Production of advanced biobased hydrogen enriched

methane from waste glycerol in a two-stage continuous

system

A. S. Dounavis1,2, Ι. Νtaikou1, G. Lyberatos1,3

1 Institute of Chemical Engineering and Scienses (ICEHT/FORTH)

2 Department of Chemical Engineering, University of Patras

3 School of Chemical Engineering, National Technical University of Athens

IWWATV Conference, President Hotel, Athens 21/05/2015

Glycerol A trivalent alcohol found naturally in all animal

and vegetable fats in the form of glycerides

When fats undergo transesterification with the addition of alcohol to form biodiesel, glycerol is generated as a by-product

…In the recent years

The rapid growth of biodiesel industry has generated

a significant amount of crude glycerol as a by-product

Used in:

Industries such as food, cosmetics and pharmaceutical

PROBLEM:

• Large availability

• Low market price

Proposed Solution:

Use as a carbon source for the production of bio-fuels or

other high added value bio-products via biological

processes

To optimize the microbial conversion of industrial

glycerol towards a novel gaseous biofuel i.e hydrogen

enriched methane in a two stage system

The aim of the present study:

1st Stage :Anaerobic

fermentation

2nd Stage: Anaerobic digestion

Blending

H2 + CO2 CH4 + CO2

Advantages of proposed

methodology

The first stage is biohydrogen production

The effluent from this process is rich in 1,3-propanediol and

fatty acids

The propanediol has possible industrial use

It is however possible to conjugate biohydrogen production

with:

Biogas production (CH4 and CO2) via anaerobic digestion

Bioplastics production

Complete utilization of crude glycerol

Hydrogen enriched methane: Hythane®

The blended gas of H2 with methane:

a) improve the combustion efficiency

b) decrease the fuel consumption

c) reduce the emissions of CO, CO2, NOx

d) So far its production was based on the catalytic conversion of natural gas

Main advantage : direct used at internal combustion engines

Hythane

The challenge of

a) producing low-cost

b) sustainable

c) more environmentally friendly biofuel than methane alone

d) high hydrogen-enriched methane

To attain its potential market position

How can the hythane be produced?

• The combined biological production through a two-stage biological

fermentation

• Hydrogen is produced through anaerobic dark fermentation of carbohydrates in

the 1st stage

• The effluent of the 1st reactor is converted to methane in the 2nd reactor

1st Reactor

H2 Production

2nd Reactor

CH4 Production

Effluent from

1st reactor

waste

Hydrogen

c) highest specific calorific value (142 kJ/g)

b) no emissions during its combustion (only water production)

d) combustion in internal combustion engines and fuel cells for

electricity generation

a) environmentally friendly and renewable

Fermentative H2 production is accomplished using with:

a) pure culture, or

b) mixed culture

Advantage of mixed culture:

Low cost and easy operation

Biohydrogen production

by dark fermentationTwo main metabolic pathways for fermentative biohydrogen

production from glycerol :

Methane

c) the main component of natural gas (70-90%)

b) dissolves readily in organic solvents, not easily detected

d) important for the production of electricity in so-fired gas turbine and boiler

steam turbine

a) colorless and odorless gas, slightly soluble in water

e) used as vehicle fuel and was regarded as existing environmental friendly than

other fossil fuels

Experimental apparatus and materials

Reactor:

Up-flow Column Bioreactor, double jacket

Plexiglas, h: 35cm, Øin: 9cm, 1,5L working

volume

Acidogenic mixed culture from anaerobic activated sludge from the Patras

Municipal Wastewater Treatment Plant

thermal pretreatment 20 min at 100oC (to suppress methanogens)

used as inoculum at ratio 1:5 with cultivation medium

sparging with CO2+N2 for 2 min to ensure anaerobic conditions

Conditions:

35±1 oC (recirculation of hot water in the

jacket of the reactor),

immobilization of cells

Immobilization agent:

Ceramic beads 0.5*1cm

Hydrogen production in a up-flow column bioreactor (UFCB)

Components Concentration(g/L)

FeSO4 *7H2O

CaCL2*2H2O

NH4Cl

MgCl2*6H2O

KCl

MnCl2*4H2O

CoCl2*6H2O

H3BO3

CuCl2*2H2O

Na2MoO4*2H2O

ZnCl2

NiCl2*6H2O

H2WO4

Yeast Extract

0.07

0.225

0.359

0.162

1.17

0.018

0.027

0.00513

0.00243

0.0023

0.00189

0.002

0.0001

0.75

COMPOSITION OF THE FEED

Feed:

• 20g WG /L, HRT: 24h

• kept at 4oC, supplemented with

0.75g/L yeast extract, trace

elements, phosphate buffer

• pH: 6, 6.5 and 7

Crude glycerol was supplied by the

biodiesel production company PETTAS

SA and had the following

1 COD commercial glycerol 1,217 gr O2/gr glycerol

Characteristics WG value

purity, % 92,330,17

COD, g O2/g waste1 1,280,00

color Brown-yellow

pH, aqueous solution. 10%, w/v 5,2

Experimental apparatus and materials

Reactor:

