Scientific Project

Ahmed Hussein

ANAEROBIC DIGESTION OF CHICKEN MANURE, OLIVE POMACE AND WINE POMACE

Written by:

Ahmed Hussein, Student ID#: 173666, 3rd

Semester, 2012

Course of Study:

Energy Conversion and Management (International Program of ECM)

College Supervisor:

Prof. Dr.-Ing. Joachim Jochum

Company Name, Department and Internship Duration:

MT-Energie GmbH (Biogas-Technologie)

Department of Sales & Project Management (East Europe)

From April 16th till September 30

th

Company Supervisor:

Mr. Jan Ludeloff

Director Sales & Project Management (East Europe)

Hochschule Offenburg

Badstraße 24, 77652 Offenburg

Department: Mechanical- and Process-Engineering

Study course: Energy Conversion and Management

Hochschule Offenburg Mt-Energie GmbH

Scientific Project ‘A.D. of Chicken Manure, Olive and Wine Pomace’

Ahmed Hussein Page II

Abstract

The Anaerobic Digestion; used in its both Ecological and Industrial terminologies,

has been a bright solution for both environmentalists and engineers in the last couple

of decades. The liaison between the rise of the Earth’s temperature; known as the

Green House Effect and the world’s race against time to find renewable and clean

resources for energy has framed the objectives for using this methodology to con-

front with the depletion of the world’s both Oil and Coal resources and reserves by

the next 50-75 years (according to the American Petroleum Institute). The Anaerobic

Digestion (AD) is an appropriate technique for the treatment of almost any biode-

gradable wastes. Unlike both Wind and Solar energies which are vulnerable to extra-

neous variables (biggest being weather conditions), the Anaerobic Digestion is

known to be more reliable. On different scales, the biodegradable wastes could be

simple kitchen wastes or wastes that reckon on both agricultural and livestock in-

vestments. Throughout this scientific report, a hands-on practical trial will be dis-

cussed as a field experiment for feeding dry chicken manure, olive pomace and wine

pomace into 750 and 950-liter trial wet fermenters with daily observations for the A.D.

process in the mesophilic range and in a run of 6 Months. (© 2012 MT-Energie and

Ahmed Hussein All Rights Reserved)



Ahmed Hussein Page III

Table of Contents

Table of Contents .......................................................................................... III

List of Figures and Illustrations .................................................................. V

List of Equations.............................................................................................. V

List of Tables ................................................................................................. VII

Nomenclature (Latin Symbols) ............................................................... VIII

Nomenclature (Greek Symbols) ................................................................. IX

List of Abbreviations ..................................................................................... IX

1 Introduction ................................................................................................. 10

2 Basics ............................................................................................................ 11

2.1 History of Anaerobic Digestion ............................................................................. 11

2.2 What is Anaerobic Fermentation? ....................................................................... 12

2.3 Formation of Gas Mixture ..................................................................................... 13

14

2.4 Ambient Conditions ............................................................................................... 15

2.4.1 Oxygen ........................................................................................................... 15

2.4.2 Temperature ................................................................................................... 16

2.4.2.1 Psychrophilic Temperature Range ............................................................ 16

2.4.2.2 Mesophilic Temperature Range ................................................................ 16

2.4.2.3 Thermophilic Temperature Range ............................................................ 17

2.4.3 pH Value ........................................................................................................ 18

2.4.4 Nutrients and Trace Elements Supply ............................................................ 18

2.4.5 Inhibitors ........................................................................................................ 19

2.4.6 FOS (Volatile Organic Acids) ........................................................................ 21

2.4.7 TAC (Total Alkalinity) ................................................................................... 21

2.4.8 FOS/TAC Ratio .............................................................................................. 21

2.5 Operating Parameters ........................................................................................... 21

2.5.1 Loading Rate and Hydraulic Retention Time of the Fermenter ..................... 21

2.5.2 Productivity, Recovery and Degradation Efficiency ...................................... 24

2.5.3 Mixing ............................................................................................................ 25

2.5.4 Gas Formation, Potential and Methanogenic Activity ................................... 26

2.5.4.1 Possible Gas Yield .................................................................................... 26



Ahmed Hussein Page IV

2.5.4.2 Gas Quality ............................................................................................... 27

3 Experiments ................................................................................................. 28

3.1 Anaerobic Digestion of Chicken Manure ............................................................. 29

3.1.1 Introduction .................................................................................................... 29

3.1.2 Acquisition and Properties of Chicken Manure ............................................. 30

3.1.3 The Experiment .............................................................................................. 32

3.1.3.1 Building up the trial Fermenter ................................................................ 32

3.1.3.2 Putting the fermenter into operation ......................................................... 38

3.1.3.3 Feeding and measuring ............................................................................. 41

3.1.3.4 Observations (results) ............................................................................... 53

3.1.3.5 Conclusion ................................................................................................ 56

3.2 Anaerobic Digestion of Olive Pomace .................................................................. 58

3.2.1 Introduction .................................................................................................... 58

3.2.2 Acquisition and properties of Olive Pomace .................................................. 58

3.2.3 The Experiment .............................................................................................. 60

3.2.4 Observations (results) ..................................................................................... 60

3.2.5 Conclusion ...................................................................................................... 63

3.3 Anaerobic Digestion of Wine Pomace .................................................................. 64

3.3.1 Introduction .................................................................................................... 64

3.3.2 Acquisition and properties of Wine Pomace .................................................. 64

3.3.3 The Experiment .............................................................................................. 66

3.3.4 Observations (results) ..................................................................................... 66

3.3.5 Conclusion ...................................................................................................... 69

4 Acknowledgement ....................................................................................... 70

5 Bibliography ................................................................................................ 71

6 Appendix ...................................................................................................... 72



Ahmed Hussein Page V

List of Figures and Illustrations

Figure 1: Biogas in ancient China ....................................................................................... 11

Figure 2: Decomposition in absence of Oxygen ................................................................. 12

Figure 3: Formation of Biogas and trace gases ................................................................... 13

Figure 4: Fermentation Process ........................................................................................... 14

Figure 5: Mesophilic bacteria .............................................................................................. 16

Figure 6: Thermophilic bacteria .......................................................................................... 17

Figure 7: Relation between loading rate and hydraulic retention time by different ODM

concentrations ........................................................................................................................... 23

Figure 8: Dry Chicken Manure Barrels ............................................................................... 30

