by Dr. Satinder Brar, Lassonde School of Engineering
In a world of increasing “wants”, lies a parallel increase in “wastes”. We are observing a record surge in the production of goods for human consumption, and likewise, its wasteful consequences. From wasted agricultural produce, post-consumption or unused food waste, municipal and industrial wastewater, forestry and textile waste, there is a lot that can be recovered or redirected for further use. Historically, this practice of circular economy has been intrinsically bound to our civilizations, cultures and way of life. However, somewhere along the way with industrialization, rapid technology advancements, the hygienist movement etc., we focused on the linear economy a little too much. While ending the circularity of certain goods from the public health perspective was a giant leap towards eradicating some preventable diseases, it also paved the path towards consumerism and the global issue of waste management [1].
Let us look at some interesting numbers. According to the World Food Programme, ‘One-third of food produced globally for human consumption is wasted or lost’. This is about 1.3 billion tonnes per year [2]! One-third of the forest cover has been wiped off the earth to fulfil human needs including expansion of agricultural land [3]. This consequently has increased agricultural waste when production surpasses the needs or rather the disproportionate division of the produce leading to unnecessary spoilage or wastage. Furthermore, the use of wood in a range of other applications, for instance, the pulp and paper industry. On the other hand, municipal waste alone accounts for 2 billion tonnes of it getting diverted to landfills [4].
So much potential ‘wasted’ indeed. What do we do, moving forward? We go back to our roots of course, with a wealth of knowledge acquired over the years to generate the ‘wealth from waste’. Not just using the resources to expand the technological advancements, but rather using the technologies as well to expand the end-of-life path of those resources.
If we look at the organics, also called as biomass, consisting of food, crops, forestry products, wastewater etc., their complex chemical makeup offers a wide range of possibilities for value-addition. Wastewater and sludge from treatment plants have been widely studied and used for the production of methane and hydrogen gas which are valuable biofuels. The technology used for this conversion is known as anaerobic digestion where the complexity of wastewater or sludge is reduced to a simpler state by harnessing the power of microorganisms. Not just biofuels, a multitude of by-products like fatty acids are also generated in this process which again have a broad range of applications like creating bioplastics, animal feed, fertilizers, flavouring agents, perfumes, and other industrially-relevant chemicals. This bioprocessing is also applicable to other organic matrices from waste streams. Since they all differ in terms of their basic composition, there are different alterations required for the overall process or a shift observed in the final product.
Sludge generated in the wastewater treatment is highly rich in organic matter, especially carbon, which in the absence of oxygen is ideal for reduction to methane gas. If we look at food waste, it has a different chemical makeup with carbohydrates, proteins, and fats. Thus, requiring different conditions than sludge can favour the production of other by-products like volatile fatty acids than biogas. Another commonly practised process of composting results in a nutrient-rich humus-like product suitable for enhancing soil fertility. Moving further to agricultural and forestry waste, they comprise even more complex sugars or carbon sources, that can shift the process towards a specific product and require different conditions for full utilization. As they are rich in cellulose and lignin, these can also be used to generate biochar which is a stable form of carbon useful in improving soil quality. Livestock waste is rich in nitrogen and phosphorus, which when digested or converted to manure is highly useful for soil fertility. Therefore, the suitability of these various waste streams for specific biological processes is dependent on their physical characteristics, chemical composition, nutrient and moisture content etc. A deeper understanding of the intricacies behind these properties and the activity of microorganisms opens more opportunities for designing waste management strategies for their value addition in the economy.
Thus, there is an art behind mindful resourcefulness in our everyday lives, and science supports resourceful recycling for a better future.
References:
[1] Aggeri and Franck, “From waste to urban mines: a historical perspective on the circular economy,” http://journals.openedition.org/factsreports, no. Special Issue 23, pp. 10–13, Nov. 2021, Accessed: Mar. 14, 2024. [Online]. Available: http://journals.openedition.org/factsreports/6530
[2] “5 facts about food waste and hunger | World Food Programme.” Accessed: Mar. 14, 2024. [Online]. Available: https://www.wfp.org/stories/5-facts-about-food-waste-and-hunger
[3] “Deforestation and Forest Loss - Our World in Data.” Accessed: Mar. 14, 2024. [Online]. Available: https://ourworldindata.org/deforestation#article-citation
[4] “Trends in Solid Waste Management.” Accessed: Mar. 14, 2024. [Online]. Available: https://datatopics.worldbank.org/what-a-waste/trends_in_solid_waste_management.html