JOMO KENYATTA UNIVERSITY OF AGRICULTURE AND TECHNOLOGY
SCHOOL OF BIOSYSTEMS AND ENVIRONMENTAL ENGINEERING
DEPARTMENT OF AGRICULTURAL AND BIOSYSTEMS ENGINEERING
DEVELOPMENT OF BIOGAS PRODUCTION SYSTEM FOR SISAL WASTE: CASE STUDY LOMOLO SISAL ESTATE NAKURU COUNTY
PROJECT SUPERVISOR: DR SYLVIA MURUNGA
EBE 2515: ENGINEERING PROJECT-II
This project research is submitted in partial fulfilment of the requirements of award of degree of Bachelor of Science, Agricultural and Biosystems Engineering at Jomo Kenyatta University of Agriculture and Technology.
We hereby declare that this is our original work and has not been presented elsewhere for the award of a degree or any other purpose whatsoever.
NAME: KEITANY CHRISEN264-0538/2013
Signature ………………….Date ………………………
NAME: LAGAT NICODEMUSEN264-0539/2013
Signature ………………….Date ………………………
I certify that the above mentioned students carried out the work detailed in this report under my supervision.
Supervisor’s Name: DR. SYLVIA MURUNGA
Signature ……………………………..Date …………………
We would like to thank God for his sufficient grace throughout the project period. We wish to express our sincere gratitude to our supervisor Dr. Sylvia Murunga for her guidance and supervision in the research progress. Our heart-felt gratitude is extended to our family members for their exemplary support throughout the project. We thank our classmates for their moral support. . We also want to thank Lomolo sisal estate management for allowing us to collect sisal sample for our research and finally, we want to thank to Dr. P. N. Karanja (Chief Technologist, Food Science Department) for his excellent assistance.
This paper presents the step by step procedure of producing biogas from sisal waste water through anaerobic digestion. It is due to the environmental effects as a result of sisal waste that prompted this study. The objective was to design and fabricate a biogas production system for sisal waste and to analyse the status of the sisal wastewater before and after anaerobic digestion and to check if it within the allowable standards to be released to the environment. Also to check on the quality of biogas produced. The methods employed included; sample collection, sample taken to the laboratory for testing on important parameters such as pH, COD, BOD5, alkalinity, and suspended solids as per the APHA 2015 and analysis of biogas composition using gas chromatography. At the end of the study, a household biogas production system was developed, the composition and quality of biogas gas produced was also obtained
Table of Contents
TOC o “1-3” h z u 1.0 Introduction PAGEREF _Toc522000530 h 11.1 Problem statement PAGEREF _Toc522000531 h 21.2 Justification PAGEREF _Toc522000532 h 21.3 Scope PAGEREF _Toc522000533 h 31.4 Objectives PAGEREF _Toc522000534 h 31.4.1 Main objective PAGEREF _Toc522000535 h 31.4.2 Specific objective PAGEREF _Toc522000536 h 3CHAPTER TWO PAGEREF _Toc522000537 h 4LITERATURE REVIEW PAGEREF _Toc522000538 h 42.0 Sisal production PAGEREF _Toc522000539 h 42.1 Properties of sisal waste PAGEREF _Toc522000540 h 52.2 Biogas potential in Kenya PAGEREF _Toc522000541 h 52.3 Anaerobic digestion PAGEREF _Toc522000542 h 72.4 Anaerobic digestion process PAGEREF _Toc522000543 h 72.4.1 Factors affecting anaerobic digestion PAGEREF _Toc522000544 h 92.5 Types of anaerobic digesters PAGEREF _Toc522000545 h 11CHAPTER THREE PAGEREF _Toc522000546 h 13METHOD AND MATERIALS PAGEREF _Toc522000547 h 133.0 Introduction PAGEREF _Toc522000548 h 133.1 Design and fabrication of a biogas digester. PAGEREF _Toc522000549 h 133.1.1 Design consideration PAGEREF _Toc522000550 h 133.1.2 Requirements and materials PAGEREF _Toc522000551 h 133.1.3 Design and fabrication PAGEREF _Toc522000552 h 133.2 Analysing the characteristics of sisal wastewater before and after of anaerobic digestion PAGEREF _Toc522000553 h 163.2.1 Sisal waste collection and lab analysis PAGEREF _Toc522000554 h 163.2.2 Analytical methods PAGEREF _Toc522000555 h 163.3 Determining the quality of biogas produced PAGEREF _Toc522000556 h 223.3.1 The working principle of GC PAGEREF _Toc522000557 h 22CHAPTER FOUR PAGEREF _Toc522000558 h 24RESULTS AND DISCUSION PAGEREF _Toc522000559 h 244.0 Introduction PAGEREF _Toc522000560 h 244.1 Biogas digester PAGEREF _Toc522000561 h 244.2 Properties of sisal wastewater before anaerobic digestion PAGEREF _Toc522000562 h 244.3 Properties sisal wastewater after anaerobic digestion. PAGEREF _Toc522000563 h 274.4 Composition of biogas PAGEREF _Toc522000564 h 304.5 Discussion of results PAGEREF _Toc522000565 h 31CHAPTER FIVE PAGEREF _Toc522000566 h 34CONCLUSION AND RECOMMENDATION PAGEREF _Toc522000567 h 345.1 CONCLUSION PAGEREF _Toc522000568 h 345.2 Recommendations PAGEREF _Toc522000569 h 34REFERENCES PAGEREF _Toc522000570 h 34Appendices PAGEREF _Toc522000571 h 361.Bill of quantities PAGEREF _Toc522000572 h 362.0 Effluent standards from WARMA PAGEREF _Toc522000573 h 373.0 work plan PAGEREF _Toc522000574 h 40
1.0 IntroductionBiogas is the mixture of gas produced by methanogenic bacteria when acted upon by biodegradable materials in an anaerobic condition. The gas generated contains methane which is combustible and is used to produce heat or electrical power. (Kowalczyk et al, 2011)
Economies and technologies today largely depend on energy resources that are not renewable. It is therefore necessary to identify, research and develop alternative sources of energy that are sustainable and environmentally friendly. In many developing nations’ government and institutional research centres such as universities and colleges are trying to address the problematic concerns arising from these energy resources. Efforts and resources are being channelled towards research of biogas production system, a technology that generate biogas and an environmental friendly biogas waste.