Figure 9: Dry Chicken Manure 1………………………………………………………. 30

Figure 10: Dry Chicken Manure 2……………………………………………………… 30

Figure 11: Prototyping the actual Biogas fermenter…………………………………… 32

Figure 12: Inside the trial fermenter……………………………………………………. 33

Figure 13: Temperature control valve…………………………………………………... 33

Figure 14: Main components of the trial fermenter……………………………………… 33

Figure 15: Upper components on the fermenter…………………………………………. 34

Figure 16: Impeller coupled with the motor……………………………………………… 34

Figure 17: The module’s control panel…………………………………………………… 34

Figure 18: TFT screen interface…………………………………………………………...34

Figure 19: 1st Gasline auxiliaries…………………………………………………………. 35

Figure 20: Input and output syphon to the gas counter………………………………….. 35

Figure 21: Gas counter box………………………………………………………………. 35

Figure 22: Pressure retaining Syphon……………………………………………………. 36

Figure 23: Surge chamber…………………………………………………..…………… 37

Figure 24: Creating head difference…………………………………………………..…. 38

Figure 25: Pumping the maize silage…………………………………………………….. 38

Figure 26: The silage being pumped into the fermenter………………………………… 38

Figure 27: The fermenter’s upper part immersed with water……………………………. 40

Figure 28: A gas leak found from the fermenter’s hatch………………………………... 40

Figure 29: The hole for Temperature sensing…………………………………………… 42



Ahmed Hussein Page VI

Figure 30: Temperature Probe…………………………………………………………… 42

Figure 31: Wöhler digital pressure gauge……………………………………………….. 43

Figure 32: Laser distance meter…………………………………………………………. 44

Figure 33: Silicone based defoamer……………………………………………………... 44

Figure 34: Fermenter’s operating volume vs. distance………………………………….. 45

Figure 35: Density meter………………………………………………………………… 46

Figure 36: Dräger device………………………………………………………………… 47

Figure 37: Gas quality measurement…………………………………………………….. 47

Figure 38: Fermenter’s feeding hole……………………………………………………. 48

Figure 39: Scale…………………………………………………………………………. 48

Figure 40: Manual agitator………………………………………………………………. 48

Figure 41: pH meter……………………………………………………………………… 49

Figure 42: Titrator………………………………………………………………………... 49

Figure 43: Sample preparation…………………………………………………………… 49

Figure 44: Drying Oven…………………………………………………………………. 50

Figure 45: Muffle Furnace………………………………………………………………. 50

Figure 46: Nitrogen titration device…………………………………………………...… 51

Figure 47: Dräger Ammonia vial………………………………………………………… 51

Figure 48: Liquid chromatography………………………………………………………. 52

Figure 49: The Rheometer……………………………………………………………….. 52

Figure 50: pH values……………………………………………………………………... 53

Figure 51: FOS/TAC ratio……………………………………………………………….. 53

Figure 52: FOS and TAC in comparison………………………………………………… 54

Figure 53: Volumetric gas production…………………………………………………… 54

Figure 54: Volumetric Methane quantity………………………………………………… 55

Figure 55: HRT vs. DM…………………………………………………………………. 55

Figure 56: Sand in chicken manure substrate……………………………………………. 56

Figure 57: Gas production per kg ODM…………………………………………………. 57

Figure 58: Olive pomace barrels…………………………………………………………. 58

Figure 59: Olive pomace………………………………………………………………… 58

Figure 60: pH values…………………………………………………………………….. 60

Figure 61: FOS/TAC ratio………………………………………………………..……… 61




Ahmed Hussein Page VII

Figure 63: Volumetric gas production…………………………………………………… 62

Figure 64: Volumetric Methane quantity………………………………………………… 62

Figure 65: Gas production per kg ODM………………………………………………… 63

Figure 66: Wine pomace barrels…………………………………………………………. 64

Figure 67: Wine pomace………………………………………………………………… 64

Figure 68: pH values…………………………………………………………………….. 66

Figure 69: FOS/TAC ratio……………………………………………………………….. 67


Figure 71: Volumetric gas production…………………………………………………... 68

Figure 72: Volumetric Methane quantity……………………………………………….. 68

Figure 73: Gas production per kg ODM………………………………………………… 69

List of Equations

Equation 1: Loading rate ..................................................................................................... 22

Equation 2: Hydraulic retention time .................................................................................. 23

Equation 3: Methane productivity ....................................................................................... 24

Equation 4: Methane recovery ............................................................................................. 25

Equation 5: Degradation efficiency ..................................................................................... 25

Equation 6: Ideal Gas Law .................................................................................................. 42

List of Tables

Table 1: Permissible concentration for different trace materials ......................................... 19

Table 2: Inhibitors and their harmful concentrations .......................................................... 22

Table 3: Specific Biogas and Methane contents in corresponding groups of materials ...... 26

Table 4: Average compositions in Biogas ........................................................................... 27

Table 5: DM and ODM values for Chicken Manure ........................................................... 31

Table 6: Agrolab analysis results......................................................................................... 39

Table 7: DM and ODM values for Olive Pomace ............................................................... 59

Table 8: DM and ODM values for Wine Pomace ............................................................... 65



Ahmed Hussein Page VIII

Nomenclature (Latin Symbols)

Symbol Unit Description

.

V / max

.

V - Charge

.

V h

m3

volume flow

Pab kW power output

Pzu kW power consumption

p mbar Pressure

n min

1 rotation speed

M Nm Torque

.

m s

kg mass flow

Nl litre Norm litre

J mechanical work

s

m relative inlet velocity of the water jet

s

m relative outlet velocity of the water jet

s

m absolute velocity of the jet flow

s

m absolute inlet velocity of the jet flow

s

m absolute outlet velocity of the jet flow

U s

m circumferential speed

T °C Temperature

m kg mass

g 2s

m gravitational acceleration



Ahmed Hussein Page IX

Nomenclature (Greek Symbols)

Symbol Unit Description

α ° angle of the relative outlet velocity vector with the

horizontal datum

η - degree of efficiency

ρ 3m

kg density

ω s

1 angular frequency

List of Abbreviations

Abbreviation Description

Fig. Figure

FOS Flüchtige Organische Säuren

TAC Total Alkalinity

HRT Hydraulic Retention Time

TS Trockensubstanz

oTS Organische Trockensubstanz

DM Dry Material

ODM Organic Dry Material

PLC Programmable Logic Control

TFT Thin Film Transistor

R.H.S. Right Hand Side

L.H.S. Left Hand Side

C.P. Centrifugal Pump



Ahmed Hussein Page 10

1 Introduction

Historically, the Bio wastes were considered as an agricultural resource due to its

beneficial effects to the soil. Particularly, the chicken manure was used as a natural

fertilizer for cropping soils while both olive and wine pomace were disposed by either

inhumation or incineration. After the considerable growth in production of Bio wastes

due to the huge dimension of the modern and intensive farmhouses and the great

daily productions in both wine and olive oil industries, odour problems and

contamination of the underground water and soil and other negative consequences in

different environmental sectors have been spotted as a point of interest for many

scientists (Burton et al., 2003). Industrialization has set the start for a new technology

named Biogas. Biogas production was not of a great importance till the problem of oil

and coal resources’ depletion has arisen. Although the Biogas production using an-

aerobic digestion could be a new and reliable source of Energy, firm regulations and

legislations have been set to control the bio by-products and bio sludge that are pro-

duced in the end phase of this technology.




2 Basics

2.1 History of Anaerobic Digestion

It has been reported that the Chinese were the first to extract and use the Biogas

from the fermentation process. Information about the first Biogas installations in

China refers back to yearly 16th century BC. However, it was first reported in the 17th

century by both Robert Boyle and Stephen Hale who have noticed that a flammable

gas would be released by disturbing the sediment of the streams and lakes1. In 1808,

Sir Humphry Davy has realised that the Methane was present in the cow manure23. It

has also been thought that the ancient Egyptians were the first to use the solidified

cow manure for flaming up their ovens.

4

Figure 1: Biogas in ancient China

1 Fergusen, T. & Mah, R. (2006) Methanogenic bacteria in Anaerobic digestion of biomass, p49, 29 May, 2012

2 Anaerobic digestion, waste.nl. Retrieved 19.08.07.

3 Cruazon, B. (2007) History of anaerobic digestion, web.pdx.edu. Retrieved 17.08.07.

4 http://www.onetoremember.co.uk/xcart/images/P/chinese-biogas-plant.gif, 29 May, 2012

http://www.waste.nl/content/download/472/3779/file/WB89-InfoSheet(Anaerobic%20Digestion).pdf

http://web.pdx.edu/~cruzan/The%20Magic%20of%20Methane/History%20of%20AD.htm

http://www.onetoremember.co.uk/xcart/images/P/chinese-biogas-plant.gif




2.2 What is Anaerobic Fermentation?

As the upper headline states, the Anaerobic digestion is the biological process

where the decomposition of the organic wastes or products will take place in the

absence of oxygen. In the contrary with the aerobic digestion which is done under

“aerated” conditions, the anaerobic fermentation are usually done in oxygen-free,

sealed and heated environments. In both types, different kinds of decomposing

bacteria tends to break down fats, protiens and carbohydrates into simpler

constituent materials.

5

Figure 2: Decomposition in absence of Oxygen

5 http://www.skyrenewableenergy.com/wp-content/uploads/2009/05/digester.jpg, 11 June, 2012

http://www.skyrenewableenergy.com/wp-content/uploads/2009/05/digester.jpg




2.3 Formation of Gas Mixture

Since the anaerobic digestion is originally an exothermal biological reaction, it

produces heat in addition with Biomass (substrate or base material) and Biogas. The

Biogas produced consists of Methane 50-75 Vol.-percent, Carbon dioxide 25-50 Vol.-

percent, gases like (Hydrogen, Hydrogen Sulphide and Ammonia) and other trace

gases. Generally, the composition of the gas mixture will depend on the fed base

material, the processing of the fermentation and other technical parameters. Since

the development of the Biogas can be divided into several sub-steps, these steps

should be processed in an optimal sequence and without any interruptions.

The first step is called, the ‚Hydrolysis’, when all the complex compounds of the

feedstock (e.g. Carbohydrates, Proteins and Fats) are biochemically decomposed in

to simple organic compounds (e.g. Amino acids, Sugar and Fatty acids) by the effect

of an enzyme released by the bacteria.

The resulting intermediate products will then be degraded in a second step by the

fermentation (acid-forming) bacteria in the so called ‚acidification phase’

(acidogenesis) into lower fatty acids (Acetic, propionic and butyric acids) as well as

carbon dioxide and hydrogen.

6

Figure 3: Formation of Biogas and trace gases

6 http://water.me.vccs.edu/courses/ENV149/lesson4.htm, 11 June, 2012

http://water.me.vccs.edu/courses/ENV149/lesson4.htm




In addition to that, a small amount of lactic acids and alcohols will be formed. The

nature of the formed products in this stage is influenced by the concentration of the

intermediately formed hydrogen.

The third step is called the ‚Acetogenesis’. In this ‘Acetic acid formation’ process,

these products (acetic acid, hydrogen and carbon dioxide) will; subsequently, be im-

plemented by the acetogenic bacteria as Biogas precursors.

