Natural Resource Management and the Circular Economy
Around the world, there is a move towards a ‘circular economy’ where products and waste materials are reused, repaired, refurbished, and recycled with significant economic and environmental benefits.
Since the Industrial Revolution, the total amount of waste has constantly grown as economic growth has been based on a ‘take-make-consume-dispose’ model. This linear model assumes resources are abundant, available, and cheap to dispose of. While the current linear economic model has generated an unprecedented level of growth, it has led to constraints on the availability of natural resources due to rising demand, generation of waste, and environmental degradation.
From the sustainable development perspective, the linear economy is leading to the rapid accumulation of human and physical capital at the expense of natural capital, impacting the ability of current generations to ensure future generations have at least the same level of welfare. While weak sustainability proponents argue that depleted natural capital can be replaced by even more valuable physical and human capital, the strong view is that natural capital should be protected, not depleted, due to it being exhaustible, often unevenly distributed geographically, limited in availability at times, and undervalued, as associated benefits, including their non-use benefits, are not reflected in market prices of natural resources.
The circular economy
Around the world, there is a move towards a ‘circular economy’ where products and waste materials are reused, repaired, refurbished, and recycled with significant economic and environmental benefits.
A key aspect of the circular economy is that materials, which have accumulated in the economy, constitute important man-made stocks that can be exploited through recycling to gain secondary raw materials and reused and remanufactured to keep products in the commercial lifecycle. The overall aim of the circular economy is to decouple economic growth from resource use and associated environmental impacts.
Helsinki’s circular wastewater treatment plant
Helsinki’s Viikinmäki Wastewater Treatment Plant processes wastewater from industry and 800,000 people in Helsinki and its 7 neighboring municipalities. The average wastewater flow is 280,000 m3/day and peak flow is 700,000 m3/day. Of the waste, around 85% is domestic wastewater and the rest is from industry.
Recovering energy
The sludge generated in the treatment process is processed in digestion tanks, with the methane gas generated in the digestion process utilized in energy generation to produce electricity and heat. The electricity generated corresponds to 70% of the wastewater treatment plant’s electricity needs, with the aim of reaching 80% soon.
Recovering nutrients
Meanwhile, the digested and dried sludge from the wastewater treatment plant is transported to the Metsäpirtti composting field in Sipoo. The sludge is mixed with peat in a ratio of 1:1. The mixture is composted in stacks for around 6 months, after which sand and biotite are added to the mixture. In the last stage of the process, the soil mixture is screened (with the screen size set at 20 mm). Following which, Metsäpirtti soil products for gardens is created, enabling the wastewater treatment plant to recycle around 580 tons of phosphorus and 620 tons of nitrogen per annum.
Conclusion
Wastewater treatment plants facilitate the development of the circular economy by recovering valuable materials from waste.