Rising energy prices, more restrictive environmental regulatory requirements and increasing concerns over greenhouse gas emission are causing many people to consider anaerobic digestion of waste from their operations. An anaerobic digestion technology is viewed as an alternative way to address environmental concerns, generate environmentally sustainable renewable energy. In addition of generating renewable energy, biogas systems can increase crop yields, decrease deforestation pressure, reduce waste and pathogens, elimination of waste odour and improve household.
Sisal industry traditionally utilises only 5% of the total weight of the leave in the sisal fibre production and the remaining 95% is being discarded as waste. This waste is often dumped on
Land or nearby rivers in untreated form where it degraded by microorganisms under uncontrolled conditions. This leads to land, water and air pollution. Sisal waste, however, constitutes a major potential source of clean and renewable energy if digested anaerobically under control conditions to generate methane. (Salum et al, 2009)
Sisal waste are available in large quantities at various production factories and is associated with serious environmental pollution. This waste can be digested anaerobically to produce methane and less harmful waste to the environment as the end products. The use of sisal waste for production of methane could be a cost-effective option at the sisal factory level, while at the same time reducing environmental pollution.
This project therefore seeks to contribute towards environmental management by changing waste to energy which is in line with the big four agenda within the framework of vision 2030
Description of the study area
Lomolo sisal estate is located about 50km north of Nakuru at a geographical position system of 0.0167N and 36.0000E. Company mainly deals with production and processing of sisal. The company is a source of livelihood to the local community employing approximately 500 people. The sisal is cultivated in a large track of land and when matures, the suckers are cut and taken to the factory for decortication. During this process, sisal fibre and sisal waste water is obtained as the end product. The sisal waste is approximately 95% of the sisal leaf and only 5% is utilized as sisal fibre. The sisal waste water is collected in lagoons since the factory at the moment have no modern waste disposal method. As waste settle in lagoons, they produces a very bad odour which causes discomfort among the workers in the factory. There is a permanent river flowing near the factory hence there is a possibility of water pollution for the people living downstream.
1.1 Problem statementThe main environmental impacts of sisal factories are related to water pollution and greenhouse gas emissions by sisal waste and by-products. Both the solids waste at the disposal site and the wastewater in the lagoons increases emissions of methane gas to the atmosphere, generated after the decomposition of the degradable organic carbon in the waste. Methane has been known to be having a global warming higher than that of carbon dioxide, it is estimated to contributing 18% overall global warming. (Ayalon et al, 2001). The bad odour emanating from the sisal wastewater also causes air pollution leading to discomfort among the nearby community.
The factory currently spends a better amount of its income in paying electricity bills. The increase in cost of production has led the factory not to maximise its’ profits.
As outlaid in the problem statement above, it therefore makes it inevitable to develop an economical technology that uses sisal waste that will generate clean and renewable energy and less harmful waste to the environment.
Under modern environmental regulations, organic waste is becoming more challenging to dispose of into the natural environment through traditional means. The recent measures that has been taken by the ministry of environment and natural resources in Kenyan which has ban use of plastic bags, it is expected that the demand for sisal made products will increase. This will lead to high production of sisal generating more waste which will be harmful to the environment.
This sisal waste can be used to produce biogas which will be converted to electrical energy to generate electricity. The power generated can be used to supplement the existing power hence reducing the cost of production.
In article 42 of the Kenyans 2010 constitution, which states that; every person has the right to clean and healthy environment, which includes the right-
To have the environment protected for the benefit of present and future generations through legislative and other measures.
In the Environmental Management and Coordination Act 1999 part II section 3 subsection (1), it states that;
Every person in Kenya is entitled to a clean and healthy environment and had the duty to safeguard and enhance the environment.
The project covered the design and fabrication of biogas production system and physio-chemical analysis of sisal waste. The project was done at JKUAT behind ABED department.
1.4 Objectives1.4.1 Main objectiveTo develop a biogas production system for sisal waste.
1.4.2 Specific objectiveTo design and fabricate a biogas production system for sisal waste.
To analyse the characteristics of sisal wastewater before and after of anaerobic digestion
To evaluate the quality of biogas produced.
CHAPTER TWOLITERATURE REVIEW2.0 Sisal productionSisal, with botanical name Agave sisalane, is a species of Agave, indigenous to the arid regions of north and Central America but widely cultivated and naturalized in many other countries. The plant is characterized by its leaves which grows to a length of over 1m and yield a long, creamy white and very strong fibre. It is hardy plant which prosper in areas of limited rainfall and able to withstand extended periods of drought.
