New Humphrey School Study, Published in Nature Climate Change, Shows Potential of Cities to Reduce Greenhouse Gases, Improve Health
Concerns over global climate change and local air pollution have led many cities around the world to get creative in their efforts to reduce the use of fossil fuels. They’re going beyond conventional single-sector strategies such as energy-efficient buildings and power plants to look at innovative ways to capture waste heat from industries and businesses—from cement plants, to pulp and paper mills to grocery stores—and pipe it to homes and buildings up to 30 kilometers away.
Some cities are also reusing waste materials from industries in urban construction as a substitute for cement and other construction materials, helping reduce the demand for these materials.
Scientists use the terms “cross-sector strategies” and "circular economy strategies" to describe such novel approaches to urban infrastructure planning, which have several goals: to reduce material and energy use; to reduce reliance on fossil fuels; to improve air quality; and to improve the health of residents in urban areas, while simultaneously creating value from resources that were previously wasted.
New research by Professor Anu Ramaswami of the Humphrey School of Public Affairs at the University of Minnesota, published Monday in the latest online edition of Nature Climate Change, is the first to demonstrate just how successful these strategies would be, if widely adopted.
“Cities are the critical centers of change when it comes to taking action on greenhouse gases,” said Ramaswami, who led this study that looked at all 637 cities in China at the same time. “Our research shows there’s great potential for cities to reduce energy demand and carbon emissions by adopting cross-sector strategies, such as reusing industrial byproducts like waste energy, on a mass scale. And that means a better quality of life for residents. It’s a win-win.”
The study finds that if all cities in China adopt these strategies, they would reduce greenhouse gas emissions by up to 36 percent—and at the same time, protect up to 57,000 people from dying prematurely due to poor air quality. Researchers base these findings on models that examine potential carbon reductions and the expected health improvements.
The study also found that the benefits varied from city to city, depending on the locale.
For example, two cities can take similar actions and reduce emissions or energy use by the same proportion, and see very different health and environmental outcomes, due to differences in how air pollution flows into and out of their cities from the surrounding areas.
Ramaswami noted that most research on greenhouse gas emissions up to this point has focused on what national-level policies can do, typically impacting individual sectors of the economy such as power generation, transportation, or energy-efficient building construction. This is the first of its kind to measure the impact of holistic urban planning in cities that encourages compact city development, eco-industrial parks, waste-to-value projects and district energy systems. Cities can readily adopt these practices, Ramaswami said, but they rarely get credit for them in terms of reducing greenhouse gases.
Since her study is the first to collect information at the city level, it’s a starting point for analyzing the science behind what cities can and cannot do to help reduce greenhouse gases on a nationwide basis, and what those steps mean for the local communities.
“The insights we gained from this study will inform how we design sustainable urban areas in China and elsewhere around the world in the future,” said Ramaswami. “That’s important because we expect to see another 2.5 billion people living in cities by 2050, with most of that population growth in Asia and Africa.”
The collaborations were enabled by a Partnership for International Research and Education (PIRE) grant from the National Science Foundation. The PIRE project concentrates on reducing greenhouse gas emissions from cities, while addressing broader sustainability goals such as economic development, water scarcity, environmental pollution, and public health.
Ramaswami is the Charles M. Denny, Jr., Chair of Science, Technology, and Environmental Policy (STEP) at the Humphrey School of Public Affairs. The STEP program integrates science with public policy, community action, and multi-sector governance.