Luận văn establish an anaerobic batch system by using guideline vdi 4630 and determine the biogas yield of different substrates in food processing villages

VNU UNIVERSITY OF SCIENCE - TECHNICAL UNIVERSITY OF DRESDEN TECHNISCHE UNIVERSITAT DRESDEN Bui Dieu Linh ESTABLISH AN ANAEROBIC BATCH SYSTEM BY USING GUIDELINE VDI 4630 AND DET

VNU UNIVERSITY OF SCIENCE - TECHNICAL UNIVERSITY OF DRESDEN

TECHNISCHE UNIVERSITAT DRESDEN

Bui Dieu Linh

ESTABLISH AN ANAEROBIC BATCH SYSTEM

BY USING GUIDELINE VDI 4630 AND DETERMINE THE BIOGAS YIELD OF

/NU UNIVERSITY OF SCIENCE - TECHNICAL UNIVERSITY OF DRESDEN

UNIVERSITAT DRESDEN

Bui Dieu Linh

ESTABLISH AN ANAEROBIC BATCH SYSTEM

BY USING GUIDELINE VDI 4630 AND DETERMINE THE BIOGAS YIELD OF

DIFFERENT SUBSTRATES

IN FOOD PROCESSING VILLAGES

Major: Waste Management and Contaminated Site Treatment

Topic

Establish an anaerobic batch system by using guideline VDI 4630 and

determine the biogas yield of different subsirales in food processing villages

Task

The first task is to establish an anaerobic batch system in Environmental Chemistry

laboralory, Facully of Chemisty, Hanoi University of Nalural Sciences, Hanoi

National University by using German guideline - VDI 4630 With this system,

different mocula from various sources around Haro: will bs assessed their quality to

choose the good one for next experiments with substrates Reforonce substrate is

sodium acetate Substrates as wastes (cassava residues, rice residues, water

hyacinth, pig manure) in Dai Lam village - a craft village of wine production and pig, breeding will be sampled, prepared and fermented in free-oxygen environment The processing parameters are biogas production, biogas composition (CI, and CO;), pH - value, TS (total solids), VS (volatile solids), COD (chemical oxygen demand) ‘Ihe biogas yield (per amount of substrate, per VS of incoulum, per COD

of substrate) and the degradability of different substrates will be evaluated

Objective

The aim of this thesis is from learung the methods of gindehine VDT 4630 to

establish in practice an anaerobic batch system in the conditions of a Vietnamese

laboratory Then it is to control this system to investigate the quality of inocula, the

fermentabilily/ the biogas potential/ the specifie biogas activily of different organic wastes from food processing and livestock of a Vietnamese craft village it is also

close lied 10 the one chjeclive of education and technology bansfer of INHAND

project (project funded by the Federal Ministry for Education and Rescarch of

Germany - BMI’, with the project coordinator Institute of Waste Management and

Contaminated Site Treatment, Dresden University of Technology) about Integrated management of water, wastewater, waste and energy in craft villages in Vietnam

2.1, Basics of Anaerobic Digestion

2.1.1 ‘the four stages of decomposition

2.1.2 Influence Factors of Digestion

2.1.3 Biogas potential of different substrates

2.2, End products of fermentation

3 Materials and methods

3.1 VDI survey about batchtests for biogas yield determination

3.1.1 Scope and purpose of Fermentation batchtests

3.1.2 Methods of ¥DT 4630 in detecting the biogas yield

3.1.3 Method of VDI 4630 in approaching the batchtests

Contents

conlent in biogas

33, Experimental procedure

3.3.1 ‘Test condition and batch apparatus

3.3.2 Method to calculate the biogas production, the biogas yield, the

biogas composition, the degree of degradation

4.E

luxtion and điscussion oÍ the batch exneriments 4.1 Activity potential of different inocula

4.2 Biogas production and biogas composition of different substrates

4.2.1, Biogas yield (mb VSyondaan Mx/@CODedatcates Mb! g substrate)

4.2.1.1 Biogas yield of trial 6 with inoculum 5

42.1.2 Biogas yield of trial 7 with imoculum $

42.1.3 Biogas yield review of different substrates with inoculum 5

4.2.1.4, Biogas yield review of different substrates with inoculum 6

4.2.2 Comparison of biogas yields wilh theory and Hterature

4.2.3, Biogas composition (CH, and CO, content)

4.3 Residue of biogas produetion

4.3.1 Degree of degradation of volatile solids

4.3.2 Degree of degradation of total solids

4.3.3, Degree of degradation of COD total,

4-4 Bnor analyis

5 Conclusion fe ee eee 12H 1.2 1011 tư

References

Annex- Data records

GŒCR Cassava residues sample

cob Chemical oxygen demand

he standard liter, volume under normal condition

my standard milliliter, volume under normal condition

P/PM Pig manure sample

Figure 3-2; Gas volume measurement with a gas pressure measurement

instrument (8 Meier, 2009),.ccsesssssssesesseeuiensensienvannene 18 Vigure 3-3: Map showing position of Dai Lam village eo 2Í Figure 3-4; Water hyacinth at main sewer cscs 2t Figure 3-5: Riceresidues and cassava residues sampling athouseholds 22 Figure 3-6: Pig manure at a sinall swine farm of a household vee 2B Kigure 3-7; Homogenizing cassavaresidues by blender 23

