Greenhouse Gas Mitigation in Cities

  Total carbon emission and mitigation scale in 2020 and 2030 Total carbon emission and mitigation scale in 2020 and 2030 (Source: Philippen, 2011; FCN Study Thesis)

Countries all over the world face the challenge of drastically reducing their greenhouse gas (GHG) emissions. The European Union, for instance, recently declared their intention of an 80% reduction in GHG emission from 1990 levels by 2050. In the recently adopted twelfth edition of the five-year plan, China announced a proposed reduction of the economy’s carbon intensity of 17% per unit of GDP. The shift towards a low-carbon economy takes decades and requires strategic, long-term planning. Revealing cost-effective emission reduction measures and ensuring their implementation via policy measures is one of the major challenges society faces as a whole.

Cities, as significant sources of carbon emissions, should be at the forefront of the emission reduction agenda because they are amongst the most energy-intensive ecosystems. In 2006, for example, cities accounted for roughly 70% of worldwide energy-related carbon emissions. In recent years, scientists and policy-makers alike have realized the importance of cities in global carbon mitigation, a role that is expected to increase with urban population growth.

Economic and technological evaluation methods are necessary in order to assess the GHG mitigation challenges and possibilities that exist in growing cities with growing energy demands. In this context, the application of marginal abatement cost curves (MACCs) has become a standard method to illustrate the supply-side economics of abatement initiatives. MACCs already exist for plant level analyses but also at the country, regional and sectoral level. Recent literature fails to consider the special network aspects and interdependencies within cities; also, there is a lack of current and detailed bottom-up assessments of GHG reduction costs and opportunities. This research is dedicated to fill part of this gap.

Buildings account for more than two-thirds of London’s GHG emissions. In our research we model, bottom-up mitigation possibilities for building-related energy usage and associated carbon emissions. The investigations are based on a case study for an eco-town in the United Kingdom, encompassing living space for 6500 people with roughly 480,000 m2 of domestic surface area. All simulations were conducted with the SynCity toolkit, an urban energy model developed in the Energy Futures Lab at Imperial College London. As system optimization model, SynCity takes all interdependencies between the abatement levers explicitly into account. Together with the applied bottom-up approach, we are able to overcome some of the aforementioned shortfalls in recent literature.

Many of the actions required to reduce city-related CO2 emissions (i.e. licensing, land-use planning, zoning, transit and transportation plans) fall under the jurisdiction of municipal or regional governments. They play a major role for the achievement of national emission reduction targets. Policy implications derived from the simulated mitigation opportunities are potentially useful for policy-makers.

Our research follows certain lead questions. First, we set the broader context for research on GHG mitigation, reasoning why GHG mitigation is necessary and why such actions should be concentrated on cities. With the introduction of MACCs, we are able to provide an evaluation method for mitigation options. The study ends with a discussion of the policy implications that arise from the technological GHG mitigation measures suggested and how policy frameworks may be implemented for the maximum up-take of the mitigation options revealed.