this
generates a big confusion. Why ??
1. Sometimes rules proposed a specific method adopting limit for the biological
stability definition, derived from another methods (no adequate scientific
support !!!)
(e.g. Italy proposed UNI methods performed at 20 °C, adopting values coming
from SRI methods (DiProVe) performed at higher temperature)
2. Different result expressions can give erroneous interpretation of the value
proposed (e.g. maximum values or mean of 24 hours; data refereed to VS or TS))
3. Different interpretation of what it is biological stability (e.g. German
and Austria indicate very low limits for biological stability; this mean
biological treatments of 4-6 moths, on the contrary Italy indicate
processes of 15-30 days)
Potential biogas production vs treatment time derived from
respiration index adopted to indicate the biological stability:
Germany (D) and Italy (I)
Residual Biogas
(kg TS-1)
Biogas reduction
(%)
Treatment time
20 (D)
90-95 (D)
2-6 month (D)
60-80 (I)
75-85 (I)
15-40 days (I)
Biological stability = 5000 mg kg ST 96 h-1 (D)
Biological stability = 1000 mg O2 kg VS-1 h-1 (I)
DRI Research
Reproducibility of the method
Result expression
Microbial growth during analysis
Collabaoration between
DiProVe – University of Milano (I)
National Institute of Health (I)
Accuracy (trueness and precision) by ISO 5725-2 (1994)
First phase: 4 laboratories Including private and public laboratories
Second phase: 7 laboratory Including private and public laboratories
End of work : december 2002
Result obtained for DRI determination operated by two
laboratories (A and B, from Seccafieno, 2001; other
samples from Adani and Genevini, 2001)
Sample
A
B
BT-i-1
BT-i-3
BT-f-3
ST-1
DRI
(mg O2 kg VS-1 h-1)
Lab 1
2430
Lab 2
2373
Lab 1
2375
Lab 2
2517
Lab 1
2529
Lab 2
2693
Lab 1
3255
Lab 2
3262
Lab 1
918
Lab 2
823
Lab 1
2272
Lab 2
2407
Mean
STD
Variation
coefficient
2401
40
1.7
2446
100
4.1
2611
116
4.44
3258
4.95
0.15
870.5
67.18
7.71
2339.5
95.46
4.1
Result obtained for SRI determination operated by two
laboratories (A and B, from Seccafieno, 2001; other
samples from Adani and Genevini, 2001)
Sample
BT–i-1
BT–i-3
ST-1
SRI
(mg O2 kg VS-1 h-1)
Lab 1
532
Lab 2
540
Lab 1
529
Lab 2
421
Lab 1
487
Lab 2
373
Mean
STD
Variation
coefficient
536
5.66
1.05
475
76.38
16.08
430
80.61
18.75
Result expression
⊇ maximum value
⊇ mean of 24 hours with intense microbial activity
⊇ cumulated 96 h
⊇cumulated of 96 h, no lag-phase
UNI, SOUR (I, UK)
DiProVe (I)
Sapromat, AT4 (D)
ASTM (USA)
DRI regressions found between DRI calculated in different way
a vs b
a vs c
160000
3000
2500
140000
R2 = 0,96
p<0,01
2000
R2 = 0,96
p>0,01
120000
100000
80000
1500
60000
1000
40000
500
20000
0
0
0
500
1000
1500
2000
2500
3000
0
1000
a vs d
2000
1800
1600
1400
1200
1000
800
600
400
200
0
R2 = 0,92
p<0,01
120000
100000
80000
60000
40000
20000
0
0
(a)
(b)
(c)
(d)
(e)
500
1000
1500
3000
a vs e
160000
140000
2000
2000
2500
3000
R 2 = 0,95
p<0,01
0
1000
2000
3000
mean of the 12 highest values measured during the test (mgO2*kg VS-1*h-1) (Di.Pro.Ve. method)
maximum DRI value registered (mgO2*kg VS-1*h-1)
cumulates of DRI on a 96 hours basis (mgO2*kg VS-1*96 h-1)
cumulates of DRI on a 96 hours basis without lag phase (mgO2*kg VS-1* n.h-1)
cumulates of DRI on a 96 hours basis phase normalized respect time (mgO2*kg VS-1*h-1)
Results expression
- Maximum value is one !!!!. Analysis takes about 47 h
- Cumulative approach takes long time (96 h) !!
