Most of our air emissions come from burning fuel to produce energy and from recovering chemicals used in the pulping process. Other airborne chemicals are released during the production of wood and pulp products. We're proud of our steadily reducing air emissions over the past few decades. Between 2000 and 2010 we lowered our sulfur dioxide emissions by more than 55 percent, particulate matter by 49 percent and volatile organic compounds by 33 percent. More recently, from 2014 to 2015, sulfur dioxide emissions decreased by 20 percent, particulate matter decreased by 6 percent, and volatile organic compounds increased by .5 percent.
We remain committed to sharing our companywide air-quality data and continue to work on additional reductions, including significant upgrades to many of our facilities to comply with new regulations limiting hazardous air pollutant emissions from boilers and process heaters. Many of our improvements are the result of process modifications and the use of lower-emitting additives as well as pollution-control equipment that captures or destroys significant amounts of emissions. In 2015, we made additional capital investments at several of our mills to continue to reduce our air emissions — including cleaner-burning units, energy optimization and upgrades to emission control systems.