- Asphalt, Brick, and Concrete
- Batteries (Lead Acid and Lead Gel)
- Batteries (Dry Cell)
- Corrugated Cardboard
- Fluorescent Light Tubes and Ballasts from Fluorescent Lighting
- Electronics and Cathode Ray Tubes (CRT’s)
- Food Waste & Biodegradable Packaging
- Greenhouse Waste
- High Grade Paper
- Leaves, Yard Waste, Animal Bedding
- Light and Heavy Iron and Stainless Steel, Copper, Brass
- Scrap Metal
- Single Stream Recyclables
- Toner Cartridges
Commodity: Asphalt, Brick & Concrete (ABC)
Tons Recycled: Concrete: 82.5 tons Asphalt: material from road repair operations at UMass is accumulated and sent to Warner Brothers of Sunderland for re-use in making new asphalt.
Revenue or (Cost): ($1,430)
End Use. Associated employs a combination of manual and mechanical sorting processes. The ABC material is cleaned and crushed into specified sizes and qualities. The resulting product material is called “aggregate” and is sold for use in road, parking lot and other building applications. Concrete can be recycled numerous times and the recycled material is often used like new raw material. Occasionally, steel that has been used as concrete reinforcement, along with any other materials that may be embedded in the concrete, must be removed. If necessary, contaminating materials such as asphalt, soil and clay balls, chlorides, glass, gypsum board, sealants, paper, plaster, wood, and roofing materials must be removed as well. This can be done through various processes such as crushing, screening, air separation, and size reduction. Recycled concrete aggregate, or RCA, contains original aggregates as well as hydrated cement paste, which increases the porosity and absorption of the original aggregate. Sand is often used in the process as well, increasing the feasible amount of RCA in natural crushed course aggregate to up to 30%, without compromising the quality. RCA can be transported in the same manner as its conventional counterpart, and the two are often mixed in the production of new concrete.
The final product can be used as pavement, shoulders, median barriers, sidewalks, curbs, gutters, bridge foundations, and structural bases. Environmentally, RCA decreases the need for virgin aggregate as well as the amount of construction materials placed in landfills. RCA also absorbs carbon dioxide from the surrounding atmosphere (Portland Cement Association).
Commodity: Batteries (Lead Acid and Lead Gel) as found in vehicle batteries and emergency lighting
Vendor: Interstate Batteries
Tons Recycled: 6.6 tons
Revenue or (Cost): $1,436
End Use: Lead acid batteries are broken into pieces in a hammer mill. The pieces are then put in a vat, where the heavy materials such as lead sink to the bottom while the plastic floats. The polypropylene (plastic) is then scooped out of the vat and the liquids drawn off. The polypropylene is washed, blown dry, and sent to recycling facilities where it is melted into a quasi-liquid material. This liquid is then pushed through an extruder to create small, uniform plastic pellets, which are then sold to battery case manufacturers and the battery manufacturing process beings anew (Battery Council).
The lead oxide found in lead “grids” is cleaned. This material is smelted in furnaces and the molten lead poured into ingot molds – where the impurities float to the top. These impurities are scraped offand the molten lead left to cool. The lead ingots are sent to battery manufacturers where they are re-melted and used again in battery manufactur.
The sulfuric acid in batteries is neutralized with the industrial version of household baking soda. This process turns the acid into water which is then treated, cleaned, and tested in waste water facilities to ensure that it meets clean water standards. Alternatively, the acid is sometimes processed and converted to sodium sulfate - an odorless, white powdery substance that is found in laundry detergent, glass, and textiles (Battery Solutions).
Commodity: Batteries – hazardous dry cells (types include; mercury, lithium, cadmium, nickel-metal hydride). Per Massachusetts Depratment of Environmental Protection (DEP) recommendation, UMass Amherst disposes of akaline batteries in trash.
Tons Recycled: 0 tons
Revenue or (Cost): ($1,162)
End Use: Non-lead acid batteries include: alkaline, mercury, zinc carbon and zinc air batteries, lithium ion batteries, nickel-cadmium and nickel metal hydride batteries, lithium batteries.
Alkaline, zinc carbon, and zinc air batteries are recycled in a process that is temperature controlled and utilizes mechanical separation – sorting battey components into zinc and manganese concentrate, steel, and paper and plastic. After separation, 100% of the material from these batteries are directed to relevant mills and reclaiming operations.