Globally, the total fibre produced annually is approximately 220,000 tons from growing areas which account to 5% of the leaf in total fibre. During the decortications process, about 100 m3 of wastewater and 25 t of solid residues (pulp) are generated for each ton of sisal fibres (Mshandete et al, 2008). It is grown in South America specifically Brazil and Mexico, East Africa (Kenya and Tanzania), china and Madagascar. Kenya is one of the largest sisal producers in the world. In 2005 Kenya was the fourth largest producer of sisal fibre after Brazil, China and Mexico with production of 25,000 tonnes per annum (Export Processing Zones Authority, 2005).
In the last decade, sisal as a natural product is becoming more and more demanding again. Recent years have shown tremendous increase in market and production. This is as a result of high demand of sisal made products such high quality carpets, bathing or polishing cloth, wire rope coarse, or manufacture of aggregate paper and bank note. The high demand of these sisal made products is attributed to their ability to degrade hence can decompose easily in the environment without posing any threat. In Kenya, Sisal is mainly grown in large plantations specifically in Mwatate, Kilifi, Taita Taveta, Mogotio and Voi.
2.1 Properties of sisal wasteSisal waste principally contains plant tissues (lignocellulosic biomass), primary and secondary metabolites and water.
Feedstock characteristic are important factors affecting biogas production and process stability during anaerobic digestion. The main characteristics of feedstocks include moisture content, total solids (TS), volatile solids (VS), particle size, pH, biodegradability, chemical oxygen demand(COD), biological oxygen demand (BOD).
The theoretical COD in sisal decortications wastewater is 11.5g/l and its biodegradability are 87%
2.2 Biogas potential in KenyaThere have been several promotion efforts by the ministry of energy and petroleum, development partners and private stake holders since the 1980s, but the spread of this technology has remained low. According to the feasibility study, ‘promotion biogas system Kenya’, commissioned by Shell International in 2007, a high proportion of biogas digesters operated below capacity, were dormant or incomplete disuse after construction. The report further indicated that only 30% of the 2,000 biogas plants earlier constructed were fully operational at the time of study. To date, it is estimated that the country has 20,000 biogas systems which is great improvement, although the potential is much high. (Ministry of Petroleum and Energy, 2017)
Biogas technology was introduced in Kenya in the mid-1950s by white settlers’ farmers. Initially, two types of biogas systems were promoted viz: the floating drum (Indian digester) and the fixed dome type (Chinese digester). Later in the 1990s a low cost tabular plastic (TP) bio-digester developed in Colombia was also introduced and has been widely used in many parts of Kenya. (Imalenga et al, 1996). In efforts to raise awareness and use of biogas and reduced demand on wood fuel, the ministry of energy demonstrated biogas production technology all over the country since early 1980s.Various NGOs and Christian organizations have also been actively involved in dissemination and promotion of biogas technology. Despite its potential benefits, the penetration rate of biogas technology in Kenya is still very low. So far about 1392 family biogas plants (10m3) have been installed and each producing on average about 1.2m3 of biogas per day (Ministry of energy; 2008). However, according to the Intermediate Technology Development Group (ITDG) now Practical Action, approximately 1100 biogas units are in operational in Kenya. The gas is used for cooking and to some smaller extent for lighting.
Widespread adoption of biogas systems has been hampered by lack of adequate information on its production, and potential benefits and also prohibitively high cost of earlier designs, and the fact that most households in the rural areas do not have piped water. The main problems reported are; poor maintenance, poor design of the digesters, high maintenance cost and poor technical support (ETC UK, October 2007).
Interest on large scale biogas plants has been rising gradually and now has shifted to large scale plants providing gas for electricity production using various types of waste as feedstock such as waste from municipal and agricultural processing. In 2007, two plants were commissioned; one is generating 150 Kw of power from a mixture of sisal waste processing and cow dung at Kilifi Plantations Limited in Kilifi County, and another 10kw plant was installed at Kamahuha Marketing Centre in Murang’a County using banana leaves, stems and fruit waste as feedstock.
There are two existing pilot producing plants for biogas production from sisal waste, located at Hale in Tanzania and the other one in Kilifi. This shows the feasibility and economic viability of the technology.
2.3 Anaerobic digestion
Anaerobic digestion is the use of biological processes, in the absence of oxygen, for the breakdown of organic matter and the stabilization of these materials, by conversion to methane and carbon dioxide gases and a nearly stable residue. Anaerobic digestion process is gaining more acceptance in the present situation due to production of biogas, which can be used to supplement the existing energy demand. Bio-methanation technology may be perceived as potential alternative which does not only provides renewable source of energy but also utilizes recycling potential of degradable organic waste and reducing the effects of waste on the environment.
2.4 Anaerobic digestion processThe process involves a series of reactions by several kinds of anaerobic bacteria feeding on the raw organic matter. Anaerobic digestion is divided into four steps;
Occurs as extracellular enzymes produced by hydrolytic micro-organisms for example lipase, amylase, cellulase, and protease, decompose complex organic polymers into simple soluble monomers that are soluble in water: peptides, saccharides and fatty acids. It is slow process and it is limits the overall anaerobic process.