Vw of 3 L

cylindrical in shape,

made of stainless steel,

periodically stirring and feed supply

externally surrounded by a jacket in which

water circurated, maintaining water at 35±1 oC

Acidogenic mixed culture from anaerobic activated sludge from the Patras Municipal

Wastewater Treatment Plant

sparging with CO2+N2 for 2 min to ensure anaerobic conditions

Methane production in a continuous stirred tank reactor (CSTR)

Components Concentration(g/L)

FeSO4 *7H2O

CaCL2*2H2O

NH4Cl

MgCl2*6H2O

KCl

MnCl2*4H2O

CoCl2*6H2O

H3BO3

CuCl2*2H2O

Na2MoO4*2H2O

ZnCl2

NiCl2*6H2O

H2WO4

Yeast Extract

0.07

0.225

0.359

0.162

1.17

0.018

0.027

0.00513

0.00243

0.0023

0.00189

0.002

0.0001

0.75

COMPOSITION OF THE FEED

Feed:

5 g commercial glycerol/L (period (a) )

5 g crude glycerol /L (period (b) )

effluents from the hydrogenogenic reactor,

diluted to a concentration of 5, 7.5 and 10

g COD/L (periods (c), (d) and (e)

respectively )

kept at 4oC, supplemented with

0.3g/L yeast extract,

trace elements,

sodium hydrogen carbonate 5.5g/L

(NaHCO3),

di-Ammonium hydrogen phosphate 1.18

g/L (NH4)2HPO4

From the period (c) to (e), there was no addition of inorganic

elements in the feed

The bioreactor was operated in batch mode for 24h and subsequently,

in continuous mode at an HRT of 24h and a feed pH of 6, 6.5 and 7

The concentration of waste glycerol in the feed was 20g / L

Sampling:

daily from reactor

parameters monitored: T.S.S., V.S.S., d-COD,

glycerol, PDO, VFAs, alcohols, pH, % H2, Vbiogas

1st stage : hydrogen production

• Increased pHfeed resulted to increase in

pH reactor

• Glycerol uptake was complete only

for the highest pHfeed

0 10 20 30 40 50 60 70 80 90 1000

5

10

15

20

25

Cglycerol feed

Cglycerol reactor

Cgly

cero

l (g

/L)

Time (d)

( pH=6 ) ( pH=6.5 ) ( pH=7 )

1st stage : effect of pHfeed on reactor performance

0 10 20 30 40 50 60 70 80 90 1004.0

4.5

5.0

5.5

6.0

6.5

7.0

7.5

8.0

(pH=7)

pH ( reactor)

pH (feed)

pH

Time (d)

(pH=6)

(pH=6.5)

• The main metabolic product

was 1,3-PDO (~3-3.5g/l)

• VFAs: mainly butyrate and

hexanoate

0 10 20 30 40 50 60 70 80 90 100

0

1

2

3

4

5

6

TSS (g/l)

VSS (g/l)

So

lids (

g/L

)

Time (d)

( pH=6 ) ( pH=6.5 ) ( pH=7 )

0 10 20 30 40 50 60 70 80 90 1000

500

1000

1500

2000

2500

3000

3500

(f)

(c)(b)

acetate

propionate

butyrate

hexanoate

vfa

s (

mg/l)

Time (d)

(a)

( pH=6 ) ( pH=6.5 ) ( pH=7 )

1st stage : effect of pHfeed on reactor performance

0 10 20 30 40 50 60 70 80 90 1005000

10000

15000

20000

25000

30000

cod feed

cod reactor

d_C

OD

(m

g/L

)

Time (d)

( pH=6 ) ( pH=6.5 ) ( pH=7 )

pH-value in the

feed

Volumetric H2 production

and molecular H2 yield

0 10 20 30 40 50 60 70 80 90 1000

1

2

3

4

5

6

( pH=6 )( pH=6.5 ) ( pH=7 )

Rate (biogas)

Rate (hydrogen)

Rate

(L/L

reacto

r/d)

Time (d)

0 10 20 30 40 50 60 70 80 90 100

0.15

0.20

0.25

0.30

0.35

0.40

0.45

yield H2

Yie

ld H

2 (

mol H

2/ m

ol cons. gl.)

