The administration of Mayor Bill de Blasio of New York has set clear, aggressive goals for reducing greenhouse gas emissions that would make the city a national leader in mitigating climate change. But other decisions now in the works could prevent the city from meeting them.
In the wake of last year’s Paris climate agreement, the mayor announced plans to cut emissions from activities controlled by the city government by 80 percent by 2050. Mr. de Blasio’s pledge included cutting emissions from the city’s vehicle fleets by 50 percent by 2025, and by 80 percent by 2035.
Halving emissions in less than a decade requires immediate, concerted action. But the Department of Sanitation — the city agency with the highest vehicle fuel consumption and greenhouse gas emissions — plans to buy 340 new refuse trucks this year, with at least 300 powered by diesel engines. That would lock in high diesel emissions for the seven-year service life of these trucks — and put the 2025 emissions goal out of reach.
The city has made some progress toward the new goals, cutting fleet emissions by 11 percent by running more than half of its vehicles at least partly on nonpetroleum fuels. New Yorkers are already seeing more hybrid and all-electric passenger cars and light-duty vehicles in city livery.
But the city has done little about its heavy-duty vehicles, the largest source of fleet emissions. Its 5,200 heavy-duty diesel trucks account for only a fifth of the fleet, yet emit more than 60 percent of its greenhouse gas emissions. Because these trucks need higher power and torque than other types of fleet vehicles, the options for alternative fuels are limited. The city mandates blending the diesel fuel with 5 to 20 percent biodiesel, but that won’t enable the de Blasio administration to reach its ambitious targets.
There is an alternative fuel that could: renewable natural gas. Chemically, this substance is nearly identical to geologic natural gas, so trucks and buses equipped with natural gas engines can also run on renewable natural gas. But it’s not a fossil fuel like shale gas; it’s a renewable, made from biogases emitted by decomposing organic waste, like wastewater or food waste — both things New York has plenty of.
According to the California Air Resources Board, renewable natural gas is the lowest-carbon fuel available. In fact, where food wastes are a major source, as they are in New York City, renewable natural gas can be carbon-free or even net carbon-negative over its life cycle. This is because renewable natural gas captures powerful climate-warming gases like methane produced by decomposing organic matter, and prevents their escape into the atmosphere by burning them as fuel.