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Uncontrolled greenhouse gas emission from sewage waste will be reduced by using simple technology like utilizing this waste in making biogas



Population increase of students and Inmates in Kenyan schools and prisons has led to an increase in quantity of the human waste that is produced within these institutions. Waste is generated from the student dormitory and other existing facilities in the schools.The human waste has been of concern to every society and the concerned local authorities have set up waste collection and disposal systems. There are numerous reasons why we need to be concerned with human waste at Kenyan schools.

It is costly to dispose, and the generation of large amounts of this waste affects the environment, especially water table and other water bodies within the vicinity of drainage system.Human waste contaminate water and this pose health hazards to humans.Biogas technology can help Kenya achieve some of the MGDs,especially MDG 7 and MDG 8. Some biogas plants were introduced in Kenya in 1980s,but their uptake has been very low due to low level of awareness and financial constraints.

Literature indicates that the guiding principle in their installation was the experience of pioneering individuals and organization rather than a defined scientific approach. The proposed project will ensure that scientific approach takes the center stage and efficiency in the operation developed.

Some important factors like optimum design of plant,use of efficient burners and optimum utilization of digested slurry.The aim of this project therefore is to come up with simple techniques of installing efficient and low cost biogas and create awareness on the benefits of biogas technology in Kenya.Low cost and efficient different types of biogas plants will be installed to act as demonstration models.

After 6-12 months,these plants will be evaluated in order find out the most suitable technology and cost efficient to the community.Afterward, training courses for artisans and other interested groups will be held on how to install and manage biogas plants,manure and growing high value crops.

Category of the action

Reducing emissions from waste management

What actions do you propose?

Our main aim and objective is to do justice climate system by cutting down the greenhouse gas emissions from waste sector by using simple technologies to curb their release into the atmosphere.Motivated by this, we propose for the construction of bio-digesters in Kenyan schools and prisons to contain human waste and make biogas to be used for cooking and lighting,since many large institutions which are remote from main sewage facility services have problems with sewage disposal.

The impacts of human waste on the environment will be reduced as the project improves sanitation in turn reducing health risks and smell for both students/prisoners and the neighboring residents, at the same time curbs methane emissions. Anaerobic digestion process is very effective at destroying wide range pathogens like E-coli. This greatly reduces the incidence of water-borne infectious diseases and parasitic infections, as related medical expenses. This is because the process occurs in aid of bacteria and is temperature sensitive (range is 6- 80°).

Basic biogas system involves an anaerobic digester (usually underground) with an inlet pipe, an outlet pipe,and a tube for the biogas.The feedstock is human waste plus water.It ferments in the digester tank to produce biogas, which contains 60-70% methane (CH4). The basic chemical reaction is:2 C + 2 H2O » CH4 + CO2.

The decomposition of waste matter by anaerobic bacteria occurs in two phases:acidic anaerobic bacteria break down the organic waste into peptides,glycerol,alcohol,sugars that are then further converted by other anaerobic bacteria into methane and carbon dioxide.

The biogas plants will have various latrine connections and one extra connection to feed the digester with any other waste available within the place of use such as animal and kitchen waste.Upon digestion and producing biogas,this waste will be ejected from the digester to the composition pits.This process converts the human manure  into a fertilizer.

This link shows the canal for post-treated effluent;soak away pits and dried residuals entrenched in banana field and use of manure for pepper breeding in Rwanda(left to right).(Mottet, 2009).

The drawings shown in this ,plus the one below depicts a model of simple fixed digester.

Image Credit: Kangmin and Ho, (2006).
Overall objective:To contribute to greenhouse gas emission reduction through the development of a viable biogas sector and dissemination of 5,000 domestic biogas plants to secondary school and prisons in Kenya.

Specific objectives

  • To provide a long term solution to tackle the problem of poor sanitation and  the associated human health risks
  • To create an alternative source of “green” energy for rural schools
  • Create awareness on the importance of biogas technology in the mitigation of climate change
  • To optimize benefits that are currently underdeveloped in the Kenya biogas sector, specifically related to:

 Gender aspects, women economic and children’s educational status
 Improved health from nutrition and reduced indoor air pollution
 Environmental protection through reduced deforestation and environmental degradation
 Employment creation, especially in the rural areas
 Improved food security due to agricultural application of bio‐slurry
 Tapping of carbon finance


Programme phases: (i) Preparatory phase — 6 months;Programme areas:National; phased progression to be adopted,managed through Kenyatta University.The biogas development and extension programme and all policy and financial issues will be managed through the same campus.

Target market: Kenyan secondary schools, prisons and municipal slaughter houses.

