Shredding plant operators and many other secondary commodities processors attempt to recycle the highest percentage of inbound material they receive. Best intentions alone, however, cannot create a market for certain fractions. That is one reason why several associations are working with the European Commission’s Joint Research Centre on the Best Available Techniques (BAT) Reference Document for Waste Treatment.
The BAT document, which is still in the working draft stage, addresses many aspects of waste and recycling plant operation, including air emissions, groundwater treatment and odor monitoring.
The creators of the document say its purpose is to identify “the key environmental issues for the waste treatment sector” and then identify, examine and select “the best available techniques (BAT), their associated emission levels (and other environmental performance levels) and the associated monitoring” techniques to help ensure these treatments are put in place.
CHAPTER AND VERSE
Within the overall BAT document, with an initial draft running some 1,030 pages, Section One of Chapter Three is of particular interest to operators and to prospective operators of metal shredding plants in the EU.
The “Mechanical Treatment in Shredders of Metal Waste” chapter may start out on a disappointing note in that most metals recyclers would prefer not to hear of their valuable feedstock referred to as “waste.”
Beneath the headline, however, the document’s authors quickly point out that in metal shredding, “The main output is quality steel scrap with a high density, high degree of purity and predominantly homogeneous size. This shredded steel scrap can be used directly in metal works to produce steel.”
While another acknowledged fraction is nonferrous metallic products, the BAT document also notes the shredder residue fraction. Beyond grappling with what to do with this residue, the BAT additionally notes that shredder plants produce dusts and emissions that must be contained and properly handled.
As do metals recyclers, the BAT (which was created with input from Bureau of International Recycling [BIR] member companies and staff members) authors identify the nonmetallic, or shredder light fraction (SLF), stream as the one most in need of waste diversion or waste processing measures.
The document identifies the SLF fraction as consisting of 10% to 20% of the material that has been shredded, including:
- screws, nuts, aluminium pieces, foils, rust and other small pieces of metal;
- textiles (such as auto seat covers);
- foamed plastics (including cushioning for seats);
- plastics and plastic sheeting;
- mineral components (dirt and rocks that are attached to vehicles’ wheelhouses and undercarriages); and
- wood and elastomers.
The BAT notes that shredder plant operators, or allied companies they select, voluntarily treat the SLF fraction to recover any remaining metals. Several postshredder steps and technologies are portrayed within the document, such as:
- manual picking and sorting;
- mechanical screening and sifting;
- air and density separation;
- magnetic eddy current separation;
- induction sorting systems;
- optical, X-ray and electrostatic sorting systems; and
- sink-float tanks.
After these steps have been completed, of course, a sizable nonmetallic fraction remains. Of that, the BAT states, “Increasingly today (2015), the nonmetallic materials are being further refined in order to extract recyclable plastics, aggregates and solid recovered fuel while minimising the residual waste to landfill.”
CLEARING THE AIR
Additional residual streams are created in small, barely visible amounts through particles and dust that are created when metals are moved, dropped and (most noticeably) shredded.
“Emissions to air from a shredder plant are likely to be dust-including metallic particles, VOCs (volatile organic compounds), water vapour or, occasionally under other-than-normal operating conditions: smoke, dust and potentially dioxins in the event of a deflagration,” according to the BAT.
The document outlines several steps that can be taken (and that are addressed through existing EU regulations) concerning lead, mercury, PCBs (polychlorinated biphenyls) and dioxins.
The BAT additionally notes that a shredder “has to be equipped with dust collection systems compatible with deflagrations, comprising cyclones and Venturi scrubbers.”
The shredding and material handling processes are day-to-day sources of dust and particle emissions, but the BAT also includes a section on what it calls deflagrations—small explosions and incidents of combustion.
“Deflagrations can be caused by residual fuel left in end-of-life vehicles,” the document states. “Analysis of the amount of dust that is emitted during a deflagration is not known [and] the number of deflagrations varies from one shredder site to another,” the BAT authors add. “An efficiently managed shredder has less than one deflagration per year.”
AVOIDING A STORM
Shredder plant operators also can find guidance on stormwater management in the BAT, including an overview of the most common techniques.
“Rainwater runoff is collected and drained, as is any water released by processes on-site, including water for dust suppression or process water releases. Surface water runoff also includes those waters that percolate through the stored waste input and output,” the BAT says.
The BAT document describes the reliance of shredder yards on paved surfaces to help properly manage stormwater on-site, stating, “Plants have sealed surfaces composed of concrete paving, which drain via grit traps or settlement tanks to oil/water interceptors and then to a discharge point.”
The document continues, “The objectives are to reduce the quantity of any water to be discharged from the plant and to reduce the degree to which this water is exposed to potential contaminants. Where not reused, waste water is preferably discharged to a sewer. Only where locations or other engineering constraints prevent connection to a sewer should the discharge be connected to controlled water. Connection of discharge to controlled water may require additional treatment to meet the consent limits.”
The sections on air and water emissions provide results of studies that recyclers and their associations have conducted voluntarily to determine problem areas and to what extent such problems are real or falsely perceived.
As staff members and volunteer officers of the Brussels-based BIR and other recycling associations have noted, it most often behooves recyclers to cooperate in crafting documents such as the BAT. Without their input, regulators are more likely to take actions that do something “to” recyclers rather than do something “for” them, these organisations say.