innovative methods for biogas upgrading by the addition of
TRANSCRIPT
Innovative methods for biogas upgrading by the addition
of hydrogen to anaerobic reactor
Gang Luo, Postdoc
Irini Angelidaki, Professor
BioEnergy Research Group
2
Biogas production and utilization
• Biogas can be produced from all kinds of organic wastes/residues
• Biogas utilization as vehicle fuel or natural gas is very promising
Organic
substrate
Digested
substrate
Biogas
50-70% CH4
30-50% CO2
Anaerobic reactor
Electricity
Heat
CH4>95%
Vehicle fuels
Natural gas
Organic
substrate
Digested
substrate
Biogas
50-70% CH4
30-50% CO2
Anaerobic reactor
Organic
substrate
Digested
substrate
Biogas
50-70% CH4
30-50% CO2
Anaerobic reactor
Electricity
Organic
substrate
Digested
substrate
Biogas
50-70% CH4
30-50% CO2
Anaerobic reactor
Heat
Electricity
Organic
substrate
Digested
substrate
Biogas
50-70% CH4
30-50% CO2
Anaerobic reactor
CH4>95%
Vehicle fuels
CH4>95% CH4>95%
Vehicle fuels
CH4>95%
Natural gas
Vehicle fuels
CH4>95%
Natural gas
Vehicle fuels
CH4>95%
Natural gas
Vehicle fuels
CH4>95%
Natural gas
Vehicle fuels
CH4>95% CH4>95%
Vehicle fuels
CH4>95%
Natural gas
Vehicle fuels
CH4>95%
Natural gas
Vehicle fuels
CH4>95%
Natural gas
Vehicle fuels
CH4>95%
Natural gas
Vehicle fuels
CH4>95%
3
Biogas upgrading
• Current industrial biogas upgrading technology
– Chemical absorption
– Pressure swing adsorption
– High pressure water scrubbing
– Membrane separation
• Physical and chemical technologies
• High pressure or chemical addition
• 0.15-0.28 Euro/m3 biogas treated
• 0.1%-15% methane loss
An alternative method for biogas upgrading is needed!
4
Biological method for biogas upgrading
• CO2 together with H2 could be used by hydrogenotrophic methanogens for
methane production.
4H2+CO2=CH4+2H2O
• In Denmark, H2 could be obtained by electrolysis of water using the
surplus electricity from wind mills.
Water
electrolysis H2 CO2, CH4
Wind mill Biogas reactor
CH4
5
• Increased CH4 production and no CH4 loss
• Minimal chemical and energy requirments
• Storage of wind power as CH4
– Wind power is not stable
– Water electrolysis for H2 production
– High cost for H2 storage and transportation
– CH4 is easier to be stored and distribution
Advantages
6
Concept 1: In-situ biogas upgrading
• Very simple process for biogas upgrading
Organic wastes
Biogas with high
CH4 content
Effluent
Water
Electrolysis
H2
Biogas reactor
7
Manure as substrate
8
Manure as substrate
• The addition of H2 significantly decreased the CO2 concentration
• pH was increase upon the addition of H2
• Around 80% H2 was consumed, but still some left in the biogas
50 55 60 65 70 75 80 850
400
800
1200
1600
2000
Met
han
e pro
du
ctio
n (
ml/
d)
Time (d)
Reactor with hydrogen
Control
Reactor with H2 Control
pH 8.3±0.1 8.0±0.1
Acetate (mM) 24±0.93 7.2±0.73
CH4 (%) 65±3.3 62±2.5
H2(%) 20±2.5 0
CO2 (%) 15±2.1 38±3.2
9
Increase of pH to higher than 8.0
Solutions: Co-digestion
On-line pH control
Technical Challenge 1
Parameters Cattle manure Whey
pH 7.15±0.11 4.33±0.13
COD (g/L) 40.4±2.3 150±5.7
TKN (mg/L) 1092±210 460±78
NH4+-N (mg/L) 540±56 89±25
• Whey is a kind of byproduct from cheese factory
• Whey has lower pH and contains lower amount of nitrogen
10
0 20 40 60 800