Lithium ion batteries, as well as nickel-cadmium and nickel metal hydride batteries, are recycled after plastic and metal components are separated. The metals are then directed to a smelting process, called High-Temperature Metal Reclamation (HTMR), which melts together all of the nickel, iron, manganese, and chromium in the batteries (known as the high-temperature metals). The low-melt metals, zinc and cadmium, separate during this process. 100% of the materials are then directed back into the manufacturing of new products.
Lithium batteries are processed through either a shredder or a high-speed hammer depending on their size. The resulting materials are placed in caustic water, which neutralizes electrolytes. Ferrous and non-ferrous metals are then recovered and sold to metal recyclers. The remaining solution is filtered, and carbon is recovered and pressed into carbon cake sheets. Some carbon stays with and is recycled with cobalt. Lithium hydroxide is converted to lithium carbonate, and the resulting technical grade lithium carbonate is used to make lithium ingot metal and foils used in battery production. Some of the lithium is sold to manufacturers of sulfur dioxide batteries.
Mercury batteries are broken down and processed in a temperature-controlled process. However, the amount of mercury oxide in batteries has continued to decrease since 1996, when the Mercury-Containing Rechargeable Battery Management Act was passed, limiting the sale of certain types of batteries containing mercury in the United States (Battery Solutions).
Commodity: Used Books
Vendor: Discover Books
Tons Recycled: 34.2 tons
Revenue or (Cost): $0 (books are picked up for no cost and sold or donated)
End Use: OWM collects large volumes of books (hard and soft cover) from the UMass campus and accumulates them at the WRTF. When the boxes are filled, Discover Books picks up the the book gaylords (cubic yard storage boxes) and transfers them to their Ohio warehouse. Discover Books has a software system that identifies the marketability of each book. The books are classified as: market-value, donation-value, or of no value. Books that are recognized as marketable are resold to online retailers such as Amazon, Ebay, or Safeway. Books that are identified as still useful to the public are donated to a literacy-focused or community-based non-profit organization. Discover Books partners with many charitable foundations such as “The Children’s Reading Foundation”, “Communities in Schools”, and “BookPals." Many of these organizations share the similar mission to provide books to under-served communities in order to promote literacy. Lastly, books that are of no-value cannot be resold or donated and so they are either recycled or sent to a landfill. Discover Books aims to reduce the amount of books that go to a landfill, and so they work to send many of their no-value books to a recycling facility instead of a landfill. At these recycling facilities, the covers from the hardbound books are removed, and the leftover paper undergoes a pulping process. First, a machine chops the paper and then water is added to the pulper. Next, a screen is used to filter out contaminants. The paper is then cleaned and de-inked. Water then passes through the pulped paper to wash it, and sometimes bleach is added if a white color is desired. The “refined” pulp is used to create a new paper product. The process water is then cleaned through dissolved air flotation so it can be used again. This recycling process creates byproducts, and these byproducts are usually burned for energy at the paper mill. Some books that are ruined from mildew, water, or insect infection cannot be recycled and are sent either to incineration or to the landfill. (All-Recycling-Facts).
Tons Recycled: 5,181 1bs from student move out
Revenue or (Cost): $0 (clothing is picked up at no charge and donated)
End Use: Unwanted clothing collected at student move-out was once collected by OWM and directed to one of several local charies. Since 2013, the Sustainable UMass NU2U program has taken over this function. At the end of the spring semester, Sustainable UMass sets up donation tents across campus where students can donate their unwanted clothing & furniture to the NU2U tents or to the Salvation Army donation box.
Sustainable UMass stores the clothing from the New2U donation box over the summer, and then resells the clothing along with other items on move-in day at the NU2U sale. Leftover clothing from the NU2U sale is then donated to the Amherst Survival Center (ASC). The ASC transfers these clothing to their Community Store. The clothes in the “store” are free to shoppers, and the only restriction is that shoppers cannot take more than one bag of clothing per day.
