Visualizing Environmental Science

PROCESS DIAGRAM

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Crane feeds waste

into furnace.

2

Enclosed receiving

area

1

Clean

smoke

6

Smoke (hot air

and fire ash)

3

4

Waste

bunker

Path of smoke

Wastes to be treated

or disposed of

Ash conveyor

Bottom

ash

Polluted

water

Treated

and reused

Hazardous

waste landfill

Fly ash

Electrostatic

precipitator

Scrubber

Steam piped to generate

electricity or warm buildings.

5

Boiler

Furnace

Hazardous

waste landfill

Pollution control devices

trap dangerous and

dirty emissions.

Why should bottom ash

and flyash be disposed of in a hazardous

waste landfill?

Think Critically

large and designed to recover the energy produced from
combustion (ˆ}ÕÀiÊ £È°È). Modular incinerators are
smaller incinerators that burn all solid waste. Assembled
at factories, they are less expensive to build. Refuse-
derived fuel incinerators burn the combustible portion
of solid waste. First, noncombustible wastes, such as glass
and metals, are removed by machine or by hand. The
remaining solid waste, including plastic and paper, is
shredded or shaped into pellets and burned.

Composting Yard waste, such as grass clippings,
branches, and leaves, is a substantial component of
municipal solid waste (see Figure 16.2). As space in sani-
tary landfills becomes more limited, other ways to dis-
pose of yard waste are being implemented.
One of the best recovery methods for yard waste is to
convert it into soil conditioners such as compost or mulch
(ˆ}ÕÀiʣȰÇ). In 2010, about 58 percent of yard wastes in
the United States were composted or otherwise recycled.

Modern incinerators have pollution-control devices such as scrubbers and
electrostatic precipitators to trap dangerous and dirty emissions.

Yard waste separated from municipal waste

U ˆ}ÕÀiʣȰÇÊ

Many communities either encourage or require that yard waste

be separated from other waste so that it can be composted and

reused.

✓✓THE PLANNER

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