Cooking using my waste ?
Biogas, what is it?
Biogas is a type of biofuel that is naturally produced from the decomposition of organic waste in the absence of oxygen (also known as anaerobic digestion). Biogas consists mainly of methane (CH4) and carbon dioxide (CO2) with the exact proportions depending on the type of feedstock being digested and processing techniques. The amount or volume of biogas is normally expressed in ‘normal cubic meters’ (Nm3), a common unit used in industry to refer to gas emissions or exchange. The energy value of biogas varies between 4.5 and 8.5 kWh/Nm3, depending on the relative amounts of methane, carbon dioxide and other gases. This corresponds roughly to half a liter of diesel oil or 5.5 kg of firewood. Both methane and carbon dioxide are odorless. Yet, the biogas can contain a variety of Sulphur compounds, responsible for an unpleasant odor. In terms of its constituents the biogas is comparable to natural gas, which is composed of as much as 99% methane. The major difference is that the methane present in the natural gas has fossil origins. Biogas can be used to replace natural gas in many applications such as cooking, electric generation or heat production. If the biogas is upgraded or purified, the so called biomethane can be used as vehicular fuel.
So how does it work?
The biogas production-and-use cycle is continuous. Organic materials like manure, crop residues, wastewater sludge or domestic waste are fed into a biogas digester. Within the digester, fermentation of biodegradable materials is taking place slowly (it takes between 14 and 40 days) producing biogas. Contrary to popular beliefs, biogas plants are not filled with pressurized explosive gases, the reservoirs are filled mainly with wastewater and only the top of these reservoirs contains gas. Therefore, if handled and maintained properly, biogas digesters are not dangerous infrastructures. During the anaerobic digestion, maintaining a constant adequate temperature as well as using water to maintain the bacteria culture are critical factors for maximizing the gas production.
What comes out of a biogas digester?
According to our partner (B)energy, 15 kg of cow dung (or organic kitchen waste) and the same amount of wastewater produce around 1 Nm3 of biogas, with which one can cook for approximatively 3 – 4 hours. Once the anaerobic digestion process is completed the remaining organic compounds are transformed into a high-quality fertilizer called bio-slurry or digestate. This bio-slurry can be separated: the solid part can be composted and the liquid part can be used as liquid fertilizer. When the available bio-slurry cannot be used at once, it can be stored and added to composting with other biodegradable materials. The resulting composted fertilizer can then be stored for several weeks.
 In Benin, a typical household waste is mainly composed of kitchen waste, food leftovers and vegetable and fruit peel and skins.
What makes the biogas a sustainable energy alternative?
Nearly three billion people in developing countries rely on wood, charcoal, animal dung, crop residue or coal to meet their energy needs for cooking. This reliance on solid fuels has serious consequences for their health, the environment and the social and economic development. According to the World Health Organization, household air pollution from cooking and heating kills over 4 million people every year and sickens millions more. Presently, in Benin 94% of the population is using slid fuels for cooking. By introducing a new business model of mobile biogas solution for domestic use and providing clean cooking solutions our pilot project in Toffo addresses therefore the most basic needs of the poor, while also delivering broader benefits such as the emancipation and engagement of the communities through increased ownership.
Since biogas production is a natural form of waste-to-energy that uses organic matter, the production is easily maintained even in rural areas due to readily available organic waste. Therefore, for households in developing countries, biogas utilization could lead not only to cost savings and health benefits from the reduced use of unsustainable sources of energy, but also to an overall improvement on families’ standard of living as the waste they produce become a valuable resource they can bring to the plant and receive payment for.
Finally, with our pilot project, ReBin creates new job opportunities providing decent work conditions and engaging women throughout the whole entrepreneurial model. We consider that women in Benin play an important role for the adoption of innovative and cleaner fuels and equipment, since they are the primary users of energy equipment and have significant knowledge about local conditions and resources.
The adoption of biogas technology is therefore an intervention that combines economic development, environmental and social impact and, last but not least, sustainability.