Technological and Financial Sustainability:

Since the project will need a continual source of funding,the committee members have their own fundraising skills which will be applied as a continuous process to raise funds from various funding agencies. Schools will provide in-kind,and our role will be to subsidize the cost of digester construction.Carbon credits is a potential source of funding to this project. We focus to partner with other NGOs and other organizations to ensure financial sustainability.

Capacity building

To ensure a sustainable operating staff, technicians will  trained to enable easy access of  artisans in every 47 Counties of Kenya. The training will Create a Pool of Trained Biogas Masons;through rigorous theory and practical technical training.In addition, promotion,institutional energy needs assessment, extension services, and documentation. This will be conducted on a vocational training trajectory.Three point training platform: (i)Training; (ii)Certification (iii)Re‐training.
(i)Task- Biogas Mason Supervisor and Inspector Training
Group 1: Biogas Masons:1‐day theory and 10 days’ practical course (construct and demolish model).
Group 2: Experienced Biogas Masons and Contractors:3‐day orientation to realign practices to KENDBIP ‐already trained and currently involved in construction of biogas plants on an open market basis,hence full training not required.

A total of 366 masons will be trained from Group 1 and Group 2.
Group 3: Supervisors and Inspectors: 5‐day course – training in supervision,inspection and training of trainer (ToT) skills.A total of 49 Supervisors and 14 Inspectors will be trained.This will produce people who will operate the digesters.

Using Coltri gas compressors, biogas will be be packaged in portable plastic containers and sold to neighbors or be distributed to customers directly from a central storage facility.Electricity generated from biogas will also be metered and sold to the school’s and prisons' immediate neighbors.

The cash earned will sustain the long term costs of maintaining an operating unit such as remuneration for the artisan(s), water supply and maintenance of the gas distribution system and converters from gas energy to various forms of energy as required by the school. R&D will explore practical viability, costing levels and sustainability of these and other alternatives of commercializing biogas energy. 

Continuity of AD knowledge and skill:It is crucial that the number of members in the O&M group remains constant.This will prevent loss of knowledge and skills when AD-competent detainees are released. In case of succession, significant attention will be dedicated to transfer the required knowledge and organizational understanding to ensure continued smooth AD operation.

Promote and Market Biogas Technology

Kenyatta University seeks to introduce a unique strategy to ensure mass adoption of biogas plants countrywide.This will require a well developed promotion strategy to activate the sector and incentivize stakeholders. The University's awareness creation and consumer education programme will take into consideration and address concerns related to the challenges, barriers, risks, constraints and the lessons learned in the biogas sector in Kenya and elsewhere. According to Devkota (2011), a well constructed digester unit using bricks and concrete has a life time of  is 20-30 years, and  it requires less maintenance costs.

AD technology, design and site selection
External heating of the digester is hardly ever an option due to an unfavorable institutional setting as well as an unfavorable energy balance and associated financial issues.Suitable average local temperature is thus crucial and should not go below 15°C,as this would slow down microbial activity too much.

The site for the digester will include a suitable ground conditions for construction work, possibly an un-shaded location as close as possible to the toilets and kitchen to minimize pipe lengths. In addition, it will need to be inspected before hand during rainy season to identify potential areas of stagnant water and to ensure sufficient gradient to enable discharge of the effluent by gravity.

The Kenya Biogas Model (KENBIM), a fixed dome underground bio-digester which have been adapted to local circumstances is considered to be most suitable for the prison context in developing countries as the technology is well known and widespread, cost-effective, few moving parts and simplicity of design and the required components are locally available.The project will utilize 4 m³ to 20 m³ fixed dome digesters.

The digester walls can either be built with bricks, stones or concrete hollow blocks instead of using concrete. The framework below shows the summary of the effects of cooking with wood fuel, which you realize is the opposite when using biogas as a clean fuel.Framework 2 in  the other key benefits slide  depicts benefits of using biogas.

Image Credit: Kangmin and Ho( 2006).

Health risks and mitigation measures
If a biogas system is properly designed, constructed, operated and maintained,the risks to human health can be kept with in reasonable limits.Although from a technical and economic point of view,reduced flushing water inflow is desirable (higher Hydraulic Retention Time, smaller dimensioning of digester i.e.lower costs),it needs to be in balance with the demand for sound hygiene.

A compromise will be found to avoid excessive water use and to still keep up the level of hygiene required to avoid transmission of diseases. The compensation chambers will also need to be covered with reinforced slabs (detainees were reported to have fallen inside the chambers (EREP, 2004).

