Biogas

What is biogas?

Biogas is a combustible gas mainly consisting of methane and carbon dioxide. It originates from bacteria in the process of bio-degradation of organic material in the absence of air. When this natural process is encouraged in a contained space, called a digester, biogas can be captured and harnessed as an energy source. The methane producing bacteria are the last link in a chain of micro-organisms which degrade organic material and return the decomposition products to the environment. A biogas digester therefore also reduces harmful decomposing materials and produces high quality, natural fertiliser.

Shaped bricks according to the various curves of the dome

The advantages of biogas

Domestic biogas technology has been recognized as an ideal solution for various challenges faced by low-income communities in the developing world. Well-functioning biogas systems can yield a large range of economic and environmental benefits, including:

  • the production of affordable energy
  • the transformation of organic waste into high quality fertilizer
  • the improvement of hygienic conditions through reduction of organic waste and pathogens
  • environmental advantages through protection of soil, water, air and woody vegetation
  • micro-economic benefits through energy substitution and increasing yields of agriculture
  • macro-economic benefits through decentralized energy generation, job creation and environmental protection

Domestic biogas technology in Africa

Global experience shows that biogas technology is a simple and readily usable technology that does not require overtly sophisticated capacity to construct and manage. It has also been recognised as a simple and adaptable technology for Africa. But, despite the recognised technical viability and the estimates of large potential markets, the technology has not been widely adopted by sub-Saharan African households. The main reason for this state of affairs is that, unlike in countries like Nepal, India and China, no truly large scale, coherent and continuous biogas dissemination programme has been backed by an African government.

The history of biogas in Africa is that of relatively limited projects conducted by NGOs. Most of these projects have been based on the presupposition that mere demonstration would automatically lead to replication and dissemination. Implementers generally perceive their work as the introduction of a "mere thing" rather than as the introduction of a practice where the tool and the user are mutually determinative. It is therefore no surprise that what remain of many biogas projects are unused digesters instead of a practice of utilising biogas technology. When biogas technology is not driven and supported by a government of other institution on a permanent basis, it can only be introduced successfully when it is contextualised and adapted to the potential of communities.

The Nova approach

In research and development consultation may have two very different meanings. In any development approach that takes community participation seriously, the concept of consultation plays an important role. Usually consultation means "consulting the community". We, on the other hand, understand consultation as "the community consulting us". The concept of consultation implies an agent - somebody who takes responsibility and initiative. And, this agent is the party that does the consulting. To be consulted implies not to take initiative. That a development agency consults a community signifies the activity of the agency and the passivity of the community. If communities do the consulting, it signifies that they are the agents of development. Our approach is to treat community members as the agents of development and view ourselves as consultants. From the very beginning the challenge of developing a new practice rests on the shoulders of those who would practice it.

The question of who the agents of a project should be is not often explicitly contemplated. Both donors and development agencies usually take it for granted that the latter is the agent of development. This is clearly reflected in project proposals where development agencies formulate clear outcomes, objectives, strategies and activities that they have decided upon. However, if it is true that the people who are responsible for sustaining a particular practice should also be responsible for developing that practice, then they are also to be responsible for determining the outcomes and activities of the project. In such a case development agencies can't do more than study the practices that are to be realized and to sketch the goal of the project in terms of its conditions of possibility, and be available to be consulted.

In our investigation we could find no projects aimed at redesigning existing conceptions of a domestic biogas practices for low-income African communities. With this we do not claim that implementers do not take indigenous contexts into account. We rather claim that they do not question their conceptions of domestic biogas practices in terms of these contexts. That is to say: Implementers tend to try to recreate communities and their situations to conform to their conceptions of a sustainable biogas practices rather than to allow communities to recreate a domestic biogas sector so that it conforms to their reality. We do not take a project approach. That is to say that we do not decide on fixed outcomes and actions before we engage a target community. Instead we support representatives from a target community to re-create domestic biogas technology and practices according to their own possibilities, requirements and context. We create a situation in which representative community members can design technology and practices which address their needs and desires; which they can afford and maintain; and which is suitable to their physical, social and cultural context.

An example from KwaZamokuhle, Hendrina

The acquisition of initial capital and maintenance of domestic biogas digesters is beyond the means of low income households. The popular solution is to attain funds from government or abroad from subsidies and loans. However, this creates the difficulty that biogas programmes become dependent on these interventions, and quickly become unsustainable when there is no long term commitment by a government - something that is conspicuously evident in Africa. This issue was taken to heart by the participants from the very beginning of the project. ICCO-Kerk in Actie requested Nova to develop domestic biogas digesters for the African context, and enabled Nova to investigate previous projects, learn the lessons that should be learned, and invite and guide a team of residents of a local township to design their own biogas digester. In designing their own biogas digester the participants kept what people from their community - people they know well - can afford in mind. This included the cost of the materials and the reduction of costs by designing a simple building technique so that people are enabled to participate in the construction process as much as possible.

