Alaska’s Unnatural Resources
Recylced and used materials in construction
Will Young (left) and Donald Forestner (right) of Central Recycling Services sweep up debris at their recycling facility.
Construction projects can have a significant impact on the environment. To illustrate, it is estimated that the global cement industry contributes approximately 5 percent of global carbon dioxide emissions. During the three-step production process required to create cement, combined minerals are crushed into three-inch pebbles before being sent to a kiln heated to 1,500 degrees Celsius (it is during this process that harmful carbon dioxides are released). The resulting material is called clinker. Once the clinker is cooled, it is ground into a super-fine powder and mixed with either gypsum to produce Portland cement or lime to produce masonry cement.
According to the US Environmental Protection Agency, the United States is the world’s third largest cement producer, with production occurring in thirty-seven states. Alaska is one of nine states equipped to grind finished clinker into usable concrete or cement.
A Central Recycling Services worker sorts raw materials at the company’s recycling facility.
Cement is Necessary, Environmental Contamination Isn’t
Because cement is essential to the production of concrete, a primary building material for the construction industry, ceasing concrete production isn’t a solution. Instead, many environmentally-minded individuals and businesses search for ways to reduce waste or repurpose already manufactured products.
Recognizing the potential to reuse concrete as a building aggregate, Alaska’s Central Recycling Services (CRS) and sister company Central Environmental Inc. (CEI) combined forces to offer grinding services to local contractors. The result is an aggregate that can be used for a variety of projects. Smaller pieces of concrete can be used as gravel for new construction projects. Sub-base gravel can be laid down as a base for fresh concrete or asphalt. Uncontaminated recycled concrete can also be crushed and used as dry aggregate for brand new concrete. Finally, well-graded concrete can be provided as a substitute for landscaping stone or mulch.
CRS’s founders have been working in construction and demolition for the past twenty-five years, but according to Civil and Environmental Engineer Donna Mears, the company itself has been in operation for the past decade.
“About ten years ago we demolished Clark middle school, and the Anchorage School District and the architect requested that we do material recycling to meet LEED standards. Recycled asphalt, pavement, and concrete crushing is something that happens a lot, so we're not the only game in town for that, but we have pivoted to be able to process a variety of different materials,” Mears says.
Much of CRS’s work is repurposing concrete from CEI demolition projects, but they also focus on exploring potential uses for recycled glass, metal, and tires.
“The recycled glass is our success story because there was a use for it and it was supported by the municipality. Once a new material is proven as successful people kind of say, ‘Oh okay, maybe I will give it a try,’ and you end up getting attention for it. That’s when things really take off,” says Mears.
One early adopter of using recycled glass in new construction was Anchorage Water and Wastewater Utility (AWWU). In the fall of 2017, AWWU undertook a major construction project to remove 4,000 feet of 1965 vintage ten-inch cast iron pipe and replace it with updated sixteen-inch PVC pipe between Northern Lights Boulevard and Bragaw Street in Anchorage. The project required a new bedding material to encase the updated pipes. In lieu of traditional Class E bedding material, which is primarily made of sand, AWWU partnered with Solid Waste Services and Southcentral Construction to use reclaimed glass produced by CRS.
The AWWU project used glass from residential drop-offs to the CRS facility, but Mears hopes that as demand increases for glass aggregate, local businesses will contribute by providing glass for recycling.
“Right now, all [of the glass we have onsite] is residential drop-offs, but we are starting to get enough demand for the finished product to start increasing the material coming in on the commercial end,” Mears says. “The fee to drop off glass at CRS will be less than it is to take it to the central transfer station or to the landfill. But businesses will have to leverage the lower fee against pick-up costs to get a sense for cost effectiveness.”
Mears believes that if a business has multiple dumpster pickups each week and some of the dumpsters are only filled with recycled materials that cost less to be picked up, the cost effectiveness for businesses to recycle increases. Creating aggregate in an Anchorage location also cuts costs for contractors who would otherwise face trucking and material fees from outside vendors.
Located one mile from the CRS main Anchorage processing plant is their smaller metal yard. At this location, CRS can accept everything from steel, iron, and batteries to electronics and vehicles. Waste from this location is culled to be sold locally for reuse or processed by onsite machinery to be sold out of state. The yard’s location near the railroad makes transportation of materials both affordable and possible.
Workers add debris to an unsorted pile of materials awaiting processing at Central Recycling Services’ recycling facility.
When the Rubber Hits the Road
Although CRS has successfully located markets for their aggregates and metal products, they have another innovative recycled material they hope to establish a market for—tires.
“There was a company in the late ‘90s—Alaska Tire Recycling out in the Valley—that [had the equipment] and were making crumb rubber, hoping to use it on highway projects. It didn't pan out, so they started making rubber shred for playgrounds and mats. In a lot of ways, I think maybe they were ahead of their time,” says Mears.
When CRS saw the potential for repurposing tires, they initially envisioned following in the footsteps of Alaska Tire Recycling and tried making shreds. They quickly realized that the twelve-inch threads of their industrial shredders were too large to process smaller tires into useable rubber chunks. Rather than abandon the enterprise, CRS discovered that by compressing the tires into large tire bales, they could craft non-frost susceptible fill for road construction.
“We have a monofill facility up in Salcha, Alaska, and it was a little mucky, so we excavated the native material and placed the tire bales down as a driving surface. Since they are free draining and not susceptible to frost, they worked like a charm,” says Mears.
The tire bales, which measure approximately three by five by five feet and weigh between 1,750 pounds and 2,300 pounds, also have the potential to serve as temporary road structures linking oil rigs. Mears believes that the portability, endurance, and temporary nature of tire bale roads could be an asset to the Alaska oil industry.
“We've had some inquiries about using them on more remote exploration projects that are required to return sites to their natural conditions. So, if you bring in aggregate roads then you need to take those aggregate roads back out again. If you have a tire belt road, you lay the tire belt and then you can take them back out again and use them on another project,” she says.
At this time CRS is not actively working on a project, but Mears is quick to add that if the demand is there, CRS will likely jump on the opportunity. Until the demand for tire bale roads is established, CRS will continue to use their tire bales onsite for everything from retainer walls to gabions.
Although Alaska is slowly beginning to incorporate the use of recycled materials in construction projects, there are factors that limit the viability of using such products: each item requires an immense amount of raw materials to produce (for example, it takes sixty to eighty tires to make one tire bale); the Alaska construction season is so truncated that is difficult to convince contractors to take a risk on a material that has not already been used successfully; and continued innovation depends on market demand.
“I wish I had a recipe book to make everything as successful as our glass aggregate has been. [In Alaska] we seem to stumble around with it more than we should, and it's a little hard when you're doing something cool and wondering why everybody can't see the same potential you see, but sometimes it just takes a while for something to catch on,” says Mears.
O'Hara Shipe is a freelance writer in Anchorage.