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1.1. Background.

According to recent UN projections, Kenya’s population has doubled over the last 25 years, to about 40 million people, and rapid population growth is set to continue; Kenya’s population growing by around 1 million per year – 3,000 people every day. This has changed settlement patterns of people and now due to scarcity of land, most people settle on staying in areas such as hillsides which face major challenges such as lack of accessibility to proper road networks electricity and even water supply. This raises concern in terms of waste management since the country still relies upon old technology for waste treatment that was not designed for the current waste capacities. In turn, this calls for newer and improved methods of sewage and waste management that benefits both the society and the environment.

1.2. Problem statement And Justification.
The rampant population growth has with it brought challenges to the environment in terms of sewage and waste control and the current on site waste disposal units such as septic tanks or city sewage systems provide very little when it comes to treatment. These waste ends up making their way back to most water bodies polluting the environment. However, developments of high tech treatment systems have come up but most of them are expensive and not cost effective for small households. Further to this, sewage systems are so difficult to establish in an area like this because of its geographic location that puts it in an elevated area. The supply of water to this area is also a challenge since establishment of boreholes is a challenge being that it is in a rocky hilly location. This makes the use of flush toilets a challenge despite their availability and so most people still resort to the use of pit latrines. With this comes the problem of sanitation and pollution since most of these pit latrines are not built to standard. They then pose health risks and pollution since some of these wastes are washed down back to the water points available
The use of a bio toilet thus provides a more cost effective solution for sewage collection and treatment both at the source since the faecal matter and liquid wastes are separated within the toilet and so the liquid waste that joins up with the municipal sewerage system is less contaminated with solid wastes making it easier to recycle and clean. Since fertilizer is got from the system, it will be used in farms improving soil conditions for agriculture and the bio gas , also produced as a by-product, can be used as a fuel alternative for liquid petroleum gas and firewood. This reduces the need to degrade the environment in order to have access to an energy source
1.3. Objectives
1.3.1. Broad objective.

To design a composting toilet that effectively produces manure and biogas as by products and doesn’t pollute the environment with bad odour.

1.3.2. Specific objectives.

To determine the average volume of waste produced by a household within a particular period
To identify the conditions necessary for the waste to be aerobically converted to manure and biogas
Develop a system that channels the biogas to the house and the manure to the farm without any wastage.


2.1. The bio-toilet mechanism.

A  bio-toilet also known as a composting toilet is an assemble unit of toilet super structure with a bio digester process unit for complete decomposition of human sewage waste into gases and digested nutrients rich liquid fertilizer residual. Alternatively it can be described as an alternative sewage treatment mechanism that decomposes faeces on-site and converts into compost that is often used for gardening and soil amendments. The bio-toilet mechanism is usually followed by anaerobic and aerobic operation but the most popular ones are the bio toilet technology that is followed by the aerobic bio-digestion process. This means it uses oxygen for the decomposition process which in turn leads to emission of carbon gases and makes use of technology similar to that of a backyard composting pit. Given that it relies on aerobic bacterial activity, it is vital to ensure that an ideal environment for these micro-organisms is created. This allows the bacteria to break down the waste efficiently.

The composting process includes the degradation of organic matter by thermophilic aerobic bacteria (a thermophile is an organism that thrives at relatively high temperatures, between 45°C and 80°C). Under optimal conditions the bacteria can produce temperatures within the composting heap above 50°C and can therefore provide a fast and substantial pathogen reduction. Due to its complexity, however, the composting process may be difficult to manage within the composting vault. Temperature measurements have shown that it is not easy to reach temperatures above 40° C in the composting vault and the normal operating temperature range is often mesophilic(mesophylls are organisms that grow in moderate temperatures usually 15 to 35°C). Pathogen content is nevertheless reduced in a composting toilet, but complete pathogen reduction cannot be guaranteed. Pathogen reduction will most often require either long maturation times or a secondary composting or storage period outside of the toilet vault .

2.2. Composting Toilet systems.

Depending on someone’s requirements, there are several bio toilet systems. Regardless of the type chosen, however, they all share the same basic features. Generally, they all require the use of electricity for heaters or fans, a composting chamber, an air and exhaust system, and an access door for emptying. They include:
Continuous or single composters: These contain only one chamber. With this self-contained system, all excrement and composting materials go into the top and are removed from the bottom in a continuous fashion.

Double or batch composters: They consist of either two or more containers. This type of system is such that the composters are filled then allowed to age for a while before additional excrement and other materials are added to the system.

Aside from these, we also have true toilets and dry toilet systems.

True toilets: From their design, they basically provide the best ventilation and decomposition. These can also be referred to as active systems and include everything from heaters to fans to mixers etc.

Dry toilets: These are systems that are considered passive. They require more maintenance since they need additional heating elements or other features that aid with the decomposition process. As a result, composting takes longer to occur this type of system.