In this context, the hydrogen partial pressure plays an important role. As the hy-

drogen content rises in the biological process, it will obstruct the implementation of

the Acetogenesis process’s intermediates. As a result, the concentration of the or-

ganic acids (propionic, iso-butyric, iso-valeric and caproic acids) will rise and hence

will reduce the methane production.

In the subsequent ,Methanogenesis’ process; the last step of the Biogas for-

mation, all the acetic acids as well as the Hydrogen and carbon dioxide will be con-

verted from the strict anaerobic methanogens to methane.

Figure 4: Fermentation Process




2.4 Ambient Conditions

Since the anaerobic fermentation is basically a biological reaction, maintaining

reliable and convenient conditions for this reaction is indispensable. Speaking about

the environmental conditions, parameters like the Temperature, amounts of Oxygen,

PH value, Nutrients and Inhibitors are worth to be mentioned.

2.4.1 Oxygen

The methanogenic archaea are among the oldest living beings on earth which

were created about three to four billion years ago, long before the atmosphere has

been formed the way we know nowadays. For this reason, these microorganisms are

still surviving in savage living environments where oxygen does not exist. Most

methanogenic species are killed with even small amount of oxygen. In general, the

oxygen entry inside the fermenters cannot be avoided completely.

The reason that methanogenic archaea are not immediately inhibited in their

activity or even die entirely lies in the fact that they live together with oxygen-

consuming bacteria from the previous reduction steps.

Some of them are called facultative anaerobic bacteria. These bacteria can

equally survive in the presence of oxygen and in its absence. As long as the oxygen

is not too large, they use up the oxygen before it damages the methanogenic

archaea, which depend on an oxygen-free environment.

Also for the biological desulphurization which is done in the gas space of the

fermenter and with the assistance of small amounts of atmospheric oxygen, the

methane production will not be harmfully affected by these amounts of oxygen.




2.4.2 Temperature

In principle, the higher the ambient temperature, the faster the chemical reaction.

But this cannot be constantly applied to biological degradation and transformation

processes where optimum operating temperatures should be maintained for the

microorganisms. Therefore, the microorganisms involved in the wastes degradation

process can be divided according to their optimal operating temperature into 3

groups.

2.4.2.1 Psychrophilic Temperature Range

The psychrophilic microorganisms have their optimum degree at temperatures

below 25 °C. At such temperatures, there is no need to heat up the substrate or the

fermenter because the performance of the degradation process as well as the gas

production will be, however, low.

2.4.2.2 Mesophilic Temperature Range

Most of the known methanogens has its growth optimum degree in the mesophilic

temperature range 37-42 °C. Biogas plants operating in the mesophilic range are; in

practice, the most widely used. It has been observed that in this temperature range,

relatively high gas yields can be achieved as well as good process stability.

7

7 http://aretusa.ice.it/SchemaSite/images/UserImageDir/177/EN/Presentations/Biogas.pdf, 25 July, 2012

Figure 5: Mesophilic bacteria

http://aretusa.ice.it/SchemaSite/images/UserImageDir/177/EN/Presentations/Biogas.pdf




2.4.2.3 Thermophilic Temperature Range

In order to facilitate faster reaction rates and; hence faster gas yields, a

Thermophilic temperature range is maintained at 50-60 °C. Although Thermophilic

digestion systems are considered to be less stable with higher energy input, they

facilitate greater sterilization for the digestate. In contrary to the Thermophilic

species, the Mesophilic species are more tolerant to changes in the environmental

conditions and more stable.

8

Practice has shown in this context, that the distinctions are blurred between the

temperature ranges. Primarily, a rapid change in temperature may lead to a damage

for the microorganisms, whereas the methanogenic microorganisms can adapt to

slower temperature changes at different temperature levels.

8 http://aretusa.ice.it/SchemaSite/images/UserImageDir/177/EN/Presentations/Biogas.pdf, 25 July, 2012

Figure 6: Thermophilic bacteria





2.4.3 pH Value

Similar to the temperature range, the pH value will have the same coherence with

the execution and optimization of the biological process. The microorganisms require

different pH values with which they could increase and develop. The optimum pH

value for the hydrolytic and acidogenic bacteria should lie between 5.2-6.3. The

Acetic acid-forming bacteria and the methanogenic archaea require an optimal pH

value range from 6.5-8. The pH value inside the fermenter will be automatically

changed through the alkaline and the acidic metabolites which are produced during

the anaerobic digestion. At the time when the fermenter is fed with too many organic

materials or the methane production; for some reason, has dropped down, so the

acidic metabolite of the acidogenesis should be increased. Normally, the pH values

are manually adjusted when it arises by using either carbonate or ammonia buffer

solutions.

2.4.4 Nutrients and Trace Elements Supply

The microorganisms of the anaerobic digestion have a typal demand of macro and

micro-nutrients as well as vitamins. The concentration and the availability of these

components influence both activity and growth rate of the assorted populations. For a

stable processing, the ratio between the macro and micro-nutrients should be

balanced.

Right after the carbon, nitrogen is the most needed nutrient. Nitrogen will be used

for the production of the enzymes which will be used later for the production of the

metabolites. The C/N-ratio also plays a vital role in the methane production. When

the C/N-ratio increases (more carbon and less nitrogen), the present carbon amount

cannot be fully implemented by the lack of the metabolism and hence the maximum

gas yield is not achieved. For a stable process flow, the C/N-ratio should be main-

tained in the range of 10-30. Another nutrients (phosphorus and sulphur) should be

taken into consideration so that, the C:N:P:S ratio should be kept within the range of

600:15:5:3 for stable reactions.




Besides the nutrients supply, there are some trace elements which are essential

for the microorganisms to stay alive and productive.

a. Absolute minimum concentration by the Biogas system

b. Recommended optimal concentration

2.4.5 Inhibitors

Inhibitors are meant to be those materials which can stop or even reduce the

progression of the gas yield production. Inhibition and reduction of the gas production

could be caused by different reasons. It could be either of a technical or Biological

reason. By feeding the fermenter, it should be considered that the overfeeding

amounts of the substrate could have an inhibiting effect on the biological process

since the concentration of the different elements within the substrate will rise

harmfully to stop the reaction. This includes substances such as antibiotics,

disinfectants, solvents, herbicides, heavy metals or salts that can inhibit; even in

small amounts, the degradation process (see Table 2). The existence of antibiotics is

due to the feeding of manure or fats that are excreted by animals being given

antibiotics, however the inhibitory effect of certain antibiotics varies widely. Not only

antibiotics in high concentrations could be harmful but also some essential trace

elements in slight higher concentrations could be toxic for the microorganisms.

Inhibitors could also result from the interaction of different substances within the

substrate. Heavy metals; for example, can act as an inhibitor when they are

dissolved rising up the potential of forming hydrogen sulphide as a paired, undesired

but acceptable gas within the produced methane.

9 http://www.fnr-server.de/ftp/pdf/literatur/pdf_208-leitfaden_biogas_2010_neu.pdf, p. 25, 15 August, 2012

Trace ele-ments

Concentration range [mg/l]

For [2-18] For [2-19] For [2-16]a For [2-17]b

Co 0.003-0.06 0.003-10 0.06 0.12

Ni 0.005-0.5 0.005-15 0.006 0.015

Se 0.08 0.08-0.2 0.008 0.018

Mo 0.005-0.05 0.005-0.2 0.05 0.15

Mn N/A 0.005-50 0.005-50 N/A

Fe 1-10 0.1-10 1-10 N/A9

Table 1: Permissible concentration for different trace materials

http://www.fnr-server.de/ftp/pdf/literatur/pdf_208-leitfaden_biogas_2010_neu.pdf




This is not applied for the copper compounds, which due to their antibacterial

effect even at very low concentrations (40-50 mg/L) are very toxic.

During the fermentation process, a series of materials will be produced which can

inhibit the methane production. Along within this context, the high adaptation

capability of the bacteria should be observed since it is not allowed to exceed the

concentration limits of these materials.

Especially, the free Ammonia (NH3) will act harmfully; even in small amounts,

against the bacteria. High temperatures as well as pH values will affect directly on

the tolerated amounts of the free Ammonia within the substrate since the amount of

the free Ammonia will increase by the increase of temperature and pH value. For ex-

ample, an increase for the pH value from 6.5 to 8 will lead to an increase in the con-

centration of free Ammonia by 30 times. Also by higher temperatures, the concentra-

tion of free Ammonia should not exceed the safe limits. For a stable Ammonia con-

centration, the NH3 should stay within the range of 80-250 mg/l. With higher Ammo-

nia contents, adding distilled water inside the fermenter would reduce the ammonia

concentration but increases the fermenter’s volume and decreases the HRT as well

as the gas yield.