Step 2: Acidogenesis
Is the process that results in the conversion of the hydrolysed products into simpler molecules with a low molecular weight, like volatile fatty acids (for example acetic, butyric and propionic acids), alcohols, aldehydes and gases like carbon dioxide, hydrogen and ammonia. Acidogenesis is usually the fastest step in the anaerobic conversion of complex organic matter in the liquid-phase digestion.
Step 3: Acitogenesis
In this step, acetogenisis, the products of the acidification are converted into acetic acids, hydrogen and carbon dioxide by acetogenic bacteria.
Step 4: methanogenesis
It is the last step of anaerobic digestion process, the products of the acid fermentation (mainly acetic acid) are converted into carbon dioxide and methane gases.
The first three steps of anaerobic digestion are often grouped together as acid fermentation. In each of the four sequential steps, the catabolic reactions described above develop together with anabolic activity. The free energy released in the reactions is partially used for synthesis of the anaerobic bacterial populations (Deubleim et al, 2008). A stable anaerobic digestion process requires maintaining a balance between several microbial populations. The hydrolysis and acidogenesis step have the most active microbes, which thrive in the broadest environmental range.
Anaerobic digestion of sisal residues is reported by many authors Mshandete et al 2008, 2004).
2.4.1 Factors affecting anaerobic digestionThe production of biogas is affected by several factors. They include; pH, temperature, pre-treatment, particle size, mixing of the digester content, rate of organic loading, retention time, concentration of micro-organisms and type of substrate. Any change in one of the parameter can adversely affect the production of biogas through the process of anaerobic digestion (Wanasolo et al, 2013, Yadvika et al, 2004).
It should be kept in a range of 6.5 to 7.5. The methane formers are pH sensitive and pH values outside of the range will affect their metabolic rates and slow or completely stop methane production, resulting in decreased biogas production or digestion failure.
Anaerobic digestion can take place at any temperature between 40C and 600C. There are two main temperature ranges corresponding to two different sets of bacteria, usually called the mesophiles, those which operate best at 200C -400C, and thermophiles which work best at temperatures between 400C-600C. Digestion can also occur in the psychrophilic range, 40C-200C, but is much lower. The rate of gas production increase with increase in temperature but there is a distinct break in the rise around 400C, as this favor neither the mesophiles nor the thermophiles.
Hydraulic retention time
The average time that a given volume of feedstock stays in the digester is one of the design parameters affecting the economics of a digester. For a given volume of feedstock, a small digester (lower capital cost) result in a shorter hydraulic retention time. This may not be long enough to reach the optimum results such as higher biogas production, lower emission of odour and greenhouse gases, and higher destruction of chemical oxygen demand, total solids, volatile solids, pathogens, and weed seeds.
A higher hydraulic retention time range of a few to 40 days is recommended depending on digester type and solids content in feedstock.
Loading rate is the amount of volatile solids feed daily to the digester. Uniform loading on daily basis, of feedstocks generally works better. To maintain uniform gas production and to minimize the possibility of upsetting the balance between the two bacteria processes in the digester, the loading rate should be maintained as uniformly as possible.
When loading rate is too high it inhibits gas production, but it may be possible to gradually increase the loading rate once the microbial population is properly established.
Mixing of the digester content
Slow stirring of the digester content is necessary for efficient and rapid digestion. It is possible for the momentum of the daily load to give a stirring action. If the inlet pipe is set so that the force of ingoing load makes the content swirl, then some stirring is achieved. Self-mixing by the gas generation may provide enough agitation in some situations. Where the daily load is pumped in, an even better stirring can be achieved by recirculation. When the digester is large and efficient digestion is required, a peddle system or gas recirculation is used so that stirring is gentle, constant and reliable.
Lignocellulosic biomass, such as agricultural residual and energy crops, consists mainly of cellulose, hemicelluloses, and lignin. These are three compounds render lignocellulosic biomass resistant to biodegradation. Therefore, physical, chemical or biological pretreatment are preferred.
The size of the feedstock particles has an influence on the gas production.
If the particles are too large the digester might be clogged and also the digestion of the particle will be difficult for micro-organisms. On the other hand, smaller particles would provide large surface are for absorbing microorganisms and enzymes this will lead to increase in microbial activity and hence increased gas production
2.5 Types of anaerobic digestersCommercial digesters are not widely available but producers can make or design their own quite cheaply. Different types of digesters have been developed and as follows;
Batch-filled in one go and allow to digest, then emptied and refilled.
Continuously Expanding- start one third full, filled in stages and then emptied.
Plug flow- waste added regularly at one end and over-flows the other.
Contact- a support medium is provided for bacteria.
Continuous flow- filled initially and waste added and removed regularly (Harris 1998)
The most common are the floating canopy Indian type and fixed dome Chinese models (Lewis 1983), which are of self-mixing, continuous flow design. A major development was invention of plastic digesters by centre for research in sustainable systems of agriculture production (CIPAV) in Colombia. It is easy to make and available.CHAPTER THREEMETHOD AND MATERIALS3.0 IntroductionThis chapter presents methods and materials used to achieve the objectives of the research, from design and fabrication of biogas digester to analysis of biogas using gas chromatography.
3.1 Design and fabrication of a biogas digester.3.1.1 Design considerationSeveral considerations were taken into account;
Length of the pvc pipe
Volume of samples used
Diameter of the pvc pipe
Hydraulic retention time
3.1.2 Requirements and materialsBio-digester-where anaerobic digestion occurs.
Valve-for controlling the flow of gas produced.