Clothing placed during Move-Out in the Salvation Army Donation box goes to the Salvation Army Store to be sold. Clothing that is not sold within a month is transferred to the back room. In the back room, workers bale the clothing. The bales are sent to a secondhand textile processor in the U.S. There, workers sort through clothing to seperate high-quality clothing from the low-quality clothing. Higher-quality clothing is sold to vintage thrift shops and some of the lower-quality clothing is sent to a factory that converts the clothing to industrial wiping rags. Most of the clothing is sold overseas, specifically to ports in sub-Saharan Africa. (Cline 2012)
Commodity: Corrugated Cardboard
Vendor: Northstar Pulp & Paper
Tons Recycled: 506.0 tons
Revenue or (Cost): $58,594.99
Tons Recycled: 506.0 tons
Revenue or (Cost): $58,594.99
End Use: Corrugated cardboard and old corrugated cardboard (OCC) refers to a 3 layer material that comprises items such as pizza boxes and shipping boxes. “Cardboard” refers to a thick paper stock known in the industry as ‘paperboard” and it applies to items like cereal boxes and other small consumer goods packages (Kaszubowski 2012). OWM collect OCC from campus and bales it at the WRTF. Bales weigh 1,500 lbs. each. Baled OCC is shipped to the Northstar Pulp & Paper Mill in Springfield, MA. Northstar tests the bales to assess contaminants, and then sends acceptable OCC to a Sonoco Paper Mill in Holyoke, MA. The paper mill breaks the bales and places the OCC in a repulper. The repulper mixes the material with water until a slushy pulp is created. Then, a chained rope swirls around the repulper and catches contaminants such as string or tape. Subsequent pulp processing equip ment removes other contaminants such as metal (which falls to the bottom), and light weight contaminants (which float to the top of the pulp and are scraped off). The pulp is then poured onto a moving screen where water drains off. The pulp starts to develop into a fiber mat and further water is excreted by moving the mat through heated cylinders. Lastly, the dried fiber mat is rolled up on a spool and then cut to become smaller rolls. Sonoco uses the corrugated rolls to manufacture brown kraft paper. The kraft paper is used to create paper cores (cores are the inside of paper rolls). The OWM’s OCC specifically is manufactured into paper cores, but OCC can be recycled into other items such as paperboard like cereal boxes or shoe boxes and shipping boxes (Corrugated Recycling Process).
See also: single stream
Commodity: Fluorescent Light Tubes and Ballasts from Fluorescent Lighting
Vendor: Northeast Lamp Recycling, Inc.
Tons Recycled: 4.6 tons
Revenue or (Cost): ($4,485.89)
End Use: Following EPA regulations, NLR utilizes tri-phase technology that allows for lamp recycling at a rate of up to 5,000 lamps per hour. NLR separates lamps into four main components to be processed. First. Lamps are drawn into a trammel housing under negative air pressure (to prevent mercury releases) where they are crushed. End caps and insulator wires are separated from the rest of materials and collected. After they are tested for hazardous waste content, they are sent to a scrap metal yard. Glass is then “polished” and put on a conveyor belt to be placed in dumpsters. Under the Mass. DEP assessment process called a “Beneficial Use Determination” or BUD, the potential utility of the glass is analyzed. The glass may then be used for construction activities such as embedding pipes or daily cover at landfill facilities. It may also be placed directly as waste in a landfill if it cannot be used. NLR recycles mercury, which can present an environmental and health hazard if nor properly managed because it does not break down and can build up in the food chain and contaminate it. The calcium phosphate powder that is contaminated with mercury, as well as elemental mercury, are put directly in sealed containers. Finally, vapors that are released throughout this process are filtered through charcoal-activated filtration systems to keep air emissions below .05 mg/m. PCB (Polychlorinated bi-phenols) containing ballasts found in older fluorescent light fixture are separated and incinerated. The remaining metals are cleaned, categorized, baled, and sold to various smelters (Northeast Lamp Recycling, Inc).
Commodity: Electronics and Cathode Ray Tubes (CRT’s)
Vendor: PC Survivors of Massachusetts
Tons Recycled: 71.5
Revenue or (Cost): $1,736
End Use: PC Survivors of Massachusetts track all materials received using serial numbers, and sends stored media to undergo data destruction. Through Hard Drive destruction and Kill Disk Hard Drive Erasure, data is destroyed in a process that physically pulverizes and mangles media and hardware into unreadable pieces, which are then disassembled and separated so as to be stripped of valuable metals, a process called “urban mining.” In order to increase recycling for cathode ray tubes, which contain lead, the EPA has expanded CRT recycling standards, so that used and unbroken CRTs can be recycled into new CRT glass or smelted for lead (PC Data Destruction).
