Air Force develops mobile waste-to-energy system
Combustible waste lowers fuel usage and costs
Researchers with the United States Air Force are
developing a transportable waste-to-energy system
to produce electricity at forward military operations.
A prototype, mounted on a 48-foot flatbed semi-trailer,
is being tested at Tyndall Air Force Base in Florida
by the Air Force Research Laboratory Materials and
Manufacturing Directorate, which conducts programs
that enhance readiness, deployment, fire protection,
peacetime training, and crash and rescue operations.
The transportable waste-to-energy system could reduce
the amount of fossil fuel used at each forward military
operation and could also be used at domestic bases,
according to Walt Waltz, the leader of the robotics
group at the directorate.
By consuming combustible waste the system “will
reduce the need for outside contractors to dispose
of waste created at deployed military locations,”
Research on the transportable waste-to-energy started
in 2004. The system consists of two stages, a furnace
and an energy recovery unit. Researchers have completed
the first stage, referred to as a transportable
furnace system. The system includes a 9 foot tall
furnace and an 8 foot tall shredder. The flatbed
semi-trailer for the system also holds two hoppers
for the shredded material and two air blowers.
The furnace needs to be preheated with a fuel burner.
After 30 minutes the burner is removed. No additional
liquid fuel is needed besides for preheating the
Solid waste items are first dropped into a hopper
on the shredder. The solid waste material then is
shredded down to less than a half of an inch in
all three dimensions.
The material falls from the shredder into a box,
where it is vacuumed through a hose into the system’s
second hopper. The waste material next drops through
a rotary feeder into a pipe with air blowing through
it and flows into the furnace and is turned into
fuel. During testing, the prototype has operated
continuously for up to six hours.
Researchers at the directorate are now working on
the second stage of the transportable waste-to-energy
system, known as the energy recovery component.
This component will generate steam using the heat
released from the burning waste.
The Air Force intends for the steam to eventually
be used for heating, air conditioning and electricity
generation at forward operating bases or rural domestic
bases. The system is designed to burn up to 500
pounds of waste per hour.
Consultant Nick Patz, president of Ceres Associates
in Benicia, California, expects to see more transportable
waste-to-energy systems in the next few years.
Patz is working with Balboa Pacific Corp., in Del
Mar, California, on a portable system that was originally
designed for the hazardous and medical waste markets.
“As tipping fees and energy costs have increased
over the past several years the system is now profitable
for municipal solid waste,” Patz says, adding that
the portable method would also work well for cleaning
up after natural or manmade disasters.
The transportable unit designed by Balboa Pacific,
which fits on two flat-bed trailers, has the potential
to consume approximately 50 tons of solid waste
Patz says it is possible to set up the waste-destruction
technology in as little as eight hours. The system
can be set up and start producing energy within
Transportable systems to incinerate hazardous waste
are more common than waste-to-energy systems, says
Tom Brown, project manager at the Kansas City, Missouri-based
environmental consulting firm Burns & McDonnell
Engineering Co., Inc. “Waste-to-energy was generally
viewed as an unnecessary complication,” he says.
But with the rising cost of energy and a growing
focus on renewable energy, this is changing. “Transportable
waste-to-energy offers the benefits of waste-to-energy
with the added benefit that the facility is not
fixed and can therefore travel,” Brown says.
A military unit using a transportable waste-to-energy
system, for example, could carry less conventional
fuel for electricity generations in remote locations.
The unit could instead carry additional quantities
of other types of critical supplies, Brown says.
There are disadvantages to portable generation,
however. Generation temperatures and pressures are
limited with transportable waste-to-energy systems,
Brown says, resulting in low efficiency in conversion
to electricity and low energy outputs.
“In general, small-scale, waste-to-energy systems
that generate electricity are not cost effective
when compared to other methods of waste disposal
or with other methods of electric energy generation,”
Brown says, noting that emerging technologies, such
as plasma arch, pyrolysis or anaerobic digestion
may reverse the economic equations.