400
800
1200
1600
2000
Time (d)
Bio
gas
pro
du
ctio
n r
ate
(mL
/L/d
)
0
10
20
30
40
50
VF
A co
ncen
tration
(mM
)
0 20 40 60 805
6
7
8
Time (d)
pH
40
60
80
Bio
gas co
mp
ositio
n (%
)
0 20 40 60 805
6
7
8
pH
CH4
H2
CO2
Time (d)
pH
0
20
40
60
80
100
Bio
gas co
mp
ositio
n (%
)
0 20 40 60 800
400
800
1200
1600
2000
Biogas
Acetate
Propionate
Butyrate
Valerate
Time (d)
Bio
gas
pro
du
ctio
n r
ate
(mL
/L/d
)
0
15
30
45
VF
A co
ncen
tration
(mM
)
Technical Challenge 1
Reactor with H2 Control Reactor
pH 7.8
68% CH4
8% CO2
24% H2
pH 7.3
55% CH4
45% CO2
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H2
Liquid
Liquid
Membrane module
H2
Hollow Fiber
Membrane
Influent Effluent H2
Biogas
Membrane
module
Technical Challenge 2
Lower gas-liquid mass transfer rate of hydrogen
Solutions: Hollow fiber membrane
12
• Bubbleless diffusion of
hydrogen could be
achieved by using hollow
fiber membrane
• There was no detectable
H2 left in the produced
biogas, and CH4 content
was as high as 90-95%
Technical Challenge 2
13
• In-situ biogas upgrading in UASB
• Microbial community characterization
On-going Research
Influent
Effluent H2
Biogas
Liquid
recirculation
Membrane
module
UASB
14
Concept 2: ex-situ biogas upgrading
Organic wastes Effluent
Water
Electrolysis
Biogas reactor
H2
Biogas
Biogas with high
CH4 content
Mixed
hydrogenotrophic
culture
15
• Enrichment at thermophilic temperature (55oC) resulted in CO2 and H2 bioconversion rate of 320
mL CH4/(gVSS·h), which was more than 60% higher than that under mesophilic temperature
(37oC).
Enriched mixed cultures
Mesophilic Thermophilic
16
Reactor performance
• Higher CH4 (90-95%) content could be achieved with lower gas retention time
0
5
10
15
20
25
0 20 40 60 80 100 120 1400
20
40
60
80
100
1h
2h
Gas
flo
w r
ate
(L/(
Ld
))
Gas loading rate
Biogas production rate
4h
Upgra
ded
Gas
Com
posi
tion (
%)
Time (d)
CH4
H2
CO2
17
• Innovative methods for biogas upgrading has been developed
• pH increase and gas-liquid mass-transfer are the two main challenges for in-situ
biogas upgrading
• CH4 content between 90-95% could be obtained by co-digestion of manure and
whey when using hollow fiber membrane for H2 diffusion
• For ex-situ biogas upgrading, thermophilic enriched culture is more effective
• CH4 content as high as 95% could be obtained under lower gas retention time (2h)
• Surplus electricity from wind mill could be stored as biomethane in this process
Conclusions
18
1 Funding from Danish Agency for Science, Technology and Innovation
An innovative process for simultaneous utilization of hydrogen and in-situ biogas upgrading, 3,240,000 DKK
2 Publication
Gang Luo, Sara Johansson, Kanokwan Boe, Li Xie, Qi Zhou, Irini Angelidaki. Simultaneous hydrogen utilization and in-situ biogas upgrading in an anaerobic reactor. Biotechnology and Bioengineering, 2012,109, 1088-1094
Gang Luo, Irini Angelidaki. Integrated biogas upgrading and hydrogen utilization in an anaerobic reactor containing enriched hydrogenotrophic methanogenic culture. Biotechnology and Bioengineering, 2012, In press.
1 Patent
Irini Angelidaki, Poul Lyhne, Gang Luo. Methods and apparatus for hydrogen based biogas upgrading, US patent, Application number:61/563,247
Achievements