Commodity: Food Waste & Biodegradable Packaging (from food service operations)
Vendor: Martins Farm Composting
Tons Recycled: 1,533.1 tons
Revenue or (Cost): ($36)/ton or ($55,188)
End Use: UMass Amherst ships its food waste and associated compostable packaging to Martin Farm in Greenfield, Mass. Martin Farm employs windrow composting – an aerobic composting technique where a blend of various organic material is mixed in long narrow piles called windrows (FAO).
In order to aerate the compost, the windrows are turned periodically with a Scarab windrow turner. Turning the piles aerates the material and so controls the odors produced when compost piles go anaerobic. To further control potential odors, Martin Farm employs a specific recipe of copos inputs to help ensures the carbon-nitrogen ratio is optimal. They also apply an odor control formula to the piles. Martin also monitors the temperature and moisture levels of their windrows to ensure the growth of desirable microbes. In order to create a proper temperature range, the windrow piles must be “large enough to generate enough heat and maintain temperatures [but] small enough to allow oxygen flow to the windrow’s core” (EPA Sustainable Food Types). This process takes around 3 months to create a rich, dark compost affectionately named Black Gold. Martin’s Farm allows the compost to mature for another month or so and then the compost is screened. The farm screens out contaminant materials that did not break down properly such as wood chips, plastic or non-biodegradable materials - screening materials down to as small as 3/8 of an inch. Martin’s Farm then either stockpiles the compost (applies the compost to their farmland) or sells the compost. A majority of the compost is stockpiled.
During the composting process liquids are released called leachates. Martin Farm employs a squeegee mechanism in order to prevent the leachates from running into the ground-water. Martin’s Farm mixes the food waste it receives with leaves, manure, grass, cardboard, and paper in order to create compost. It takes about three months for the food waste to turn into a rich and dark compost. During this time, the pile temperatures are monitored. After the compost matures for another month, it is then screened and stockpiled or sold. The Office of Waste Management no longer sells compost to private consumers so as to allow the University Landscape Management Department greater ON-CAMPUS use of the material (Martin's Farm Compost).
Commodity: Greenhouse Waste
Vendor: University of Massachusetts Landscape Services
Tons Recycled: 38.8 tons
Revenue or (Cost): No out of pocket cost
Greenhouse wastes are added to leaf and yard waste which is composted by the UMass Landscaping Dept. in aerated windrows. The final screened product is applied to campus garden beds, or used to “top dress” campus lawns.
Commodity: High Grade Paper
Vendor: Northstar Pulp & Paper Company, Inc.
Tons Recycled: 45.9 tons
Revenue or (Cost): $18,840
End Use: High grade paper (HGP) refers to “letterhead, copier paper, envelopes, and printer and convertor scrap that has gone through the printing process” (EPA).
The source of most HGP is the confidential papers and documents which OWM collects from campus depts. and brings to the WTRF. These confidential documents are shredded in a powerful shredder and then accumulated in a 40 cy roll-off for shipment to Northstar Pulp & Paper in Springfield, MA. Northstar sends HGP to paper mills such as Erving Tissue (in Erving, MA), SCA Tissue, or Kruger. These paper mills pulp and deink the paper and use it to make tissue, paper towels, and napkins.
The pulping and deinking process downgrades the quality of paper so that it is only useable in the production of lower quality paper products such as tissues and napkins. These products cannot be recycled again.
Northstar, through its 60 employees, uses large-scale machinery to crush, grind, pulverize, and compact materials into 1,500 or 3,000 pound bales (or bags), at a rate of up to 60 tons of waste processed per hour. Northstar primarily deals with “run-around” scrap from plastic or paper manufacturers and finishers, as opposed to post-consumer scrap. These materials are then sold to third party paper mills for reuse. Paper is shipped primarily in trucks, though some is transported using rail shipping.
Vendors, such as paper mills including Erving Paper, which processes high grade sorted office paper 37, use the material for re-pulping, and turn it into products such as new paper, facial tissue, tissue paper, and toilet paper. Northstar estimates that it processes up to 150,000 tons of paper and plastic a year (Northstar).
Commodity: Leaves, Yard Waste, Animal Bedding
Vendor: UMass Landscape Services
Tons Recycled: 342 tons (Leaves/Yardwaste), 405 tons (Animal Bedding)
Revenue or (Cost): No out of pocket cost
End Use: Leaf and yard waste from campus landscaping activity is composted at the WRTF by the UMass Grounds Dept. in aerated windrows. The final screened product is applied to campus garden beds, or used to “top dress” campus lawns.