- Mean of 24 hour is a compromise; analysis takes about 58 h
Microbial growth
RI
Microbial growth
ln(N/N0)=kt
DRI=DRI0 ekt
k = specific growth (h-1)
Specific growth (k h-1) duplication time (h) for different organic matrix
Sample
DRI2
DRI1
T2-T1
K
Td
1
2438
87
31
0.11
30.861
2
2202
203
36
0.07
36.12
3
2526
818
13
0.09
12.96
4
1013
434
21
0.04
21.191
5
1071
126
33
0.07
32.924
6
1503
212
15
0.13
14.951
7
927
63
33
0.08
33.195
8
895
179
18
0.09
18.084
9
1401
340
20
0.07
19.944
10
1043
596
7
0.08
6.9952
11
1059
177
25
0.07
24.846
12
1544
185
50
0.04
50.518
13
1542
201
45
0.05
45.278
14
801
372
53
0.02
51.131
15
506
149
26
0.05
26.013
16
1545
616
37
0.03
36.781
17
742
483
11
0.04
11.009
TABLE 4.
k and td value calculated for composts
k
(h-1)
td
(h)
Biost.
0.080
9.33
Comp.
0.040
21.1
Differences depended by substrate availability (hydrolysis) that is a
function of the material typology e.g. linocellulosic or food waste
Practical use
Biomass characterization
Plant Airflow-rate
Organic matter content in the residual waste
Residual Biogas production in landfill
Odor production
Biomass characterization
Typology
DRI (mg O2 kg VS-1 h-1)
Organic matter from mechanical separation
of the MSW (Ø < 50-60 mm)
2000-2800
Separate collection (OM= 80-85 % p/p)
4000-5000
MSW Biodrid/biostabilized
(10-12 days)
500-700
Stabilized OM from machanical separation
(15-30 days)
800-1200
OM sep. collection/lignocellulosic
(2:1 p/p)
2500-3500
Evolved compost (OMEI > 0.6)
200-500
MSW landfilled (age : 20 years)
70-150
Residual waste from road containers
(dry + wet fractions= MSW)
1000-1300
Residual waste from double road containers
(dry fractions)
800-1000
Residual waste from door separate collection
(dry fractions)
300-400
DRI vs airflow-rate
Airflow-rate can be calculated as (Keener et al., 1997)
q (θ
θ) = { [(1-β
β) / ρ] x [( k1 hc )/ (HAO-HAI)] x e-kθθ }
q (θ
θ) = airflow rate (m3 / kg fraz. compostabile * giorno);
ρ = air density (kg/m3);
hc = combustion heat of degradable OM, es. (20.000 kJ /kg),
(HAO-HAI) = entalpic content
1-β
β = degradable fraction
k = reaction rate (d-1)
Degradability = k (1-β
β) (Adani, 1999)
180
Flusso (mc / t s.s.)
160
140
120
100
80
y = 1690,3x - 4,0824
R2 = 0,9369
60
40
20
0
0,000
0,020
0,040
0,060
0,080
k(1-beta)
k (1-β) vs airflow rate
0,100
0,120
Airflow rate (mctss-1) vs total solids (kg)
O2= 14 %)
2
y=0.36724255+0.0065667832 x
r2
=0.800461288 DF Adj2 r
=0.756119352 FitStdErr=5.06697223 Fstat=40.1155886
45
40
airflowrate3/t(m
ss)
35
30
25
20
15
10
5
0
0
2000
4000
DRI (mgO2 * kg SV-1 * h-1 )
6000
Airflow rate (mctss-1) vs volatile solids (kg)
2 O2= 14 %)
y==0.36724255 +0.0065667832 x
r2
=0.986052559 DF Adj2 r
=0.982953128 FitStdErr=1.94592084 Fstat=706.977424
60
40
3
Airflow-rate
(m
/t SV)
50
30
20
10
0
0
2000
4000
DRI (mgO2 * kg VS-1 * h-1 )
6000
OM in residual waste vs DRI
(Collaboration with Environmental National Agency)
DRI vs Organic fraction
R 2 = 0.92, p< 0.01
90
80
Organic fraction (%)
70
60
50
40
30
2020
10
0
0
1000
2000
DRI (mg O
2
kg VS
-1
4000
h -1 )
6000
DRI vs BIOGAS
Pozzo
depth [m]
depth [m]
Age of MSW
1K
2K
3K
1B
2B
3B
4B
5B
6B
7B
1C
2C
3C
4C
5C
6C
7C
25,00
25,00
20,00
17,30
15,30
16,60
13,40
13,90
13,40
14,50
28,35
30,00
28,80
27,15
27,95
29,55
29,55
n.d.
from 1987 till 1989
from 1984 till 1987
from 1972 till 1982
from 1990 till 1991
from 1990 till 1991
from 1990 till 1991
from 1989 till 1990
from 1989 till 1990
from 1989 till 1990
from 1989 till 1990
from 1991 till 1993
from 1991 till 1993
from 1991 till 1993
from 1991 till 1993
from 1991 till 1993
from 1991 till 1993
from 1991 till 1993
n.d.
n.d.
