Inside a MRF

We all remember going to school and learning the three Rs—reading, writing, and arithmetic.

To keep up with the times, Montgomery County, Md., and other municipalities promote another three Rs: reduction, reuse, and recycling.

The first two—reducing the quantity of waste and reusing household and commercial items—are personal choices. But recovering material from municipal solid waste (MSW) has become the responsibility of municipalities.

In general, municipal recyclables include aluminum, steel, plastic, and glass containers as well as various paper grades, which are gathered through curbside collection programs and public drop-offs. These recyclables usually end up at a material recovery facility, or MRF (which rhymes with “surf”). There, the recyclables are sorted by hand and machine into separate commodity streams. Only then can they be sold to a consumer and complete their recycling journey.

This peek inside the Montgomery County Recycling Center in Derwood, Md., shows how a MRF works.

A MRF Is Born

As with many municipalities, Montgomery County created its curbside collection programs—first for ONP, then for commingled containers—in the late 1980s and early 1990s when public recycling was a hot topic. To process these recyclables, it built an $8.4-million MRF. Soon thereafter, it also constructed a waste-to-energy plant to transform the remaining MSW into electricity.

To encourage its 200,000 households, 98,000 multifamily units, and 25,000 businesses to recycle, Montgomery County organized a public information program, including a recycling hotline. Volunteers spread the word by participating in community functions and giving presentations to schools and civic organizations. Scheduled tours of the MRF are offered to groups, and county residents can view the facility anytime. In addition, the county’s Web site provides solid waste and recycling information.

To pay for its recycling program and to support its MSW infrastructure, Montgomery County levies a systems benefit charge on all taxpayers, collecting this charge on their tax bill. Waste haulers bring all recyclables from single-family homes to the MRF, dropping the MSW they collect at the transfer station for shipment to the waste-to-energy plant. This method ensures that all recyclables and MSW from individual homes are processed by the county. 

In contrast, multifamily units and businesses sign their own contracts with waste haulers who are free to transport the recyclables and MSW to other locations.

Processing the Recyclables

Montgomery County’s residential recycling efforts are based on a blue bin curbside collection program. Each single-family household receives a blue plastic bin for commingled recyclables, which are collected separately from MSW and yard trim (which is transported directly to the county’s composting facility).

The blue bin program collects:

• unbroken green, brown, and clear (or flint) glass jars and bottles;
  
• clean, uncapped plastic containers with necks (“Check for the neck,” advises the county), regardless of the polymer identification number printed on the bottom; and
  
• aluminum, steel, and bimetal cans, as well as aluminum foil and plates.
  

ONP, which is collected at the same time, should be tied in bundles or contained in brown bags.

Though the MRF has the capacity to process 100 tons a day of commingled recyclables in a 40-hour workweek, it currently receives about 70 tons daily. By weight, this material is 65 percent glass, 13 percent steel and aluminum used beverage cans (UBCs), 18 percent plastics, and 4 percent nonrecyclable waste.

After arriving at the MRF, the commingled recyclables begin their journey through the facility’s sorting process, which uses both manual sorting and mechanical separation based on the material’s magnetic and bulk density properties.

From the tipping floor, the recyclables are loaded onto a conveyor belt and enter the first manual sorting station. Here, employees remove aluminum foil items (which are baled separately) and any material that can’t be handled by the plant (such as metal plumbing fixtures, auto parts, mirror glass, and plastic containers without necks). Manual sorting provides the necessary quality control to ensure that final commodity streams meet consumer specifications.

After this initial sorting stage, the recyclables pass under a magnet, which pulls the steel and bimetal cans from the nonmagnetic materials. These cans are then processed into 1,200-pound bales.

The remaining recyclables pass over a vibrating screen through which small pieces of material (mostly broken glass) fall. The pieces of glass are processed together to make a mixed-color product, which is used as an aggregate in the gas collection system at the closed Oaks Landfill in Montgomery County. The county can also sell the mixed cullet to companies that sort it by color using optical sorting technology.