Eigue 3-8: Homogenizing water hyacinth by blender

Figure 3-9: Filling the bottles by weighing method tee tee 30

Figure 3-11; Crealing the vacuum inside the Dollles cccccceneeseenen ẤT Eigure 3-12: Lovibond onditioning cabinet s2 221 2 2 z7 32

Figure 3-13 K2000 Pressure table - EXTECH manomcter 407910 32

PL722N instrument in measuring COD

Gas chromatograph Shimadzu GC-2010 Biogas yield without blank om different inocula [mly Biogas’ g

COD sodium acetate]

Ringas yield with blank on different inocula [mly Biogas! ¢ CÓD sodium aeetate]

Biogas yield with blank on inoculum 5 of trial 6 [my Biogas/ g

VS Inoculum]

Biogas yield without blank on inoculum $ of trial 6 [mby

Riogas/ g COD substrate]

Biogas yield with blank on inoculum 5 of trial 7 [inky Biogas! g

'V§ Inoculum[ "-

Biogas yield without blank on inoculum 5 of trial 7 |mhy

Biogas/ g COD substrate]

Biogas yield with blank on inoculum 5 of trial 6-7 [mks Ringas/ g VS Inoeuluu]

Biogas yield without blank on inoculum $ of trial 6-7 [mls Biogas/g, COD substrate] cscsessenessssiestintnineeneene ee Biogas yield wilh blank on inoculum 6 of trial 9 [nly Biogas! g

List øf Tables

List of Tables

Table 2-1: Average composition of biogas (FNR, 2005)

Table 2-2, Factors influencing the anaervbie degradation (WETLAND,

‘Table 2-3; Micro-ndtrients for the anaerobic degradstion

‘Table 2-4; Inhibitory concentstions ofvariơus clements (WEBSSELAAK, 2009)

Biogas composition and yield of different groups of

substances (Biogas Guide 2006), Properties of renewable resources (FNR, 2005)

Description about sources of six inocula Description of the batchtests for investigating the quality of six

Descriplion of the balchiests for investigating the biogas

potential of different substrates Description of the experimental approach and parameters in

trials investigating quality of six inocula,

Summary of biogas yield without blank and SLR on different

Summary of biogas yield and SLR of trial 7

Description of the experimental approach and parameters in trial 9 Summary of biogas yield and SLR of tưial 9

Comparison of biogas yields with thery

Comparison biogas yields of water hyacinth samples with literature

Biogas composition of different samples in trials 6, 7, 9 Volatile solids of different samples

Degree of degradation of volatile solids

‘Total solids content of different samples

Degree of degradation of total solids Chemical oxygen demand of different samples Degree of degradation of COD

Dogrce of degradation of COD

Degree of degradation of COD

Acknowledgements

Acknowledgements

Special thanks I would like to say to my supervisor Prof Dr Nguyen Thi

Diem Trang for giving me the opportunity to make this thesis at Faculty of

Chemistry, Hanoi University of Science in the Double-Degree-Program between the Tlanoi National University and the Dresden University of Technology Many thanks

also to my German supervisor Prof Dr Peter Werner

Special thanks also to Msc ‘Ivan ‘Thi Nguyet (from Institute of Waste

‘Management and Contaminated Site Treatment, Dresden University of Technology) and Dipl-Ing Scbastian Mcicr (from Institute for Water Quality and Waste Management, Leibniz University lannover) team members of INILAND project who enthusiastically supervised me during the course of this thesis

‘Thanks to the help in inocula collecting of Prof Dr Nguyen Viet Anh, from the Centre for Environmental Engineering of Towns and Industrial areas (CEETIA), Hanoi Universily of Civil Engineering and the help in gas composition analysis of

Mr, ‘Thai Ha Vinh, from Monitoring and Environmental Analysis Department,

Monitoring and Analysis of Working Environment, Staton, National Tastitute of

Labor Protection Thanks also to the help in sample preparation of the staff (Mrs

Nguyen Thị Diem Luong, etc) in the laboratory of Monitoring Centre for Natural

Resources and Environment of Bac Ninh province

‘Thanks to the students of the Unvironmental Chemistry laboratory (Thang, Cham, Thao, Lan, ete) for their friendship with me during the experimental period

Gime,

Special thanks also to my family members for their great support in all the

(ime of this inaster course!