Organic wastes like animal bedding from the horse farm, and greenhouse waste, leaves, and yard waste from campus are composted at the WRTF. The WRTF employs window composting in which leaves, yard waste, and animal bedding are placed into long, narrow piles. The rows are turned regularly with a bucket loader in order to speed the composting process. The turning of the materials ensures that the piles are aerated and the proper temperature range is maintained. Once the piles are properly decomposed, the finished compost is screened. The compost is then used by Landscape Services for application in planting beds and lawns, and as mulch. See food waste for in-depth description of windrow composting.
Commodity: Light and Heavy Iron and Stainless Steel, Copper, Brass
Vendor: Joseph Freedman Co.
Tons Recycled: 416/376
Revenue or (Cost): $19,432
End Use: The Joseph Freedman Co. accepts non-ferrous metal (brass and copper) such as red metals, white metals and stainless steels, and aerospace alloys, and ferrous metals - including all grades of iron and steel. Ferrous metal is prepared for direct foundry or mill consumption The facility is equipped with waste oil recovery and spill-prevention systems.
Tons Recycled: 6.2
Revenue or (Cost): $0
End Use: K & W Materials and Recycling begins processing mattresses by splitting the bottoms open and “filaying” off the pillow coverings and fiber and sending them to landfills (ScientificAmerican). The metal contained in the mattresses, along with the wood contained in box springs, is sent unsorted and loose to Kane Scrap Iron & Metal in Chicoppee, MA, or wTe Corp in Greenfield, MA. The final use of the materials is determined by available markets, and many of the metals are shipped throughout the country and internationally. Some of the metals may end up in construction or automobile materials.
Commodity: Scrap Metal
Vendor: Wm. F. Sullivan
Tons Recycled: 416 tons (scrap metal)
Revenue or (Cost): $25,714
End Use: Sullivan Metals receives scrap metal (light and heavy iron/steel, copper, brass) from the UMass WRTF. The metal is sorted by type of material and then compacted into dense bales using the non-ferrous conveyor-fed baler. Non-ferrous metals (non-iron, non-magnetic) are sorted using a variety of techniques including forklifts, bobcats, and manual sorting. Ferrous metals (iron) are sorted using magnetized grapples. The metal is then baled and sold to steel mills throughout the Northeast where they are melted and formed into ingots (dense blocks of metal shaped so that they are easy to store) (Recycling Depot). Sullivan & Sons’ facility is finished in concrete with underground piping designed to control rainwater and waste fluids for the prevention of contaminant migration into the soil. The waste fluids and water are treated and disposed of in accordance with environmental regulations (Sullivan Metals).
Commodity: Single Stream Recyclables
Destination: Commonwealth of Mass. Springfield Materials Recovery Facility MRF
Facility Operator: Waste Management Inc.
Tons Recycled: 489
Revenue or (Cost): ($17,832) for hauling
MRF Processing & End Uses:
Bottles and cans, the most commonly recycled material next to paper, are recycled for the most part at a Materials Recovery Facility (MRF). Roll-offs containing single stream recyclables are brought to the MRF for sorting. At a MRF trucks dump or “tip” the materials onto a tipping floor and the items are moved onto a system of conveyor belts and sorters that group like items. The sorted recyclables are then baled and sent to recyclers that process the materials. Once processed, the materials may be used to manufacture new products (Recyclingworks).
Aluminum cans are recycled into new products including aluminum cans, rain gutters, window frames. Steel cans become new steel cans, bicycles, or steel beams (Recyclingworks).
Glass containers may be recycled at glass mills into new jars and bottles or they may be crushed and used for daily cover at landfills (Recyclingworks).
Plastic bottles are recycled into polyester fleece and carpeting. Some beverage manufacturers use small amounts of recycled plastic in their containers (Recyclingworks).
Cardboard found in single stream recycling is shipped to paper mills to manufacture new paper products. The material is inspected, pulped, rolled into sheets, corrugated, glued into new sheets, and cut into shape ready for the market. Recycled corrugated cardboard is often used in new packaging material and boxes (Recyclingworks).
