According to the United Nations, more than half of the world’s population now lives in cities, a number that is projected to increase to two-thirds by midcentury. This trend represents both a blessing and a curse as it relates to climate change. On the positive side, urban modes of living are quite sustainable in relative terms. City-dwellers are far more likely to utilize public transportation rather than personal automobiles, and typically live in smaller spaces in buildings with shared heating and cooling systems, allowing for efficiency gains. All this is to say that as the planet’s population continues to grow, sustainability goals are more easily accomplished if its residents are living in cities.
Unfortunately, cities are also particularly vulnerable to the effects of climate change. Due to historical reasons, cities tend to be located along coasts and rivers, putting them at the mercy of increasingly violent weather events, namely hurricanes, bringing storm surges and floods. We saw this play out in New York with Hurricane Sandy in 2012, where a storm surge inundated many of the city’s low-lying areas. Seven years on, New York is still cleaning up, with the most notable Sandy casualty probably being the L Train-carrying Canarsie Tunnel under the East River. More recently, Hurricane Harvey’s historic deluge of 40 inches of rain in four days over Houston resulted in catastrophic flooding, essentially drowning the city. In dense urban areas, catastrophic storm events can result in incalculable damage.
Given cities’ unique vulnerability to the effects of climate change, they cannot simply rest on their residents’ relatively small carbon footprints. Cities cannot afford to be passive actors in the fight against climate change. Central to their role in this fight is a conversion to renewable energy sources. Within that, however, converting cities away from fossil fuels is an extremely challenging task, particularly in dense urban areas dominated by multifamily buildings and large office towers. The task of converting carbon-driven cities to renewable energy cities is extremely complex, and involves a number of separate but interrelated challenges.
Dense urban agglomerations like New York City stand out in that their chief source of carbon emissions is not vehicular transport, as it is in most of the United States, but instead buildings. In order to become renewable energy cities, these buildings must utilize renewable energy sources. In many cases, however, this is far more challenging than it would seem. For one, buildings may be able to produce some energy through the use of solar panels or wind turbines, but they are still dependent on renewable energy sourced from the electric grid. In order for buildings to help cities along the path towards a renewable energy future, the grid needs to be prepared to supply renewable energy to match demand. Currently, while our grid has become cleaner over the last decade, this has been in large part due to the advent of cheap, plentiful natural gas replacing coal. Utilities are still a long way from meeting 100% of our energy needs with renewable sources.
Alongside the challenge of a greener grid is that of electrification. Currently, many of our buildings are dependent on fossil fuels for their heat and hot water. Fuels used vary by building, with the worst offenders burning highly polluting diesel fuels. Combustion-based heating and hot water systems represent a health hazard to local communities while contributing disproportionate quantities of climate change-inducing greenhouse gases. In many cases, the systems our buildings depend on essentially represent small oil and gas power plants in the midst of our cities. We would object to an oil burning power plant being situated across the street from our homes, but we accept it in our own buildings as a necessary evil.
Long term, electrification is central to moving our cities towards a renewable energy future. Electrification is the process of shifting energy use from localized combustion of fossil fuels – think furnaces – to grid-supplied energy. Buildings currently burning oil and gas to supply heat and hot water would shift these systems over to electric. Ultimately, oil and gas are not and cannot be renewable energy sources. They must eventually be retired if our cities are to minimize their respective carbon footprints and undergo a largescale shift to renewable energy sources.
As it pertains to greenhouse gas emissions, however, electrification poses challenges of its own. Primarily, our grid is still quite dirty as currently composed, with coal, oil, and natural gas continuing to play a major role in electricity production. It can reasonably be predicted that grid power will get significantly greener in the coming years as large solar and wind projects, including offshore wind, come online alongside improved and scaled up battery storage. This transition will take time, however, and in the interim the grid will become more carbon-intensive as comparably clean nuclear plants reach the end of their lifespans and are subsequently decommissioned. New York City is at the front lines of this challenge, where the Indian Point nuclear facility supplies approximately 25% of power used in the city, essentially emissions free. With the plant set to be closed by 2021, the carbon intensity of New York City’s grid stands to increase in the short-term.
Greenhouse Gas Emissions
Converting building systems is not a simple or quick process. Just as a homeowner installing a new furnace expects it to last twenty years or longer, buildings operate on capital plans that span decades. These long timespans represent a complicated signal as we push for electrification. In the short-term, the reality of electrification might be increased carbon emissions, in light of the grid getting dirtier before it gets cleaner. But without electrification, buildings installing new combustion-based systems in the next few years will be polluting unnecessarily a decade from now, with the current goal being for renewables to make up 50% of New York State’s grid power by 2030. While we know that electrification is the answer in the long run, how to address the process in the short term remains a challenge.