Furthermore,there is need to avoid gas leakages, especially in areas of human activity (e.g. kitchen).To minimize the risk of leaks, exposed gas pipes (prone to stumble over) will be properly covered and vulnerable plastic pipes in the kitchen  (connected to the stoves)  be protected from  mechanical and thermal damages.As hydrogen sulfide is a highly toxic and flammable gas that is heavier than air, it tends to accumulate at the bottom of poorly ventilated spaces.

However, due to its smell (similar to rotten eggs),it helps to detect leakages (methane and carbon dioxide are both odorless).Still, if the kitchen environment cannot be properly ventilated, the installation of a H2S-trap as recommended by (Mottet, 2009) is advisable, since hydrogen sulfide, a natural component of biogas, is extremely reactive with most metals,kitchen equipment such as stoves and stovepipes are prone to corrosion.

It is therefore advised to install a H2S trap (Mottet, 2009): The trap entails two columns (one for desulfurization, one for regeneration) filled with iron oxide for absorption of H2S; the H2S reacts with the iron oxide to form iron sulfide and water. Addition of sufficient air converts the iron sulfide back to the oxide and leads to precipitation of elemental sulfur.

Another safety device recommended is the installation of a simple gravel filter in the gas pipe to prevent back-flow of the flame (EREP, 2004). There is a theoretical risk of explosion if 6-12% of CH4 is mixed with air (Deublein & Steinhauser, 2011).When manually desludging the digester, a prior ventilation of the digester is indispensable to avoid exposure to toxic gases and suffocation.

In addition,as a result of the explosion issue, open fire or smoking has to be prohibited when working in the digester. Special attention will be dedicated when handling effluents for Agriculture.The World Health Organization (WHO) lists two indicator organism for safe agricultural use of greywater, excreta and faecal sludge (WHO, 2006):E.Coli and helminth eggs.

The quality of the effluent directly after the anaerobic digestion process may  be found to be acceptable for restricted irrigation in (crops that are not eaten raw).An adequate form of post-treatment will therefore be required when using the slurry to irrigate crops that are eaten row.

Another option is to mix the digested effluent with raw material (e.g. agricultural waste) in covered compost pits.In the resulting exothermic aerobic digestion process,high temperatures (70°C) are generated that lead to elimination of remaining pathogens.A photo of a compost pit is shown here.


Who will take these actions?

At its inception,Kenyatta University will play a key role in developing and strengthening the technical and institutional capacity of all the key partners associated with the biogas in Kenya.Training programs to be conducted by the University will be critical in establishing and strengthening the capacity of among others,the biogas Inspectors,the staff and even biogas end-users.

The individuals who will execute this includes two PhD persons (Dr. Cecilia M.Gichuki-Lecturer Department of Environmental Education and Dr. Martin M.Nzomo-Dean, School of Engineering and Technology)-both from Kenyatta University and a team of 10 Undergraduate students.

An operating principle of the University will be to collaborate with private and public sector to implement and achieve its objectives. As a result, Kenyatta University will technically support the creation and certification of private Biogas Construction Companies (BCCs).

To work with BCCs, clear procedures for installation, contracting, quality control, service repair and maintenance will be developed.Besides construction of biogas systems,the certified BCCs will provide after installation services.We shall work with Kenya National Federation of Agricultural Producers(KENFAP), which is the government body envisaged with the mandate of biogas plant making.KENFAP will bring  the experience they've had in this industry.

The University will take the Center role of coordinating and implementing  this program.This means that it will have the mandate of overlooking on the use of the financial resources for accountability purposes.An important factor in the successful promotion of this technology in Kenya will be strict enforcement of carefully defined quality and design standards as well as the accountability aspect.This will be achieved by imposing penalties for noncompliance to be observed and enable a high ratio of success of biogas system. More of the stakeholders' responsibilities are shown on this link.


Where will these actions be taken?

Our strategy is to replicate this project based on agreements to be made between us and various schools and prisons in Kenya.We've had contacts with Nyabururu girls secondary schools' administration,and they've shown interest of adopting this our project when work commence.

We intend to see the idea done to more institutions in Kenya,not alone schools and prisons,but also lobby for policy adoption of this project in urban slaughter houses,hospitals and in Kakuma/Daadab refugee camps.Kenyatta University will adopt a multifaceted and multi‐stakeholder approach to ensure that only high quality biogas systems are installed and that sustainability of the market is achieved through a strong spirit of partnership with rural‐based organizations,and application of a commercial market process.

The strategy is informed by past barriers and challenges associated    with dissemination of biogas plants,both in Kenya and elsewhere.The technical features to cushion the program include biogas plant structural durability,reliability,robustness,affordability,size,ease of use,safety,after installation maintenance and service,performance and technical guarantee arrangements.

