A Closer Look at Circular Economies, Organic Waste and Phosphorus (Part Two)

A phosphorus recovery case study.

This is Part Two of a two-part series. Part One is available here.

Beyond moving toward zero waste systems, organic waste provides an opportunity to recycle valuable nutrients. To appreciate the value of organic "waste," let us take a closer look at the example of phosphorus. Phosphorus is a major plant nutrient meaning that all plants, including food crops, require this element to grow. Generally, phosphorus can be found in small quantities in the soil, but over time, when land is continually used for agriculture, this soil resource becomes depleted. After soil stocks have been used up, it is necessary to apply additional phosphorus.

This additional phosphorus often comes in the form of mineral fertilizers, and most of these mineral fertilizers come from non-renewable phosphate rock reserves. To make matters more complicated, these phosphate rock reserves are geographically concentrated; nearly 80 percent of all mined phosphate comes from just five countries and more than 70 percent of global phosphate rock reserves are located in Morocco and the Western Sahara 1. Not only do these rock reserves become diminished over time with extraction, but many are also located in areas that are geopolitically unstable which can lead to concern around future accessibility to this resource.

On the other hand, high levels of phosphorus inputs to water bodies can act as a pollutant. Because the phosphorus in mineral fertilizer is often easily dissolved in water and applied on top of soil, excess phosphorus can run-off agricultural land and cause pollution to near-by waterways leading to problems such as algal blooms 2.

As one further level of complexity, phosphorus is non-substitutable, which means there are no substitutes that can be used to grow food in the case where phosphorus reserves become inaccessible or depleted. At its best, phosphorus is a valuable resource that is harnessed to benefit global agricultural production. At its worst, it can act as an aquatic pollutant and an expensive, environmentally demanding agricultural import. In either case, it becomes valuable to investigate the potential to recycle phosphorus through organic food and waste systems—this recycling could reduce dependence on mined and imported fertilizer and create more local, circular systems.

There has been isolated progress seen in recent years through the establishment of infrastructure and the development of policies which aim to ban the disposal of organic waste going to landfills (e.g. Massachusetts, Vermont, Vancouver). These bans require municipalities and citizens to divert this organic waste away from landfills and process it in another way. Other areas have taken a less regulated approach and focused simply on the development of infrastructure to support organic waste collection and processing.

This progress seems promising, but recovery and recycling of organic waste is still limited and initiatives regarding organics recycling seem to be hit-or-miss. A lot of questions remain. Why do some areas have waste diversion programs and bans while others do not, and why are some programs more successful than others? What factors and processes facilitate or act as barriers to the success of organic waste diversion, and what encourages residents to actively engage versus not engage in such programs?

Recent research has started to explore these questions by examining trends in organic waste diversion associated with socioeconomic factors, management strategies, and human behavior. Results are encouraging and indicate that management strategies, such as economic incentives and accessible infrastructure, can act as important facilitators to organic waste diversion, despite existing socioeconomic structures 3. Research on human behavior has also started to indicate which patterns lead to higher organic waste program engagement and could therefore shed light on what trends can be cultivated to increase success in waste reduction and organic waste diversion 4,5. However, while early results are hopeful, better data and more research is needed to understand complexities across different regions and to work with local decision makers to learn how to make policy initiatives more successful and less hit-or-miss.

If we want to seriously move towards circular economies and zero waste systems to start recovering and recycling more and more of our waste products, we need to have a clear understanding of what makes this feasible and what our barriers are. We also need to have clear goals about what we are trying to achieve and ensure that our actions move us toward those goals. For example, there are a lot of people making a concerted effort to divert organic waste, but there is a lack of available information regarding what is happening once the organic waste is diverted. If the goal—or part of the goal—is to strive toward circular economies and nutrient recycling, an emphasis should be placed on returning processed organics, rich in nutrients such as phosphorus, to arable land to grow more food.

More collaboration between researchers and government, as well as collaboration between different departments within universities and governments, can lead to a clearer understanding of the entire system and will be an important first step to facilitating more sustainable waste and nutrient management solutions. As individuals, we can make sure we put that yogurt in the organics bin and the container in the recycling bin—if those bins are not accessible in your region or workplace, find out why and write to your local representative to voice your concern.

With small steps we can move toward more circular economies that will benefit not only us, but the environment as well.


  1. Jasinski, S. M. Phosphate Rock. USGS Miner. Commod. Summ. 120–121 (2016).
  2. Carpenter, S. R. et al. Nonpoint pollution of surface waters with phosphorus and nitrogen. Ecol. Appl. 8, 559–568 (1998).
  3. Treadwell, J. L., Bennett, E. M. & Clark, O. G. The role of management instruments in organic waste diversion and phosphorus recycling.(In preparation).
  4. Refsgaard, K. & Magnussen, K. Household behaviour and attitudes with respect to recycling food waste – experiences from focus groups. J. Environ. Manage. 90, 760–771 (2009).
  5. Parizeau, K., von Massow, M. & Martin, R. Household-level dynamics of food waste production and related beliefs, attitudes, and behaviours in Guelph, Ontario. Waste Manag. 35, 207–217 (2015).


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