By Putu Virgina Partha Devanthi, Ph.D.
Faculty of BioTechnology
According to Economist Intelligence Unit (2017), Indonesia has contributed as the second largest food waste producer in the world after Saudi Arabia. Every year, each person throws almost 300 kg of food. Such food loss is an irony, when 7.6 % of 260 million people in Indonesia are still undernourished. This does not only cause huge economical losses, but also a serious environmental damage. More than half of the kitchen waste produced in Jakarta ends up in the landfill, which is further decomposed by anaerobic microorganisms, producing a large amount of methane and carbon dioxide. Both of these gases are known as main greenhouse gases, causing global warming and climate change. However, methane is 30 times more effective at trapping heat than carbon dioxide.
How can we prevent the food waste from causing global warming and climate change? Food waste decomposition by anaerobic microorganisms can be achieved under controlled condition to produce biogas, in a process called anaerobic digestion. Biogas is composed of around 60% of methane and 40% or carbon dioxide. Instead of escaping to the atmosphere and causing global warming, the biogas can be collected and used for heating, cooking, and generating electricity.
Anaerobic digestion is simply done in a large sealed tank in the absence of oxygen. The naturally occurring microorganisms will act on the food waste through several steps, called hydrolysis, fermentation (acidogenesis and acetogenesis), and methanogenesis. During hydrolysis, complex organic matter contained in the food waste, such as carbohydrates, proteins, and fats, are broken down into simpler molecules including sugar, amino acids, and fatty acids, respectively. These molecules are then turned into short-chain organic acids during acidogenesis and acetogenesis process. Then, bacteria will convert these acids into methane and carbon dioxide through methanogenesis, which is known as biogas. Anaerobic digestion may also produce liquid and solid material that can be utilized as organic fertilizer.
All in all, anaerobic digestion does not only reduce greenhouse gas emission at landfills, but also provides an alternative renewable energy source replacing fossil fuels. In addition to biogas, there is also a nutrient-rich solid and liquid material leftover from this process, which can be returned back into the soil ecosystem as plant fertilizer.
References
http://jakartaglobe.id/business/indonesia-second-largest-food-waster/
https://www.businessgreen.com/bg/sponsored/2317075/everything-you-need-to-know-about-anaerobic-digestion
https://www.epa.gov/recycle/reducing-wasted-food-home