2- 6” End caps
Funnel-for conveying the effluent to the digester
Horse pipe-for connecting the digester and the gas holder
2-45? and 3-90? elbow.
3.1.3 Design and fabrication
The size of the digester was obtained by considering the cost of transporting sisal wastewater. Using two twenty litters containers was desirable. Thus the volume of the samples
Vs=40 littresThe cross-sectional area of the digester considering 6” pipe;
C.Area=?d24c. Area=?×15.2424=182.41 cm2volume=?r2l40,000cm3=182.41×ll=219.29cm40 litres of sample requires a length of 219.29 cm3 of the digester.
The volume of sample should be a ¾ full to give space to formation of biogas.
Thus, the length of the digester;
=43×219.29=292.38 cmVolume of digester =43×40,000=53,333.33cm3
Figure 3 STYLEREF 1 s 0 SEQ Figure * ARABIC s 1 1 Engineering drawing of the digester
Figure 3 STYLEREF 1 s 0 SEQ Figure * ARABIC s 1 2 Final assembly of the digester
3.2 Analysing the characteristics of sisal wastewater before and after of anaerobic digestion3.2.1 Sisal waste collection and lab analysisThe sisal waste that was used in the research was collected from Lomolo sisal estate in Nakuru County. The effluents were collected from a channel that conveys the effluent to the lagoons immediately after decortication process. The sisal waste was then taken to the lab for lab analysis. The parameters of interest were; pH, alkalinity, total suspended solids, biological oxygen demand (BOD), chemical oxygen demand (COD). Their results were very useful in controlling and evaluating the performance of the system.
Figure 33 sisal wastewater diversion channel (collection point)
3.2.2 Analytical methodsDigestions were left to run from 15th June to 20th July 2018 .The biogas composition was then analysed using gas chromatography. In this method, N2, CH4, CO2, O2 and other gases were determined. The digester contents was then analysed for total suspended solids (TSS), pH, alkalinity, biological oxygen demand (BOD) and chemical oxygen demand (COD) before and after digestion.
Total suspended solids (TSS), Alkalinity, biological oxygen demand (BOD) and chemical oxygen demand (COD) was determined according to standard methods. The pH was measured using pH meter.
Procedure for testing chemical oxygen demand of sisal waste water using closed reflux- titrimetric
Samples were collected from sisal waste water conveyance line at Lomolo sisal factory. Weighed 2.45g of Standard Potassium Dichromate (K2Cr2O7) 0.0167M and add it to 500ml of distilled water.
Into well clean digestion tubes, place 2.5mls of sample and one blank experiment, add 3.5mls of Standard Potassium Dichromate digestion solution (K2Cr2O7) into the digestion solution. 3.5mls of sulphuric acid reagent was then carefully run through the walls of the digestion tube. The solution then thoroughly mixed by slowly inverting the tube several times. It was then allowed to cool to room temperature and the tubes placed in a COD Digester, where they were heated for 2 hours at 150o C.
The contents were then transferred to a conical flask and 100mls of distilled water added. Add 1-2 drops of Ferroin indicator. The blank experiment and the samples was titrated against Standard Ferrous Ammonium Sulphate titrant (FAS) to a sharp colour change from blue-green to a reddish brown.
Calculations of chemical oxygen demand
Chemical oxygen demand was obtained from the following formula;
COD=(A-B)×M×8000VWhere; A= volume of FAS used for blank (ml.)
B= Volume of FAS used for sample (ml.)
C= Volume of sample (ml.)
8,000 Milli equivalent weight of oxygen(8)×1000ml
Figure 34 laboratory analysis of COD
Procedure for testing biochemical oxygen demand (BOD)
Took the sisal samples collected from the factory. It was collected in BOD bottles filled up to the rim.
Preparation of reagents
Dissolved 8.5g KH2PO2, 21.75g K2HPO4, 33.4g Na2HPO4. 7H2O and 1.7g NH4Cl in 500ml distilled water.
Magnesium sulphate solution
Dissolved 22.5g, MgSO4.7H2O in distilled water and added dilute water to 1 litre.
Calcium chloride solution
Dissolved 27.5g CaCl2 in distilled water and diluted it to 1 litre.
Ferric chloride solution
Dissolved 0.25g FeCl2.6H2O in distilled water and diluted to 1 litre.
Into 1000ml distilled water, add 1ml of each of the above reagent. Aerate the above solution till the DO was at least 8mg/l. into a 250 ml beakers, add the sample in 10, 20 and 30ml amounts, making one as a blank of only aerated water. Make up to 200ml using the aerated water. Measure the DO of each of the above solutions. Transfer the solution above into the BOD bottle ensuring that there is no air trapped. Incubate at 20 ?C for 5 days.
Determining BOD5 mg/l =D1-D2PD1-dissolved oxygen of the dissolved sample after preparation
D2- dissolved oxygen of dilute sample after 5 days
P- Decimal volumetric fraction of the sample
Figure 35 BOD bottles with samples
Procedure for testing sisal waste water characteristics using Lovibond kit
Test for suspended solids.
Set the lovibond to test for suspended solids. Once again placed a dry and clean vial of distilled water in the sample chamber, made sure the markings were aligned and press ZERO. Filled a clean vial with 10ml of sample sisal waste water, closed the cap tightly and wiped dry.
