Cities are leading the way in the circular economy transition. But what does it take to become a truly circular city? This series of articles explore the key services that cities need to adapt in order to become fully circular. These include energy, construction, water, food and mobility. This article delves in the challenges associated with designing circularity into urban food systems.

Why are circular food systems important?

Roughly 1.3 billion tons of food are thrown out annually. That is the equivalent to the amount of food that 37 million people eat in their entire lifetime. The water, energy and land used to grow, process and transport this wasted food is staggering. What is more, virtually all wasted food ends up in landfills where it decomposes, giving off vast amounts of methane emissions and significantly contributing to climate change. Perhaps the saddest consequence of food waste is that, according to the FAO, 795 million people remain chronically undernourished.

Eradicating urban food wastage by designing more efficient circular food systems in cities, where more than half of the world’s population lives, is therefore not only an environmental imperative, but a moral one too.

What would a circular food system look like?

The solutions for circular food systems, although based on the fundamental principles of circular economy, are likely to differ significantly compared to the likes of construction or e-waste which are referred to as ‘technical’ nutrients. This is because rather than preserving the resources in an infinite loop, as with technical nutrients, food has a shelf life before it starts biodegrading, therefore the cascading process is much more time dependent and logistically complex than with technical resources.

Furthermore, biological waste is a bulk resource and so is unlikely to become economically feasible to transport around the world to be used elsewhere – therefore the waste must be absorbed into local value chains and markets.

Based on these unique characteristics of biological (food) waste, cities must form a two-pronged approach to building circular food systems. Firstly, the efficiency with which they grow, transport and process food must significantly improve. Secondly, they must nurture and support businesses to form more adaptable but effective cascade value chains to deal with biological by-products (not waste!) at every point in the food value chain.

Thankfully, cities around the world are beginning to rise to the challenge and are now setting ambitious goals for transitioning to more sustainable circular food systems.

Production Efficiency

There are a number of ways cities can increase food system efficiency. They can ban supermarkets from landfilling perfectly edible (slightly wonky) food such as in Paris. They can fine homeowners and restaurants based on the amount of food waste they produce such as in San Francisco. They can even run widespread educational and awareness campaigns aimed at helping the public reduce their food waste.

However, these solutions tend to target one specific problem and are unlikely to address the systemic problems faced in urban food systems such as a near total dependence on imported food from around the world (and the associated social, environmental and economic consequences).

One of the most effective ways of increasing efficiency in the food system is encouraging the uptake of urban vertical farming. Food entrepreneurs in many cities around the world are now experimenting with a range of vertical farming technologies such as aquaponics and hydroponics. Such technologies offer up to 90% reductions in the water usage and up to 10 times more productive per square meter compared to traditional growing methods.

The aquaponics technology developed by the London-based Grow Up Urban Farms, for example, allows them to farm fish and leafy greens at scale in the city center. Intelligent Growth Solutions, in Scotland, are building what is potentially a game changer for the commercial viability of urban farming. They are currently constructing a £2.5 million ($3 million) vertical farm that makes use of their patented super efficient LED lighting system to produce a wide variety of leafy greens while using 50% less energy than conventional vertical farming systems. What is most promising about these businesses is that they are located in the city center, so transport and wastage is virtually non-existent.

food systems

Using spent whisky grain for bio-butanol. Celtic Renewables.

Yet, these current vertical farming techniques are limited in what they can grow and have yet been able to grow many legumes, root vegetables and staple grains which make up a significant proportion of our diet.

A more effective strategy may be to combine the production from vertical farms with produce grown from farms surrounding the city and from individual growers living within the city boundary. San Francisco has fully embraced the idea of partnering with local producers whereby roughly 600 tons of food waste is converted into compost per day and distributed to local farmers and gardeners who grow produce to sell in the city. This solution also deals with the problem that organic waste is very heavy and transport is expensive so there need to be localized economic solutions to deal with it.

Bottom-up social movements for urban farming also offer significant opportunities for localizing food systems. Take the people of Detroit for example, who have directly experienced the raw injustice of globalization. They have taken food resilience into their own hands and launched America’s first ‘agrihood’ through the Michigan Urban Farming Initiative which has grown over 50,000 pounds of produce to date. In London, a social initiative called the Energy Garden Project has worked tirelessly for 4 years to transform disused space in 50 subway stations into flourishing gardens producing lots of fresh produce for the surrounding neighborhoods.

It is therefore evident that we have the technologies, the business models and to some extent the social movement to significantly increase the efficiency of our food system. But how do we deal with unavoidable leakage from the system?

Closing Resource Loops

Some leakage in the food system is unavoidable. Firstly, there are scraps from households (such as peelings and trimmings). Then there are by-products from the food processing industry. The Scottish Whisky industry alone produces 4.3 million tons of by-product (in the form of spent grains and liquid residue).

Unavoidable leakage in the food supply chain is certainly a major opportunity for economic arbitrage. By thinking in terms of the circular economy, such biological waste streams are potential gold mines for companies to valorize the waste in multiple ways depending on the needs of the market.

The challenge is therefore to capture the most value from the biological feedstock locally before it is degraded to a lower level and eventually returned to land as nutrients to start the cycle again.

food systems

The Biological Cascade Process. Ellen MacArthur Foundation

Valorization of food waste can come in the form of leveraging industrial biotechnologies to create fuels or chemicals. The waste from this process can then be anaerobically digested, where energy is directly created from the biodegrading waste, and finally the digestion waste can be composted and returned to the land as fertilizer.

Celtic Renewables, a Scottish based company, is a great example of this cascading valorization process. They are utilizing microbial fermentation to convert spent whisky grains into the likes of bio-butanol, which can be used in biofuels or chemicals. The waste from this process is then dried and pelletized and fed to animals as a high protein rich food source.

food systems

Using spent whisky grain for bio-butanol. Celtic Renewables

Global discussions are now taking place around the concept of a biorefinery, which runs exactly like an oil refinery, except instead of crude oil entering the refinery, it is biological feed stock (and waste) which is then valorized into a whole range of bio-plastics, fuels and chemicals.

Dealing with Dynamic Flows in the Food System

There are two key ways to increase the efficiency of urban food systems; namely increase the efficiency and closing the resource loops. Yet, perhaps biggest challenge is that these two solutions are slightly at odds with one another. For example, if company A is trying to significantly increase its production efficiency (and hence reduce its waste) and company B has based its entire business on company A’s waste, company B will not last long unless it finds another waste source.

Therefore the fundamental challenge of simultaneously increasing efficiency while dealing with unavoidable waste at the system level has yet to be fully explored and is likely to be the toughest on-going challenge for cities to address when transitioning to circular food systems.