Before Houston, Texas, and its suburbs were built, a dense forest naturally purified the coastal air along a stretch of the Texas Gulf Coast. The land grew thick with pecan, ash, live oak, and hackberry trees. Then, the woodland was mostly wiped out by settlers in their rush to clear land and build communities.
Now, one of the world's largest chemical companies and one of the U.S.'s oldest conservation groups have forged a partnership. They are seeking to recreate some of that forest to curb pollution.
The plan drafted by Dow Chemical and the Nature Conservancy is only in its infancy and faces many hurdles. But it imagines a day when expensive machines used to capture industrial pollutants might be at least partially replaced by restoring some of the groves of native trees that once filled the land.
"It looks very promising at the early stage of the research," said Mark Weick. He is the director of sustainability programs for Dow. The company has facilities located around the world, including Mexico, Canada, Italy, Poland, India, and Thailand.
Many plants, and especially trees, capture pollution naturally when it hits their leaves. Trees with the biggest leaves and the widest canopies capture the most pollutants, especially nitrogen oxide. This common byproduct of combustion contributes to the formation of ground-level ozone and irritates people's lungs. The reforestation proposal imagines emissions from Dow's largest North American factory drifting downwind into the trees near Freeport, Texas.
The project had an unlikely beginning. Dow and the Nature Conservancy began working on a six-year, $10 million plan in 2011. They came together to look at ways natural resources could be used to save the company money.
After reading an obscure note by the U.S. Environmental Protection Agency (EPA) that suggested reforestation could improve air quality, the two groups decided to research how the idea might work and if it could be cost-effective.
The EPA requires companies to rid the air of industrial pollutants released by factories. Currently, Dow uses expensive machines called "scrubbers" to do the job.
"The big discovery was that you could combine the traditional infrastructure with reforestation and still meet [EPA requirements]," said Laura Huffman. She is the conservancy's director in Texas.
The trees, Huffman said, may not completely replace traditional technology, but they could work with it. They would allow factories to use smaller, cheaper equipment.
The research found that over 30 years, a 1,000-acre (405-hectare) forest would remove 4 to 7 short tons (3.6 to 6.4 metric tons) of nitrogen oxide annually, said Timm Kroeger, a senior environmental economist with the conservancy. By contrast, a scrubber removes about 50 to 70 short tons (45.4 to 63.5 metric tons) annually.
This means that a 10,000-acre (4,047-hectare) forest does the job of one average industrial scrubber, Kroeger explained. And in the area near Freeport, Texas, where open land is ample, reforestation may be within reach.
The cost of the project, not including the land, would be about the same as using traditional forms of pollution control, Weick said. A recent progress report determined that the cost of cleaning a short ton (0.9 metric tons) of nitrogen oxide through reforestation was $2,400 to $4,000, compared with $2,500 to $5,000 using traditional equipment.
The research is still being reviewed by other scientists. Before any formal plan could be adopted in the U.S., it would have to win approval from state and federal officials. They would require any pollution-cleansing method to be calculable and enforceable. Trees may not fit the bill. Unlike machines, they are living things that are subject to diseases, fires, droughts, and other threats.
Back in 2005, another scientific group researched a similar idea and decided that it would not pay off.
"The conclusion that we reached was that what they were trying to do was difficult and that the degree of uncertainty was larger than the benefits," said Mark Estes. He is a senior air quality scientist with the Texas Commission on Environmental Quality.
Even if it wins broad support, the plan won't be approved quickly. In Texas, it can take up to four years to change clean-air rules. And that's before any proposal goes to the EPA.
As he looked out over land ripe for reforestation, Jeff Wiegel, the conservancy's director of strategic initiatives in Texas, was realistic about the pace of progress.
"It's a long road…," he said.
The Associated Press contributed to this story.
Dig Deeper
Reforestation is one way scientists are working to improve air quality in cities and suburbs. The quality of air depends on how much air pollution is in it. Scientists classify the separate types of air pollution. Pollutants are either gases or particles.
Gas pollutants include carbon monoxide, methane, and ozone. They also include sulfur oxides and nitrogen oxides. Some of these gases occur naturally in the atmosphere. They are considered pollutants only when they are likely to cause harm. For example, ozone gas is good in the stratosphere. But it is harmful to breathe. When ozone is in the troposphere, it is a pollutant.
Particle pollutants can be easier to see than gas pollutants. Particulates are tiny particles or droplets that are mixed in with air. Smoke contains particulates. The wind can pick up other particulates. These may be dust and dirt, pollen, and tiny bits of salt from the oceans.
In cities and suburbs, most air pollution comes from the burning of fossil fuels. Fossil fuels include oil, gasoline, and coal. In London in the 1800s, burning coal provided much of the heat and energy for homes and factories. It caused smoke. The smoke and local weather conditions often produced a thick fog or cloud called smog. A newer kind of air pollution is also called smog. Sunlight causes the fumes from gasoline, car exhaust, and other gases to react chemically. The reactions form new pollutants such as ozone. Together, they are called smog. In cities, there can be enough smog to make a brownish haze. The burning of fossil fuels in power plants, cars, factories, and homes is a major source of pollution in the United States and around the world.
Background photo of smog with table placed over it showing sources of air pollution from humans compared with those from humans. The sources of air pollution from humans include: Gases and particles from burning fossil fuels. Smog caused by unburned fuels. Gases, chemicals and particles from manufacturing, waste treatment, and other industries. Dust and soil from construction, mining, and farming equipment. And chemicals from fertilizers and pesticides. The sources of air pollution from nature include: dust, spores, pollen, soil and salt. Ash, gases, soot and smog from wildfires and volcanoes. And other gases and particles given off by plants, animals, rocks, swamps, etc.
Image credit: trekandshoot/Alamy Stock Photo
The primary source of air pollution is the burning of fossil fuels in cars, factories, power plants and homes in both the U.S. and worldwide.
QUESTION 6
QUESTION 6 OF 8
6 / 8
The article states:
Many plants, and especially trees, capture pollution naturally when it hits their leaves. Trees with the biggest leaves and the widest canopies capture the most pollutants, especially nitrogen oxide.
Which would be the closest synonym for the word canopy?
A.Overhang
B.Inventory
C.Undergrowth
D.Territory