Urban Metabolism Urbinsight Dispatches

Urban Metabolism and its Impacts in Cusco, Peru

Cusco, Peru. Photo by Joshua Castro Camacho
Peter Bennett
Written by Peter Bennett

Urban Metabolism diagram for Lima’s San Isidro municipality tracking the story of water as it moves through the district, from its source locations, through the built environment (demands), and back to nature (sink).

This is the first entry in a series entitled “Urban Metabolism: Shifting city resource flows from linear toward circular,” a collaboration by the Global Initiative for Resource Efficient Cities (GI-REC) and Ecocity Builders to raise awareness of the importance of systems approaches at city level and their impact on the transition towards sustainable cities.

To appreciate the profound impacts and results of utilizing the urban metabolism model, one must first understand how it works. Urban Metabolism is the study of resource flows through a city that looks at the city as an ecosystem or living organism. It can be used as a tool to study cities holistically, thus laying the foundation for improving their overall health and sustainability. Urban Metabolism Information Systems, or UMIS, is the standardized “source to sink” framework, often rendered through metaflow charts, that provides a visual understanding and analysis of urban systems as they process through the built environment.

The first case study in this series focused on the metropolitan area in and around the city of Cusco in southern Peru, where several small study areas are located just outside the main city. Through workshops and roundtables that are part of Ecocity Builders’ Urbinsight project, community members communicated the changes they wanted to see in their city: better management of waste, a cleaner environment, and healthier food. Based on this information, local citizens and the Urbinsight team decided to focus primarily on solid waste flow and how it could be altered in a way that would be more sustainable, as well as reach local improvement goals.

Community member Estefany Sinsaya found that in order to understand urban metabolic flows it is first necessary to understand the origin of these flows, their distribution within the city, and how resources are being used. Bringing this kind of insight into the use of urban metabolic flows that empowers people around the world to create change in their own unique urban contexts is one of the Urbinsight team’s primary goals.

Cusco’s San Pedro and Camino Real neighborhood residents share their concerns and ideas with Ecocity Design Advisor Stephanie Weyer.

Pointing to a potential solution based on findings from the UMIS flow charts, the president of the Santa Ana neighborhood, Alberto Garcia Montes, said that the people in the area need to put their focus on properly separating their waste in order to increase efficiency and decrease landfill levels. While this includes recycling, citizens can see more immediate positive results from honing in their efforts on proper composting techniques. Separating compostable items not only cuts down drastically on the amount of waste that ends up in landfills, it can also be used to produce healthier soil, leading to healthier food and produce. This narrow and achievable goal helps to solve the three main problems the citizens themselves identified: poor waste control, soiled local environments, and lack of access to healthy foods.

Residents determine that sanitation issues are the city’s most pressing problem. Daily consumer goods from supermarkets and other sources have turned into piles of overfilled plastic bags in streets too narrow for trash collectors to maneuver. The community teams scope out their neighborhoods and collect data on material flow. Weighing and separating the waste for households, restaurants, and hotels, students at Universidad Alas Peruanas establish that the composition of waste is 49% organic solids. Under the guidance of Team Urbinsight, they then analyze both city and citizen generated data to determine a course of action.

With this new focused goal, the citizens and the Urbinsight crew got to work on making this dream a reality. Working together, everyone on the project developed two separate but similar solutions, a rotating compost bin and a worm bin. The rotating bin includes a recycled 50 liter plastic barrel and meets the needs of people who are uncomfortable with worms in their homes. Composting without worms still produces quality soil that adds nutrients to plants.

On the other hand, using worms is expected to speed up the compost production process but adds an extra layer of planning. Teresa Sanchez, a resident of one of Urbinsight’s pilot neighborhoods of San Blas, reports that one must be careful when feeding the worms, as certain compostable items like citrus are not in the worms’ diet and could even kill them. The worm bins here are made of buckets stacked on top of each other, making for layered processing and easy retrieval of the finished product – worm castings. Worm castings are incredibly nutritious for produce, and when paired with standard soil and compost will create ideal conditions for growing healthy, nutritious food.

It is determined that a home composting program — easily built and used by community members — will be the most effective intervention to reduce waste and bring about a circular materials cycle. The project partners then collaborate on designing a composting model. Using the specs, community members build the compost bins to be used in their own homes, changing the materials/resource element of Cusco’s urban metabolism from linear to circular.

This project is still under way, and results will be measured and well-documented in the months to come. The primary goal of using UMIS methods is to place the power and responsibility of creating sustainable cities in the hands of people on the ground. In Cusco, the initial focus was to make meaningful change in the solid waste flow through the city and citizens are now tackling the challenge while also spreading the word about living more sustainable lives.

About the author

Peter Bennett

Peter Bennett

Peter Bennett is a recent grad from UC Berkeley, who studied Sustainable Environmental Design and Forestry and Natural Resources. Peter is interested in the intersection of cities and the environment, and creating a sustainable world for the future destinations.

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