Đế

rural areas, the utilization of renewable energies has to be advanced In this context,

the usage of biogas plays an exceptional role as it is a highly flexible fuel with

respect to a wide range of input substrates Biogas also offers various options in

providing and using energy ona local, regional and global scale

Vietnam is no exception to the trend biogas applications to replace fossil energy

Phogas production has been studied and applied long in Vietnam, bul until 2003, iL

became the real attention whon the Ministry of Agricullure and Rural Development

collaborated with the Ketherlands Development Organization to build renewable

energy project, the “Support Project to the Biogas Program for the Animal

Tlusbandry Sector in Some Provinces of Viemam.” By the end of 2008, the project

has supported construction of over 56,000 household biogas plans, provided

training for $00 provincial and distriet teckmicians, 700 biogas mason cams, and organized thousands of promotion workshops and trainings for biogas users Up to now, the project has become a national program “I3iogas program for the Animal Linsbandry Sector of Vietnam” that supports the implementation of household

biogas digesters throughout Vietnam By the end of 20)2, the team aims to complete 164,000 biogas plants (including large plans) m 58 provmees throughout

Vietnam and gain 1.5-3 tradable emission rights per year per digester ‘This

program raises the effective movement of production technology and application of biological energy, reduces environmental pollution i rural areas, creates jobs and

improves living standard for Vietnamese farmers and minimizes the greenhouse effects Along with that, the World Bank is also currently funding an array of

manure management demonstration projects in Vietnam, ranging from small

household -scale systems to village-scale systems”

© hup-biogas org vntvietncm!

Introduction

The studies! of biological energy have been simulancous developing, as well as

Prof Dr Bui Van Ga director of Da Nang University and his colleagues at the Research Center for Environmental Protection (Da Nang University) with research focused on biogas refining and motor applications, or the teams from Ilanoi Polytechnic University and Ho Chi Minh Polytechnic University with research on completed conversion of gasoline and diesel lo biogas Lucl running engines Therefore, Vietnamese farmers now are utilizing the produced biogas uot only in cooking, lighting, heating but also generating electricity for their own farms by their own capital The only pity is that the farmers can not sell surplus generated power into general grid Besides, the Bio-Gas Project in the framework of the "Ga Green -

Green Journey" by Toyota Viclnam (TMV) in collaboration with the General Department of Environment and Ministry of Education and Training has been

installing 500 generator powered by bio-gas in households, farms, small and medium enterprises from 2008 up to 201 2

Based on those, biological energy has developed at a larger scale, focusing on the factories, farms, producing biogas from waste walcr of tapioca starch plants, seafood processing plants, rubber production plants, ete Up to now, Vietnam has achieved 11 Chat Projects! in validation, with the credit period from 2009/2010

to the end of 2020/2030, in the field of waste/ waste water treatment and biogas

capture (mainly in tapioca starch sector) with the parties involved as limited

companies, corporations from Japan(4), France(1), Netherlands (5), Germany(1)

?) hutp-/awwie dongeobiogas.mn

® CDM (Clean development mechanism) is the one of three market-based mechanisms in Kyoto Protocol which requires developed countries io reduce green house gas (GIG) emission CDM enables emission reduction projects, like biogas capture projects, in developing countries to get CER (certified emission reduction) credits which can be taded with developed countries 10 meet part of their emission reduction commitnents

'8) ulp:/noccop.org.vn

Introduction

The development of biogas produshon and application with all the domestic potential and overseas support has been bringing great benefits for Vietnam’s

economic development and environmental improvements For that, contributing to

the studies of biogas in Vietnam, this thesis focused on the incthod of Gennan

guideline (VDI 4630) to assess the potential of recovery of organic waste in a

Vietnamese food processing village by biogas production Firstly, it is lo establish

an anaerobic batch system for biogas production in the laboratory in the North of

Vietnam ‘hen, experiments with this system were set up to investigate the quality

of mocula from ch{ferent sources around Hanoi And with chosen mocula, substratcs

as organic waste of Dai Lam village - a wine production and pig breeding village in Bac Ninh province were assessed Parameters of process were pl, temperature, TS,

VS, and COD Biogas potential aud the fermentubihty of hese substrates were

evaluated and interpreted by using VIDI- 4630 guideline

Theoretical Basics

2 Theoretical Basics

2.1 Basics of Anaerobic Digestion

2.1.1 The four stages of decomposition

‘The methane fermentation process comprises four stages that organic materials being degraded by anaerobic microorganisms in the absence of oxygen The degradation of high molecular weight starting substrates such as carbohydrates, fats and protein via low molecular weight compounds (fatty acids and alcohols) to methane, which is the main component of biogas Figure 1 shows a degradation

process which is described below:

Fats

Carboxylic

acids

Alcohols

Hydrolytic Bactoria Fermentative Acetogenie Methanogenic

Figure 2-1: Four stages of anaerobic degradation (WEILAND, 2003)

In the first stage (hydrolysis), facultative anaerobic microorganisms hydrolyze the

biomass with the aid of extracellular enzymes (exoenzymesf”) to low molecular

weight components Here, the organic substance is transferred by addition or

temporary storage of water molecules in a dissolved form The facultative anaerobic

"S Hyoenzymes are synihesized by the bocteric-consuming enzymes, which serve lo break up nutrients,

Theoretical Basics

bacteria which were created to consume the remaining dissolved oxygen present with low required redox potential (less than - 330 mV) are the obligatory anaerobic

bacteria (methanogens) The rate of hydrolysis is determined by the substrate

composition, (cmperature, pH value (oplimun pH 6, (BISCHOFSBERGER, cL

al, 2005)), and the concentration of microorganisms For example, sugar and

hemicellulos: are liydrolyzed very well, whereas pectin and lignin are difficull to hydrolyze Therefore, the higher the propartion of shares in the easily cleavable substrate is, the faster the digestion process of the bacterial cells run ‘I'he hydrolysis

is therefore generally regarded ay rate-lnniling step of anacrobie (and acrotie) degradation (ROEDIGER et al., 1990)