The participants decided that a fixed-dome digester would be the easiest to build because they were familiar with the kind of work it required. We agreed that affordability should be among their first considerations and that they should stick to a budget of no more than a R1000 per digester. This meant that buying bricks was not possible and that they would have to use cheaper material. All of them were familiar with the traditional way of building where a mixture of soil and cow dung is used to plaster a wooden structure

Wire is a very popular material among low-income communities in South-Africa and people show amazing skill at working with this commodity. Wire is employed in almost any task - from fixing cars to making toys. The thought of using wire in the construction of the dome came very naturally to the participants and they decided to replace the wooden structure with a wire structure since it is much easier to shape the latter. We had our doubts about whether this would work because wire does not have the firmness of wood. Amazingly they succeeded in constructing the sides of the digester in this way, but they found it impossible to finish the dome because of the fact that wire is not firm.

They then decided to make bricks with the mud-manure mix (picture 1). With the building of the first digester they never succeeded in making a mixture that delivered constantly strong bricks. Only about halve of the bricks could be used in the construction process. Problems included dung not mixing properly with the soil and dung rotting away in the bricks. Adding cement did not solve the problem. With the second set of bricks they first made a watery paste with the dung before adding it to the soil. The participants decided to add some salt to the paste in order to prevent rotting. The result was a much stronger brick. Another difficulty was caused by rain. Although rain did not destroy the new kind of brick, it drenched them so that they had to be left to dry every time it rained. Covering the bricks with sail did not entirely solve the problem because the participants were not always able to cover the bricks in time. An obvious solution was adding cement. Making cement bricks would not fit the budget. Instead we suggested that they only add a little bit of cement to the dung paste. This prevents the dung that keeps the brick together to soften when it rains.

When it proved to be difficult to build the top part of the dome with square bricks, they accepted our suggestion of shaping their bricks according to the various curves of the dome. Eventually they decided to use this method throughout the whole digester and they constructed about six different shapes of forms for making the bricks.

Picture 1 showing the various shapes of bricks for the building of the digester        Picture 2 shows the building of the digester

Building domes with bricks requires special skill, no matter what shape of brick you use and they decided to reintroduce their idea of a wire frame for the dome in order to support the bricks while they dry. Picture 3 shows a dome that is constructed from very thick fence wire, commonly known as "blou-draad", and dove wire. The dome is then constructed on top of the wire dome, as can be seen in picture 3.

Picture 3 - a dome that is constructed from very thick fence wire

We calculated the dimensions of the wire structure wrongly which caused the dome to crack at the top. However this error also demonstrated that it is easy to fix this kind of construction. Picture 4 also shows that the digester worked after it had been repaired. You will also notice that they painted the digester black. We suggested this after it was discovered that the bricks had good heat retention capabilities. The black paint increases the heat the digester gains in the daytime. The good heat retention capabilities of the digester also led to the idea that this type of digester should be built above ground rather than underground as fixed-dome digesters are usually built.

Picture 4 - A functioning biogas digester

The digester has been functional for more than two years now and there are still no signs of the structure weakening. On the inside of the dome they used a mixture of salt and cement. We suggested this to them after obtaining advice from farmers who use a mixture of salt and cement to seal leaks in their dams. This is where the participants got the idea to add salt to the dung paste used for brick making. Getting the dome to be gastight also has its difficulties. Initially we advised the participants to use the acrylic-cement plastering method. This proved to be too expensive. We also advised them that wax is often used in sealing digesters domes. After some experimentation they decided to rather use this method.

The status and future of the program

We believe that we have facilitated the design of a biogas digester that is suited to low income rural African communities. Our digester model allows the circumvention of situations that usually cause the failure of proper dissemination of domestic biogas technology, namely high construction cost and the need for expensive skills - and by implication the need for the continuous involvement and financial support of outside parties like governments. The reason for this is that our digester model has been designed by people from low income African communities themselves to specifically fit their possibilities regarding skills and expenses. The challenge is now to get the solution out there amongst the people who need it. This means spreading knowledge of the biogas digester and its benefits to as many communities as possible. In order to accomplish this we are in need of business partners and investors.

Business opportunities

Although domestic biogas technology has diverse social advantages for low-income communities, it is the great economical advantages and huge untapped markets that should make businesses sit up and listen. Domestic biogas technology has been promoted in various Asian countries to the advantage of both low-income communities and industries that trade in biogas technology and carbon credits. Once the Nova Biogas programme has been implemented in Africa, a huge untapped market will open up. Domestic biogas technology also has the possibility to increase the buying power of low-income households by...

  • presenting a free source of energy replacing expensive sources like coal, charcoal, paraffin, electricity, wood, candles and so more;
  • increasing the income generated from crops;
  • and creating job opportunities.

This increased buying power may then be channelled into a new domestic biogas market providing potential investors with profits. Such a market would enable trade in various commodities, including...

  • parts for the construction, installation and maintenance of biogas digesters;
  • utilities like methane stoves and lamps;
  • technology for quality control;
  • and carbon credits

All that is needed is business partners and investors with the vision of recognizing the potential of domestic biogas technology to become partners in realising this potential.