CPS Energy Calaveras Power Station hosts the Deely and Spruce coal power plants.
CPS Energy Calaveras Power Station hosts the Deely and Spruce coal power plants. Credit: Bonnie Arbittier / San Antonio Report

Most of San Antonio’s global warming emissions are tied to energy use in buildings and from motor vehicles, according to the most thorough attempt to date at measuring the city’s carbon footprint.

The inventory of 2016 greenhouse gas emissions is one of the first products of the City of San Antonio’s Climate Action and Adaptation Plan, a collaborative effort involving the City, CPS Energy, consulting firm Navigant, and the University of Texas at San Antonio. The plan will outline how the City will make good on its promise to do its part to help meet the climate goals of the international Paris Agreement.

Doing so might require San Antonio cutting its emissions by half, climate planners say.

The inventory uses two different protocols to account for emissions at the community level and those from the City’s operations, though there is some overlap. Emissions from CPS Energy and San Antonio Water System (SAWS) fall under the community category.

However, the inventory does not include emissions from some important sources, including direct emissions from industrial sites inside City limits, such as refineries or cement kilns. It also does not account for leaks from privately run natural gas pipelines that supply CPS Energy.

That’s because of the difficulty of obtaining comprehensive data for these sources, experts from the City, CPS Energy, and Navigant said.

For those emissions that have been counted, 50 percent of those at the community level come from the use of electricity and natural gas in buildings, mostly for cooling and heating. Another 38 percent comes from vehicles used in transportation, with 9 percent from the electrical use at CPS Energy power plants, 3 percent from waste, and the remainder from wastewater treatment and leaks from CPS Energy’s network of pipelines delivering natural gas to its customers.

At the municipal level, the emissions sources are more varied. The inventory states that 32 percent come from emissions escaping from closed landfills owned by the City, 22 percent from buildings and facilities, 17 percent from supplying water, 12 percent from treating wastewater, 11 percent from the City’s vehicle fleet, and 6 percent from street lights and traffic signals.

Overall, most of San Antonio’s emissions come from the same sources as in other cities, said Doug Melnick, the City’s chief sustainability officer. Before coming to San Antonio, Melnick worked on a climate plan for Albany, New York, and has been speaking with his counterparts in other cities about their plans..

“The next question is, how do we tackle it?” he said.

The difficulty for San Antonio, Melnick said, is cutting emissions during a time of explosive growth. From 2016 to 2017, San Antonio’s population grew by 24,408 people, more than any city in the United States, according to U.S. Census data, and demographers predict the city will add 1 million people by 2040.

Emissions numbers for 2016 will serve as the baseline for determining how much the level of emissions needs to be cut to keep San Antonio within its share of U.S. emissions under the goals of the Paris accord.

Danielle Vitoff, an associate director for Navigant, stressed that climate planners don’t know yet how deep those cuts will have to be, but they think it will probably be around half. Navigant staff did most of the work on the inventory, with data gathered by UTSA researchers and CPS Energy staff.

“We don’t have a final number,” Vitoff said, adding that a 50 percent reduction “is somewhere we’re heading, but the target is not complete at this point.”

How to achieve such steep cuts is an open question. Only two other U.S. cities have said how they plan to meet the Paris goals. New York City, which in October 2017 passed the first Paris Agreement-compliant climate plan in the country, proposed some specific measures to tackle emissions.

They included requiring cuts in emission from existing large buildings, more stringent building codes for new buildings by 2025, expanding access to electric vehicle chargers, purchasing 100 percent renewable power for all municipal operations, adding a tax on “millionaires” to fund subway upgrades, and expanding the city’s bike network by 50 miles.

In its Paris-compliant plan passed in February, the City of San Jose, California, pledged to make 100 percent carbon-free electricity available to all users by 2021 and retrofit existing residential and commercial buildings to eliminate the use of natural gas.

But San Antonio is no New York or Silicon Valley.

“My big priority is making sure that it’s going to work for San Antonio,” Melnick said. “What a road map is in New York or Portland or San Francisco isn’t necessarily going to work in San Antonio.”

San Antonio is already making progress reducing some emissions, at least according to the last greenhouse gas inventory the City commissioned in 2014.

Comparing that inventory with the 2016 numbers shows a 7 percent reduction in emissions. Navigant’s analysis points to shifts in CPS Energy’s power generation to explain why emissions went down.

“The coal units have not been running as much, and we added more renewables,” said Angela Rodriguez, CPS Energy’s climate and sustainability director.

Coal made up 45 percent of the utility’s generation portfolio in 2014 and 29 percent in 2016, according to the inventory; wind and solar went from 11 percent to 13 percent. Nuclear rose from 25 percent to 32 percent.

Natural gas’s share also increased from 19 percent to 25 percent. While the fossil fuel emits less carbon dioxide than coal, leaks of natural gas from pipelines also contribute to global warming. Methane, the main component of natural gas, is 28 times more potent than carbon dioxide as a greenhouse gas.

The inventory accounts only for methane leaking from CPS Energy’s distribution system, not from commercially operated pipelines that carry natural gas to San Antonio, Rodriguez confirmed.

Also missing from the inventory are direct emissions from private industrial sites, including cement kilns, corporate-owned landfills, and a handful of others.

San Antonio doesn’t have the large industrial base of a city like Houston, for example. Still, a search of a federal database of greenhouse gas emissions from 2016 shows significant greenhouse gas emissions from two cement kilns, two landfills, a petroleum refinery, a circuit manufacturer, and an auto manufacturing site in San Antonio.

Taken together, emissions from these seven facilities would make up nearly 10 percent of San Antonio’s community-level emissions if they were included in the inventory.

But because the EPA only accounts for the largest emitters, an attempt to add up all industrial emissions would be incomplete, Melnick explained. Emissions from smaller machine shops, for example, wouldn’t be counted.

“We’ve looked at a couple plans that address industrial emissions,” Melnick said. “They sort of bookmark it. They don’t go into this whole deep dive because the data’s not there.”

The inventory does include emissions related to electricity and natural gas use at industrial sites, Melnick said.

As with natural gas leaks from gas suppliers, these industrial emissions fall under a difficult-to-calculate category called “scope 3 emissions” by climate planners.

“We have experts working across the world on this, and as far as we’re aware, we have not seen a comprehensive scope 3 assessment for a city at this point,” Vitoff said. “There are definitely cities that are considering it.”

Vitoff and others involved with the plan will be hearing questions about these kinds of issues from the volunteers serving on the climate plan’s steering committee and technical working groups.

“It’s very nice CPS has reduced emissions so drastically in past few years,” said Russell Seal, a local Sierra Club member and retired pharmacist who serves on the plan’s energy and buildings group. He added that “a lot of [the inventory] just doesn’t make sense to me.”

The groups will discuss the inventory over the next month of meetings, Melnick said. For the general public, the City extended the public comment period to July 18 after originally ending it on Friday.

Under a new schedule proposed in June, a draft version of the plan will likely be ready by late January or February, with a final plan done by April 2019.

Brendan Gibbons is a former senior reporter at the San Antonio Report. He is an environmental journalist for Oil & Gas Watch.