Making Biogas.
The world is slowly but surely and inevitably moving towards what is being touted as a green future. A future where we wean ourselves from our dependence on fossil fuels which are unsustainable since they are no renewable to a world where we acquire our energy primarily from sources that are not only earth friendly but also those which are sustainable in the long run, to these ends technologies like solar, wind power and the use of Bio-fuels have of late become all the rage.
This, in the area of Bio-fuels specifically the production of biogas is where the potential is largely untapped and it is a relatively cheap piece of technology that has the potential of transforming homesteads and livelihoods in many parts of the world more so in the developing world where there is often a very large energy deficit in the average household. Most of the women and girls of these households especially in sub-Saharan Africa, spend a great deal of the day collecting wood for fuel for cooking, this is puts them in a particularly precarious ;position considering the ever dwindling and overexploited forest cover in these areas.
Biogas is a mixture of methane, carbon dioxide; hydrogen sulphide and nitrogen dioxide in the ratios of roughly 65%, 34% and the rest cover a paltry 1%. It is created when anaerobic bacteria (bacteria that exist in an environment devoid of oxygen) act on dead and decaying organic matter like leaves and discarded vegetative matter. On the other hand animals like cows that eat a lot of plant material also produce plenty of this gas, methane which is the same gas that you have in your gas cylinder only that in the case of natural gas the methane content is much higher than is the case with biogas usually containing the combustible gas methane at level of upwards of 80%.
The process of making biogas requires some critical raw materials which include the vegetative material or cow dung or any other animal droppings for that matter and a big tank or container that will act as the biodigester. A biodigester is the particular container where you place the biomass and water mixture; it is here that they will eventually ferment producing the cooking gas. It is the in this container that enzymatic reactions place, that is where the anaerobic bacteria initiate their biochemical reactions converting the organic matter into methane, carbon dioxide, some hydrogen and other gases in traces, very little heat and a final product with a higher nitrogen content than is produced by aerobic fermentation (fermentation that takes place in an environment that has oxygen).
This process is dependent on many interlinked factors including temperature, acidity and the Carbon-Nitrogen ratio of the organic material being fed into the biodigester. There is a very narrow band of temperature the ideal temperature is within 32C and 35C for continuous methane production, because there are two different classes of bacteria that break down the organic matter one kind thrives between 29C and 41C the other between 49C and 60C so the ideal is the 32C to 35C range. The pH range, that is the measure of acidity or alkalinity, should fall between 6.8 to 8.0 because if the mixture is too acidic or basic mixtures will ferment at a lower speed.
The Carbon-Nitrogen ratio should also be carefully checked to ensure the optimal production of methane gas from your biogas plant. The bacteria responsible for the anaerobic process require both elements, as do all living organisms on the face of this planet, but they consume carbon roughly 30 times faster than nitrogen. Assuming all other conditions are favorable for biogas production, that is the temperature and acidity is ideal, a Carbon – Nitrogen ratio of about 30 – 1 is ideal for the raw material fed into a biogas plant. A higher ratio will leave carbon still available after the nitrogen has been consumed, starving some of the bacteria of this element.
India which is a world leader in this kind of technology has had a pioneering role in leading research into making these Biogas units more efficient. In the traditional setup where the biodigester is fed cow dung or human excreta you require 40 kilograms, 80 pounds of dung to produce 250 grams of methane, whereas if you use Dr Anand Karve’s, of the Indian NGO Appropriate Rural Technology Institute, new technology ‘new compact biogas technology’ method requires 1 kg of starch or sugar (in the form of vegetable waste, flour collected from the floor of a flour mill) and just 24 hours to produce 250 gms of methane gas. With better and improving technology and easier to build Biogas kits being readily available on the internet, why don’t you take the plunge by doing your part to save the planet and build one of these biogas kits in your backyard.
