FOUNDRY SAND WASTE
Foundries create metal castings for use in the automotive,
art, construction, agriculture, and mining industries. In this
process, molten metal is poured into a
mold, usually made from sand or ceramics.
As castings are created, the sand has to be removed and
replaced due to abrasion from the high heat and mechanical
stress. The sand that is removed is either recycled or disposed.
Green sand, the most commonly used in metal casting, is made
up of silica sand or lake sand. Foundries may also use
chemically bonded sand, which use a hardening component.
Millions of tons of foundry sand waste are generated each
year, with only a small percentage of this waste being recycled.
While a low percentage of this waste may be hazardous,
most of the foundry sand waste could be recycled or reused for a
number of other purposes.
FOUNDRY SAND RECYCLING
Some state and local agencies regulate the beneficial uses of
recycled foundry sand.
The following uses are common throughout the country.
1.
Use in other
Raw Materials:
Foundry sand can be used in the manufacturing of other raw
materials, such as asphalt, bricks, cement, grout, and concrete
blocks.
2.
Structural
Fill: Support bases or foundations for roadways, buildings, and
parking lots can be constructed using foundry sand.
3.
Soil:
Foundry sand can be mixed to produce horticultural soils,
potting soils, turf mixes, and compost.
4.
Landfills:
Foundry sand can cover a landfill surface or be used as a
backfill for landfill drainage systems.
5.
Pipe Bedding:
Trenches used for storm drains or sanitation sewers can
utilize foundry sand as backfill.
CHALLENGES &
CONSIDERATIONS
1.
Though
facilities may dismiss the beneficial use of foundry sand due to
possible toxicity, many states encourage the recycling of
foundry sand.
2.
Many beneficial
uses of foundry sand require an additional crushing or screening
process, in order to ensure usability.
Foundries that use a proactive screening system increase
the likelihood that the sand will be reused and recycled.
3.
The
availability of a close recycling processor is often a deterrent
for foundries. Foundries can consider collaborating with other
foundries to transport sand waste for recycling.
4.
Some uses of
foundry sand require mass amounts not feasibility generated by
one foundry.
Collaboration or a proper storage system could assist in usable
quantities of recyclable sand.
5.
State and local
agencies may require testing and sampling of foundry sand before
it is approved for reuse or recycling.
6.
Consideration
of the binders used in foundry sand should be noted.
Depending on the process and type of binders used,
organic contaminants may develop under certain high heat
conditions.
7.
Some state and
local agencies have strict requirements on the use of foundry
sand directly on land.
Processors should consider this when considering foundry
sand as a composting or soil additive.
8.
Despite its
proven recyclable value, another barrier to reusing foundry sand
is its dark brown or black coloration.
This aversion is paired with some end users’ resistance
to utilizing industrial by-products. Possible end users,
including construction companies and local government agencies,
should consider the numerous case studies and engineering
reports, which confirm foundry sand’s comparable use in building
and road projects. Focus can be placed on these types of
projects, in which the recycled sand is covered or rarely seen.
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