Utilities’ energy efficiency and renewable energy programs reduced levels of carbon dioxide emissions from power plants on the southeastern grid by 3.3 million tons last year. That’s roughly equivalent to the amount of CO2 emitted by Washington, D.C. in 2014. 
Energy efficiency and renewable energy also removed nearly 2,600 tons of sulfur dioxide and 2,200 tons of nitrogen oxides, according to the NC Department of Environmental Quality.
DEQ’s information was included in a mandatory annual report to the NC Utilities Commission. The NCUC, in turn, provides the information to the Environmental Review Commission.
These EE measures and RE standards were passed in 2007 in landmark legislation, Senate Bill 3, which created the Renewable Energy Portfolio Standard, or REPS. Since the law’s passage a decade ago, conservative lawmakers have attempted to undo or undermine some of its tenets. However, DEQ data shows that regulations on RE and EE, along with the 2002 NC Clean Smokestacks Act, have helped improved the state’s air quality.
DEQ calculated the avoided pollution levels for the regional grid, not solely North Carolina. But North Carolina’s RE and EE programs largely contributed to the decrease; until 2014, it was the only state in the Southeast to have a REPS.  South Carolina now has a very modest voluntary program.
I n addition to solar and wind, new RE sources have the potential to further remove pollutants from the air. As of December 2016, the Division of Air Quality permitted or registered 31 facilities — landfills (19), swine waste (11), and poultry litter (1) — receiving renewable energy credits under the REPS.
These RE facilities supply energy through biogas to electric power plants. Since they do emit some pollutants, they are legally required to limit those emissions through Best Available Control Technology rules.
Along with the good news, there are several troubling pieces of data in DEQ’s report. First, stack tests show that several poultry litter/biogas operations, including one in Lumberton , are exceeding BACT limits, which the Division of Air Quality is investigating.
Second, the state’s legal definition of “renewable energy” includes biomass, such as wood pellets and “tire-derived fuels.” There are three such permitted facilities in North Carolina.
Wood, a more popular biomass fuel produced at Enviva’s three pellet plants, is not carbon-neutral; burning it, in fact, releases carbon dioxide into the air. And scientists have found that the act of cutting the timber does a double whammy on carbon dioxide levels: It releases the carbon dioxide while reducing the number of trees that can absorb the gas.
Old trees are better “carbon sinks” — storers of carbon dioxide than younger trees. Artificially regrowing forests, in addition to damaging the ecosystem, does not fully mitigate the pollution.
Equally puzzling are tire-derived fuels, which get an RE designation because the source material is natural rubber. More than 200 ingredients go into the making of a tire,  including synthetic rubber, chemicals, silica and metals — this is why tire fires are so toxic.
Containing those pollutants is difficult. One of the “tire-derived biomass” facilities in North Carolina, CPI in Brunswick County, has violated air quality standards for sulfur dioxide. DAQ has entered into a special consent order with that facility to address its noncompliance.