The other recyclables, which at this point include glass bottles, UBCs, and plastic containers, are fed onto an inclined table that uses rotating chain curtains and brushes to sort the containers. Heavier items—those with high bulk density such as glass containers—fall past the chain, while lighter items—those with low bulk density such as UBCs and plastic containers—are fed into another sorting process.

The glass containers head directly to a manual sorting station, where employees separate green, brown, and clear glass and remove contaminants such as ceramic, mirror, and window glass. The three pure glass streams are sold for recycling into new bottles.

The UBCs and plastic containers, meanwhile, pass over another vibrating screen with rectangular openings through which the UBCs and residue contaminants fall. An eddy-current nonferrous separator then ejects the UBCs from the residue stream to another line for baling and shipment.

The plastic containers that pass over the vibrating screen are conveyed to a manual sorting station, where employees remove unwanted plastics and contaminants. The clean plastic—mostly PET and HDPE—is compacted into 1,600-pound bales for shipment to a firm that processes the material into fiber for carpet, clothing, and insulation.

That’s the end of the cycle for the commingled recyclables.

ONP is handled in an adjacent part of the MRF, which features two truck bays and high ceilings that allow trucks to unload their paper indoors, safe from inclement weather. The MRF receives about 155 tons a day of ONP. The paper is loaded loose into trucks for transshipment to a scrap paper broker, who buys the ONP under long-term contract with Montgomery County, currently paying $15 a ton. The broker also takes telephone books and magazines that residents drop off at the transfer station.

Selling the Goods

The task of marketing the MRF’s various recyclables, except ONP, falls to Maryland Environmental Service (MES), a state agency based in Annapolis, Md., that’s currently contracted to operate the facility.

Sales agreements for the MRF’s commodities usually run six months, though some are annual. MES can also enter into less formal agreements as needed. Each buyer sets its own specifications for the quality of the commodities. In general, the prices MES receives vary depending on the quality of the material, the quantity of material (trailerload quantities are often required), and the reputation of the buyer and its stature in the industry.

Contracts specify the quantity of material to be delivered and the unit price, which is sometimes fixed for the life of the contract and sometimes floats for the period. Aluminum prices are tied to the LME, while ferrous prices reference the Iron Age scrap price bulletin. 

Glass prices are based on bids from potential buyers. The ONP price is tied to the No. 6 news price, Southeast region, as stated in the second issue of each month of Official Board Markets. Since there’s no industry-accepted index for recovered plastic prices, MES sells its plastic to a buyer under an informal agreement, with the price adjusted as market conditions change.

The MRF brings in more than $2 million a year from the sale of its recyclables—$671,000 from aluminum, $390,000 from glass, $147,000 from steel, $320,000 from plastics, and $568,00 from ONP. This income defrays about half the MRF’s annual operating cost, which was approximately $3.97 million in fiscal year 1997. The $1.87 million not covered by the MRF’s revenue is made up by the service fees paid by county residents.

The MRF’s revenue has fluctuated in the past several years as commodity prices declined from their high levels in the mid-1990s. In fiscal year 1997, for instance, the MRF received an average of $36 a ton for its recyclables compared with $64 in 1996 and $48 in 1995. The volume of incoming material, however, has been fairly level, though glass has shown a downtrend as plastic continues to claim a greater share of the packaging market. On the paper side, the county anticipates that its new mixed-paper recycling program will contribute a much greater share of revenue when it’s fully implemented by the end of next year.

Where the Rest Goes

Out in Dickerson, Md., about 25 miles from Washington, D.C., is the Montgomery County waste-to-energy plant. It’s called a resource recovery facility, or RRF, because it generates and sells energy, scrap metal, and ash. Though many county residents view the plant as nothing more than an incinerator, “it’s actually a trash-burning power plant that produces income,” says Jim Reynolds, RRF program manager of the Division of Solid Waste Services.

This 1,800-ton-a-day facility, completed in 1995, is operated by Ogden Martin Systems of Montgomery Inc. (Dickerson, Md.) under a 20-year service agreement with its owner, Northeast Maryland Waste Disposal Authority (Baltimore).

The plant, which receives MSW by rail from the county’s transfer station, has a simple mission: Burn MSW and, in the process, generate 63 megawatts of electricity. Montgomery County receives 92 percent of the revenue from the sale of the electricity to Potomac Electric Power Co., the local electric utility, while Ogden Martin receives the remaining 8 percent.

