The concept of the circular economy has gotten a lot of attention, but what does using resources in a circular way really mean? Simply put, it means that our use of resources doesn’t deplete them by reducing their future usefulness or availability. This is a much different way of thinking than the common understanding of resource consumption: products or materials are produced, then used, then disposed of as waste. In other words, we typically follow a model of consumption that is linear.

Resource use can be considered cyclical, when “waste” is not only useful but a valuable resource that is integrated into the production system. Of course, if the waste in our linear system was considered valuable, we wouldn’t send it to landfills. Another distinction between cyclical and linear resource use can be seen at the production stage. When waste is not reused, materials and energy for production must be obtained from some external source (i.e., a depleting base of natural resources). In a circular system, however, materials and energy don’t need to be externally acquired because they are already available for use within the system itself.

If we look at how other species consume and produce natural resources, we see that resources are frequently maintained in self-sustaining cycles in nature. For sectors that deal directly with natural resources and wastes, like food production systems, water and sewage systems, and land management, we can look to nature to inform our design and approach.¹ The strategy of identifying and mimicking natural patterns in design is based on the concept “nature knows best.” In the field of permaculture, this phrase is understood to mean that, due to long-term evolutionary processes, natural systems have organized themselves to be as efficient as possible; therefore, a management scheme based upon these natural efficiency laws presents reliable inspiration for optimizing resource use.²

An important example of cyclical resource use in nature can be seen in the role of livestock in an agricultural system: animals naturally contribute to soil health with the nutrients in their manure, which in turn supports the production of vegetation in their habitat. Interestingly, livestock are well-known for their inefficient use of nutrients, with only a 5 to 20% retention of nitrogen in products.^3,4 According to David Holmgren, the co-originator of permaculture, such “inefficiency” of nutrient use does not implicate suboptimal species performance, but is rather an indication of the role that livestock are naturally intended to perform within agroecosystems.² In other words, nature demonstrates that manure is a valuable resource.

Within our linear consumption model, however, there is an increasingly common case of industrial and concentrated livestock operations. Such centralized facilities result in quantities of manure that cannot be used in an economically or environmentally productive manner. This treatment of manure as a waste rather than a resource leads to nutrient imbalances that exist broadly on a regional scale.⁴ When manure is wasted at the end of the linear model, the production process depends upon external inputs, like artificial fertilizers. This is because growing crops uses up the soil’s nutrient stores, which then must be replaced. Our reliance on nitrogen fertilizers as a quick solution has resulted in an increase of their use by 800% since 1961.⁵

For the example of livestock and their manure, a potential solution to close the loop is somewhat straightforward: we would need to incorporate them into agriculture in a reasonably decentralized manner to sustainably return nutrients to the soil.⁴ This solution is, of course, easier said than done. And when it comes to other industries like manufacturing and technology, the best way to achieve a circular economy is even less clear. However, rethinking the way we view waste and consumption is an important step in the right direction, especially for natural resources that were already designed by nature to be used cyclically.

Resources

1. Mollison, B. C., & Slay, R. M. (2013). Introduction to permaculture. Tasmania, Australia: Tagari Publications.
2. Holmgren, D. (2015). Permaculture: principles & pathways beyond sustainability (2nd ed.). Retrieved from https://store.holmgren.com.au/product/principles-and-pathways-ebook/
3. IPCC. (1997). Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories. Retrieved from https://www.ipcc-nggip.iges.or.jp/public/gl/invs6.html
4. Steinfeld, H., Gerber, P., Wassenaar, T., Castel, V., Rosales, M., & De haan, C. (2006). Livestock’s long shadow: environmental issues and options. Rome: Food and Agriculture Organization of the United Nations
5. IPCC (2019). Mbow, C., C. Rosenzweig, L.G. Barioni, T.G. Benton, M. Herrero, M. Krishnapillai, E. Liwenga, P. Pradhan, M.G. Rivera-Ferre, T. Sapkota, F.N. Tubiello, Y. Xu: Food Security. In: Climate Change and Land: an IPCC special report on climate change, desertification, land degradation, sustainable land management, food security, and greenhouse gas fluxes in terrestrial ecosystems [P.R. Shukla, J. Skea, E. Calvo Buendia, V. Masson-Delmotte, H.-O. Pörtner, D.C. Roberts, P. Zhai, R. Slade, S. Connors, R. van Diemen, M. Ferrat, E. Haughey, S. Luz, S. Neogi, M. Pathak, J. Petzold, J. Portugal Pereira, P. Vyas, E. Huntley, K. Kissick, M. Belkacemi, J. Malley, (eds.)]. In press.