Depending on the pH value and the temperature, this corresponds to an Ammonia

concentration of 1.7-4 g/l. Practical experience has limited an overall concentration of

Ammonium nitrogen (NH3-N) by 3000-3500 mg/l with an expected nitrogen inhibition

effect for the Biogas process.

Another product of the fermentation process is the hydrogen sulfide (H2S), which

acts in the undissolved or undissociated form as a cytotoxic inhibitor and in a concen-

tration of about 50 mg/l can stop the degradation process. With decreasing pH val-

ues, increases the proportion of H2S, and hence increases the risk of inhibition. It

could also condense in the flue gas system of the CHP stations and form sulphuric

acid (H2SO4) which causes corrosion and also reduces the service life of the engine’s

lube oil.




2.4.6 FOS (Volatile Organic Acids)

The volatile organic acids are simply the sum of all acids present in the acetic ac-

ids without distinction of possible different types. This value should be maintained

lower than 10000.

2.4.7 TAC (Total Alkalinity)

The Total Alkalinity measures the ability of a solution to neutralize acids to the

equivalence point of carbonate or bicarbonate. TAC value or buffer includes all buffer

substances, as if they were all carbonates. This value should be maintained over

10000.

2.4.8 FOS/TAC Ratio

FOS / TAC ratio is an indicator for rapid assessment of the fermenter’s condition.

This value should be maintained in the range from 0.2-0.6.

2.5 Operating Parameters

2.5.1 Loading Rate and Hydraulic Retention Time of the Fermenter

By building the Biogas systems, the economic considerations would stand in the

foreground. Thus, in the choice of the fermenter size, the maximum gas yield as well

as the potential of the complete degradation of the organic material in the substrate

might not necessarily be taken into consideration.

If a complete degradation of the organic material is required to be achieved, some-

times very long hydraulic retention periods should be maintained and hence, a rela-

tively larger container volumes will be used cause some ingredients within the sub-

strate will require longer times to be degraded. Another way to achieve this is to build

up a large number but with smaller size containers in order to decrease the hydraulic

retention time of the substrate but this will be an expensive alternative.

http://en.wikipedia.org/wiki/Acid

http://en.wikipedia.org/wiki/Equivalence_point




In this regard, the loading rate is an important operating parameter. It indicates

how many kilograms of organic dry material per m3 working volume can be supplied

per unit time.

10

Equation 1: Loading rate

Inhibitor Inhibitory con-

centration

Notes

O2 >0.1 mg/l Inhibition of the obligate anaerobic

methanogenic archaea.

H2S >50 mg/l H2S Inhibition effect increases with decreased pH-

value.

Volatile fatty

acids

>2.000 mg/l HAc

(pH=7.0)

Inhibition effect increases with lowered pH-

value. High adaptation activity for bacteria.

NH4-N >3.500 mg/l NH4+

(pH=7.0)

Inhibition effect increases with the increase of

the pH-value and temperature. High adapta-

tion ability of bacteria.

Heavy metals Cu > 50 mg/l

Zn > 150 mg/l

Cr > 100 mg/l

Only dissolved metals act as inhibitors.

Detoxication by sulfide precipitation.

Disinfectants

antibiotics

N/A Inhibition effect is product-specific. 11

Table 2: Inhibitors and their harmful concentrations



Loading rate

Substrate mass flow rate

Concentration of organic dry material

Fermenter’s volume






The loading rate can be specified for each stage (gas-tight, insulated and heated

fermenters), for the entire system (the sum of all working volumes at all levels), with

and without inclusion of material back feeding. By changing the dimensions of the

reactor, different values for the loading rate shall be expected. For a descriptive

comparison of loading rates for different Biogas plants, it is advisable to determine

these parameters for the overall system and without consideration of material recy-

cling into the fermenter. By determining the right speed of degrading the Bio wastes,

the hydraulic retention time will be calculated successfully.

Another important parameter for dimensioning the reactor’s size is the hydraulic

retention time. It is simply the time duration when the fed substrate will remain inside

the fermenter till it is discharged. This value should be daily calculated during the op-

eration.

12

Equation 2: Hydraulic retention time

13

Assuming a uniform substrate composition, the increasing loading rate will

require more input material to be fed in to the fermenter and thus the hydrau-lic retention time will be reduced.



Fermenter’s working volume

Daily feed

0

20

40

60

80

100

120

140

160

1 1.5 2 2.5 3 3.5 4 4.5 5

Hyd

rau

lic r

ete

nti

on

tim

e [

d]

Loading rate [kg oTS/(m3 d)]

50 kg oTS/mᵌ

100 kg oTS/mᵌ

150 kg oTS/mᵌ

Figure 7: Relation between loading rate and hydraulic retention time by different ODM concentrations






In order to obtain a proper fermentation process, the hydraulic retention time

should be calculated in such a way that through the constant exchange of the sub-

strate inside the digester, there will no longer be growing microorganisms that might

be flushed away and lost at this time. On the other hand, if the hydraulic retention

time was miscalculated to be too short, then the microorganisms will not be able to

fully produce the methane out of the substrate. In order to maintain a proper retention

time with increasing loading rate, mostly more than one fermenter is being used but

that will definitely increase the construction cost.

2.5.2 Productivity, Recovery and Degradation Efficiency

When stating the performance of a certain Biogas plant, Productivity (P(CH4)), Re-

covery (A(CH4)) and Degradation efficiency (ηoTS) are of a great importance to be men-

tioned.

Productivity is what simply describes the relation between the Biogas production

and the volume of the fermenter. It should be considered as the quotient of the daily

gas production from the fermenter which is absolutely influenced by the effectiveness

of the fermentation process. The productivity will be based on both the amount of

Biogas produced (P(Biogas)) and the methane production (P(CH4)).

14

Equation 3: Methane productivity

Since the gas production also depends on the input materials, so it also affects the

gas recovery (gas yield). The gas recovery can also depend on the Biogas (A(Biogas))

and the methane production (A(CH4)). It is defined as the quotient of the produced gas

quantity and the fed organic substance.






The gas recovery simply indicates the efficiency of the Biogas as well as the me-

thane production out of a specific substrate. Being only a single parameter makes it

very low informative, since it doesn’t conceive the loading rate of the fermenter. Be-

cause of that, mentioning the gas yield should always be accompanied with the load-

ing rate.

15

Equation 4: Methane recovery

The degradation efficiency (ηoTS) refers to the efficiency of the substrate utilization.

The degradation efficiency can; by means of the organic dry substance or the chemi-

cal oxygen demand, be determined. Due to practical experience, it is advisable be-

fore carrying out the analysis to determine the ODM degradation efficiency.

16

Equation 5: Degradation efficiency

Organic dry substance content in the fresh fed materials [kg/t FM].

Organic dry substance content in the fermenter [kg/t FM].

Mass weight of the fed material [t].

Mass weight of the digestate [t].

2.5.3 Mixing

In order to achieve a maximum Biogas production, a sufficient contact should be

maintained between the bacteria and the substrate inside the fermenter which would

be achieved by an efficient mixing. In a non-mixed fermenter for some time, a sepa-

ration of contents will be observed with concomitant formation of layers indicating the

differences in density between the individual ingredients of the substrate and the

buoyancy caused by gas formation. In such case and due to the difference in densi-

ties, a layer that separates the fresh substrate from those where the bacteria are

highly concentrated will be formed reducing the amount of gas yield.








Also by clustered substrate due to poor mixing, the formed floating solids will im-

pede the mixture from being pumped. It is also important to maintain a direct contact

between the microorganisms and the substrate, while a strong mixing could be really

harmful depending on the substrate’s viscosity.

2.5.4 Gas Formation, Potential and Methanogenic Activity

2.5.4.1 Possible Gas Yield

What is the amount of Biogas that might be produced out of a specific type of sub-

strate?. A question that will only be answered by performing pretests on the sub-

strate. Another way to know is to calculate the total gas output as long as there are

no resources to rely on.

Name Biogas content [l/kg oTS] Methane content [Vol.-%]

Digestible protein 700 71

Digestible fat 1.250 68

Digestible carbohydrate 790 5017

Table 3: Specific Biogas and Methane contents in corresponding groups of materials






2.5.4.2 Gas Quality

Biogas is a formation of many gases which consists mainly of Methane (CH4) and

Carbon dioxide (CO2) as well as water vapor and other different trace gases. The

most important product among these products is the Methane gas. The composition

of the produced gas is totally depending on the fed material as well as the formerly

mentioned operating parameters. The concentration of the trace gases also plays an

important role in defining the gas quality, since the concentration of the Hydrogen

Sulphide (H2S) will act as an inhibitor for the Biogas production process when ex-

ceeding the permissible limits.