From 1996 to 1998, MSW incinerated at the RRF increased from 423,000 tons to 449,000 tons a year. After the MSW is burned, large metallic items, mainly ferrous scrap, are recovered from the ash through screening and manual separation. Then, the ash passes under a magnet, which extracts smaller ferrous items. The RRF recovers about 12,500 tons annually of ferrous scrap from its ash. Ogden sells this scrap for $35 per ton, f.o.b. plant, with Ogden Martin and the county each receiving 50 percent of the revenue.

(Many large ferrous items are manually separated at the transfer station before the MSW is shipped to the RRF. The transfer station has a collection container for residents to bring large metallic recyclable items such as bicycles, lawn equipment, and playground equipment. This is in addition to the special curbside pickup of large household recyclables.)

The remaining ash is landfilled out of state—but probably not for long. American Ash Recycling Corp. (York, Pa.) has tested the ash and reported that it meets or exceeds all environmental and physical requirements to be a construction aggregate. Analysis of 12 heavy metals showed that eight, including cadmium, mercury, and lead, were nondetectable in the ash. Beginning last June, about 150 tons a day went to Pennsylvania to be used in construction and road building. If this ash use is fully implemented, then the need for landfilling the ash would be eliminated and all the MSW collected by the county could be considered to be recycled or used for energy generation.

Onward and Upward

Though Montgomery County’s recycling efforts thus far have been successful, it continues to expand and improve its recycling program to increase its countywide recycling rate.

One example is the new program to collect residential mixed paper at curbside. These new items include magazines, telephone books, junk mail, OCC—virtually any paper product found in the home. Previously, residents brought these materials for recycling to the transfer station or to private recyclers. Office Paper Systems (Gaithersburg, Md.) has signed a 15-year contract to sort the mixed paper into six grades. It’s receiving $1.35 million a year from the county to recycle up to 90,000 tons of mixed paper. About 15,000 homes were served beginning in early 1999, and all households will be included by late 2000.

Another boost could come by fully counting recyclables generated in the county but not processed by the MRF, such as material from multifamily residences and businesses. Both contract with private firms to collect their MSW and recyclables. Some of this material is shipped out of state or to private recyclers and possibly isn’t fully reflected in private hauler reports provided to the county from which recycling rates are calculated. Tighter auditing of such hauler reports could provide better and more complete data in this area.

In 1998, the county’s single-family residences had a recycling rate of 45.3 percent, while multifamily and commercial sources recycled about 27 percent, for a countywide recycling rate of 35.1 percent. The national average is 27 percent.

Montgomery County’s goal is to reach a 50-percent recycling rate by 2000. Mixed paper recycling should boost the single-family home recycling rate. But the county will also have to promote greater participation by and closer documentation of recycling in the multifamily and commercial sectors. If those sectors increase their rate to the current rate of single-family households, another 125,000 tons of recyclables could be credited to the county. To improve in these areas, the county is providing more technical and personnel support on reporting, site assessments, and management.

Will the county reach its ambitious recycling goal? With the millennium almost upon us, it won’t be long until we find out. 

What’s in a Recycling Rate?

The definition of recycling and methods for determining recycling rates can be contentious and often vary from jurisdiction to jurisdiction.

Though most municipalities base their recycling rates only on quantities of MSW collected, Montgomery County bases its rate on the quantity of MSW generated. In addition to the recyclables and MSW it collects, the county includes in its generation figures an estimate of the amount of yard trim that’s home composted or “grasscycled” (the process of returning grass clippings to the lawn). 

As a result, the county’s estimates of recycling rates are higher than those computed by the state of Maryland, which excludes such estimates. “Home backyard recycling cuts down on the waste stream and is true recycling,” says Esther Bowring, senior planner for Montgomery County’s Division of Solid Waste Services. The current estimate for backyard recycling is 500 pounds per household per year.

The county is also considering the inclusion of 110,000 tons of ash produced annually from its waste-to-energy facility when that material is sold and used. That’s getting the last squeal out of the pig, as the saying goes. •