POWER September 2016 - 66

FUELS
Waste to Energy: An Opportunity Too
Good to Waste, or a Waste of Time?
Inexpensive natural gas, increased renewable energy utilization, and evertightening
environmental regulations have limited the use of waste feedstocks
for power generation. But while often dismissed out of hand, with
proper planning and understanding of the market, power producers can
realize benefits from waste-to-energy projects.
Una Nowling, PE
I
t was a tropically hot day at the plant, and
it wasn't even 9 a.m. As I rode up to the
power building in an F-350 packed with
five other engineers, the driver, sweating so
much he looked like he'd just come back
from a few laps across the Mississippi, told
me, " You better drink a lot of water working
around the boiler, ma'am, or you're gonna
die. " So, needless to say, I was dreading the
day to come.
But upon entering the ice-box chill of the
control room to start my data collection, I
stopped and laughed out loud at what was on
the wall before me. It was a novelty Frenchdesign
menu-a blackboard with a wooden
pig on one side and a caricature of a French
chef with puffy hat on the other. Chalked in
rather elegant script was the message shown
in Figure 1.
It was my first experience working at a plant
that converted waste to energy (WTE), and during
the project I learned much about the challenges
of utilizing what are commonly called
" waste fuels. " Definitions vary, but a waste fuel
is typically a post-production or post-consumer
substance that has no better purpose than to be
used for energy production.
Waste fuels are sometimes called " opportunity
fuels, " because they may offer a
preferential price, give direct benefits to the
power station, or provide indirect or co-benefits
from their use. In the example I've given
in Figure 1, the sawdust was a no-cost fuel
that provided a small carbon emissions benefit,
the sewage sludge reduced the landfill
needs of the city's treatment plant, the tires
were cheap and high-energy, and the municipal
solid waste (MSW) helped the city both
utilize improved recycling and extend its
landfill life.
Highly Variable Fuel Quality
Waste fuels (Figure 2) represent an energy
source with perhaps the most highly variable
quality of any fuel known. Some of the most
common waste fuel types include the following:
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POWER | September 2016
■ Municipal solid waste is the most variable
type of waste fuel, consisting of everything
from banana peels to ball bearings. It may
also contain varying amounts of industrial
and even hazardous waste, depending
upon the landfill location and local regulations.
Waste screening and segregation is
critical for the success of WTE projects
using this fuel source (Figure 3).
■ Post-production waste often is more uniform
in quality, due to more restrictive
sourcing. Examples of this include saw1.
Plat du jour. Source: POWER and Una Nowling
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POWER September 2016

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