Cities Discover that Street Sweeping Offers Plenty of Opportunities to Help Environment
Nov 08, 2010
On land, sea, and air, the humble job of street sweeping is becoming environmentally “cool.” As the cumbersome sweepers lumber along city roadways, their effect on the environment is clearly moving into the green zone. The machines are quieter. They run more efficiently. Their role in keeping waterways and shorelines cleaner is becoming more obvious. And the debris itself is being used in creative ways. Almost every aspect of street sweeping is contributing to making the environment better for everyone. When it helps the bottom line of operators, the benefits are even more welcome.
The days are past when the humble street sweeper provided a way to simply make streets look better by brushing or vacuuming litter along curbs. Today, spurred by tougher federal air and water regulations, restrictions on wastewater treatment plants, and creative ways to reuse sweeper waste, the benefits of sweeping are much more than aesthetic. In short, it is easy for a city operator to justify a street sweeping budget when the benefits to the environment are so obvious.
Here is a rundown on some of the latest environmental advantages of street sweeping, starting with the land:
Land: Street sweeping does a great job of cleaning pavement. But what happens to the debris that is collected? In places such as Tampa, Florida, the waste goes through strainers and a small portion ends up at the McKay Bay Refuse-to-Energy Facility. There, it is burned—along with other “clean” waste—and the energy is used to provide electricity to 15,000 Tampa homes.
The amount of street sweeping debris that ends up being used for energy is quite small. About ninety-nine percent of it goes to the Manatee County Landfill and is used as a cover. While the amount of street sweeping debris that is converted into electricity in Tampa is miniscule, it does provide a creative and environmentally sound way for some of the waste to be reused, keeping at least a small portion out of a landfill. The city of Tampa swept 29,000 miles of streets last year, and collected 6,300 tons of debris.
One product that may be making its way to the United States marketplace soon is a street sweeping debris recycling system, manufactured by the Siltbuster Ltd. Company, based in the United Kingdom.
The Siltbuster company’s Gritbuster machine allows trucks to back up to an area and dump their debris. Inside, the machine washes and separates the material, whether it is dry, semi-dry, or wet. The company maintains it can recycle ninety-five percent of road waste. The cleaned and sorted material is then sold to companies that can use it for fill, to manufacture block, or to make certain types of concrete. The goal is to reduce the environmental and economic costs of dumping waste in a landfill.
Sea (or Water): Cigarette butts, plastic wrappers, foam cups, and other flotsam that washes up on shorelines mars the seascape. It also creates a danger to shorebirds, fish, and humans. The Environmental Protection Agency has long recognized the impact that trash has on our coastlines; marine debris can sink, smothering coral reefs. Animals can get entangled in trash and die. There is an economic cost as well: polluted beaches are turnoffs for tourists, and pieces of garbage can get sucked into motors or propellers and damage vessels.
Street sweeping in towns near beaches has focused on both the large pieces of trash as well as on the fine particulates or heavy metals that come from brake pads and other car parts. While the visible debris generally is removed via conventional mechanical brush sweepers, the microscopic particles tend to be removed best by vacuum and regenerative air sweepers. Cities, such as Pacific Beach, California, and others, often use a combination to keep their beaches as clean as possible and to comply with federal and state environmental standards.
Minneapolis cleans its 1,100 miles of streets twice a year, and another 400 miles of alleys annually. Why twice a year? In the spring, street sweeping helps remove road sand used for snow and ice control. The fall cleanup primarily gets rid of leaves, which can cause backups in storm drains. An even more significant problem arises when leaves wash into storm drains and wind up in lakes and rivers, the biggest, of course, being the Mighty Mississippi. Leaves are great when they are used as compost and in other “natural” ways, but too many of them can over-fertilize lake water and cause an overabundance of harmful plants and algae. Too many plants in fresh water eventually can harm wildlife, according to the city’s website, which justifies the environmental value to its residents.
Air: As street sweeping equipment gets better at picking up tiny—or “fine”—particulates, waterways get cleaner. Oils, road salt, and other pollutants that end up on streets are picked up. Without street sweeping, they often end up in delicate wetlands. But the impact on the air can be profound, too. Noise pollution has been cut dramatically through better equipment design. Air quality improvements can also be significant. The equipment has gotten better at keeping noise down and controlling fine particulates that in the past were blown into the air where they might be inhaled by humans.
TYMCO, based in Waco, Texas, produces the number one regenerative air sweeper in the world. The company’s website has an extensive environmental section that touts the benefits of its sweepers and their effects on the environment.
“Protecting the environment is critical to the sustainability of our planet and the conservation of precious natural resources. TYMCO recognizes its responsibility to that sustainability and continually strives to reduce the environmental impact of the sweepers we build and the work we do,” according to the company’s website.
TYMCO has designed its sweepers to run as efficiently as possible. For example, its Model 500x uses a digital multiplex electrical system that cuts the amount of wire in the machine by several hundred feet. Components are manufactured to be lighter than in the past in order to help reduce fuel consumption. Components are modular, when practical, which allows them to be easier to maintain and decreases the amount of welding on the machine, saving energy and gases during the fabrication process.
As for dust control, TYMCO Regenerative Air Sweepers use a centrifugal dust separator, which removes the majority of fine particles from the air stream before it is recycled. Plus, the company’s machines use relatively little water—just enough to dampen airborne dust, not the ground. The result? Dust that can be collected, with no mud left behind.
Good engineering is crucial. “Our engineers take several other aspects into account when designing for better dust control, such as air flow direction, velocity, and other opportunities to separate out as much dust before the air reaches the dust separator,”notes TYMCO.
Diesel exhaust in the air has also been under scrutiny by the federal government. As a result, sweeper manufacturers have been paying close attention to the machines they put on the streets. The clean air standards are requiring companies to make changes to new machine designs to comply with the regulations. These changes mean that new sweepers are getting better at not only keeping fine particulates out of the air through more efficient sweeping but also at drastically reducing exhaust that can throw those same particles into the air while the machines are operating.
Land, sea, and air. Street sweeping on a regular basis plays a vital role in keeping the environment clean. Cities are making room in their tight budgets for the equipment, despite the cost. With the federal government putting pressure on cities to reduce pollutants in waterways and treatment plants, effective sweeping is the best way to get the job done.