Component Concentration

Methane (CH4) 50-70 Vol.-%

Carbon dioxide (CO2) 25-45 Vol.-%

Water (H2O) 2-7 Vol.-% (20-40 °C)

Hydrogen Sulphide (H2S) 20-20000 ppm

Nitrogen (N2) ˂ 2 Vol.-%

Oxygen (O2) ˂ 2 Vol.-%

Hydrogen (H2) ˂ 1 Vol.-%18

Table 4: Average compositions in Biogas






3 Experiments

Rules of the Thumb

Before approaching with the experiments, some rules of thumb shall be known.

The first rule to cohere with is to keep the FOS/TAC ratio in a range from 0.2-0.4 for

stable operation and due; the amount of the feed can be increased. In the range from

0.5-0.6, a slight correction; under circumstances, should be done in the operation of

the trial fermenter. When it exceeds 0.7, the feed should be stopped. At higher critical

values, Slaked Lime (Calcium Hydroxide Ca(OH)2) could be used to increase the to-

tal alkalinity and hence, reduce the FOS/TAC ratio. In cases when a secondary fer-

menter is used (in large scale plants), a recirculated substrate can be mixed together

with a new fresh wastes and pumped back to the primary fermenter to improve the

flowability. Another advantage is to make use of the “hungry” bacteria that are still

active and ready to work immediately with breaking down the organic matters. If a

drop down with the Methane production is noticed, so it is probably a problem with

the measuring process or the fed amounts were larger than enough. The Ammonium

level should remain in the range of 1000-3000 mg/L. In high Ammonia content mate-

rials, the level should be observed not to reach 5000 mg/L. In some cases, a me-

chanical drying mechanism could be used to reduce the NH4 content, but that would

produce offensive odors and be expensive. The ration between the propionic and the

acetic acid should be 1:3. The viscosity also is an important parameter to be consid-

ered, to be noticed that a value from 5000 mPas, the substrate won’t be steerable.




3.1 Anaerobic Digestion of Chicken Manure

3.1.1 Introduction

The Poultry farms in many countries all over the world represent a very high percent-

age of this country’s animal wealth (in the so called Broiler Belt in the United States,

chickens have outnumbered people by as much as 400 to 1)19. With the fact that the

Poultry wastes (represented mainly in the chicken manure) are of a Toxic nature, the

laying hens will tend frequently to excrete it and in high amounts. With this very vast

amounts of chicken manure (could reach sometimes to 0.02 million cubic meter per

year for a poultry farm contains around 10 million chickens), an appropriate tech-

nique for both treatment and disposal should be embraced. As for the direct usage of

the chicken wastes with high ammonia content for fertilizing crops would lead to both

soil and ground water contamination, a solution has been proposed to use mechani-

cal dryers in order to reduce the ammonia content, but due to its high initial costs and

production of offensive odors makes it a controversial solution and sometimes inapt.

The AD in its current consolidation between waste treatment and Biogas production

will have a Surpass to dissolve both disposal and treatment problems accompanied

with the production of chicken manure.

19 http://www.pewenvironment.org/uploadedFiles/PEG/Publications/Report/PEG_BigChicken_July2011.pdf, 29 May, 2012

http://www.pewenvironment.org/uploadedFiles/PEG/Publications/Report/PEG_BigChicken_July2011.pdf




3.1.2 Acquisition and Properties of Chicken Manure

The fresh and dry chicken manure has been obtained from a neighboring Biogas

plant that belongs to Ernst Schnakenberg which lies in Tarmstedt (a municipality in

the district of Rotenburg in lower Saxony). The manure has been shoveled and

stored in big blue plastic barrels so that to be used later for the manual feeding oper-

ations (see figs. 8, 9&10).

Figure 9: Dry Chicken Manure 1

Figure 10: Dry Chicken Manure 2

Figure 8: Dry Chicken Manure Barrels




Both the dry substance and organic dry substance contents in the manure were

measured gradually (once per week) to concern the effect of the ambient conditions

(hot, cold, humid and rainy days) as well as the influence of storing method (some

barrels were kept in shadow and some in sun).

TS = 60.7 % Analyzed on: Applied till: oTS = 43.9 % 31/07/2012 06/08/2012


TS = 53.8 % Analyzed on: Applied till:

oTS = 45.5 % 13/08/2012 20/08/2012 TS = 59.1 % Analyzed on: Applied till: oTS = 45.4 % 21/08/2012 28/08/2012 TS = 57.5 % Analyzed on: Applied till: oTS = 48.8 % 03/09/2012 10/09/2012 TS = 62.2 % Analyzed on: Applied till: oTS = 39.5 % 10/09/2012 17/09/2012 TS = 55.7 % Analyzed on: Applied till: oTS = 41.9 % 17/09/2012 25/09/2012


TS = 61.0 % Analyzed on: Applied till: oTS = 42.6 % 13/06/2012 TS = 55.7 % Analyzed on: Applied till: oTS = 42.6 % 20/06/2012 TS = 58.7 % Analyzed on: Applied till: oTS = 40.0 % 13/07/2012 TS = 56.1 % Analyzed on: Applied till:

oTS = 43.9 % 17/07/2012 23/07/2012 TS = 59.4 % Analyzed on: Applied till: oTS = 41.9 % 23/07/2012 30/07/2012

Table 5: DM and ODM values for Chicken Manure




The test of the dry substance and organic dry substance would usually last for 3

days (the dry substance test lasts for 48 hrs. and the organic dry substance test lasts

for about 6 hrs.) and that to be done once per week.

3.1.3 The Experiment

3.1.3.1 Building up the trial Fermenter

This experiment has taken place on the 1st of May, 2012 in the R&D Biogas plant

of MT-Energie in Rockstedt, Kyffhäuserkreis, Thüringen under the supervision of

Prof. Dr.-Ing. Joachim Jochum as my university’s supervisor and Mr. Jan Ludeloff as

my company’s supervisor. A 750-liter stainless steel container has been modified to

simulate the large fermenters used by MT-Energie Biogas power plants (see fig. 11).

Figure 11: Prototyping the actual Biogas fermenter

http://de.wikipedia.org/wiki/Kyffh%C3%A4userkreis

http://de.wikipedia.org/wiki/Th%C3%BCringen




Figure 14: Main components of the trial fermenter

A stainless steel hot water hoses have been rotated on the inner round surface of

the container and along with its circumference to assure an equally distributed heat

to the substrate (see fig. 12). The heating system has used hot tap water as a work-

ing fluid and a house-used ordinary thermostatic valve for temperature control (see

fig. 13), whilst the temperature inside the fermenter was observed using an analogue

temperature gauge (see fig. 14). Also to retain the heat, a sheet of glass wool insula-

tor has been wrapped around the fermenter. The trial fermenter has been fitted with

three big ball valves at different levels for either filling up or emptying out the fer-

menter.

Figure 12: Inside the trial fermenter Figure 13: Temperature control valve




At the top of the fermenter we could notice the existence of a 3.0 kW Electric Mo-

tor (69Nm, 500/min) with a gear box which is coupled with an impeller protracted

deep down inside the fermenter to maintain an appropriate mixing for the substrate

for optimal gas production (see fig. 15&16). The Motor is riveted with a welded steel

support which is eventually fixed to the fermenter’s body using screw bolts.

The power control for the Mixer is done by a small 7-Input PLC unit which enables

us to either manually or automatically switch ON/OFF the fermenter. Also the Module

has been programmed to automatically switch ON/OFF the Mixer at different time

intervals through the whole day (see fig. 17&18).

Figure 15: Upper components on the fermenter Figure 16: Impeller coupled with the Motor

Figure 17: The module's control panel Figure 18: TFT screen interface




From the other components on the upper side of the fermenter, there are two

Gaslines. The first Gasline (on the R.H.S) is branched into two paralleled sections;

the first section is connected with two black Gas Sacs which act as pressure indica-

tors when inflated or deflated (see fig. 15), while the other branch is connected with a

sludge filter (with a fine-meshed net) preceded with two ball valves, the first is used

as a Gas outlet port for gauging both pressure inside the fermenter and the Gas

Quality, whilst the other is used as a control valve (see fig. 19).

After the water condensate out of the produced gas due to the temperature differ-

ence between inside and outside the fermenter is being trapped in the sludge filter,

the dry gas is then routed through the syphon gas pipes directly to the gas counter to

measure the daily gas production in cubic meters (see fig. 20&21).

Figure 19: 1st Gasline auxiliaries

Figure 20: Input and output syphon to the gas counter Figure 21: Gas counter box




Complementary to the sludge filter for trapping the condensate, the syphon has a

further line extension with a small attached condensate tab for wasting out the water.

The output syphon line from the gas counter is also branched into two sections, the

first line extension is for draining out the condensate (if there is any left) and the other

is connected to a pressure retaining siphon shown in fig. 22.

