Woody Biomass Background
Some History
• 1970’s energy crisis results in government
subsidies and research
• 1978 Public Utilities Regulatory Policy Act
(utilities must buy energy from other
producers)
• During 1980’s, 6,300 megawatts of new
wood fired capacity added (from 200
megawatts in late 1970’s)
And then…
• 15 plants in CA alone are bought out and
closed by utilities (to reduce costs
associated with buying their power;
Bergman and Zerbe 2005)
• During the 1990’s not many new plants
are built
• It is believed that this is due to limited tax
credits, increased conventional power
capacity and overall low fuel costs
Now
• Resurge in interest in biomass
• Costs of energy is increasing
• At the same time forest fires are
increasing and forest fuels reduction
needs have reached epidemic levels in
some parts of the country
• Great public interest in renewable energy
• Public concern about CO2 etc.
US energy use
US Energy Use (Scary Numbers)
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About 100 Quads per year (DOE 2000)
A quad is a quadrillion BTU’s
100,000,000,000,000,000 BTU’s is US use
100,000,000,000 MMBTU’s
US Energy Use (Scary Numbers)
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•
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About 100 Quads per year (DOE 2000)
A quad is a quadrillion BTU’s
100,000,000,000,000,000 BTU’s is US use
100,000,000,000 MMBTU’s
• Roughly the energy in 5,882,352,941
cords of aspen (just for comparison)
• MN cut less than 3,000,000 cords of
pulpwood in 2001
We will not be replacing all energy
consumption with biomass, but it
can be part of the picture
What is Feasible
• About a 30% replacement of energy needs
using ag residue/products and forest
residue (Perlack et al. 2005)
• Total forestland unutilized residue at this
point (368 million dry tons)
• Ag land (998 million dry tons) this is based
on several changes that we will not
discuss
Mike Math (obviously sort of gross
measurements)
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13.8 mmbtu per oven dry ton
368 million dry tons in US of wood residue
5,078,400,000,000,000 btu
About 5 quads in all wood residue in US
(about 5% of current use)
Outline
1. Benefits of wood
2. Problems
3. Potential users
1. Benefits of Wood
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Domestic and LOCAL source
Renewable and carbon neutral (?)
Low heavy metal emissions
Extremely low sulfur dioxide emissions
Low ash with good reuse potential
Benefits of Wood
• Domestic and LOCAL source
– MN imports most of its energy (no coal, oil or gas
deposits) resulting in large amounts of money
leaving the state
– The US has a low level of self-sufficiency in
energy production
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•
•
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Renewable and carbon neutral (?)
Low heavy metal emissions
Extremely low sulfur dioxide emissions
Low ash with good reuse potential
Benefits of Wood
• Domestic and LOCAL source
• Renewable and carbon neutral (?)
– Generally, wood is a renewable resource if the site
is not degraded by the harvest
– Wood uses CO2 to grow and harvest removes
less CO2 than is stored on the site, generally
carbon used equals or exceeds carbon harvested
• Low heavy metal emissions
• Extremely low sulfur dioxide emissions
• Low ash with good reuse potential
Benefits of Wood
• Domestic and LOCAL source
• Renewable and carbon neutral (?)
• Low heavy metal emissions
– Mercury levels are very low in wood
– Other heavy metals are low
– Land application of ash is possible and
common
• Extremely low sulfur dioxide emissions
• Low ash with good reuse potential
Benefits of Wood
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•
•
•
Domestic and LOCAL source
Renewable and carbon neutral (?)
Low heavy metal emissions
Extremely low sulfur dioxide emissions
– Generally there are very low levels of sulfur in
wood
– Low sulfur coal is generally more expensive than
high sulfur coal
– Scrubbing to reduce sulfur emissions is
expensive
• Low ash with good reuse potential
Benefits of Wood
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•
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•
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Domestic and LOCAL source
Renewable and carbon neutral (?)
Low heavy metal emissions
Extremely low sulfur dioxide emissions
Low ash with good reuse potential
– Wood with bark is usually less than 2 % ash and wood itself is
less than 1 %
– Wyoming coal from Powder River Basin (an example) is 5%
– This results is 2-5 times as much ash
– While both fly ash (free-$40 per ton) and bottom ash (free to $6
per ton) have markets, their disposal (particularly bottom ash) is
usually not a cashflow, it is usually a cost
Problems
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Collection
Freight
Storage
Burning
Problems
• Collection
– Existing concentrated sources already used
– Dispersed sources require new technology or
different operation of equipment while
harvesting
• Freight
• Storage
• Burning
Problems
• Collection
• Freight
– Shipping is one of the highest costs, often 50
miles is quoted as the maximum freight (this
is subject to a lot of debate however)
• Storage
• Burning
Problems
• Collection
• Freight
• Storage
– Chips have limited storage life
– Bundles have much longer storage but
require an additional step in the processing
– Other methods?
• Burning
Problems
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Collection
Freight
Storage
Burning
– Wood as a “chunk” is as strange fuel (part is cooking,
part is having volatiles produced and part is charcoal
all at the same time, therefore it is hard to control)
– In most large plants it has to be pulverized
– In nearly all cases, moisture of the material reduces
harvestable heat. Wood is generally to high moisture
without some natural or artificial drying.
Potential Users
• Heat
• Electric
• Co-gen
Conclusions
• Biomass for energy is a very viable energy
source for the US
• There is a large resource out there
• As energy prices increase, the economic
viability of these fuels is also increasing
• However, care needs to be taken not to
repeat errors from the 1980’s
• 1 KWh = 3413 BTU
1 therm = 100,000 BTU
• 1 kilowatt hour of electricity = 3,413 Btu
1 cu. ft. natural gas = 1,008 - 1,034 Btu
1 therm gas = 100,000 Btu
1 gallon crude oil = 138,095 Btu
1 barrel crude oil = 5,800,000 Btu
1 gallon gasoline = 125,000 Btu
From CO Biomass