Subsequently, the hydrolysis products in the second stage of fermentation (avidiftcation) fermented intracellularly by the bacteria, the bacleria exerele mainly carboxylic acids, ethanol, ammonia, hydrogen sulphide and carbon dioxide ‘the acidogenic bacteria here have a large tolerance, so that the plI value for the acidification of carbohydrates may fall below 4.0 (BISCHOFSPERGER et al, 2005) ‘The degradation of the hydrolysis and acidification can be inhibited by its own metabolic products One hand, the bacteria produce only insufficiently dissolved substrate cxoenmymes, on the other hand, (hese exoenzymes are sensilive

to pI values less than 6.5 (ROLDIGER et al., 1990)

Because methanogenic bacteria produce methane only from acetic acid, hydrogen and carbon dioxide in the third stage (avclogenesis), Ile carboxylic acid and alcohol

of the second stage can be converted to acetic acid, carbon dioxide, water and hydrogen Anunonia is mineralized to ammonium

In the fourth stage (methanogoncsis) methanogenic bacteria convert acetic acid, hydrogen and carbon dioxide to methane ‘the methane formation is carried out for 70% of the acclic acid degradation (also called avelate-degrading, see equation 2-1) and about 30% of the conversion of carbon dioxide and hydrogen (ROKDIGER et al., 1990) See equation 2-2

CH,-COO" | HQ > CH, | HCO; (Equation 2-1)

2005) For methanogenesis, the optimum pH is 7 and the oplimum lomperature is al

35° Cand 55 ° C (ROLDIGER et al., 1990)

There are 13 species of methane-forming bacteria, of which 11 spevies have their

optimum working environment in the mesophilic range and one type in the thermophilic environment Another type is thermo-tolerant and can operate in mesophilic and thermophilic range

‘Throughout the fermentation process, hydrogen inhibits the acetogenic bacteria ‘he close symbiosis between the acetogenic bacteria and the methanogenic bacteria is

au inporlanl prorequisile, since methanogenic bacteria prevent the inbibitory cflects

of excess hydrogen, by converting the hydrogen with carbon dioxide to methane (see equation 2-2) The symbiosis should be adjusted by the mixing process in the

reactor with registered shear forces, in order nol to destroy iL

After a trouble-free decomposition of organic substrates, there is an energy-rich gas

mixture which consists mainly of methane and carbon dioxide An average biogas

composition is given in Table 2-1

Table 2-1; Average composition of biogas (F'NR, 2005)

Theoretical Basics

2.1.2 Influence Factors of Digestion

Arwurobie degradation processes mvolve a number of factors thal determine the growth and activity of microorganisms significantly We distinguish effects due to operational factors (temperature, mixing, residence time, organic loading rate) and the influence of substrate components (C: N: P ratio, pH - value, concentration of inhibitory substances and nutrients, etc) Some of these factors influence each other and are mutually dependent Selected factors are briefly explained in the following sections

Mixing

Optimum mixing of the reactor is set to ve sufficiont contacl between bacteria

and fermentation substrate Temperature and concentration differences are

compensated in the fermenter by mixing Without or with insufficient mixing, the

amass of bacteria would decrease and easily demolished at the bottom to rise up the

fermentation and form a floating layer through which the gas outlet would escape

more difficult On the contrary, with vigorous mixing, there is the danger to those

living in small communities, symbiosis acetogenic and methmogenic bacteria communities are affected by too high shear forces (GRONAL et al, 2007)

Theoretical Basics

the species Mothanosarcina barken(2) are both the mesophilic and thermoplitic methane bacteria (DORN ACK, 2001), Since methane bacteria are very temperature- sensitive, and are adversely affected even at low temperature, a constant temperature control of anaerobic reactors is necessary (ROEDIGER et al,, 1990) With extreme temperature fluctuations, the bacteria respond with lower metabolic

rates and reproductive performance (DORNACK, 2001)

pH value

‘The pll - value arises from the metabolic products of naturally present microorganisms and the different self-regulating buffer system The predominant organisms in the degradation phase specics have different optimal pH During hydrolysis and acid-forming, bacteria find their pli optimum at 4.5 to 6.3, methane bacteria thrive best in a very narrow pH - 6.8 to 7.5 (FNR, 2005) A shift in the pH - value out of the narrow range from 6.6 to 8.0 can be rough interference to substrate degradation, result in the bacterial growth rate and metabolism (TAULSTICII, 1995) For example, the slable of hydrolyzing substrates can be inbibited by an excess of lime, because the required optimum pH is not created by the buffering action of the lime The consequence is lower gas yields

Factors influencing the anaerobic degradation are summarized in table 2-2 below

Table2-2: Factors influencing the anaerobic degradation (WEILAND, 2001) modified

Hydrolysis / acidification | Methane fermentation

Theoretical Basics

Ratio of nutrient elements

The C/N ralio and the C/N/P/S ratio can be used as an indicator of the optimal supply of carben and nutrients If the C/N ratio is too high then the used carbon is not completely eliminated and therefore the methane potential not fully exploited

