Commercialized plasma gasification of solid waste offered
by S4 Energy
by Mike Breslin
One need not be a physicist or chemical engineer to understand
what plasma gasification can mean to the future of
solid waste. This intriguing technology for converting
solid waste into chemicals and energy has been in the
demo phase since the mid-80s. But in May it took a
major step forward towards commercial deployment when
Waste Management (WM) and InEnTec announced a joint
venture to form S4 Energy Solutions. S4 plans to build
plasma gasification plants and WM has the nationwide
infrastructure to deliver a smooth flow of segregated
WM, North America’s largest waste management company,
is embracing plasma gasification for the first generation
of commercial facilities. “We are choosing some sites
right now and have a few identified. Short term, we
are looking at three to five different locations. Long
term we are going to be looking at the majority of
the 50 states. We expect to announce our first plant
in three to six months. At that time we will expect
to have already started construction. We are beginning
the permitting process in a few cases and doing prep
work for those facilities,” stated Jeff Surma, president
and CEO of S4.
“The point lost on a lot of people is that this technology
has been around for a while. From a chemistry perspective
it works,” said Joe Vaillancourt, senior vice president
of S4 Energy Solutions. “What no one had done in the
past is put together a model where the collection of
waste can be done efficiently, routed and pre-processed
efficiently. This collaboration allows the technology
to marry a very large WM infrastructure that from an
economic standpoint allows it to work commercially.”
This is how InEnTec’s Plasma Enhanced Melter (PEM) technology
works. Solid waste is fed into an oxygen deprived chamber
and heated to temperatures reaching 10,000 degrees Fahrenheit
using an electricity-conducting plasma arc gas. Intense
heat rearranges the molecules and transforms organic,
carbon-based material into a synthesis gas, called syngas.
Syngas is then converted into fuels such as ethanol and
diesel, and into hydrogen and methanol that can be substituted
for natural gas to make heat or electricity.
Recovered pure hydrogen can also be sold to commercial
customers or used for fuel cell technology. In a secondary
stage of the process, inorganic materials like glass
and rock are drawn off as slag which can be incorporated
into a number of construction materials.
The PEM process has been field proven in a number of
small pilot plants, including a plant in Taiwan for the
past four years that treats medical wastes and NiCad
batteries. InEnTec also sold a system to Kawasaki in
Japan, which was used to process hazardous waste and
asbestos containing waste materials. Kawasaki continues
to develop opportunities in Japan for the PEM technology.
For the past nine months, InEnTec’s 25 ton per day plant
in Richland, Washington has been running tests on various
solid waste feedstocks for analytical purposes. “Once
you have the analysis of syngas relative to waste composition
and energy content you can calculate what you can do
with the various energy off-take options,” said Surma.
The syngas produced from the Richland plant is not actually
used for chemicals or energy, rather disposed though
an EPA approved combustion process.
Permitting and emissions do not seem to pose problems
for this type of plasma gasification configuration. “We
have actually permitted a number of these plants. Even
though they were small we did not have any permitting
issues,” Surma said.
Beside the Richland plant, InEnTech has had five other
United States permits issued. Another in Washington to
process radioactive and toxic wastes, one in California
and another in Hawaii for medical wastes and two in Nevada,
one for a municipal solid waste system and the other
for medical waste. Permits usually take from 90 to 180
days. The direct emissions from the PEM system itself
are negligible. Primary emissions from the PEM system
would be those of the generator itself if the syngas
was used to generate electricity, in which case all emissions
would comply with EPA standards,” Surma claimed.
The initial S4 plants will handle 25 tons per day and
will be co-located at landfills or recycling centers,
or as independent facilities close to feedstock supplies.
In the near term, S4 will concentrate on processing high-value,
high tipping fee materials such as medical waste and
other commercial segmented waste streams.
Short term, medical waste will be S4’s primary focus.
Long term, as they prove out the technology, plants will
be scaled up to 125 tons per day, which will be the common
size for a plant. These will be deployed to sites as
single or parallel units depending on the nature of feedstocks.
Once S4 reaches the 125 ton scale they will be able to
handle larger streams from industrial sites such as auto
shredder residue. Eventually, S4 hopes to prove out the
technology to process general residential waste.
“Whether we are talking about the very small 25 ton per
day, or even the larger plants, they are still of the
size that allows us the flexibility to site them as close
to waste generation points as possible. So even with
a larger facility, it is still significantly smaller
than other alternatives,” Vaillancourt noted. The 25
ton per day plant has a relatively small footprint, about
7,500 square feet and can be run 24/7/365 with a staff
of 12 to 15, even fewer if co-located with another facility
that has maintenance and operations staff. The PEM process
itself can be operated by as little as two people.
InEnTec’s Richland pre-commercial plant provides insight
into material segregation before entering the PEM process.
Municipal solid waste was received from the City of Richland
landfill in raw form. Prior to a course shredding, large
ferrous and non-ferrous metals, aluminum cans and large
rocks were removed. Rocks, glass and other inorganic
materials have no recovered energy value and result in
slag. While the demo plant has run a number of different
feed streams, it has been running municipal residential
waste to understand how the technology performs. It has
also processed rubber tires, wood waste, auto shredder
residue and industrial non-hazardous solid waste streams
like cardboard and plastic. The plant has not run medical
waste because InEnTec has extensive experience with this
material at its other facilities.
When it comes to recovering energy from waste, WM is
not putting all its eggs in one basket. They are, after
all a leading developer of waste-to-energy incineration
and landfill gas-to-energy facilities in the United States.
As to the economics of plasma gasification, Joe Vaillancourt
characterized it this way: “Instead of looking at a thumbnail
on the cost of energy production, what we are proposing
is a service where our pricing is competitive to market,
both on the disposal and on the energy side. Where we
have customers who have a need, we can come in very competitively
and provide them a disposal way of creating energy.”
Since the plasma arc process uses large amounts of electricity
and uses some natural gas to heat vessels, the question
is what is cost of energy consumed to the resulting value
of the energy and products produced? It largely depends
on material input. Waste streams heavily laden with plastics,
cardboard or rubber will naturally have a higher BTU
value. “Generally between the variability of the incoming
waste and efficiency of conversion to different types
of energy, the system uses 30 to 50 percent and we have
a 50 to 70 percent net energy positive conversion. In
addition to the energy recovered, we are also subsidized
by tipping fees on the high value materials,” said Surma.
“Our S4 initiative is being driven by a number of factors.
Certainly the cost of energy has a significant impact
on why people are starting to look at alternatives for
the conversion of what used to be considered waste stream
with no energy value to a resource that does have energy
value. That’s primarily the factor for looking at conversion
technology like this.”
An interesting aspect of PEM technology is that it allows
S4 to mix a variety of wastes while giving WM the flexibility
to deliver the types of waste mixtures as the plants
need them. When co-located at either a landfill or recycling
center or at a customer facility there are several segmented
streams that could be combined efficiently. “It’s a technology
that we feel is very flexible and adaptable to customers’
particular economical, environmental, and logistical
needs. These units can be put close to the generator.
They will become especially cost effective for customers
who have high transportation costs and high tipping fees.”
Vaillancourt pointed out.