Science of Anaerobic Digestion

Bio-Gas Plant

• Bio-gas plants utilize a dome-like structure made of bricks to produce energy.
• A slurry of cow dung mixed with water is fed into a sealed digester devoid of oxygen.
• Anaerobic microorganisms decompose the slurry, generating gases such as methane, carbon dioxide, hydrogen, and hydrogen sulfide.
• Bio-gas contains up to 75% methane, burns cleanly without smoke, and provides high heating capacity.
• The remaining slurry is rich in nitrogen and phosphorus, serving as excellent manure.
• Bio-waste and sewage efficient disposal contribute to energy and manure supply.

Wind Energy

• Wind energy arises from unequal heating of land and water, generating air movement.
• Historically harnessed by windmills for mechanical tasks like water pumping.
• Modern windmills convert wind kinetic energy into electricity, primarily through turbines.
• Wind energy farms consist of multiple windmills to generate electricity on a commercial scale.
• Denmark is recognized as the "country of winds" due to its favorable wind conditions.

Solar Energy

• Solar cells have no moving parts, minimal maintenance, and can operate without focusing devices.
• Silicon is abundant, but special grade silicon for solar cells is limited in availability.
• High production costs and silver used for connections make solar cells expensive.
• Though costly, solar cells power scientific instruments and remote technology applications.
• Solar panels are positioned on inclined rooftops for optimal sunlight exposure.

Tidal Energy

• Gravitational pull by the moon causes sea level variations, producing tidal energy.
• Tidal energy is harvested by constructing dams at narrow sea openings with turbines for electricity generation.
• Suitable sites for tidal dams are geographically limited.

Wave Energy

• Generated by strong winds across the sea, wave energy can be converted into electricity.
• Effective wave energy harvesting depends on the strength of the waves.

Ocean Thermal Energy

• The sun heats surface ocean water, creating a temperature differential with deeper water.
• Ocean-thermal-energy conversion plants exploit this difference, requiring a minimum of 20 K.
• Warm water boils a volatile liquid like ammonia, generating vapor to drive turbines.

Geothermal Energy

• Formed by heated molten rocks in "hot spots," producing steam when subterranean water contacts hot rock.
• Operational sites are scarce, limiting commercial viability, with current plants in New Zealand and the USA.

Nuclear Energy

• Nuclear fission splits heavy atom nuclei like uranium, releasing substantial energy.
• Fusion combines lighter nuclei into heavier ones, releasing energy in processes like those in the sun.
• Fusion requires extreme conditions of temperature and pressure, notably used in hydrogen bombs.
• Both fission and fusion have potential for generating large amounts of energy, but fission is currently commercially used.

Energy Sources Comparison and Environmental Considerations

• Most energy sources are derived from solar energy, except geothermal and nuclear energy.
• Limitations in harnessing energy exist for wind, waves, and tides due to consistency and geographical constraints.
• Renewable energy sources are sustainable, while non-renewable sources are finite.
• Ideal energy sources are efficient, environmentally friendly, and economically viable.
• Solar cookers’ utility may be limited on cloudy or rainy days, influencing their broader application.
• Increasing energy demand has environmental repercussions, necessitating measures for consumption reduction.

Explore the fascinating process of anaerobic digestion, focusing on the breakdown of cow-dung slurry by micro-organisms in a sealed chamber. Understand the significance of this method in waste management and biogas production. This quiz will test your knowledge about the principles and applications of this scientific process.