Placed the vial into the sample chamber, with the markings properly aligned, pressed the TEST key and took down the reading. Repeated for every sample sisal waste water, making sure to zero for every run.
Test for alkalinity.
Set the Lovibond to test for alkalinity. Filled a clean vial with 10ml of sample sisal waste water, closed the cap tightly and wipe dry. Placed the vial in the sample chamber making sure the markings were aligned properly and press the ZERO key. Once the machine confirmed the sample has been zero-ed, removed the vial from the sample chamber.
Crush an ALKA-P-PHOTOMETER tablet on a piece of paper and transferred it to the vial with 10ml sample sisal waste water. Closed the vial tightly and swirl it severally until the tablet was fully dissolved. Now I placed the vial in the sample chamber making sure that the markings were aligned and pressed the TEST key. Took down the results displayed on the screen.
Figure 36 lovibond displaying the results
Test for pH
Fill a portion of the sample sisal waste water into a clean beaker. Dipped the tip of the pH meter into the sample of wastewater and take the reading.
3.3 Determining the quality of biogas produced
The quality of biogas produced was analyzed using a gas analyzer known as Gas chromatography (GC).
3.3.1 The working principle of GC The sample solution injected into the instrument enters a gas stream which transports the sample into a separation tube known as the column. (Helium or nitrogen is used as the so-called carrier gas.) The various components are separated inside the column.
The GC machines generates a graph showing the retention time each gas takes to reach the peak point. The area occupied by each gas is displayed and this can be used to calculate the percentages composition of each of those gases based on their total area.
The sample being measured is injected into the carrier gas using a syringe and instantly vaporizes (turns into gas form). The gases that make up the sample separate out as they move along the column (orange), which contains the stationary phase.
Figure 37 pictorial representation of gas chromatography
Figure 38 gas chromatography
CHAPTER FOURRESULTS AND DISCUSION4.0 IntroductionThis chapters shows the results obtained from analysis of pH, total suspended solids, alkalinity, chemical oxygen (COD) demand, biological oxygen demand (BOD5) and percentage composition of biogas.
4.1 Biogas digesterThe diagram below shows the biogas digester developed.
Figure 4 SEQ Figure * ARABIC s 1 1 Bio- digester
4.2 Properties of sisal wastewater before anaerobic digestionpH=4.39Total suspended solids=250mglAlkalinity=122 FAUCalculations of chemical oxygen demand
Titration results in cm3
sample Initial volume Final volume Volume
Blank 13 20.2 7.2
1. 20.2 25.8 5.6
2. 8.7 14.1 5.4
COD=7.2-5.4×0.1×80002.5=576mglAverage COD=576+5122=544mglCalculations of biological oxygen demand
D1=7.52mglD2=6.45mglSample 1. With 30cm3 of sisal waste water.
BOD5 (mg/l)=D1-D2PDecimal volumetric fractionP=1dillution factordilution factor=30030=10P=110=0.1BOD5 mgl =7.42-0.540.1=68.8mglSample 2. With 20cm3 of sisal waste water.
dilution factor=30020=15P=115=0.067BOD5 mgl =7.43-0.620.067=109.97mglSample 3. With 10cm3 of sisal waste water.
dilution factor=30010=30P=130=0.033BOD5 mgl =7.41-0.870.033=198.18mglSummary of BOD5 of sisal waste water before anaerobic digestion.
Sample DO of sample after preparation(D1) (mg/l) DO of dilute sample after 5 days(D2)(mg/l) (D1 – D2) (mg/l) Dilution factor BOD5 (mg/l)
Blank 7.52 6.45 1.07 1. 7.42 0.54 6.88 0.1 68.8
2. 7.43 0.62 6.81 0.067 101.64
3. 7.41 0.87 6.54 0.033 198.18
4.3 Properties sisal wastewater after anaerobic digestion.pH=6.37Total suspended solids
From the reading on lovibond TSS=466mglAlkalinity=246 FAUCalculations of chemical oxygen demand
Titration results in cm3
Sample Initial volume Final volume Volume
Blank 15.3 22.9 7.6
1. 6.3 12.8 6.5
2. 12.8 19.2 6.4
COD=7.6-6.4×0.1×80002.5=384mglAverage COD=352+3842=368mglCalculations of biological oxygen demand
D1=7.16mglD2=5.30mglSample 1. With 30cm3 of sisal waste water.
BOD5 (mg/l)=D1-D2PDecimal volumetric fractionP=1dillution factordilution factor=30030=10P=110=0.1BOD5 mgl =6.81-0.420.1=63.9mglSample 2. With 20cm3 of sisal waste water.
dilution factor=30020=15P=115=0.067BOD5 mgl =7.13-0.690.067=96.12mglSample 3. With 10cm3 of sisal waste water.
dilution factor=30010=30P=130=0.033BOD5 mgl =7.23-0.900.033=191.82mglSummary of BOD5 of sisal waste water after anaerobic digestion.
Sample DO of sample after preparation(D1) (mg/l) DO of dilute sample after 5 days(D2)(mg/l) (D1 – D2) (mg/l) Dilution factor BOD5 (mg/l)
Blank 7.16 5.30 1.86 1. 6.81 0.42 6.39 0.1 63.9
2. 7.13 0.69 6.44 0.067 96.12
3. 7.23 0.90 6.54 0.033 191.82
4.4 Composition of biogas
Figure 42 graph of peak points of different gases against retention time drawn by gas chromatography
The computer draws the graph above and it give time taken to reach the peak points in seconds and the area it cover. From the graph above, the following information below was obtained.