The concept of the pressure retaining Syphon is simply dependable on the length

of the water column inside the internal capillary tube where the pressurized gas has

to overcome the water to escape to the atmospheric pressure. Therefore, the pres-

sure inside the fermenter is easily controlled by the amount of water poured inside

the Syphon. Generally, the pressure inside the fermenter should be regulated in ac-

cordance with the maximum allowable Hydrogen partial pressure for a stable gas

production (see section 2.3, Formation of Gas Mixture, p. 13). However the pressure

inside the fermenter (whether in Big or Trial versions) could sometimes not be of a

significant importance (it always oscillates between 3-4.5 mbar), but it could be used

to create some points of pressure difference within the route where the Biogas

should be directed; in our case, the gas should build enough pressure to function the

gas counter.

Figure 22: Pressure retaining Syphon




The second Gasline (on the L.H.S.) is directly attached to an over pressure/under

pressure safety device (see fig. 23). This device is quite similar to the pressure re-

taining Syphon (both for working concept and design). It is simply constructed from a

small capillary tube inside a bigger surge chamber filled with water (the water column

here is much higher than in the pressure retaining Syphon) which acts like a relief

valve for over pressurized gas. The excessively pressurized gas will simply be re-

lieved to the atmosphere. This device should have the ability to compensate for neg-

ative pressure situations but that would be done manually by adding more water

through the water inlet port shown in fig. 23.

Figure 23: Surge chamber




3.1.3.2 Putting the fermenter into operation

In order to specify the optimal HRT value for the chicken manure (one of the main

purposes of this experiment), the working volume of the fermenter has been fixed on

600 liters (with a maximum permissibility to reach up to 700 liters) leaving 150 liters

from the total fermenter volume for the gas accumulation. Around 600 liters of maize

silage out of the bigger fermenters have been pulled out and pumped inside the trial

fermenter as an inoculum (see fig. 24, 25&26).

Figure 24: Creating head difference Figure 25: Pumping the maize silage

Figure 26: The silage being pumped into the fermenter




The inoculum has been then tested in the main laboratories in Zeven using the

Agrolab Analysis giving the following results:

Parameter

Unit Value i.d. OS Value i.d. DS

Dry substance % 59.1

Water content % 40.9

Total Nitrogen content % 1.5 2.5

Ammonium (NH4-N) % 0.48 0.81

Total Phosphate (P2O5) % 1.2 2.1

Total Potassium (K2O) % 1.0 1.7

Total Magnesium (MgO) % 0.59 1.0

Calcium (CaO) % 4.13 6.98

Sulphur (S) % 0.19 0.32

Molybdenum (Mo) mg/kg 1.20 2.03

Selenium (Se) mg/kg 0.288 0.487

Total Iron (Fe) mg/kg 1590 2690

Cupper (Cu) mg/kg 35.2 59.6

Manganese (Mn) mg/kg 178.8 302.6

Zink (Zn) mg/kg 155.6 263.2

Cobalt (Co) mg/kg 1.01 1.71

Nickel (Ni) mg/kg 1.94 3.28

Table 6: Agrolab analysis results




The agitator has been then programmed to work in intermittent time intervals

through the day. The inoculum has been left for around a week (30.04-06.05) without

feeding to see how stable the gas production was. Before starting the feed of the

chicken manure and after enough amount of gas being generated, a gas leak test

has been done to the fermenter (see fig, 27&28).

Also all the threaded pipe connections have been tested for leakage using a gas

leak testing solution and after the leakages have been repaired the tests have been

done one more time for confirmation of repair.

Figure 27: The fermenter’s upper part immersed with water Figure 28: A gas leak found from the fermenter's hatch




3.1.3.3 Feeding and measuring

Referring to the law of the loading rate (see section 2.5.1, loading rate and hydrau-

lic retention time of the fermenter, p. 21) and with both the fermenter’s working vol-

ume (constant) and the concentration of the organic dry substance being measured

once per week, a feeding plan is generated at the beginning of each week for the

fermenter with the BR being defined with correspondence to the amount of kilograms

chicken manure fed per day.

The feed has started with BR = 1.5 from 07.05 to 13.05 and due to the significant

rise in the FOS/TAC ratio (from 0.27 to 0.53), the BR has been reduced to 0.1 from

14.05 to 20.05 which led to a decrease in the FOS/TAC ratio from 0.53 to 0.43 leav-

ing it in a relative stable range. On the 21st calendar week, the BR has been decided

to be 1 and that to be carefully increased in accordance with the increase in the

FOS/TAC ratio and the fluctuations with other biological parameters.




From 21st of May till 30th of September 2012, the following activities have been

done daily to the trial fermenters as follows:

Temperature measurement (°C)

The temperature reading is written down out of the analogue temperature sensor

which has significance on the type of fermentation (always kept at 40 °C for

Mesophilic digestion) as well as its importance to measure the standard values of

daily gas productions at standard atmospheric pressure and temperature accord-

ing to the combined ideal gas law.

Equation 6: Ideal Gas Law

For even more precise temperature values and since the temperature sensor

mounted inside the fermenter is leveled too low to measure the gas temperature in-

side the gas accumulation room (which is the temperature required), a hole in the

outlet gas line out of the gas counter has been made and the gas temperature has

been measured using an analogue temperature gauge with probe (see fig. 29&30).

Figure 29: The hole for Temperature sensing Figure 30: Temperature Probe




It has been constantly noticed that the temperature of the produced gas is always

4 degrees lower than the temperature of the substrate inside the fermenter.

Gas meter reading (m3)

The reading out of the Gas meter has been noted down every day to calculate the

daily gas production and compare it with the frequent changes in the biological

parameters. These daily values are then corrected to the standard values for the

standard pressure and temperature.

Internal pressure (mbar)

The internal pressure has also been measured through the Gas outlet port (see

fig. 15) using a digital pressure gauge (see fig. 31).

The pressure values have been used later for calculating the standard daily gas

production values at standard pressure and temperature. Also, the pressure values

have been an indicator for a stable technical operations as well as biological pro-

cessing.

Figure 31: Wöhler digital pressure gauge




Digester Gas space (cm)

The distance between the top of the fermenter (represented at the surface of the

sight glass in the fermenter’s hatch) and the surface level of the substrate inside

the fermenter, has given the significance of the digester gas space as well as the

operating volume of the fermenter which was always kept constant at 600 liters

(around 26 cm). The lower the reading is, the more occupied volume in the fer-

menter. The distance has been measured using a laser distance meter shown in

fig. 32.

Some problems have been accompanied with measuring the distance using the

device mentioned above like the accumulation of foam sometimes on the surface of

the substrate as well as the existence of buoyant particles which could give false

measured values. It could be simply solved by switching on the agitator continuously

for a period of time till the foam disappears or to use an antifoam solution (silicone

based defoamers) with calibrated amount at the cases of severe foam accumulation.

Figure 32: Laser distance meter

Figure 33: Silicone based defoamer




The liaison between the fermenter’s occupied volume and the distance meas-

ured using the laser distance meter has been plotted as follows:

Figure 34: Fermenter's operating volume vs. distance




At the cases when the volume of the substrate inside the fermenter increases or

when it is necessary to add water to the fermenter (in the case when the DM con-

tent arises), more substrate should be taken out of the fermenter before feeding to

keep the level at equilibrium. In order to determine the exact volume of the sub-

strate taken out, the quantity is first scaled by kg and the density is measured us-

ing density meter (see fig. 35).

Figure 35: Density meter




Gas quality measurement

Since the Methane (CH4), Carbon dioxide (CO2), Oxygen (O2) and Hydrogen Sul-

phide (H2S) are the main constituent gases in the produced gas (see table 4, Av-

erage Compositions in Biogas, P. 26), they have been daily measured through the

outlet gas port using the gas quality measuring device called “Dräger”.

Figure 36: Dräger device Figure 37: Gas quality measurement




Feeding the fermenters

After calculating the appropriate value of loading rate and the correspondent

amount of chicken manure in kg, the amount is scaled and fed manually in to the

fermenter through the fermenter’s feeding hole (see fig. 38).

The amount of chicken manure is shoveled out of the barrels and scaled using the

scale (see fig. 39) and then mixed with around 10 liters of substrate out of the fer-

menter using the manual agitator (see fig. 40) and then fed back in. This process

would be done usually in stages and in more than one time.

Figure 38: Fermenter's feeding hole

Figure 39: Scale Figure 40: Manual agitator




Figure 41: pH meter

Figure 42: Titrator

Sometimes when the mixture seems to be dense and heavy, and after the feeding

is done, more 10 liters out of the fermenter would be taken and poured back in just to

sweep down the mixture into the fermenter.

