BURN POWER
From corn to nuts,
AURI chemist tests biomass for combustible fuel
By
Cindy Green
An oil field may be growing
in our own backyards. Not just the corn that is turned to
ethanol or soybeans to biodiesel, but the Kentucky
bluegrass, peat, alfalfa - even hazelnuts.
Rose Patzer, an AURI chemist in Marshall, has been
evaluating various feedstocks that have potential to be
burned as combustible fuels. The studies are often requested
by farmers or grower groups who want to capitalize on the
increased interest in renewable fuels.
“Since 9-11, we have seen natural gas prices rising and home
heating costs going up,” Patzer says. With concerns about
Iraq and homeland security, renewable fuels interest has
“definitely grown. ¡ We saw Congress waning before, now
it’s important.”
“Right here in Minnesota, we have a lot of firsts in the
renewable fuels area - as we saw in the biodiesel
legislation passed.” For a chemist working on biofuels,
“it’s really helpful to be in this state.”
Stoking
the fire
Since Patzer was hired in 1996, her AURI work has primarily
been on biodiesel. However, in the past several years, she
has tested a range of feedstocks that could be burned in
home or industrial furnaces, such as corn, straw, soybean
hulls and aspen.
This fall, Patzer conducted tests for growers of two rather
uncommon feedstocks: hazelnuts and grasses.
Badgersett Research Corporation of Canton, Minn. had already
received some AURI assistance for developing hazelnut
hybrids and inquired about the energy potential of spoiled
nuts that cannot be marketed as food. Hazelnuts’ high-oil
content made it a good candidate for combustion, Patzer
said. The other advantage is “the hard shell will protect it
from spoilage longer than other bio materials.”
About the same time, RL Growers, a Roseau and Lake of the
Woods area cooperative, asked AURI to asses the energy value
of various grass fibers -Kentucky bluegrass, alfalfa stems,
red canary straw grass, red-top straw, rye-grass straw,
timothy-grass straw and peat - to potentially build markets
for the foliage.
Both the hazelnut and grass evaluations were completed in
November with good results. However, more cost studies need
to be done, factoring in the raw material’s market value and
storage and handling costs. To get better density for the
next test, grasses will be dried and pelleted by Al Doering
in AURI’s Waseca coproducts plant.
Energy
factors
When AURI tests any biomass for its energy value,
researchers evaluate five factors: Btu content, burn
efficiency, moisture, ash and fat content. Samples are sent
through a grinder to generate a homogeneous mixture before
they are burned in a test furnace.
 The
most important consideration is Btu or British Thermal Units
per pound of material burned. Most energy sources are
evaluated by cost per million Btu. “We also have to factor
in efficiency,” Patzer says. “Some biomass materials burn
more to completion. And like home furnaces, some stoves are
designed for materials that burn more efficiently.”
Natural gas is about 90-percent efficient, while renewable
fuels are generally 70-percent efficient. Still, plugging
these efficiencies into cost calculations, natural gas is
$15.63 per million Btu and propane is $17.90. Shell corn,
calculated at $2.10 per bushel, costs only $7.74 per million
Btu, even at 70-percent burn efficiency.
Other important factors include moisture, which “assists
mold growth, especially in fibrous materials,” Patzer says.
“If a sample has high-moisture content, it will most likely
not have a long shelf life.” Also, water adds weight and
mass, but since it vaporizes rather than burns, it
“negatively affects the energy content,” Patzer says.
High-moisture biomaterials have to be dried and often
pelleted, which increases cost.
Another consideration is ash - the residual that remains
after burning. “Generally, a sample with high levels of
residual ash will not be a good candidate for combustible
fuels by itself because of disposal and handling issues,”
Patzer says. “An exception is when the ash is high in
minerals such as potassium or phosphorus ¡ that has a
potential use in fertilizers.” A high-fat content can be
advantageous because fats generally burn completely, without
leaving material behind.
The only factor AURI doesn’t test in its Marshall lab is
sulfur emissions. “If all other results are good, we will
pay for outside testing,” Patzer says.
Nuts and
grass meet first tests
Results of the hazelnuts combustion study show it yields
approximately 9,000 Btu per pound, which is higher than corn
at almost 7,000 Btu per pound and aspen at about 7,500. “The
ash content was low - about 1.5 percent by weight, and the
fat averages about 15 percent” - a good result, Patzer says.
“Moisture is about 9 percent, which is normal for biomass
material. Corn is about 13 percent moisture, and wheat
around 10 to 12 percent.”
Grass fiber varied by variety but in general was about 7,000
Btu per pound. “Moisture averaged 6 to 7 percent, ash varied
from 4 to 10 percent, and fat is too negligible to test.”
However, the average cost per million Btu, which AURI has
calculated for other biomaterials, couldn’t be assessed for
grasses or hazelnuts “because we don’t have enough
information about their industrial market values - they are
new markets,” Patzer says.
An issue with both alternative crops is “we need to have a
steady source of materials. If it’s a rare material, we
might be able to blend it with one that is more abundant,”
Patzer says.
Price
prevails
“The bottom line is biobased products as fuels can’t be
successful unless they can compete in the market.”
Availability, performance standards and cost will determine
competitiveness, Patzer says.
Over the past 20 years, she says. “when the price of fuel is
high, there is a regenerated interest in renewables. When
fuel prices level off, interest tapers off.”
“The state of the economy is a driving force for renewable
fuels.”
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