Household Biogas Plant

Start - Finish:

June 2008

Project Members

Michael Millington, Will Kinghorn and Leila Sheldrick

Keywords:

Fuel, energy, waste, power, biogas

Useful Websites:

Story Bank

Aims & Objectives:

Globally inclusive design (GID) is an extension of the concepts of inclusive design and design for sustainability. It ensures that design encompasses and recognises many groups of people who are otherwise excluded from design attention, and therefore product benefit, due to their geographic, financial, or cultural situation. This project focuses around the needs of a rural village community in southern India called Budikote. It aims to use the principles of GID to develop a product targeted to help this rural community within a poor, developing country, where the resident’s lives are far removed from our own in western countries and their daily concerns are often matters of fulfilling basic human needs, such as food, water and shelter. Recent census figures show that in India, poverty is on the rise, and education levels are below average. In order to inform this design activity, the work of a research project called StoryBank is to be used for reference. The main source of information about village life as seen through the StoryBank is within a number of journalistic stories which have been recorded by the community themselves. These, along with other associated sources will be used to identify the needs of the Budikote residents, and to design and develop a product to meet those needs. The aim of this project is to develop a design specifically for the people in Budikote village that also meets the requirements of sustainable development. It can be in the form of a new product service or technology which should use information gathered from the StoryBank project to identify the needs of the people. The solution might encourage better use of existing resources, increase economic prosperity, enhance quality of life, or address fundamental human needs.

Project Abstract

The aim of this globally inclusive, sustainable design project was to generate a sustainable solution to a ‘real’ problem, highlighted in part by videos produced by Indian villagers from the rural town of Budikote. From the videos viewed and further initial research into the climate, culture and country of India, a product was developed which was capable of solving a problem facing the villagers of Budikote. The general and specific problems of the village, villagers and local geographical environment were collected and analysed to identify areas of biggest need and possible concept solutions generated. These concepts were refined and stripped down to the strongest, through various selection techniques as part of an overall continuous design methodology. The strongest concept (bio-gas plant) was brought forward for further research and developed to minute detail, generating a product/system capable of being manufactured and used in the village to solve a number of problems. The bio-gas plant, more affectionately known as ‘NayA Jamna’ (regeneration), provides a centralised self-managed waste deposit node, which breaks down the bio-degradable material/waste inputted and outputs two valuable resources in the form of methane gas (possible to cook and be used as lighting energy) as well as organic fertiliser (foreseen to improve the farmers crop output). In evaluation of the design and overall concept, the ‘NayA Jamna’ was found to solve more than one problem identified by initial research and effectively was able to take the problems of the village and utilise them into a solution, which is beneficial to the villagers, socially and economically whilst being environmentally friendly and sustainable. The product, provides a localised energy source (eliminating transportation emissions and costs), nutrient rich fertiliser for farmers, and not to mention an incentive to use the node to collect and deposit the hazardous waste typically littering the streets of Budikote, improving the living standards of the village families if implemented in Budikote.

Development and Experimentation

After detailed technical research is carried out, and a PDS is created, the requirements for the biogas plant are clearly defined, and so design development can be undertaken in order to produce the final design. At the commencement of development, a number of concepts were proposed for different styles of plant. The following sections briefly detail initial concepts. These were conceived to be large rotationally moulded single piece digesters, similar to compost bins. They would be easy to manufacture locally, but would be difficult to add complexity to, such as inlets and outlets and gas valves. This complexity would also cause problems with nesting of components, meaning they would have to be transported individually as very large components. These were suggested to enable the users to be able to set the size of digester they require based on their needs and available feedstock. These designs were flawed in many ways as the adjustable nature meant they would be made from flexible, bag like material which is easily damaged. They were also very complicated, and offered no real advantage as the size of digester has no effect on the contents of efficiency of reaction. They also invited ambiguity as to correct amounts of feeding which could lead to over feeding and many problems. This design was based on a reclaimed oil drum being held in a large cradle to add the extra required features. It was thought that oil drums which usually cause waste and pollution could be reclaimed and utilised. The cradle could easily be flat pack, would house the inlet/outlet, and could also be mirror finish on the inside, directing sunlight to the oil drum. The drums would need to be painted black to attract heat, and also thoroughly washed to prevent contamination. These processes would add to environmental pollution and use of energy to prepare the drum. Also, it is known from previous products that oil drums used as anaerobic digesters rot after only 2 years. This design allows a square section digester to be produced (therefore making the best use of floor space). It also means that no permanent fixing may be required, and the modularity could be used to make a flat pack design which is easily transported, serviced, repaired, and replaced. This idea was taken forwards as it offered the most potential. From this point forward, the PDS and technical research was considered as the digester was developed using functionality as the primary driver to produce a thorough and detailed design. The final plant design is modular to enable easy transport, assembly and maintenance. The geometry of the components means that the digester can be packed down into a much smaller package than the final assembled product. This saves money and energy on transportation. The modular design, and fixings employed also mean that the design and components are easy to assemble, disassemble, repair, replace, and service as necessary. The walls are black to attract heat from the sun and retain it to aid the reaction. Green components indicate important features such as the inlet, outlet, and lamp.