S/NO. NAME RETENTION TIME AREA
1. Other gases 515 12441
2. Carbon dioxide 598 286765
3. Nitrogen 968 1759344
4. Methane 78 1078433
5. Oxygen 753 732886
Total Area 3869869
4.5 Discussion of resultsThe sample was too acidic, therefore neutralization was required to raise the pH to optimum value where bacteria works best. Bacteria are tolerant to pH range of 6.5-7.5. The samples was neutralized using a buffer of calcium carbonate to raise the pH from 4.39 to 6.8.
The final pH dropped to 6.37. The process of anaerobic digestion results to formation of acetic acid which was responsible for the drop in pH.
The total suspended solids at the beginning of the experiment was 250 mg/l. after the digestion the total suspended solids was 778.22mg/l. This is because the biodegradable waste had been digested leaving the solids behind the digester
There was a drop in Chemical oxygen demand (COD) of the sisal waste from 544mg/l before anaerobic digestion to 368mg/l after anaerobic digestion. This is because the amount of organic substances presence in the sisal wastewater had been broken down into simpler substances during the process of anaerobic digestion.
Biological oxygen demand (BOD5) for 5 days dropped as required. This shows that the amount of organic matter contained in the sisal waste water reduced after undergoing anaerobic digestion. The amount of oxygen required by heterotrophic bacteria for the oxidation of organic matter reduced over time.
Biochemical Oxygen Demand is an important water quality parameter because it provides an index to assess the effect discharged wastewater will have on the receiving environment. The higher the BOD value, the greater the amount of organic matter or “food” available for oxygen consuming bacteria. This will cause eutrophication and algal blooms in rivers and lakes if care is not taken care.
The alkalinity of the sisal waste increases with time. Alkalinity can be defined as the ability of a water to neutralize acid or to absorb hydrogen ions. It is the sum of all acid neutralizing bases in the water. Increase in alkalinity was as a result of acidogenesis. Acidogenesis is the process that results in the conversion of the hydrolysed products into simpler molecules with a low molecular weight. In wastewater treatment, microorganisms transform the wastes into cell tissue and gaseous, liquid, or solid conversion products. Optimum growth conditions, such as pH, nutrient availability, and alkalinity, must exist in order for the microorganisms to continue to reproduce and function properly. This was the reason why there increase in alkalinity with time.
The percentage composition of methane gas was very low based on the graph generated by the gas chromatography instrument. The value obtained was 27.87% against the anticipated value of 50-65%. This is because the conditions that favour anaerobic digestion was fluctuating with time and also low retention time of 35 days against the anticipated time of not less than 60 days
The table below shows the comparison of results obtained for various parameters against the WHO standards and there appropriate comments. This was to check if the standards meet the standards to be released to the environment or to public sewer for further treatment.
digestion After anaerobic digestion Effluent standards
Discharge into environment Discharge into public sewer pH pH
scale 4.39 6.37 6.5-8.5 6-9 within the range
Total suspended solids Mg/l 250 466 30 250 above the range
Alkalinity FAU 122 246 Max 500 – within the range
BOD5 Mg/l 68.8 63.9 30 500 above the range
COD Mg/l 544 352 50 1000 above the range
CHAPTER FIVECONCLUSION AND RECOMMENDATION5.1 ConclusionThis research undertook a waste-to-energy conversion route for sisal waste. The methane composition was found to be 27.87%. This percentage was very much low as compared to our anticipated percentage of 50-65%. The biogas production can be improved if the parameters such as temperature and pH are kept at optimum levels.
Other parameters such has pH, total suspended solids, Alkalinity, COD and BOD5 were reduced. However we did not meet the WHO standards for effluent disposal into the environment but the waste meet the standards for disposing into the public sewer.5.2 Challenges
Fluctuation in weather affecting the optimum working of bacteria. This reduces the activity of micro-organisms acting on the sisal waste hence it requires more retention time for it to produce the required composition of methane.
Limited implementation time making the anaerobic digestion incomplete because of less retention time.
5.3 RecommendationsFurther treatment should be put in place to improve the quality before it is released into the environment.
Further research should be done on monitoring of crucial parameters that affect anaerobic digestion such as pH and temperature in order to improve the efficiency of the system.
REFERENCESWanasolo, W., Manyele, S.V. and Makunza, J. (2013) A Kinetic Study of Anaerobic Biodegradation of Food and Fruit Residues during Biogas Generation Using Initial Rate Method. Engineering, 5, 577-586. http://dx.doi.org/10.4236/eng.2013.57070.
Kowalczyk, A., Schwede, S., Gerber, M. and Span, R. (2011) Scale up of Laboratory Scale to Industrial Scale Biogas Plants. World Renewable Energy Congress, Bioenergy Technology, Linköping, 8-13 May 2011, Article No.: 007. http://dx.doi.org/10.3384/ecp1105748Salum, A. and Hodes, G. (2009) Leveraging CDM to Scale-Up Sustainable Biogas Production from Sisal Waste.UNEP Risoe Centre (URC), National Laboratory for Sustainable Energy, Technical University of Denmark, Roskilde.