Measuring the pH and FOS/TAC ratio

For the periodic measurement of pH and FOS/TAC ratio, a daily fresh sample is

taken out of the fermenter and measured using pH meter (see fig. 41) and biologi-

cal titration device (see fig. 42).

Figure 43: Sample preparation




Measuring the DM and ODM

Both DM and ODM for the substrate and the fed chicken manure are measured

gradually for the process control. Normally for such a test, a daily (could also be

weekly) samples are taken to the lab in Zeven. The samples taken are weighted

in the lab and then dried using the oven (see fig. 44) under an approximate tem-

perature of 100 °C and weighted after drying to calculate the moisture. After dry-

ing, all we have is a dry material with a ratio of organic material. The sample is

then roasted under higher temperatures (around 330 °C) using a muffle furnace

(see fig. 45) for about 48 Hours long and then weighted to determine the dry and

burnt leftovers (ash) with which the Organic Dry Material could be calculated.

Figure 44: Drying Oven Figure 45: Muffle Furnace




Measuring the Ammonia content

The amount of nitrogen inside either the substrate (in the form of Ammonium Hy-

droxide NH4OH) or in the produced gas (in the form of free Ammonia NH3) is

measured gradually due to its inhibitory effect. The Ammonia in the substrate is

measured as the total Nitrogen content (N, mg/L) using the device shown in fig.

46. The free Ammonia in the produced gas is measured manually using the

Dräger vials shown in fig. 47.

Figure 46: Nitrogen titration device Figure 47: Dräger Ammonia vial




Measuring the lower fatty acids (Acetic, propionic and butyric acids)

As the increase of the lower fatty acids could be of an inhibitory effect, they have

been scaled once per week using the device shown in fig. 48.

Measuring the substrate viscosity

Viscosity is a property that is significant to how easy and efficient the mixing of the

substrate inside the fermenter will be. The Rheometer (see fig. 49) is used for meas-

uring the dynamic viscosity.

Figure 48: Liquid chromatography

Figure 49: The Rheometer




3.1.3.4 Observations (results)

pH value

FOS/TAC ratio

7.4

7.5

7.6

7.7

7.8

7.9

8

8.1

8.2

8.3

pH

-val

ue

Date

pH-value

pH

0

0.1

0.2

0.3

0.4

0.5

0.6

FOS/

TAC

Date

FOS/TAC-ratio

FOS/TAC

Figure 50: pH values

Figure 51: FOS/TAC ratio




FOS and TAC in comparison

Gas production

0

5000

10000

15000

20000

25000

30000

35000

FOS,

TA

C in

mg/

l

Date


FOS TAC

Figure 52: FOS and TAC in comparison

Figure 53: Volumetric gas production

000

000

000

000

000

001

001

001

001

001

Date

Gas production Nm³/d

Gasertrag Nm³/d




Methane quantity

HRT vs. DM

Figure 55: HRT vs. DM

HRT vs. DM

DM (%)

HRT (d)

0

10

20

30

40

50

60

70

CH

4 in

%

Date

Methane quantity

CH4

Figure 54: Volumetric Methane quantity




3.1.3.5 Conclusion

After monitoring all the vital parameters throughout the experiment, it has been

observed that the DM content inside the digester along with the high viscosity was

the main challenge (see fig. 56). According to the periodical DM tests performed on

the substrate, it has been observed that the manure is mixed with high ratio of fine

sand grains. Due to the fact that when designing a new Biogas plant, the optimal

HRT for the specific type of digestate to be fully digested and the exact amount of

added water to make it steerable are already known as well as the available amounts

of organic material fed per day, the correct fermenter’s volume can be easily calcu-

lated. While in this experiment, the fermenter’s volume has been set to be constant

and that the amounts of fed manure will change accordingly with the contained

amounts of ODM and loading rate. Therefore, the HRT should be calculated satisfy-

ing the amounts of added water (to overcome the DM problem) along with stable Me-

thane production.

As the hydraulic retention time was actually decreasing with the increase of the

DM content inside the fermenter and since the gas production was decreasing re-

spectively, so the fermenter’s volume should be whether increased or a secondary

fermenter is to be added for an appropriate and stable Methane production. Another

solution is to treat the manure before feeding by involving some separation technolo-

gy for the contained sand.

Figure 56: Sand in chicken manure substrate




The FOS/TAC ratio has shown an average value of 0.36 and the ammonia content

of about 4800 mg/L which according to the rules of the thumb should be acceptable.

Considering the amount of DM % and ODM % inside the chicken manure as well

as its price and the Methane content inside the total gas production in Nm3/t and the

total gas production per kg ODM (around 500 Nl/kg ODM), the Chicken manure

should be considered as commercially feasible (see fig. 57).

0

1000

2000

3000

4000

5000

6000

18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 2 4 6 8 10 12 14 16

Gas

pro

du

ctio

n in

Nl/

kg O

DM

Calender week

Gas production Nl/kg ODM

Gasertrag Nl/kg oTS

Figure 57: Gas production per kg ODM




3.2 Anaerobic Digestion of Olive Pomace

3.2.1 Introduction

Olive trees have been a traditional crop in so many countries in the Mediterranean

over long ages. The production of the Olive oil has been disseminated in the Mediter-

ranean basin as a leading industry in countries like Spain, Greece, Italy, Tunisia,

Egypt and Turkey. The production process of the Olive oil usually yields an oily

phase residue, a solid residue (pomace or husk) and aqueous phase from the water

content. With the fact that there are huge amounts of waste out of the olive oil pro-

duction industry, so it makes it a good and smart way to invest their wastes in Biogas

production.

3.2.2 Acquisition and properties of Olive Pomace

The olive pomace has been imported from some olive oil manufacturer in Greece

(see fig. 58 & 59) and the inoculum used was the same used for the chicken manure

experiment to start the fermentation process.

Figure 58: Olive pomace barrels Figure 59: Olive pomace




Both the dry substance and organic dry substance contents in the pomace were





TS = 38.7 % Analyzed on: Applied till: oTS = 96.8 % 13/06/2012 TS = 46.4 % Analyzed on: Applied till: oTS = 83.2 % 13/07/2012 TS = 42.4 % Analyzed on: Applied till: oTS = 94.9 % 19/07/2012 26/07/2012 TS = 39.9 % Analyzed on: Applied till:




TS = 46.5 % Analyzed on: Applied till:


TS = 47.4 % Analyzed on: Applied till: oTS = 92.4 % 11/09/2012 11/09/2012 TS = 47.1 % Analyzed on: Applied till: oTS = 97.8 % 10/09/2012 17/09/2012 TS = 42.8 % Analyzed on: Applied till: oTS = 97.3 % 17/09/2012 25/09/2012

Table 7: DM and ODM values for Olive Pomace





The experiment of the Olive Pomace was quite similar to the Chicken Manure

when talking about Building up the fermenter and ending with the feeding and meas-

uring procedures. Unlike the Chicken Manure experiment, the DM test where done in

long time intervals as it didn’t have a great influence to the liquidity since the viscosity

of the substrate was reasonably low.

3.2.4 Observations (results)

pH value

6.8

7

7.2

7.4

7.6

7.8

8

8.2

pH

-val

ue

Date

pH-value

pH





FOS/TAC ratio


0 0.05

0.1 0.15

0.2 0.25

0.3 0.35

0.4 0.45

0.5

FOS/

TAC

Date

FOS/TAC-ratio

FOS/TAC

0 2000 4000 6000 8000

10000 12000 14000 16000 18000 20000

FOS,

TA

C in

mg/

l

Date


FOS TAC






Gas production

Methane Quantity

000

000

000

001

001

001

001

001

Date


Gasertrag Nm³/d

Figure 63: Volumetric Gas Production

0

10

20

30

40

50

60

70

80

CH

4 in

%

Date

Methane quantity

CH4

Figure 64: Volumetric Methane Quantity




3.2.5 Conclusion

Unlike the Chicken Manure experiment, this experiment has shown more stability

with the DM content along with the quite low viscosity (around 1000 mPa.s). Except

for some operating problems and troubleshooting, Methane production has been ob-

served to be stable. Some operating troubles like Gas leakage and Oxygen seepage

inside the fermenter has affected the Gas yield but under stable and airtight opera-

tion conditions, the Gas production should be stable.

According to the Gas yield and investment potentials, the anaerobic digestion of

the olive pomace can be considered commercially feasible (see fig. 65) but it has

shown a lower gas production per kg of ODM (around 250 Nl/kg ODM) than the

chicken manure would have.


of about 2280 mg/L.

