METHODS FOR INCREASING THE BIOGAS METHODS FOR INCREASING THE BIOGAS YIELD IN MANURE BASED BIOGAS YIELD IN MANURE BASED BIOGAS PLANTS PLANTS

P. KAPARAJU, N. CHRISTENSEN AND I. ANGELIDAKIP. KAPARAJU, N. CHRISTENSEN AND I. ANGELIDAKI

ENVIRONMENT & RESOURCES - DTUENVIRONMENT & RESOURCES - DTUTECHNICAL UNIVERSITY OF DENMARKTECHNICAL UNIVERSITY OF DENMARK

BIOGAS FORUM BIOGAS FORUM 10 DEC 200410 DEC 2004

BACKGROUND BACKGROUND

Manure - major substrate resource Manure - major substrate resource Large fraction of TS - Particulate matterLarge fraction of TS - Particulate matter One-step CSTR digestion One-step CSTR digestion

– Methane yields of 0.2-0.25 mMethane yields of 0.2-0.25 m33/kgVS /kgVS < theoretical yield of 0.4-0.45 m< theoretical yield of 0.4-0.45 m33/kgVS. /kgVS.

BMP Test – Digested materialBMP Test – Digested material– 5-10% additional methane5-10% additional methane

RESEARCH APPROACHRESEARCH APPROACH

Focus EFP-04 project on : Focus EFP-04 project on : 1. Reactor configurations1. Reactor configurations

Serial digestionSerial digestion2. Operational procedures2. Operational procedures

Retain degradable materialRetain degradable material3. Methods for degradation of undegraded 3. Methods for degradation of undegraded

materialmaterialPost-treatmentPost-treatment

Lab-scale and pilot-scale studiesLab-scale and pilot-scale studies

1. Reactor configuration1. Reactor configuration

Serial digestionSerial digestion

Conversion eff: Conversion eff: – low - single step digestionlow - single step digestion

Split total reactor vol between two Split total reactor vol between two CSTR connected in series CSTR connected in series

Two separate methanogenic Two separate methanogenic reactorsreactors

On-going projects:On-going projects:a. Effect of different reactor configuration a. Effect of different reactor configuration

90:10, 80:20 & 70:30 Vol.90:10, 80:20 & 70:30 Vol.

b. Effect of temperature b. Effect of temperature

15 d HRT

12 + 3 d HRT

1. Reactor configuration1. Reactor configurationa. a. Effect of different reactor Effect of different reactor configuration 80:20 & 90:10configuration 80:20 & 90:10

1-10% HIGHER METHANE PRODUCTION COMPARED TO 1-10% HIGHER METHANE PRODUCTION COMPARED TO ONE-STEP PROCESSONE-STEP PROCESS

HIGHER (20-40%) METHANE PRODUCTION DURING HIGHER (20-40%) METHANE PRODUCTION DURING VARIOUS PULSES.VARIOUS PULSES.

PROCESS MORE ROBUST TO DISTURBANCESPROCESS MORE ROBUST TO DISTURBANCES

2003 2003

R1 R2 R3 R1 R2 R3

Reactor configuration 100 80 20 100 90 10

Total volume (ml) 3500 3500 1800 3500 3500 1800

Working volume (ml) 3200 3200 800 3200 3200 356

HRT (d) 15 12 3 15 13,5 1,5

Feed rate (ml/d) 213 267 267 213 237 237

Loading rate (gVS/d) 10 13 10 12

Methane production (ml/d) 1922 2726 1979 2485

Methane prod (ml/gVS/d) 184 209 189 214

% increase 12 12

a. Effect of different reactor a. Effect of different reactor configuration (contd)configuration (contd)

0

5

10

15

20

25

0 5 10 15 20 25 30 35 40 45 50 55 60Day

Bio

gas

prod

uctio

n (m

L/m

L fe

ed)

(3

day

s ro

lling

ave

rage

)

R1 R2+R3 R2 R3

New batch of manure

Steady-state period

Fig. Daily biogas production from reactor R1 operated in parallel and reactors R2 and R3 operated in series

1. Reactor configuration1. Reactor configurationb. Effect of temp. on 2-step of b. Effect of temp. on 2-step of serial digestionserial digestion

Methanogenesis in second-step Methanogenesis in second-step of serial digestion is dependent of serial digestion is dependent on temp. and chemical on temp. and chemical characteristics of the incoming characteristics of the incoming digestate.digestate.

55°C

20 ° C

37 ° C

55 ° C

b. Effect of temperature b. Effect of temperature (contd):(contd):

Fig. The effect of temperature (20-55C) on daily biogas production from reactor R3 operated in series with reactor R2.

Gas production

0

1

2

3

4

5

6

7

0 10 20 30 40 50 60 70 80 90

Days

Ga

s p

ro

du

ce

(m

L/m

L f

ee

d)

55

37

20

2. Operational procedures2. Operational procedures

Passive solids separationPassive solids separation10°C

Top 60 cm 97 cm

Top

55°C

60 cm 97 cm

After 1 d

2. Operational procedures2. Operational procedures

Passive solids separationPassive solids separation

Fig. Changes in TS and VS of digested cow manure samples over time from top, middle (60 cm) and bottom (97 cm) of column

VS

0

4

8

12

Time (hr)

TS

0

4

8

12mixed top middle bottom

Sol

ids

(%)

0 0.25 0.5 1.0 2.0 24 120 240S

olid

s (%

)

VS

0

2

4

6

Time (hr)

TS

0

2

4

6mixed Top Middle Bottom

Sol

ids

(%)

0 0.25 0.5 1.0 2.0 24 120 240

Sol

ids

(%)

3.3. Methods for degradation of undegraded Methods for degradation of undegraded materialmaterialPost-treatmentPost-treatment

Short-term aerobic/composting as post-Short-term aerobic/composting as post-treatmenttreatment

Acknowledgements:Acknowledgements: Chao PanChao Pan KanokwanKanokwan Tore & JacobTore & Jacob HenarHenar HectorHector