The Global Urbanist

News and analysis of cities around the world

Circular metabolism: turning regenerative cities into reality

In her previous article, Anna Leidreiter showed how 'sustainable' is not enough: we must start to build regenerative cities. Today she describes how the city of Oakland is building the circular metabolic systems required to turn that concept into reality with its zero waste policies.

Anna Leidreiter

Anna Leidreiter

Cities: San Francisco-Oakland, Berlin

Topics: Water, waste and sanitation, Regional governance, Sustainability, The global urban agenda

'We have become a society of abundance and harbour a throw-away mentality,' German agriculture minister Ilse Aigner said in Berlin in March 2012, after announcing that over 11 million tonnes* of food are discarded per year in Germany, 60 per cent from private households. Across the European Union we throw away 3 billion tonnes of waste per year, some 90 million tonnes of it hazardous. Such huge totals inevitably mean that huge amounts of resouces are used in vain, just as the greenhouse gas emissions caused in their production are in vain.

As cities become the primary human habitat, the reduction of waste becomes a key issue in attempts to minimise cities' ecological footprints. The relevant concept when transforming our cities into regenerative systems (see my last article) is therefore the 'metabolism of cities'. Cities need to move from an inefficient linear metabolism towards a resource-efficient circular metabolism. The latter differs in that all wastes produced are converted into nutrients for future growth. Currently urban systems externalise their wastes in ways that undermine and damage the health and well-being of ecosystems, locally, regionally and globally. Resources flow through the urban system without much concern for their origin or for the destination of wastes. Inputs and wastes are considered as largely unrelated.

Oakland: the zero waste city

The concept of zero waste goes beyond recycling discarded materials to consideration of the vast flow of resources and waste through our society, and moves to eliminate wastes by treating them as inputs elsewhere. The city of Oakland reduced its annual tonnage to landfill from 400,000 tons (363,000 tonnes) to 291,000 tons (264,000 tonnes) in only four years. This was possible by explicitly returing discarded materials to the local economy, applying the waste management hierarchy in priority order (reduce, reuse, recycle, and compost) to the maximum extent, and promoting recycling market development.

Oakland's zero waste principles promote the best use of materials to eliminate waste and pollution, emphasising a closed-loop system of production and consumption, moving in logical increments toward the goal of zero waste by undertaking the following steps: (1) improving downstream reuse and recycling of end-of-life products and materials, (2) pursuing upstream re-design strategies to reduce the volume and toxicity of discarded products and materials and promote low-impact lifestyles, and (3) fostering and supporting the use of discarded products and materials to stimulate and drive local economic and workforce development.

For example, East Bay Municipal Utility District (EBMUD) is a publicly-owned utility that supplies water to 1.3 million people and provides wastewater treatment for 640,000 people in northern California. EBMUD operates its main wastewater treatment plant in Oakland. It converts post-consumer food scraps to energy via anaerobic digestion. Waste haulers collect post-consumer food waste from local restaurants and markets and take it to EBMUD. After the digestion process, the leftover material is composted and used as a natural fertiliser.

According to the city's decision makers the major opportunities to reduce landfill lie in two areas: capturing organics (yard waste, food scraps) for composting, and increasing recovery of recyclables from waste materials hauled by private interests, especially the construction industry. In 2008, organic material (including plant debris and food scraps) was by far the largest remaining recoverable material type in all sectors, representing 48 per cent of Oakland's total landfill disposal. Furthermore, 26 per cent of Oakland's total annual landfill disposal comes from the 'non-franchised direct hauling sector' (i.e. commercial waste removal services unrelated to the government's waste collection responsibilities). This material is hauled by parties other than the franchisee (the government's contractor) to a number of landfills within and outside the county, and largely consists of construction and demolition debris.

Enabling political frameworks

Changing a linear metabolism into a circular approach means initiating a comprehensive political frameworrk. Looking at the success of Oakland, a combination of strategies enabled traditional 'end of the pipeline' recycling programs as well as upstream solutions to product waste, policy and regulatory changes. No single strategy can achieve zero waste. However, the first key step is often the simple act of target setting, since that unleashes further progress. In March 2006, the Oakland City Council adopted the goal of zero waste by 2020.

One of the main barriers to implementing an effective policy framework in cities is a lack of vertical policy coordination. Vertical support is important not only to enable local authorities, but also to support horizontal coordination around a common goal. Key to Oakland's success was the fact that the California Integrated Waste Management Board has also set a goal of zero waste in its strategic plan for the state, and that neighbouring Alameda County had established a legal framework.

Oakland shows that solutions and best policy examples exist, so there is no time to lose in developing strategies to support their implementation elsewhere. Planners seeking to create regenerative urban systems should start by studying the ecology of natural systems. Nature essentially has a circular zero-waste metabolism. On a predominantly urban planet, cities will need to adopt circular metabolic systems to assure their own long-term viability as well as that of the rural environments on which they depend.

is Policy Officer - Climate and Energy at the World Future Council Foundation in Hamburg, which aims to place the interests of future generations at the centre of policy making.

*This sentence originally read '11 million kilograms'. It was corrected on the 13th of November 2012.