Results

In order to evaluate the proposed design, two approaches were used. Firstly, a comparison between the products’ gas production and alternative methods of acquiring energy for cooking. The second was to use spider diagrams to provide a visual comparison between eight most important factors for the three cooking methods. To re-iterate and put into context the numerous advantages the ‘bio-gas plant ‘ has, the typical practices of the villagers in the solution areas of the product have been re-covered. Typically villagers throw house waste, into piles in undersigned areas, normally where someone else has thrown there wasn’t creating areas of rotting and smelly waste in random areas of the village. Villagers commonly walk to the edge of the village to defecate and urinate onto plants/crops , in the ‘waste’ appointed lake or into the open sewers running through the village which end in the ‘waste’ lake. Animal waste is found nearly everywhere, especially on the streets and near houses as typically all animals are tied up or housed in the owners homes. Therefore creating a place to deposit these wastes, is advantageous for a number of reasons; - Collects waste together into a self-managed vehicle, - Removes cow waste from the streets and near houses (improving hygiene levels), - House waste is deposited in a designated area, removing large amounts of rotting waste piles around the village, - Removes human waste from the outskirts of the village, - Locates the strong smells to one place - Creates beneficial (valuable) by-products/resources (discussed below) Typically farming fertilisers to boost the crop output each harvest is out of the reach of most village farmers, and as a result harvests are smaller than they would be if fertiliser was used. Farmers typically urinate on their plants, to provide any extra nutrients they can but does little to boost their crop. Therefore by collecting together all the bio-degradable waste from the houses and farms, combined with the bacteria found in animal waste (manure) and mixing it all in a bio-gas plant for a period, produces nutrient rich fertilisers. From this the farmers of the village will have a sustainable, continuous supply of fertiliser to use on their crops, which hopefully will increase their crop output each harvest. The advantage of this, apart from continuous supply of free fertiliser year round is the incentive to use and maintain the bio-gas plant for their own gains. This in turn provides the hidden advantage of ensuring as little waste is wasted and thrown onto the streets, perhaps to the extent that families will clear manure and bio-degradable waste from the streets to improve the output of their own household plant. Most families in the village are unable to afford the high cost of cylinder gas, as there is no piped system to the village. As a consequence of the high costs of the cylinder gas, the majority of villagers are forced to cook by open wood fires (within houses), not only is this a slow and time consuming process of cooking, but detrimental to the villagers health. The villagers normally buy the wood from land owners, or scavenge what they can from the outskirts and outlying areas of the village (fallen old trees etc.). Regardless there is an expense to buying the wood, economically as well as in the form of time, not including the time to assemble and start a fire, and weight for it to cook the food. There is also the associated health effects of cooking using a open wood fire within the house, the fumes/smoke produced enters the inhabitants and negatively affects their lungs. Only the wealthy can afford to purchase cylinder gas which is a more efficient and easier system of cooking food through the use of a simple stove. By using the methane gas produced from the bio-gas plant, the villagers are provided with a free continuous supply of gas to cook with, the advantages of this are; - Free gas supply, year round - No requirement to buy wood to cook - Time saved collecting/purchasing/assembling and cooking using an open fire. - Improved cooking system (gas produces high temperatures and so is faster and safer) - Improved health benefits (the burning of gas has far lower health implications that open wood fires)

Conclusions

In terms of the economical benefit to the villagers the most important an obvious one is the free, continuous and sustainable supply of methane gas and fertiliser. The free methane gas, allows the poorer villagers to cook more efficiently and easily, raising their standard of living, at the same time as reducing their out goings removing the expense of having to buy wood to cook with. When comparing the three different cooking material/systems, it is obvious the bio-gas plant cumulatively provides the most cost efficient way of providing energy to the cooking process (See graph) over an extensive time period of ten years. By producing energy from pre-existing materials villagers already own or can collect, the cost of continually producing the energy source is almost zero, compared to the ever increasing cost of replacing wood after it is burnt. And is likewise for gas in cylinders which is more expensive to purchase and must continually be replaced at a high cost, both economically and environmentally. The economic analysis (graph above), does highlight an economic negative to the bio-gas plant, as the set-up and purchase of the bio-gas plant is high in comparison to building a simple wood fire and although it is cheaper to install a gas cylinder system, supplying the gas for a year raises the cost considerably From analysis it can found the bio-gas plant takes on average three and half years for the villagers to pay off, a large investment for poor families, but is something that provides them with two advantageous products (cooking gas and fertiliser) and a continuous sustainable way of generating free energy and considerably reducing their out goings as a family over a time scale of a decade.

As can be seen the household bio-gas plant comes out substantially stronger in almost all eight marking criteria, except in the area of safety, as it is perceived that using steel, replaced gas cylinders pose a smaller chance of casing safety dangers for the users.