This raha is shified to nitrogen, there is the danger of the formation of ammonia

which is toxic in too high on the bacteria The C/N/P/S ratio is used to draw conclusions about the nutrient supply of the bacteria

Trace elements

For the growth and survival of the bacteria, tave elements that do nol exceed

certain levels should also be required (see Table 2-3) ‘The trace elements must

present in dissolved form The natural sources of entry for the trace elements in

agricnlursl biogas plants are agricultural soils, cic, which can be distinguished between natural and anthropogenic influences such as pedogenesis fertilizer,

emissions from industry and traffic

‘The incorporation of trace elements in plant and animal feces is based on feeding and additives and other input sources Lacking of trace elements, so as at too high concentrations, a delay occurs that can lead to the stoppage of the anaerobic degradation

Concentration (ing/l organic matter) LElement

according to SAIIM3 according toe KLOSS® According to SEYFRIED"

Inhibiting and toxic substances

During anaerobic degradation, a variety of substances in high enough

concentrations have inhibitory effects The inhibitors can be distinguished

according to their origin such as inhibitors in the degradation by addition of

substrate or inhibitors as intermediates Inhibitors which are introduced by adding

substrate, include substances which were used for cleaning and disinfection

purposes or for the treatment of animal diseases Also, herbicides, salts or heavy

metals, including essential heavy metals can be toxic in high enough concentrations

up to 600 mg/l NaS (in adapted cultures)

up to 1000 mg/1 II,S (in adapted cultures)

in the literature The different threshold concentrations also result from the

interaction between the ingredients, the type of fermenter and the operation of the

plant (KALTSCHMITT et al., 2009)

The addition of substrates with high proportions of carbohydrates and fats may lead

to the inhibition process, when the hydrolytic and acid-forming bacteria break down, organic matter faster than the acetogenic and methanogenic bacteria convert the resulting acids inlo biogas This process can be determined by the ratio of the

organic acids to alkalinity (VOA® / 1AC™) Values below 0.4 indicate a stable (8 Yalatile organic acids

`! Total cmorganic carbon

Theoretical Basics

process and ierprot values grealer than 0.8 indicale a yrocess of inhibition (MABIINERT, 2007) The degradation of proteins forms end products of acetic acid and ammonia, and there may be an increase of hydrogen sulfide If there are acolc avid, ammunia and hydrogen sulphide in chssolved, undissocialed for and tì high concentrations, these substances act as cytotoxins and the methane formation is inhibited, Methane-forming bacteria take on only the acid in undissociated form (see Eq, 2-3) The acidity constant of acetic acid is given as pKa = 4.75, ie in the pH range of methanogenic bacteria between 6.8 to 7.5 acetic acid is largely dissociated

acelate as before (BRANDENBURG, 2008) Concentrations of 50 mg /1 HS are

considered directly inhibiting process, while the failure of essential trace elements

as insoluble sulfides is possible the indirect inhibition

CU,COOLL S CL,COO "+I" (Liguation 2-3)

The inhibitory effeck of ammonia increases with higher pH values and higher

temperatures, because the equilibrium between ammonium and ammonia is strongly

pH and temperature dependent For the anaerobic fermentation, a total comeuntration of NHy/NH; + H* greater (han 3 g /1is critical (MARHNERT, 2007)

Table 2-5: Inhibitory concentrations of various heavy metals

(WESSELAK, 2009}

Theoretical Basics

2.1.3 Biogas potential of different substrates

The anaerobic degradation of glucose io carbon dioxids and methane can be

described approximately by (Eq 2-4)

CgHzO, > 3CH, | 300, (Equation 2-1) Biomass is not only [rom carbohydrates and biogas consist, not only carbon dioxide

and methane, If the exact composition of the fermentation substrate was determined

in terms of the number of carbon, oxygen and hydrogen atoms, then BUSWELLS

and MUBLLER (BUSWELL, oi al., 1952) simplified the equation

C;H,O+(n a4 b/2)H,O > (/2+ a8 b/4) COr+ (v2 a8 +04) CHy

(Equation 2-5) GHVO,N,8¡+ (- a/4 0/2 + 30/4-+ d/2)HLO >

Œ2 ø8—b/4+3c8+d/4CO,+(w2+aÐ bí 3e8 4⁄4Cl+eNIs~dlsB

(Equation 2-6) (Faustion alicr BOYLE (BOYLE, 1976)) Table 2-6: Biogas composition and yield of different groups of substances

Theoretical Basics

The equalion for BUSWELLS and BOYLE (Bq 2-6) is used to determine the

respective proportions of carbon dioxide and methane in the biogas The calculation of

the biogas potential of the three main groups of carbohydrates, fats and proteins after

BUSWELLS equation provides the resulls in Table 2-6 Under the full anacrobic

reduction a higher methane content in biogas in fats and proteins is expected than the

carbohydrates The average methane conlert in biogas is 50 - 75 vol.%,

Table 2-7: Properties af renewable resources (FNR, 2005)

Theoretical Basics

2.2 End products of fermentation

nd products of arwerobic digestion are biogas and digestale and process waler is mentioned as a possible intermediate The topic of biogas production has alrcady been discussed above in detail

