Transcript 2nd_workshop_Irene.ppt

Anaerobic digestion of crop residues at low
temperatures
Irene Bohn
Department of Biotechnology
LUND UNIVERSITY
Background
Low temperature digestion:
Digestion of manure on the farm
Degradation of low strength wastewaters +
high strength wastewaters
Post digestion or storage
Is low-temperature digestion of crop residues feasible?
Lund University, Department of Biotechnology
Motivation
Nordberg et al. 1998.
Biogaspotential och
framtida anläggningar i
Sverige. Kretslopp och
avfall No 17, JTI, VBB
Viak, Uppsala.
Digested
Available
16
12
8
Total
Crop
residues
Manure
Industrial
wastes
0
Municipal
solid waste
4
Sludge
from
wastewater
treatment
TWh per year
20
?
Lund University, Department of Biotechnology
The Swedish Biogas
Association, 2001. Swedish
Biogas production 2001.
Reactor types
Commercially
available reactor
Modified manure
tank
Cost
High
Low
Capacity vs. volume
High
Low
Heat loss
Low
High
Lund University, Department of Biotechnology
Digester set-up
Inoculum: Digested cow manure from
unheated anaerobic digestion tank
Total volume:2.2 m3
Active volume: 1.8m3
Kg
Substrate: Ensiled
sugar beet tops and
straw
4.5 % volatile solids in
ready substrate
Lund University, Department of Biotechnology
Effect of temperature on yield
0.50
3
-1
Methane yield (m CH4 kg VS )
Loading rate: 0.5 kg VS m-3 d-1 and hydraulic retention time: 90 days
0.40
0.30
0.20
0.10
0.00
10
15
20
25
30
35
40
Temperature (°C)
Methane yield decreased with decreasing temperature but no
VFAs accumulated at the high hydraulic retention time
Hydrolysis was limiting the methane yield
Lund University, Department of Biotechnology
Yield and rate
Methane yield
m 3 CH4/kg VS
0.45
0.40
15°C
0.35
30°C
0.30
0.25
0.20
0.15
0.10
0.05
0.00
0.5
1.0
1.6
2.0
3.3
4.1
3.3
4.1
OLR (kg VS/m 3,day)
1.20
15°C
1.00
m 3 CH4/m 3,day
Methane
production rate
30°C
0.80
0.60
0.40
0.20
0.00
0.5
1.0
1.6
2.0
OLR (kg VS/m 3,day)
Lund University, Department of Biotechnology
Energy-balance
3500
3000
3000
2500
2500
0
1
OLR (kgVS/m3,day)
Lund University, Department of Biotechnology
1.6
0.5
1
OLR (kgVS/m3,day)
Input
0
Input
500
Output
500
Input
1000
Output
1000
Input
1500
Output
1500
Output
2000
Input
2000
Output
kWh/tVS
3500
0.5
30C
4000
Output
15C
4000
kWh/tVS
Heating-reactor
Substrate
Gas
Input
Stirrer
Heating-substrate
3.1
Energy-balance
3500
3000
3000
2500
2500
0
1
1.6
OLR (kgVS/m3,day)
Lund University, Department of Biotechnology
0.5
1
OLR (kgVS/m3,day)
Input
0
Input
500
Output
500
Input
1000
Output
1000
Input
1500
Output
1500
Output
2000
Input
2000
Output
kWh/tVS
3500
0.5
30C
4000
Output
15C
4000
kWh/tVS
Heating-reactor
Substrate
Gas
Input
Stirrer
Heating-substrate
3.1
Yield obtained in batch-experiments
3
m CH4/kgVS
0.50
0.40
15°C
30°C
21
15
22
23
23
28
0.30
0.20
0.10
0.00
30
37
Temperature (°C)
•The effect of temperature on yield was lower for the
sludge adapted to 15C
•The yield in the batch-experiment was higher than in
the reactor
Lund University, Department of Biotechnology