16,35
14,55
15,80
13,40
14,10
13,50
14,30
21,55
16,00
24,85
25,25
22,20
27,15
20,65
Place
DRI
mean
[mgO2/(kgVS*h)]
DRI limits of Regione
Lombardia
[mgO2/(kgVS*h)]
comments
Ka
Kb
B
Ca
Cb
208
166
117
117
161
500
500
500
500
500
stable
stable
stable
stable
stable
Es. Coll. DiProVe- Dip. Ing. Sanitaria Ambientale-Fac. di Ingegneria- Univ. Brescia
DRI vs produzione residua di biogas
Test for residual biogas production shows many negative aspects:
- long time (minimum 30 days);
- analytical limits for unstable matrices (DRI < 500 mg O2 VS-1 h-1) (Adani et al., 2000)
45
40
Biogas (l/kgST)
35
30
25
20
15
10
5
0
33
53
73
93
113
133
153
173
IRD (O2mg*kgST-1*h-1)
DRI vs biogas production (da Gotti et al., 2001).
DRI vs odor
ln l im o n e n e = 6 .3 + - 3 1 2 1 /D R I
R
2
= 0 .9 9 ; p < 0 .0 1
1 50
Limonene
1 25
Reduction 85 %
6
Limonene (area 10 )
1 00
7 5
5 0
2 5
0
0
50 0
1 00 0
1 50 0
D R I ( m g O2 k g V S - 1 h - 1 )
20 0 0
25 00
2000
2500
ln t e r p e n s = 6 .4 2 + - 3 3 4 9 /D R I
R
2
= 0 .9 9 , p < 0 .0 1
150
5
Terpene (area 10 )
125
Terpens
) 100
Reduction 85 %
75
50
25
0
0
500
1000
1500
D R I ( m g O2 k g V S- 1 h - 1 )
Table 2. Do se and mo dalit y o f use of different classes o f co mpost
Tipology
Dose
Modalità
Fresh compost
agronomic dose
free commerce
Compost of quality 1
ibidem
ibidem
Compost of quality 2
100 q.li/ha dm * year
authorization need
Compost of low quality
without limits
ibidem
Table 3. Compost quality criteria
Tipology
Fresh compost (♦)
Compost of quality 1 (*)
Ni
Pb
Cu
Cd
Cr tot
Hg
(±)
(‡)
<1
<70
<50
<100
<100
<1
≤1.5
≤150
≤100
≤140
≤150
≤1.5
Zn
Phytotox
DRI
OMEI
(‡‡)
(‡‡)
(‡‡)
<300
able
<1000
-
≤500
able
<500
>0.6
Compost of quality 2 :
- for agricultural use
1.6-4 151-300 101-150 141-300 151-400 1.5-5 501-1500
able
<500
>0.6
- for other use (♠)
1.6-4
able
<1000
-
-
<1000
-
Compost of low quality
(♦)
(±)
(‡‡)
(*)
(‡)
(♠)
>4
151-300 101-150 141-300 151-400 1.5-5 501-1500
>300
>150
>300
>400
>5
>1500
For this class of compost the absence of phatogen is required; fecal indicator such should be determined: fecal
coliform = MPN/ g d.m. <10000; Salmonella MPN/ g d.m.<100; helminth eggs absent; live seed absent.
Heavy metal determination methods: Test methods for the examination of composting and compost-1st
Edition december 1997- US composting Council 44224-Montgomery Avenue Suite 102- Bethesda Maryland
20814 USA.
Dynamic Respiration Index, OMEI, phytotox method: - Compost e Agricoltura” Ed. Lombardia per
l’Ambiente – Milano.
For use in container media hydrological characteristic must be determined.
For fresh compost and compost of quality 2, Cr6+ < 0.5 mg kg-1 d. m.
Compost of this class could be use only on degraded site (e.g. quarry).