Awareness creation

Using human waste in making biogas is a challenging objective,as it requires to overcome long-standing cultural and social taboos associated with handling of this waste.To overcome this,designing an attached toilet system to eliminate and reduce any contact with this waste is crucial.

An information and outreach program to educate and change the consumers attitude(detainees and students) about the resulting biogas will be crucial.Hence,prior to the construction of biogas system,a set of relevant points will need to be discussed and agreed upon with the prison/schools authority and detainees/students.

These includes expectations and outcomes,gas consumption,user committee for O&M,and maintenance tool kit.Focused discussion,television,posters,flyers,pamphlets and banners will be used to aid this activity.

What are other key benefits?

Biogas technology is important because it has been used in Rwanda, where a 400 cubic meters fixed dome digester have been built in Cyangugu prison as shown in this The digester is fed human waste generated by 3499 prisoners and it produces 50% of the energy needed to cook for the 2500 inmates, (Lohri, 2011).

According to Kimaro (2005), a 25 cubic meters digester has been built for the Lysee de Kigali school, solving its sanitation problem.The gas produced is used to cook for 400 students and for operating Bunsen burners in the school laboratories.In Nsinda prison, using biogas has reduced 85% of 1 billion Rwandan francs ($1.7 million) used to buy firewood each year (Rosemary, 2010).The system powers 12 biogas ovens in the same prison.

A 10m3 digester in rural areas can save 2 000 kg of wood fuel, which is equivalent to reforesting 0.26-4 ha (Kangmin and Ho, 2006).The reduced indoor air pollution leads to a decline in respiratory diseases(Smith, 2007)Figure 9. Diagram of the effects of cooking with biogas

How much will emissions be reduced or sequestered vs. business as usual levels?

The project saves greenhouse gas emissions by reducing the unsustainable use of fuelwood, and by preventing the uncontrolled emission of methane from sewage pits.As an indication of this savings, if 50% of the fuel wood saved is unsustainable, then the greenhouse gas saving from the  systems is about 1000 tonnes equivalent per year.

Similarly if 20% of the biogas production has occurred with unmanaged sewage disposal, then an additional 1000 tonnes of CO2e per year would be saved (Ashden report, 2005).The table below presents an overview of greenhouse gas emissions reductions (in Gg CO2-eq ) from energy substitutions with biogas for the years 1991 to 2005 in China.The majority (95.67%) is CO2;CH4 accounted for 4.03% and N2O for 0.29%.

One gigagram (Gg) is equivalent to 500 metric tons, thus the total 14,410 Gg for 2005 is equivalent to 7.2 million tons greenhouse gas emissions reduction.

Image Credit: Liu et al. (2008).

Table 3. Greenhouse gas emission reduction by energy substitution (Gg CO<sub>2</sub>-eq)

What are the proposal’s costs?

A grant of 20,000,000 dollars is required, and it will be used in implementing the project.

The estimated costs of different sizes of digester are as follow: 6m3- EUR 740, 8m3- EUR 890, 10m3- EUR 1,030 and 12m3- EUR 1,200.

Source: (KENDBIP, 2010).

The budget breakdown is as follows:

a) Investment.

i) Subsidy Investment; 504,500,000.

b) Activities.

1.Popularization: 33,755,303.

2. Finance: 7,192,900.

3. Private sector development: 3,815,350

4. Quality management: 11,630,640

5.Training: 21,376,276.

6. Extension: 14,365,073.

7. Institutional Support: 23,327,600.

8. Monitoring and Evaluation: 6,242,250.

9. R&D : 4,331,646.

10. HR and Management: 83,300,439.

      Direct Costs: 70,545,455.

      NIA Support Costs: 12,754,984.

11. Contingencies: 5,158,437.

12.Overhead costs: 40,000,000.

c) Technical Assistance.

International TA; 151,326,000.

Total Budget: 988,463,351 Kshs

Notes on Budget

According to Central Bank of Kenya exchange rates dated (4/4/2014);

  • 1US dollar - 86.5472 Kshs
  • 1Euro -114.2258 Kshs

Credit: Daily Nation.

1a) Vehicle hire from Nairobi to Kisii and Nyamira Counties by implementing team

b) Fuel for the Vehicle KSh. 80.00 per Km

2. Food and allowances

a) Field allowances for implementing team, including perdiem and honoria for doing certain tasks like preparing reports

b) Four speakers to be invited

c) Payment for refreshments for teachers during the workshop exercise.

3. Administrative costs channeled through Kenyatta University, which charges a fee of 15% of the total budget

We did a pilot project in Ngong Nairobi in the year 2010, and i can confirm it to be in a good condition and effective. This pilot was financed by my lecturer Dr.Cecilia Gichuki. It had a cost of 100,000 Kenya shillings.

