biogas production from stillage scientific, technical and ... · biogas production from stillage...

Folie Nr. 1Prof. Dr.-Ing. Artur Mennerich, Universität Lüneburg; Dipl. Ing. Adelbert Lührung - pbe energietechnik GmbH

Biogas Production fromStillage

–Scientific, Technical and

Economical Aspects

Prof. Dr.-Ing. Artur Mennerich, University of Lueneburg

Dipl.-Ing. Adelbert Lühring,pbe energietechnik GmbH


Contents

IntroductionFactors affecting biogas productionLab scale tests for substrate analysis and processcontrolBiogas potential of different substratesFertilizer qualities of biogas plant output


IntroLeuphana-University of Lueneburg

Lower Saxony

Hamburg

Bremen

Hanover


Intro

Leuphana-University of Lueneburg

www.leuphana.de

10,000 students

4 faculties

Campus Suderburg:Campus Suderburg:

500 500 studentsstudents

Labs Labs forfor waterwater and and solidssolids analysisanalysis

Labs Labs forfor biogasbiogas teststests

WaterWater / / WasteWaste WaterWater


Factors affecting biogas production

Substrate composition (and degradability):

• organic. compound (oDS) contains approx. 48% C (Carbon)

• 1 kg Carbon is equivalent to 1,870 liters biogas (CH4 or CO2)

⇒ degradation of 1 kg oDS → approx. 0.48 x 1,870 = 897 liters biogas

degradation ratio = 85 % ⇒ 85 % x 897 l = 762 liters biogas per kg oDS

• Material with a high carbon content may produce more gas, but not unlimited!!

762 m³ / t oDS = appr. 12.1 cu ft per lb oDS



Temperature:

80 100 120 140 F

Narrow temp. range


Thermophilic vs. mesophilic digestion

Pro

Higher degradation ratioShorter HRTSmaller reactor volume(appr. 20% based on practical experiences withsewage sludge digestion)

Con

Higher energy demand forheatingNarrow range of optimumoperationDanger of AmmoniatoxicityHigher tear and wear dueto temperature gradients



pH:

Optimum for methane production: neutral to slightly alcalinic(7.0 to 7.5)

Problem: Once pH drops below 6.5, methane production mayalready be inhibited severely

Therefore, another method is needed for process control:FOS/TAC-ratio is practiced with good resultsRedox potential may also be useful



Toxic gases (NH3, H2S):


VVHRT R=

BR load of reactor (volume) [kg oDS/(m³xd)]

m feed rate [kg oDS/d]

c oDS concentration of feed [%]

VR reactor volume [m³]

HRT hydraulic retention time [d]

VR reactor volume [m³]

V feed flow rate [m³/d]

2. Anaerober Gärprozess

Volumetric loading rate :

Hydraulic retention time :

R

R VcmB ×

=





rye

grass

straw

cow manure




0

2

4

6

8

10

12

14

16

18

20

0 10 20 30 40 50 60

Verweilzeit (Tage)

oTS-

Rau

mbe

last

ung

[kg

/(m³ u

nd T

ag)]

oTS = 1%oTS = 2%oTS = 5%oTS = 10%oTS = 20%

HRT (days)

Vol

umet

ricLo

adin

gR

ate

[kg

oDS

/(m³x

d)]


Lab scale testsfor substrate analysis and process control

Batch tests:


Lab scale testsfor substrate analysis and process control

Continuous fermenters:


Biogas production from stillageResults of lab tests at the University of Lueneburg:

0

100

200

300

400

500

600

700

800

900

0 5 10 15 20 25

Zeit (d)

spez

. Gas

ertr

ag (m

³N/ t

oTS

)

Whole

Whole

Gas

-gen

erat

ion

(m³/

t O

DS)

hydraulic retention time (d)


Laboratory equipment at the University of Lueneburg:

Chemical lab fully equipped, with respect to biogas:• gas chromatography for biogas analysis• ion chromatography for VFA analysis• simple analysis (DS, oDS, pH, FOS/TAC etc.)• metal analyis (AAS, ICP)


Biogas production from stillage

Results of lab tests at the University of Lueneburg:

Example: 10 mgal per year ethanol plant;

Digestion of 1.5 mgd stillage

Stillage input metric t/d 5146 tons/d 5674

Dry solids content % 12,3 12,3

Dry solids load metric t/d 635 tons/d 700

Biogas production m³/d 414964 million cuft/d 14,7

primary energy content MW 101 Million BTU/h 346


Biogas production from stillageProperties of digested stillage as a fertilizer:

Assumption: 261 t/d digested stillage, dried to a DS content = 95%

No Nitrogen, Phosphorus and Potassium are lost during biogas process

Nitrogen Phosphorus Potassium

N P K

3,46% 1,05% 2,03% on DS basis

15,7 4,8 9,2 g/lb DS

9,89% 3,00% 5,80% onDS basis

44,8 13,6 26,3 g/lb DS

21,9 6,7 12,9 metric t/d

24,2 7,3 14,2 tons/d

48371 14679 28380 lbs/d

Contents in raw stillage

Contents in digested stillage

Daily nutrient load


Biogas production from stillageWhat we can do for you:

Analyses and lab tests for substrate evaluation

Economical evaluation of biogas projects

Technical design and supervision of construction

Support with start up and process optimization based

on on line and lab analysis/tests

Education of and support for operation staff


Process Monitoring, Optimisation

On-site or in central - laboratory Wisconsin

Determination of key process parameter

volatile organic acids

buffer-capacity

ph

dry-solids

Folie Nr. 22Prof. Dr.-Ing. Artur Mennerich, Universität Lüneburg; Dipl. Ing. Adelbert Lühring - pbe energietechnik GmbH

Biogas production from stillage

offers a possibility to make use of the energypotential still present in stillage after ethanolproductionreduces overall process water demandproduces a valuable fertilizer

Thank you for listening!

[email protected] [email protected]

biogas production from stillage scientific, technical and ... · biogas production from stillage...

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