Time (d)

( pH=7 )( pH=6.5 )( pH=6 )

1st stage : effect of pHfeed on reactor performance

Yield

( mL H2 / g COD

Feed)

pH=6 51

pH=6.5 70

pH=7 94

HRT : 24 h , c: 20 g waste glycerol /L

pHfeed pH=6 pH=6.5 pH=7

pHreactor 5.3±0 5.8±0.0 6.1±0.0

VSS , g/L 0.9±0.0 1.1±0.1 1.2±0.0

TSS, g/L 1.4±0.2 1.8±0.3 2.2±0.3

Glycerol reactor, g/L 5.0±0.3 1.3±0.4 0.8±0.1

% Glycerol removed 74.0 91.7 95.6

V H2, L/d 1.37±0.11 2.10±0.04 2.86±0.05

Butyrate, g/L 0.76±0.02 1.12±0.18 1.25±0.17

Acetate, g/L 0.26±0.02 0.48±0.09 0.85±0.09

Hexanoate, g/L 1.54±0.05 1.06±0.22 0.91±0.24

PDO, g/L 3.6±0.2 5.7±0.9 7.0±0.2

Ethanol, mg/L 0.56±0.05 0.15±0.02 0.20±0.02

Yield H2, mol/mol glyc

consumed 0.24±0.03 0.36±0.03 0.40±0.08

1st stage : effect of pHfeed on reactor performance

The reactor was filled with 3 L of anaerobic sludge and remained for 24 h

in batch mode and then was switched to continuous mode, where initially

the feed consisted of commercial glycerol (period (a) )

The feeding was intermittent and was done via a peristaltic pump,

which was set to turn on every 8 h, HRT : 20 d

Sampling:

daily from reactor

parameters monitored:

T.S.S., V.S.S., d-COD,

glycerol, PDO, VFAs, alcohols,

pH, % CH4, Vbiogas

2nd stage: methane generation

FEED

Period (a) Commercial glycerol (5 g COD/L)

Period (b) Waste glycerol (5 g COD/L)

Period (c) Effluent (diluted) from the 1st stage

(5 g COD/L)

Period (d) Effluent (diluted) from the 1st stage

(7.5 g COD/L)

Period (e) Effluent (diluted) from the 1st stage

(10 g COD/L)

0 20 40 60 80 100 120 140 160

0.00

0.05

0.10

0.15

0.20

0.25

rate biogas (L/Lreactor/d)

rate methane (L/Lreactor/d)

rate

gase

s (

L/L

rea

cto

r/d)

Time (d)

(a) (b) (c) (d) (e)

0 20 40 60 80 100 120 140 160

0

10

20

30

40

50

60

70

80

90

100

% CH4

% m

eth

ane

time (d)

(a) (b) (c) (d) (e)

• The % CH4 is almost stable

• Commercial glycerol and waste glycerol

resulted to the same yields

• Small decrease of yield for the effluent as

carbon source

• Increased substrate concentration led to

increased rates and yields

2nd stage : effect of carbon source and substrate concentration on methane production

periodYield

( mL CH4 / g COD Feed)

(a) 257

(b) 283

(c)198

(d)242

(e)273

0 20 40 60 80 100 120 140 160

0

2000

4000

6000

8000

10000

12000

cod reactor (mg/L)

cod feed (mg/L)

d_C

OD

(m

g/L

)

Time (d)

(a) (b) (c)(d)

(e)

0 20 40 60 80 100 120 140 160

0

2

4

6

8

10

12

14

16

18

TSS (g/L)

VSS (g/L)

solid

s (

g/L

)

time (d)

(a) (b) (c)(d)

(e)

• d_COD: stable and low in the reactor

COD uptake was complete while the

organic loading was increased

• TSS and VSS have a great deference due to

the supplementation with inorganic

elements during cycles (a), (b) and

beginning of (c)

A long, stable hydrogen (a) and methane (b) production was achieved at high

levels (about 41-45% for (a) and 70% for (b) ) in a continuous process

1st Reactor

glycerol uptake was complete only for the highest pH-value in the feed

1,3-PDO was the main metabolite detected in all cases (~30-40% COD),

whereas butyrate and hexanoate acids were the main acids produced (~15-45%

COD)

volumetric H2 production and molecular H2 yield

when the reactor was operated at high pH

CONCLUSIONS

2nd Reactor

The results were satisfactory for methane production

the amount of methane generated was approximately the same for

periods (a) and (b)

For periods (c), (d) and (e) (the feed was the effluent from the 1st

reactor), initially there was a decrease (35%) in the methane production

and at the end an increase (from 17.5% to 70.66%).

VFAs, glycerol, 1.3-propanediol, ethanol were not detectable

in contrast to the 1st reactor

CONCLUSIONS

Further investigation

The dilution of the 1st reactor will be diluted less aiming at feeding

to the CSTR (2nd reactor) the undiluted effluent .

This may require a higher retention time (risk for digester instability)

ACKNOWLEDGEMENTS

The authors would like to thank GSRT for funding

the above study in the framework of the project

BIOREF, 09SYN-81-715.

Information:Α. S. Dounavis

Ph.D. Candidate, Chemical Engineer B.S. and M.S.

FORTH/ICEHTLaboratory of Biochemical Engineering &

Environmental Technology +30 2610 965317 +30 2610 965318

adounavis@iceht.forth.gr

Thank you very much for

your attention!!!