Paper contained in the single stream mix is sorted using a combination of mechanical and manual systems. The resulting sorted paper is then baled and shipped to paper mills locally and abroad. At the mill, the paper is shredded into fine pieces and water is added, creating a slurry or pulp mixture. This mixture is then applied to a screen-like surface and is mechanically dried to make new paper products. During the process, the fibers in paper are broken down. High grade office paper can be recycled into new copy and printer paper. After numerous cycles through the recycling process, the material may become newspaper or magazine stock. Newspaper can be de-inked and turned into new newspaper which can eventually become bathroom tissue or paper towels, which ends its recycling lifespan. This material can then be composted.
Mixed office paper, which is a variety of low grade paper, can be recycled into products such as facial tissue, toilet paper, paper towels, napkins, egg cartons, paper grocery bags, and paperboard, which is commonly used to make game boards and book covers. Much of the recycled paper from Massachusetts has been used to make the hard covers on the Harry Potter books (Recyclingworks).
Vendor: J.P. Routhier & Sons
Tons Recycled: 11
Revenue or (Cost): ($10,772)
End Use: Waste to energy plants in Masschusetts for combustion and production of usable energy
Tire derived fuel is a major end use for scrap tires. TDF is the result of shredding tires and then removing steel components. Facilities such as cement kilns, paper mills, and electric utilities use TDF as fuel to improve boiler efficiency, lower air emissions, and decrease costs. Nationally, more than half of the 300 million tires generated each year are burned in TDF facilities. TDF is an important fuel source due to the high heat value, low moisture, and compact nature of tires. As a fuel source, tires also have a higher energy value than their coal, petroleum, and wood competitors.
Tires can be processed into fuel at different sizes depending on the combustion system. Cement kilns can process whole tires, while others require tires to be shredded to smaller sizes. The first step of processing tires to produce TDF is the chipping and shredding and metal removal process. Tires that are not fed into a shredder whole have the beads removed and are then shredded to produce 2 inch pieces, which then go through screening and magnetic separation equipment to remove steel. The 2 inch pieces fall through a screen, and the oversized chips are sent back to the shredder. Though a large amount of rubber is lost in the wire removal system, additional shredding after wire removal can mitigate this. If the facility requires smaller than 2 inch chips, such as crumb rubber, further size reduction and separation of fiber and metal is carried out before classification, screening, and cleaning of material (Scrap Tire News).
The University expects to soon begin shipping UMass’s scrap tires for combustion at the Covanta Waste to Energy Plant (Agawam) for combustion and production of usable energy.
Tons Recycled: n/a
Revenue or Cost: $0
End Use: The OWM and the UMass Environmental Health and Safety set aside surplus campus paint for re-use. The remaining paint is accumulated in gaylord bins which are used to store latex paint, oil-based paint, flammable paint, and coatings. Triumvirate picks up the full gaylords from the WTRF. The latex paint is sent to a landfill, while the oil based paint is sent to an incinerator. For every gaylord of oil-based paint shipped, there are approximately two gaylords of latex paint shipped (Triumvirate).
Commodity: Toner Cartridges
Vendor: pc Laser Services
Tons Recycled: 6
Revenue or (Cost): $2,439
End Use: Expert Laser Services is a printer company. They accept old toner cartridges that are then recycled and remanufactured into new toner cartridges that can be sold (Expert Laser)
Tons Recycled: 171
Revenue or (Cost): ($1,788)
End Use: Waste to Energy
Republic Services (Allied Waste) disposes of wood with general solid waste. However, AW picks up wood from the WRTF and hauls it to Covanta to avoid adding this wood to landfills. Covanta is one of the largest developers of waste-to-energy technology in the United States. Incinerating wood waste to use as fuel is an alternative to putting materials in landfills. Burning wood waste produces more sulfur oxide and nitrogen emissions than natural gas, but less than coal, and, unlike fossil fuels, the carbon found in wood is considered to be a natural component of the carbon cycle. One of the aspects of Covanta plants are the air quality controls, which aid in the efficient combustion of the boiler which can reach temperatures as high as 2,000 degrees Fahrenheit. Ammonia is sprayed onto materials to be burned, and air is recirculated inside the boiler, which help to reduce the formation of nitrogen oxides. After combustion is carried out, carbon is sprayed onto flue gas in order to segregate mercury, after which a “slurry of lime and water” is introduced to neutralize sulfur oxides. Then, 20-foot-by-6-foot bags collect particulates as the flue gas passes through. Remaining ash is sent to on-site landfills, while recyclable metals such as iron and aluminum are collected automatically (Covanta).