An agricultural biogas plant can be generally considered as a closed system and no technical treatment of residues, no process water is provided in this system A treatment of the digestate can be, for example separation in solid and liquid phase or

dewatering and composting Water in the waste treatment process can be subject to

various process-relevant parameters such as plL salt concentration and others,

retumed Lo the fermenter

The digestate without subsequent treatment are primarily used as fertilizer The agnicullural usc and the appheation of the fermented substrates al the recovery

fermentation depend on the bio-waste regulation ‘Ihe organic dry matter content is

reduced by the fermentation, in which the degree of degradation of manure of

species and accounting system-specific parameters and fermentation parameters are

dependent ‘Ihe viscosity of the slurry is reduced by the anaerabic digestion and thus has a positive effect on the pumping, homogenization and spreading of

degestate Odor-active substances are futher reduced by the fermentation, the

degradation of the organic acids also helps to reduce the corrosion of the plant ‘he

total nitrogen content is not reduced by the fermentation process The increase in

pH compared to unfermented manure takes the ammonia content into the digestate Ammonia losses can be increased by the storage and spreading of residues The

masses of the ingredients of the digestate as phosphorus, calcium, potassium and

magnesium arc not reduced by the fermentation The sulfur content is reduced by discharge of hydrogen sulfide and the remaining sulfur is present mainly as

clomental sulfur in the digestalc Heavy motals are not, subject to biological

degradation and accumulate in the digestate Epidemic of health hazards bacteria

are decimated within days under mesophilic conditions by 90% By short-circuit

Materials and Methods

3 Materials and methods

3.1 VDI survey about batchtests for biogas yield determination

3.1.1 Scope and purpose of Fermentation batchtests

According to guideline VD1 4630, batch procedure can be applied to all kind of organic materials which can be representative So that, organic wastes chosen in this

thesis such as cassava residues, rice residues, pig manure and water hyacinth would

be sampled and prepared as instructed in this guideline to achieve homogenous

state

Jermentation batchtests with VDI methods help to evaluate the possible biogas yield, the degradability, the degradation speed, the inhibitory effect of these wastes

in Dai Lam village — a representative crafl village of wine production and pig

breeding in Bac Ninh province which is located in the North of Vietnam

3.1.2 Methods of VDI 4630 in detecting the biogas yield

In VDI 1630, there are six possible methods of detecting the pas such as gas volume measurement with the head water systems (the eudiometer, the gas sampling, tube), with gas pressure meastrement instrument, with plastic bags, with syringe sampler and with the gas meter Each of the test apparatus has its own strengths and

weaknesses

Tn case of this thesis (with the imstruclion of the Institue for Water Quality and Wastc Management, Leibniz University Hannover, Germany) gas volume

measurement with a gas pressure measurement instrument was properly applied

The gas volume is measured indircelly by a pressure measurement instrument and caloulated from the gas pressure registered and the gas temperature measured ‘he

test apparatus of this method is shown in figure 3-1

Materials and Methods

Figure 3-1: Test apparatus according to DIN EN ISO 11734: Gas volume

measurement with a gas pressure measurement instrument (VDI 4630) This system is also known as “Constant- Volume- Reactor”, in which water and gas phase are temperature controlled at 37°C and gas quantity determination via

pressure slope The automatic model — modified of the base model - applied in the Institute for Water Quality and Waste Management, Leibniz University Hannover, Germany is shown in figure 3-2

Conditioning

cabinet

Pressure device

Silicone stopper

Figure 3-2: Gas volume measurement with a gas pressure measurement

instrument (S Meier et al., 2009)

Materials and Methods

3.1.3 Method af VDI 4630 in approaching the batchtests

According to VDT 4630, the batch fermentation tesis should be conducted al least as double determinations (or better as triple determinations) with investigated samples

as well as reference and blank (zero) samples

Based on VD1 4630 and instruction of the Institute for Water Quality and Waste Management, Leibniz University Ilannover (8 Meier et al., 2009), steps of a

batchtest with rising pressure system can be described as following:

- Pretreatment of biomass (reducing COD of inoculum) by etiolation

- Analysis 1: TS, VS, pH of inocukun, COD of substrates

- Precaloulation of substrate amount, gas space, expected pressure increase

- Preparation of inoculum and substrates

- Boille weighing and filling with inoculum, substrate, free oxygen water, bulTer

- Flushing with nitrogen Closing bottles and creating vacuum (0.2 bar.)

- Tacubating af constant lemperature (37°C) and measuring pressure increase

‘until it remains constant

- Analysis 2: Gas composition analysis (‘he methane content should be determined more than once during the fermentation test, it is best al regular intervals)

- COD, TS, VS, pH of digestate

During the course of test, the fermentation material should be sufficiently mixed such

as shaking the bottles each day to resuspend the sediments and the scum layers

3.2 Analysis method

3.2.1 Sampling

a Inoculum

The selection of inocula [or starL-up of auacrobic digesters is always nnportant

Digested sewage sludge or other anaerobic sludges may be used to provide an anaerobic digestion community of microorganisms Provided population of