0

50

100

150

200

250

300

350

18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 2 4 6 8 10 12 14 16

Gas

pro

du

ctio

n in

Nl/

kg O

DM

Calender week


Gasertrag Nl/kg oTS





3.3 Anaerobic Digestion of Wine Pomace

3.3.1 Introduction

The production of Wine has been disseminated in all Europe as a traditional indus-

try since a long time ago. The production process of the Wine usually yields a solid

residue (pomace or husk) and aqueous phase from the liquid content. With the fact

that there are huge amounts of waste out of the Wine production industry especially

in Germany, so it makes it a good and smart way to invest their wastes in Biogas

production.

3.3.2 Acquisition and properties of Wine Pomace

The wine pomace has been gotten from Neustadt, Germany (see fig. 66 & 67) and

the inoculum used was the same used for the chicken manure and olive pomace ex-

periment.

Figure 66: Wine pomace barrels Figure 67: Wine pomace




Both the dry substance and organic dry substance contents in the pomace were





TS = 32.8 % Analyzed on: Applied till: oTS = 92.8 % 18/07/2012 26/07/2012 TS = 36.9 % Analyzed on: Applied till: oTS = 95.6 % 23/07/2012 30/07/2012 TS = 34.2 % Analyzed on: Applied till: oTS = 94.9 % 30/07/2012 06/08/2012 TS = 36.9 % Analyzed on: Applied till:



TS = 37 % Analyzed on: Applied till: oTS = 90.2 % 03/09/2012

TS = Analyzed on: Applied till:

oTS = TS = Analyzed on: Applied till: oTS =

TS = Analyzed on: Applied till: oTS = TS = Analyzed on: Applied till: oTS = TS = Analyzed on: Applied till: oTS =

Table 8: DM and ODM values for Wine Pomace





The experiment of the Wine Pomace was quite similar to the Chicken Manure and

the Olive Pomace when talking about Building up the fermenter and ending with the

feeding and measuring procedures. Unlike the Chicken Manure experiment, the DM

test where done in long time intervals as it didn’t have a great influence to the liquidi-

ty since the viscosity of the substrate was reasonably low.

3.3.4 Observations (results)

pH value


7.3

7.4

7.5

7.6

7.7

7.8

7.9

8

8.1

pH

-val

ue

Date

pH-value

pH




FOS/TAC ratio




0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

FOS/

TAC

Date

FOS/TAC-ratio

FOS/TAC

0

2000

4000

6000

8000

10000

12000

14000

16000

FOS,

TA

C in

mg/

l

Date


FOS TAC




Gas production

Methane Quantity

Figure 71: Volumetric Gas Production

Figure 72: Volumetric Methane Quantity

000 000 000 000 000 001 001 001 001 001 001

Date


Gasertrag Nm³/d

0

10

20

30

40

50

60

70

CH

4 in

%

Date

Methan quantity

CH4




3.3.5 Conclusion

According to the Gas yield and investment potentials, the anaerobic digestion of

the wine pomace can be considered commercially feasible (see fig. 73). It has shown

a relative equal gas production to what the olive pomace does have.


of about 2370 mg/L which is considered to be within the safe operational range.


The feed has started in the middle of the 27th

calender week

0

200

400

600

800

1000

1200

1400

1600

1800

2000

23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22

Calender week





4 Acknowledgement

This report owes very much to all MT-Energie staff for their tremendous contribu-

tion and support in all means towards the completion of this project. I am also grate-

ful to my company’s supervisor Mr. Jan Ludeloff who without his help and guidance

this project would not have been completed. I also show my gratitude to my friends

and all who contributed in one way or another in the course of this work.




5 Bibliography

Leitfaden Biogas von der Gewinnung zur Nutzung, Fachagentur Nachwachsende Rohstoffe e.V. (FNR), ISBN 3-00-014333-5, 05.2012.

Biogas production from olive pomace, Ali R. Tekin, A. coskun Dalgis, 07.2012.

1 Fergusen, T. & Mah, R. (2006) Methanogenic bacteria in Anaerobic digestion of bio-mass, p49, 29 May, 2012

1 Cruazon, B. (2007) History of anaerobic digestion, web.pdx.edu. Retrieved 17.08.07.

1 http://www.onetoremember.co.uk/xcart/images/P/chinese-biogas-plant.gif, 29 May, 2012 1 http://aretusa.ice.it/SchemaSite/images/UserImageDir/177/EN/Presentations/Biogas.pdf, 25 July, 2012 1 http://aretusa.ice.it/SchemaSite/images/UserImageDir/177/EN/Presentations/Biogas.pdf, 25 July, 2012 1 http://www.fnr-server.de/ftp/pdf/literatur/pdf_208-leitfaden_biogas_2010_neu.pdf, p. 25, 15 August, 2012 1 http://www.fnr-server.de/ftp/pdf/literatur/pdf_208-leitfaden_biogas_2010_neu.pdf, p. 27, 17 August, 2012 1 http://www.fnr-server.de/ftp/pdf/literatur/pdf_208-leitfaden_biogas_2010_neu.pdf, p. 27, 17 August, 2012 1 http://www.fnr-server.de/ftp/pdf/literatur/pdf_208-leitfaden_biogas_2010_neu.pdf, p. 27, 18 August, 2012 1 http://www.fnr-server.de/ftp/pdf/literatur/pdf_208-leitfaden_biogas_2010_neu.pdf, p. 27, 18 August, 2012 1 http://www.fnr-server.de/ftp/pdf/literatur/pdf_208-leitfaden_biogas_2010_neu.pdf, p. 28, 20 August, 2012 1 http://www.fnr-server.de/ftp/pdf/literatur/pdf_208-leitfaden_biogas_2010_neu.pdf, p.

28, 21 August, 2012

1 http://www.fnr-server.de/ftp/pdf/literatur/pdf_208-leitfaden_biogas_2010_neu.pdf, p.

28, 21 August, 2012

1 http://www.fnr-server.de/ftp/pdf/literatur/pdf_208-leitfaden_biogas_2010_neu.pdf, p. 29, 22 August, 2012 1 http://www.fnr-server.de/ftp/pdf/literatur/pdf_208-leitfaden_biogas_2010_neu.pdf, p. 31, 21 August, 2012 1 http://www.pewenvironment.org/uploadedFiles/PEG/Publications/Report/PEG_BigChicken_July2011.pdf, 29 May, 2012 1 http://water.me.vccs.edu/courses/ENV149/lesson4.htm, 11 June, 2012 1 Anaerobic digestion, waste.nl. Retrieved 19.08.07. 1 http://www.skyrenewableenergy.com/wp-content/uploads/2009/05/digester.jpg, 11 June, 2012

http://web.pdx.edu/~cruzan/The%20Magic%20of%20Methane/History%20of%20AD.htm

http://www.onetoremember.co.uk/xcart/images/P/chinese-biogas-plant.gif

















http://water.me.vccs.edu/courses/ENV149/lesson4.htm

http://www.waste.nl/content/download/472/3779/file/WB89-InfoSheet(Anaerobic%20Digestion).pdf

http://www.skyrenewableenergy.com/wp-content/uploads/2009/05/digester.jpg




6 Appendix

The MT-Energie GmbH in Lower Saxony Zeven is a leading manufacturer of

complete biogas plants of all sizes, and biogas-engineered components. The

company has been founded in the small town of Rockstedt by Christoph Martens in

1995. In 1997 Martens invented the so-called air-supported membrane cover for

biogas plants. This technology has now become the market-leading standard and is

used by various manufacturers of biogas plants.

According to a study by the German Agricultural Society, MT-Energie is highly

respected in the field of renewable energies. The society’s “image barometer 2010”

awarded the company 87.5 of 100 possible points, positioning it in second place in

this field. In the sector of renewable energies “we can distinguish two image leaders

in the agricultural field: Enercon, Germany’s leading supplier of wind energy plants,

and MT-Energie, the supplier of biogas plants.

Beside my own activities in the R&D Biogas plants in Rockstedt performing this

experiment, I was associated with other new projects in Australia, Russia and

Pakistan. As an intern in the department of Sales and Project Management, I had to

contribute in preparing both feasibility and technical studies. Receiving orders from

customers, supplying both engineering and Biotechnological consultations,

Engineering Drawings preparation, cost estimates, looking for shareholders and

partners were all a part of my job.

The Biogas project of Landhi, Karachi, Pakistan was one of my direct Burdens. A

multi stream set of 12 Biogas plants with a total output of 22 mW electricity as the

world’s biggest Biogas plant. With 250000 Water Buffalos producing around 8000

tons/day of manure along with vegetable and restaurant wastes makes this project

very unique. Challenges like separation of solid bodies, logistics of waste collection,

dealing with high DM content in the feeding wastes, green water recovery techniques

and fertilizers’ production have risen in the horizon. By the time I was facing these

problems; my experiment in Rockstedt was solving most of them.

http://en.wikipedia.org/wiki/Air-supported_structure

http://en.wikipedia.org/wiki/German_Agricultural_Society

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