Our Co-funding already raised includes the following:-

i. Staff time contributed e.g. by supervisor, who in this project case is Dr. Cecilia Gichuki.

ii. Electricity and water

iii. Use of available communication facilities e.g. internet in the Campus

iv. Office space


v. Security.

Today's Waste
Tomorrow's Power.









Time line

Our dream is to construct 70,000 fixed biogas units in the long term of 100 years.The project will be implemented in phases, and each phase will take a term of 6 years,which is bound to renewal after a successful completion of the previous phase.And this is the timetable for the work plan


Quarter          Main activities

1                     Bringing partners together for planning meetings, PRA and selection of sites

                       Literature of different biogas technology

                       Conducting a baseline survey in Kisii and Nyamira County regions

2                     Development of posters,pamphlets and training manuals for teachers and extension staffs

                       Conducting training for artisans, the larger community on biogas technology

                       Building and installing biogas plants in selected institution

3                     Conducting trainings for women, the larger community on management for biogas, manure, growing high value crops and tree nursery management

                       Data collection

4                     Conducting field days at demonstration sites

                       Monitoring and evaluation of the project

                       Writing of scientific paper

                       Presentation of the data in an international symposium.

Studies reveal that the total amount of human waste input from sanitation facilities in the prisons can be anticipated in the range of 3.3 to 4.9 L/pers./day (human waste per adult person and day between 0.25 and 0.4 kg and between 1 and 1.5 L of urine per person plus 2-3 L/pers./day water used for flushing).This is the amount per person that flows into the biogas reactor.



The budget required may seem to be large, but the benefits accrued to this project are worthy investment. IPCC_WG2AR5 report affirms that the challenges posed to humanity by climate change will be more costly if they go unabated. Hence it's good to prevent than cure.

Related proposals

1. Integrated Energy Production, Waste Treatment in Ghazipur catchment, East Delhi.This proposal talks of producing biogas from waste. It relates with our proposal on the concept of anaerobic respiration.

Preparatory phase I
This is six months planning and piloting period during which the following activities will be conducted:establish structures of a program coordination centre at Department of Environmental Education in Kenyatta University,meetings with administrators in selected pilot schools,train extension education assistants and biogas artisans,develop full program and implementation plan.

The biogas generation units would be owned and maintained by the schools’ /prisons' management.These include the school’s directors, trustees, management committees or boards of governors in which the school head is usually a member.These bodies would hire a trained artisan to maintain the biogas unit operational.



Deublein, D., & Steinhauser, A. (2011). Biogas from Waste and Renewable Resources. 2nd Edition, Wiley-VCH Verlag, Weinheim.

Devkota, G.P. (2011). Biogas Digester Assessment in Places of Detentions in the Philippines. Practical Action Consulting.

EREP (2004). Évaluation des systèmes d’assainissement adaptés au contexte des prisons rwandaises.

Government of Kenya (GoK), 2010.National Climate Change Response Strategy.

IPCC, 2014a: Impacts, Adaptation and Vulnerability. Contribution of WG II to the Fifth Assessment Report (AR5). March, 2014.

Kangmin, Li and Mae-Wan Ho, (2006). Biogas in China. Institute of Science in Society Report.

Kigali Institute of Science, Technology and Management, ( 2005). Biogas plants providing sanitation and cooking fuel in Rwanda. Ashden Report. 2005.

Kimaro A, (2005). Biogas plants providing sanitation and cooking fuel in Rwanda. Ashden awards report.

Liu et al, (2008). Popularizing household biogas digesters for rural sustainable energy development and greenhouse gas mitigation. Renewable Energy 33, p. 2027-2035

Lohri, C. (2009). Evaluation of Biogas Sanitation Systems in Nepalese Prisons. Sandec/Eawag, Switzerland.

Mottet, A. (2009). Évaluation des systèmes biogaz des prisons rwandaises, EREP, N°: 09-5001-AM

Ngigi, A. (2010). Kenya National Domestic Biogas Programme. (KENDBIP). Report.

Rosemary, (2010).Biogas plants in Rwandan prisons treat sewage, generate biogas and crop fertilizer, and save trees. Reuters report.

Smith, Kirk R. (2007). Methane Emission Reductions: Opportunities to Promote Health, Development, and Climate. Paper presented at the Methane to Markets Partnership Expo, Beijing, 30 October – 1 November.

Smith, (2011). Facrors affecting biogas production.

World Health Organization WHO (2006). WHO guidelines for the safe use of wastewater, excreta and grey water; Volume 4: Excreta and grey water use in agriculture.