Materials and Methods

methanogens can remave inihibilory byproducts of the faster growing hydrolyzing

and acid producing processes Since investigated substrates as food process

byproduct, fresh plant might not he high on methanogen’s favorite places to live, or

substrales as resh manures which have large population of melhane producing

organisms need long time process

Kor that, six inocula around Hanoi were collected and tested the quality

Table 3-1: Description about source of six inocula

Cultured inoculum from Lab of Prof Neuyen Viet Anh in the Centre

1 frastewater ofhousehold for Rnvironmental Engineering of Towns [29% June

lseptic tank and Industrial areas (CEHTLA), Hanoi 2011

University of Civil Engineering

4 |Pigested municipal Kim Lien wastewater treatment plant, Dong |20" hme

._[Pigested revamped Kim Lien wastewater lrealment plant, Derg |S July

Cultured inoculum from Lab of Prof Nguyen Viel Anh in the Centre

4 lwastewater of household for Linvironmental Lingineering of Towns | 11 July

septic tank (dewatered) and Industrial areas (CEETLA) Hanoi 2011

Universily of Civil Engineering

5 [Digested sludge from A small housebold biogas plant in Dai Lam |11"July

6 [Digested siudge from A small houzebold biogas plant in Hai 14" July

Inoc : Inoculum

Materials and Methods

Maz showing geographical position of Par Lam village in the province

‘of Bac finh northeast of Kano:

Figure 3-3: Map showing position of Dai Lam village

Materials and Methods

- Riee residues and cassava residues were collected twice at Wine processing households, Samples were homogenized by stirring in the bucket and taken on

different areas of the bucket (on the top, at the bottom, and from the middle)

Figure 3-5: Rice residues and cassava residues sampling at households

(INHAND photo documentary)

- Pig manure was collected twice at small swine farm of a household Samples

were homogenized by taken on different areas of one pile

Figure 3-6: Pig manure at a small swine farm of a household

(INHAND photo documentary)

Materials and Methods

3.2.2 Sample preparation

Water hyacinth, rice residues, cassava residues, pig manure were preliminarily prepared in laboratory of Monitoring Centre for Natural Resources and

Environment of Bac Ninh province Then samples were transported in tight cap-

plastic box to Environmental Chemistry Laboratory, Faculty of Chemistry, Hanoi

University of Natural Sciences, Hanoi National University for next steps

Rice residues and cassava residues

The fresh sample was mixed as much as possible to crush and homogenize by blender

Figure 3-7: Homogenizing cassava residues by blender

(INHAND photo documentary) Preparing a dilution: (often rate 1: 200 for COD total and 1:10 for COD of filtered

sample)

- Dilution for COD total measurement: The homogenized sample was weighed and filled into a volumetric flask Fill up with distilled water until calibration mark

Shake the volumetric flask to homogenize the sample Transfer the liquid into a

Materials and Methods

beaker glass Put the beaker glass on a stirring plate and add magnetic stirrer (do not

stir too fast.) During stirring take the sample for analysis by pipette

- Dilution for measuring COD of filtered sample: The fresh sample was filtered two

times by coarse filter paper and by 0.45um pore size membrane filter with plastic

syringe Take the filtered liquid into volumetric flask by pipette Fill up with

distilled water until calibration mark Shake the volumetric flask to homogenize the

sample Transfer the liquid into a beaker glass, Put the beaker glass on a stirring

plate and add magnetic stirrer (do not stir too fast.) During stirring take the sample

for analysis by pipette

Water Hyacinth

Remove the leaves and the stems from the plant and cut it in small pieces separately

Mix thoroughly then weigh 200 gram of sample Put into the mill, Add 500ml

distilled water Operate the blender as the sample is homogenized thoroughly Pour

the liquid into 11 volumetric flask Wash the mill clear by 200m! distilled water Pour

the wash water into the volumetric flask Fill up with distilled water until calibration

mark, Shake the volumetric flask to homogenize the sample The dilution rate is 1:4

Figure 3-8: Homogenizing water hyacinth by blender

(INHAND photo documentary)

Materials and Methods

Transfer the liquid into a beaker glass Put the beaker glass on a string plate and add magnetic stirrer (do not stir too fast) During stinring take the sample for

analysis by pipette Dilution with appropriate rate for COT) analysis (often rate 1:20

for COD total and 1:5 for COD of filtcred sample)

Pig Manure

Fresh sample was mixed thoroughly and weighed for 200gram Put into the mill Add 500ml distilled water Operate the blender as the sample is homogenized thoroughily Pour the liquid into 11 volumetric flask Wash the mill clear by 200ml distilled water Pour the wash water into the volumetric flask Fill up with distilled

water unlil calibralion mark Shake the volumetric Mask to homogenize the sample

Transfer the liquid into a beaker glass Put the beaker glass on a stirring plate and add magnelic slirer (do nol stir 100 fasl) During stirring take the sample (or analysis by pipette Dilution with appropriate rate for COD analysis (often rate 1:100 for COD lolal and 1:10 for COD of fillered sample) The dilution rate was 1:4

