Q.Do you think microbes can also be used as source of energy? If yes, how?

Microbes are indeed powerful energy sources, and we already harness them in several practical ways. The most widespread example is biogas production, where anaerobic bacteria break down organic waste—animal dung, crop residues, sewage—in the absence of oxygen. This microbial digestion releases a mixture of gases, primarily methane, which burns cleanly and can be used for cooking, heating, or even generating electricity. The process happens inside biogas plants, which are common in rural India and help convert waste into valuable fuel while also producing nutrient-rich slurry as a byproduct for fields. …

Microbes have been quietly powering human activities for millennia, though we only recently understood the science behind their work. When we think of energy sources, coal, oil, and sunlight come to mind first. But microorganisms offer a renewable, cleaner alternative by breaking down organic matter and releasing energy-rich compounds we can capture and use.

The most established microbial energy source is biogas. This process relies on methanogens—bacteria that thrive in oxygen-free environments. When organic waste like cattle dung, vegetable scraps, sewage, or crop residues accumulates in a sealed chamber called a biogas plant or digester, these anaerobic bacteria get to work. They decompose the complex organic molecules, and in doing so, produce a mixture of gases: primarily methane (which is the combustible component) along with carbon dioxide and traces of hydrogen sulfide.

The beauty of biogas lies in its dual benefit. It solves a waste-disposal problem while generating fuel. A farmer can feed animal dung and agricultural waste into a simple gobar gas plant, and within weeks, tap methane-rich gas for cooking or lighting. The spent slurry that remains is an excellent fertilizer, richer in nitrogen than the raw dung, so nothing goes to waste. This closed loop makes biogas particularly valuable in rural settings.

Beyond methane, microbes also produce liquid biofuels. Yeast, the same organism that leavens bread and ferments beer, can convert sugars from molasses, corn, or sugarcane into ethanol. This microbial alcohol, when distilled and purified, burns cleanly in engines and is already blended with petrol in many countries to reduce dependence on fossil fuels. The process is straightforward fermentation—yeast cells consume glucose and excrete ethanol and carbon dioxide as metabolic byproducts. …

Separate the two mechanisms by the environment each one needs -- biogas needs a sealed, oxygen-free digester (methanogens breaking down waste anaerobically), while ethanol needs an open, sugar-rich fermentation vat (yeast acting on sugars). Asking 'oxygen-free or not' …