2.3.Advantages And Disadvantages of Bio toilets.

The use of bio toilet technology has several advantages that come with it, some of which include:
Less water usage since it doesn’t require any water to flush away the faecal matter. This in turn helps recharge the ground water level up through utilization of water for gardening and irrigation.

Generates a colour less and odour less inflammable bio gas that can be used as an alternative for cooking gas. This promotes the use of renewable sources of energy in place of ones that come from depletion of the environment such as firewood.

There is generation of a clear odour less water full of nutrients and minerals that can be used for irrigation purposes. The faecal matter also decomposes to manure that can as well be used in the farms and so improving soil quality as well as reduction in fertilizer costs.

The system works without the connectivity of a septic or sewage tank and so requires no sludge disposal. This makes it totally suitable for mobile toilet applications.

However it is good to note that in cases where the unit is not built and running correctly, separation of the end product may be very unpleasant and it with this comes an issue of aesthetics since some units will have the excrement in the sight of the user. Maintenance is also a required commitment from owner of the system since an improperly installed or service system may lead to production of odour or an end product that is unprocessed which may have possible health effects.

2.4 Case Study of application of Bio toilets.

Most research and development behind bio toilet technology have been based around India. This is because in the world, India has the largest open defecation rate with a ratio of more than half of which 65% is composed of rural Indians. With this comes several challenges such as health hazards from contamination of water sources and the environment though pollution. To solve this India has pushed for this kind of technology with the aim of providing access to proper sanitation facilities for the vast majority and in the process still bettering the environment.

India’s Defence Research and Development Organisation (DRDO) for example have shown exemplary versatility by developing eco-friendly bio-toilets for soldiers for human waste management in high altitude regions. With time, the high commission has showed interest and after a successful installation of 200 units of bio digesters in high altitude areas such as Siachen and Ladakh, the technology has been widely adopted in all terrains of India. Currently the technology has been adopted on the Indian railway system as well as units being constructed in the rural areas.


The methods that will be employed in the design of this project ranges from data collection, data interpretation and data analysis. This is relevant to ensure that the conditions necessary for the construction of a proper bio toilet are all incorporated in the design of this project.

Some of the material data that will be collected include:
Kajulu’s sewerage waste collection and the population data of the area to help determine the average amount of human waste produced by one household in that area.

The design parameters of a bio toilet system that will help design the reaction chamber where the biogas will be produced and the structure where the waste manure will be collected.

The topography of the land that will help determine the orientation in which the bio toilet structure will take during construction.

The climatic conditions. This will help determine if any external input is required to optimise the conditions that lead to biogas production and if so ,how much input is actually needed.

Some of the methods of data collection that will be employed include:
Questionnaires: This will help determine whether or not the project is socially acceptable in that area and so determines the viability of the project
Interviews: By conducting interviews in several homes, the information obtained will determine the average daily use of latrines by homes in the area and the average daily energy consumption per household.

Case studies: By refencing on work previously done on the topic in other areas, this can set a benchmark on the design parameters and the expected results of the project. It also gives guidelines on how to go about the project from start to finish.


The bio toilet system is expected to produce manure good enough to improve soil fertility of the area which will effectively increase the production capacity of the farm its used on an also the production biogas that can effectively be used in the household.


1. Submission of 3 design concept ideas 15sr October, 2018
2 Submission of the Expanded concept paper 2nd November, 2018
3. Submission of full proposal 5th November, 2018
4. Proposal oral defence 15th November, 2018
5. Data collection 18th November, 2019 to 12th January, 2019
6. Data analysis and interpretation 13th January, 2019 to 31st January, 2019
7. Final report development 3rd February, 2019 to 19th April 2019
8. Oral Examination (Defence) for Examination Purposes of the Project 21st March, 2019
9. Handling in of Final Report together with the Project Logbook for Assessment to the Project Coordinator
19th April, 2019.

6.0. BUDGET.

1 Data Collection (Airtime and Mobile data bundles) 2500
2 Transport 4000
3 Printing and Binding 1000
4 Miscellaneous 2000
TOTAL 9500

Zavala, L., ; Funamizu, N. (2006). Design and operation of the bio-toilet system. Water science and technology, 53(9), 55-61.

Anand, C. K., ; Apul, D. S. (2014). Composting toilets as a sustainable alternative to urban sanitation–A review. Waste management, 34(2), 329-343.

Zavala, M. L., Funamizu, N., ; Takakuwa, T. (2005). Biological activity in the composting reactor of the bio-toilet system. Bioresource technology, 96(7), 805-812.

Kumar, S. (2013). Bio-toilets for Indian Railways. Current Science(Bangalore), 104(3), 283.


REGISTRATION NO: F21/2245/2014
DATE: 30th October, 2018
In partial fulfillment of the requirements in the award of a degree in Bachelor of Science in Environmental and Biosystems Engineering of the University of Nairobi

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