Energy Efficiency in Buildings
Beyond electrification, improving buildings’ energy efficiency is also crucial to limiting their carbon output. Many buildings, particularly in older cities like New York, are quite inefficient in their use of energy. Residents on upper floors often have scorching hot apartments in January, necessitating that they open their windows, resulting in wasted energy. Residents on lower floors, on the other hand, are often freezing. Many boilers supplying heat and hot water rely on technologies developed generations ago, and do not take advantage of subsequent advances in engineering. Windows are often drafty, releasing warm air in the winter and cool air in the summer, reducing the effectiveness of heating and cooling systems. Improvements in building energy efficiency allow for improved resident comfort while also limiting energy needs, and can often be economically beneficial to building owners, as they reduce energy costs.
Some cities are utilizing innovative policy solutions to address the issue of building emissions. Tokyo stands out as a leader in this area with the world’s first emissions trading scheme addressing building emissions. Tokyo’s program utilizes a system commonly known as cap-and-trade, wherein its large buildings are limited in how much they are permitted to emit. If they go beyond that limit, they are required to buy credits from other participants in the system. These other participants generally receive their credits for reducing emissions below what the threshold required, thus providing an incentive for building owners to exceed mandated carbon reductions while also providing an alternate compliance pathway for buildings where energy efficiency measures are more expensive. New York City is in the process of following Tokyo’s lead, with a bill limiting building emissions brought before the City Council in December. Needless to say, conversion to renewable energy is central to such mandates, as its utilization allows for buildings to use energy that does not count against their carbon allowance.
While buildings often may make up a majority or plurality of carbon emissions in dense urban areas, this is not to say that that transportation is not a significant source in its own right. Urban residents’ carbon emissions from transit tend to be lower than those of suburban and rural dwellers for two key reasons. For one, zero-emissions forms of transit, namely walking and biking, are much easier when you live near things that you can walk and bike two. Secondly, and arguably more important, is that buses and trains are shared, and the emissions per passenger are far lower than for personal vehicles that often carry just one or two passengers.
Within this, however, there is still room for cities to improve their transit-oriented carbon output. Municipal rail lines are typically powered by grid electricity, and increases in renewable energy sources’ share of the grid can offer carbon emissions abatement in that area. Buses, meanwhile, typically still rely on the combustion of fossil fuels. While the fact that they can carry many passengers makes much more efficient use of these fuels, that does not change the fact that they result in carbon emissions. This is an area where transitioning to more fuel-efficient hybrid buses or electric buses can make a huge difference. Electric buses in particular have yet to see widespread adoption, but New York City is currently conducting a pilot study utilizing vehicles from two manufacturers.
Electric buses have benefited greatly from the decline in battery costs over the last ten years, and typically offer cost savings in terms of both energy – grid power being less expensive than fuel – and maintenance, as their mechanics are less complex and undergo less wear and tear than combustion-powered conventional buses. As with other modes of electrification, electric buses are only as green as the grid, but in the long-term they represent an opportunity for us to shift transportation’s energy burden to renewable sources.
Cities can also work to speed the adoption of electric personal vehicles. Adoption of electric vehicles has exploded in recent years, with Tesla probably the most prominent example, accompanied by models like the Nissan Leaf and Chevy Bolt. Unfortunately, however, these vehicles are often a better fit for suburban homes featuring garages with plugs than they are for curbside urban street parking. As it currently stands, vehicle-owning urban residents are limited in their ability to switch to electric vehicles in that they often do not have a convenient place to charge them. Some companies are working on this issue, with technologies geared towards allowing for easy, unobtrusive curbside charging. In moving our cities towards a renewable future, this is a crucial gap to solve for.
The focus on converting to limiting our carbon emissions and converting to renewable energy sources tends to be on climate change, but there are also significant localized public health benefits to a shift away from combustion-based energy. When our buildings burn oil or our cars burn gasoline, it is not just carbon that they emit; they also spew out a range of co-pollutants that poison our air, resulting in a range of health problems including stroke, heart disease, lung cancer, and respiratory problems. In some cases urban residents ingest pollutants equivalent to smoking a pack of cigarettes a day. Shifting away from fossil fuel combustion in our urban areas means removing major pollutants from those areas, promising significant health benefits. As such, in assessing the potential cost of shifting to renewable energy, we should not merely look at the cost-benefit of renewables versus carbon fuels, but also include the carbon combustion-associated health costs currently impacting our cities. A shift to renewables does not merely help in the fight against global warming, it also offers urban residents a pathway to more healthful lives.
Clearly, converting our cities to renewable energy is not something that can happen overnight. Our urban built environments reflect the reality that the combustion of carbon fuels built our current economy. Recognizing, that, however, there is a way forward to a renewable energy future. Our buildings can become more efficient and rely increasingly on electricity. Our grid can shift to more renewable sources like wind and solar. Our transportation can move away from combustion and towards batteries and electrification. In concert, this transition promises healthier, cleaner, more livable cities, benefiting residents both present and future.