Accumulation of acetate and propionate
Results from continuously stirred pilot scale
reactors fed with beet top slurry
Acetic acid
Butyric acid
Propionic acid
Valeric acid
OLR in
kg VS m-3 day-1
3.5
OLR = 0
OLR = 1
OLR = 2
Concentration of volatile fatty acids
-1
(g l )
Concentration of volatile fatty acids
(g l-1)
OLR = 4
OLR = 1.5
3.0
2.5
2.0
1.5
1.0
0.5
0.0
20-Mar
9-May
28-Jun
17-Aug
15 C
Lund University, Department of Biotechnology
6-Oct
25-Nov
3.5
OLR = 1
OLR = 2
OLR = 3
3
OLR =
0.5
2.5
2
1.5
1
0.5
0
20-Mar 9-May 28-Jun 17-Aug
30 C
6-Oct
25-Nov 14-Jan
Packed-bed methane-filters
Inoculum: Sludge from
pilot-scale reactors or
lake sediment
Substrate: Leachate from
ley-crop silage
Lund University, Department of Biotechnology
Results from methane-filters
Acetic acid
15 C
Propionic acid
0.57±0.13
0.8
0.39±0.08
Concentration (g l -1)
During
start-up:
1.0
1.0
Concentration (g l-1)
OLR in
-1
kgCOD m-3 day
10 C
0.6
0.4
0.2
25
50
75
Time (days)
0.6
0.4
0.2
25
100
0.81±0.08
1.0
0.50±0.08
0.6
0.4
0.2
Lund University, Department of Biotechnology
75
Time (days)
100
0.80±0.08
1.03±0.08
0.8
0.0
16-Aug 15-Sep
50
1.0
Concentration (g l -1)
Concentration (g l -1)
0.43±0.05
0.0
0.0
After
1 year:
0.52±0.09
0.8
15-Oct
14-Nov 14-Dec
0.8
1.00±0.08
0.49±0.06
0.6
0.4
0.2
0.0
16-Aug 15-Sep 15-Oct 14-Nov 14-Dec
Results from methane-filters
15 C
10 C
15
15
100
6
40
3
20
0
0
0
1
2
3
4
-1
80
9
60
6
40
3
20
0
0
5
0
-1
1
2
3
-1
OLR (gCOD l d )
(% of inlet COD)
60
Undegraded VFA
(% of inlet COD)
9
(% of inlet COD)
80
100
12
CH4-COD produced
Reactor sludge
12
CH4-COD produced
Undegraded VFA
(% of inlet COD)
Acetate
Propionate
other VFAs
Unidentified
CH4 produced
4
-1
OLR (gCOD l d )
15
15
120
12
100
Lake sediment
6
40
3
20
0
0
0
1
2
3
-1
-1
OLR (gCOD l d )
Lund University, Department of Biotechnology
4
80
9
60
6
40
3
20
0
0
0
1
2
3
4
-1
-1
OLR (gCOD l d )
5
(% of inlet COD)
60
CH4-COD produced
9
Undegraded VFA
(% of inlet COD)
80
(% of inlet COD)
12
CH4-COD produced
Undegraded VFA
(% of inlet COD)
100
0.5
0.8
Lund University, Department of Biotechnology
1.0
1.5
OLR (kg COD/m3,day)
2.0
3.0
15°C-R
15°C-L
10°C-R
10°C-L
15°C-R
15°C-L
10°C-R
10°C-L
15°C-R
15°C-L
10°C-R
10°C-L
15°C-R
15°C-L
10°C-R
10°C-L
15°C-R
15°C-L
10°C-R
10°C-L
15°C-R
15°C-L
10°C-R
10°C-L
15°C-R
15°C-L
10°C-R
10°C-L
COD as % of inlet
Results from methane-filters
140
120
100
Unidentified
80
Other VFAs
Propionate
60
40
Acetate
Methane
20
0
4.5
Conclusions
Yield from solid substrate decreases with
temperature
Feasibility of low temperature digestion
depends on
insulation of the reactor
utilization of the capacity
High yield is obtained for soluble substrate
at 10°C
Lund University, Department of Biotechnology
Acknowledgements
Financiation:
The Energy Supply Comittee of Southern Sweden (DESS)
The Swedish Research Council (VR)
The Swedish Energy Agency (STEM)
Co-authors:
Bo Mattiasson
Lovisa Björnsson
Andreas Bengtsson
Melvice Bessem Ayuk
Lund University, Department of Biotechnology