3.2.3 Determination of parameters: ‘I'S, VS, COD, and CIL, and CO, content

in biogas

TS (Total Salids or dry matter) measurement

TS was measured as specification APHA-SMWW "_ 2540G (103-105°C) Ceramic

emecibles (50ml or 30m!) were put in put in muffle fmace at 550°C for 1 hour (in

this case, bey were put in drying cabinet, at 105°C for 1 hour), then weighed the first time Kresh samples were poured into ceramic crucibles, weighed the second

time, then put into drying cabinet at 105°C for 24 hours (or to constant weight),

afier cooled down in glass desiccalor, weighed the third ume TS was specilied

based on fresh mass

1) 4PHA-SMWW American Public Heath Association- Standard Methods for the exendnation of

Water ema Wastewater

Materials and Methods

VS (Volatile Solids or organic dry matter} measurement

VS was measured as specificalion APHA-SMWW_ 2540G (550°C) Ceramic

crucibles with dry matter were put into muffle fumace kept at 550°C for 1 how After cooled down in glass desiccators, weighed the last time VS was specified

based on [Tesh mass

COD (Chemicai Oxygen Demand) total of homagenized fresh sample and COD soluble of the filtered sample

COD was measured as method of Environmental Chemistry laboratory, Chemistry departnent, Hanci University of Seicnces which is modified from specifivation

APHA-SMWW_ 5520D- Closed Reflux, Colorimetric Method

Reag preparation

@ Digestion solution, high range: Add to about S00 ml distilled water 10.216 g, K,Cr,0,, primary standard grade, previously dried at 150°C for 2 hours, 167 ml concentrated 1,504, and 33.3 g LigSO,4 Dissolve, cool to room temperature, and dilute to 1060 ml

& Sulfuric acid reagent: Add Ag)50,, reagent or technical grade, crystals or

powder, to concertrated HySQq at the rate of 5.5 ¢ ApoSO4/kg H)SOQq Let stand 1 to

2 days to dissolve, Mix

¢ Potassium hydrogen phthalate standard (KHP}; HOOCC;H,COOK: Lightly crush and then dry KHP to constant weight at 110°C Dissolve 850 mg in distilled water and dilute to 1000 ml KIIP has a theoretical COD of 1.176 mg Q,/mg and this solution bas a theoretical COD of 1000 pg Oo/ mil

Materials and Methods

Place 2.5m) of sample im culture tube, then add 1.Sml of digestion solution,

carefully run sulfuric acid reagent down inside of vessel so an acid layer is formed under the sample-digestion solution layer Tightly cap tubes, and invert each several times to mix complete

Wear face shield and protect hands from heat produced when contents of vessels are mixed Mix thoroughly before applving heat to prevent local heating of vessel

bottom and possible explosive reaction:

Place tubes in block digester preheated to 150°C and reflux for 2 hours behind a protective shield

b, Measurement of dichromate reduction:

Cool sample lo room tomperature slowly Lo avoid precipitate formation, place

vessels in test tube rack, Once samples are cooled, vent, to relieve any pressure gonorated during digestion Mix contents of reaction vessels to combine condensed water and dislodge insoluble matter Let suspended matter settle sa that optical path

is clear Measure absomplion of cach saruple at sclecled wavelength 605:

¢ Setting up calibration curve:

Ten standards frem potassium hydrogen phthalate solution were prepared with

COD equivalents to cover concentration range: 0 to 1000 ug O2/ ml Make up to volume with reagent water, use same reagent volumes, tube, or ampule size, and

digestion procedure as for samples Curve was linear

CH, and CO; content measurement

CH, content, was measured by GC (gas chromatography) method with FID (lame inonization detector), CO; content was measured by GC method with TCD (thermal

conductivity detector)

Materials and Methods

Principle of iromalography

In gas chromatography a mobile phase (a carrier gas) and a stationary phase (column packing or capillary column coating) are used to separate individual compounds The carer gus is nitrogen, amgonanethane, helium, or hydrogen For packed columns, the stationary phase is a liquid that has been coated on an inert

granular solid, called the column packing, that is held in borosilicale glass Lubing

The column is installed in an oven with the mlet attached to a heated injector block and the outlet attached to a detector Precise and constant temperature control of the

injector block, oven, and detcolor is maintained Stalionary-phase material and concentration, columm length and diameter, oven temperature, carrier-gas flow, and detector type are the controlled variables

When the sample solution is introduced into the coluum, the organic compounds arc vaporized and moved through the column by the carrier gas ‘they travel through the column at different rates, depending on differences in partition coefficients between

the mobile and stalionary phases

lame Inonization Detector

Flame ionization detectar—The flame ionization detector (FID) is widely used

because of ils high sensitivity 10 organic carbor-eontaining compounds The

detector consists of a small hydrogen/air diffusion flame burning at the end of a jet

‘When organic compounds enter the flame from the column, electrically charged

inlermediales are formed These are collected by applying a voltage across the flame ‘Ihe resulting, cwent is amplified by an electrometer and measured ‘Lhe

response of the detector ts directly proportional to the tolal iass entering the

detector per unit time and is independent of the concentration in the carrier gas

‘Use instrument system equipped with a thermal conductivity detector (TCD),

camier-gas [low controllers, injector and columm temperature setling dials, TCD

current controller, attenuator, carrier-gas pressure gauge, injection port, signal

Materials and Methods

Injection: 1Gul, split 10, 200°C

b Analysis of CO; by running GC/ TCD equipment program