Deubleim, D. and Steinhauser, A. (2008) Biogas from Waste and Renewable Resources: An Introduction. Wiley-VCH Verlag GmbH and Co KGaA, Weinheim.
Government of Kenya. Least Cost Energy Development plan: 2009-2029. Ministry of energy; 2008.
Mshandete M., Björnsson L., Kivaisi A.K., Rubindamayugi M.S.T. und Mattiasson B.: Effect of aerobic pre-treatment on production of hydrolases and volatile fatty acids during anaerobic digestion of solid sisal leaf decortications residues. African journal of Biochemistry Research, Bd. 2, (5) S. 111-119, 2008.
Mshandete A.M., Björnsson L., Kivaisi A.K., Rubindamayugi M.S.T. und Mattiasson B.: Performance of biofilm carriers in anaerobic digestion of sisal leaf waste leachate. Electronic Journal of biotechnology, Bd. 11, (1) S. 1-8, 2008
ETC UK, Biogas for better Life: An African Initiative, A feasibility study, October 2007.
Export Processing Zones Authority: Kenya’s Sisal Industry 2005. (http://www.epzakenya.com/UserFiles/File/kenyaSisal.pdf), 2005.
Mshandete A., Kivaisi A., Rubindamayugi M. und Mattiasson B.: Anaerobic batch co-digestion of sisal pulp and fish wastes. Bioresource Technology, Bd. 95, S. 19-24, 2004.
Yadvika, S., Sreekrishnan, T., Kohli, S. and Rana, V. (2004) Enhancement of Biogas Production from Solid Substrates Using Different Techniques—A Review. Bioresource Technology, 95, 1-10. http://dx.doi.org/10.1016/j.biortech.2004.02.010Ayalon, O., Avnimelech, Y. and Shechter, M. (2001) Solid Waste Treatment as a High-Priority and Low Cost Alternative for Greenhouse Gas Mitigation. Environmental Management, 27, 697-704.
http://dx.doi.org/10.1007/s002670010180Simalenga TE, Gohl B. Tubular plastic bio-digester: design installation and management.Harare: FARMESA; 1996.
AppendicesBill of quantitiesItem Description Size of sale Desired quantity Unit price Total cost
Transport Juja- Lomolo(Nakuru) per person 2 trips 2450 4900
Pvc pipe(digester) Waste pipe 6″ 5 meters 1 3200 3200
End caps 6″ 1 2 750 1500
Horse pipe 3m 300 600
Gate Valve galvanized 1 750 750
Funnel Plastic 1 100 100
Balloons 4 30 120
Silicon sealant 150ml tube Per piece 2 350 700
Total Ksh. 11,870
2.0 Effluent standards from WARMA-38100-115697000 WATER RESOURCES MANAGEMENT AUTHORITY
TITLE: Water Sample Analytical Certificate -Effluent Results REF. NO: F/9/1/5
ISSUE NO: 01
DEPARTMENT: Technical REV. NO: 00
ISSUED BY: DTCM DATE OF ISSUE: 15 th April, 2013
AUTHORIZED BY: TCM PAGE: 1 of 2
Name of Customer:
Purpose of Sampling:
Date of Sampling:
PARAMETERS UNIT RESULTS EFFLUENT STANDARDS
DISCHARGE INTO ENVIRONMENT DISCHARGE INTO PUBLIC SEWER
Temperature oC ±3 ambient temp. 20-30
pH pH Scale 6.5-8.5 6-9
Conductivity µ S/cm – –
BOD5 days at 20 0C mg O2/l 30 500
COD mg O2/l 50 1000
Total Alkalinity Mg CaCO3/l – –
Total Suspended Solids mg/l 30 250
Total Dissolved Solids mg/l 1200 2000
Sulfides as S2- mg/l 0.1 2
Oil + Grease mg/l Nil 5 or 10
4 Hr Permanganate Value mg O2/l – –
Nitrates mg/l – 20
Nitrite mg/l – –
Total Nitrogen as N mg/l Two guideline value –
Total Phosphorous p mg/l Two guideline value 30
Detergents (MBAS) mg/l Nil 15
Heavy Metals – Chromium, Cr mg/l 0.05 0.05
Lead, Pb mg/l 0.01 1.0
Mercury, Hg mg/l – 0.05
Copper, Cu mg/l 1.0 1.0
Cadmium, Cd mg/l 0.01 0.5
Zinc, Zn mg/l 0.5 5.0
Arsenic, As µg/l 0.02 0.02
Phenols mg/l 0.001 10
Name of analyst: VANISH KERUBO Signature.
Comments by head of laboratory
The waste water has high levels in BOD, COD, EC, TSS, Total alkalinity and nitrates. Measures should be put in place to improve the quality before it is released into the environment.
Name: JAMES MWAI
WATER QUALITY AND POLLUTION CONTROL OFFICER-RVCA
Issued by: ………………………………………………………
(Deputy Technical Coordination Manager)
(Technical Coordination Manager)
3.0 work planActivity Sep 2017 Oct
2017 Nov 2017 Dec 2017 Jan
2018 Feb 2018 Mar
2018 Apr 2018 May 2018 Jun 2018 Jul 2018 Aug 2018
Idea generation Literature review Reconnaissance Proposal writing Design and Fabrication Sample collection Implementation Data collection Data analysis Report compiling & presentation