Natural resources have been expected to provide the food,
feed, and fiber to meet our basic needs. Now they are being
called on to produce one more ‘F’—fuel. Oil has maintained a
less than $20 per barrel price throughout the 1990s moving
up to $30 per
barrel from 2000-2004 and most recently maintaining a price
of over $60 per barrel (EIA 2007). Many remembrances of the
1970s oil embargo come to mind, along with the major efforts
at developing alternative fuel sources. All that was brought
to a screeching halt in the 1980s as crude oil again became
readily available. Today there is a call for bio-energy from
those concerned with national security, global warming,
air-quality, residue disposal costs, enhancing forest
management, and revitalizing the agricultural economy. The
Energy Future Coalition in its 25x’25 vision calls for farms
and forests to provide 25 percent of the total energy
consumed in the United States by 2025, while continuing to
produce affordable food, feed, and fiber. In 2006, 18 small
enterprises were awarded $4.2 million from the U.S.
Department of Agriculture to develop innovative products and
renewable energy from woody biomass from national forests (Loyd
& Valetkevitch 2006). And President Bush has mentioned
energy production from wood chips in his State of the Union
addresses. These evidences point to a mounting seriousness
of meeting some of our energy needs from forests.
There are many alternate ways to create energy (heat,
electric, transportation) from biomass. In this regard,
there are several factors that need to be addressed when
choosing the most promising alternative: feedstock
availability including transportation, processing
efficiency, capital investment for facilities, and
compatibility with delivery infrastructure. Here we will
focus on forest and wood sources of biomass, not forgetting
that agriculture and municipal solid waste are also large
contributors to the renewable energy strategy.
Logging and land clearing debris can be
chipped on site and used or sold for fuel if within
reasonable haul to generation plant.
Forest Feedstocks
Estimates are that U.S. forest lands can sustainably produce
368 million dry tons of biomass annually (Perlack et al.
2005). There are several options that can be used to produce
woody biomass for energy production in the United States.
Considerable research has been done to develop biomass
plantations with species such as hybrid poplar and willow.
However, in the South, there are no operational plantations
of these species currently being established. In contrast,
there are over 30 million acres of pine plantations in the
southern United States. Many of these plantations could be
managed for bioenergy production.
If state-of-the-art management that integrates both improved
genotypes and intensive silviculture, growth rates of
loblolly pine in the South can exceed 10 tons per acre per
year. Southern yellow pine would be the most suitable source
as it is the greatest current stocking, suited to the soils
and climate, and having many years of research that
demonstrate the potential to increase biomass production
through intensive management. Planting densities, thinning,
and fertilization regimes may be adjusted if feedstock for
energy is the desired product.
Biomass production also fits within more traditional
management regimes where sawtimber is the desired final
product. Thinning is typically needed once or twice in the
rotation to produce sawtimber. Substantial amounts of
biomass for energy could be produced in the thinnings with
sawtimber produced at the end of the rotation.
A significant advantage of using southern pine plantations
for biomass production is that harvesting and transportation
systems are already in place and could easily be adapted to
deliver biomass to ethanol or other biomass energy plants.
This may not apply to other species being investigated for
energy production.
Harvesting Biomass
Trees are used for a wide range of products throughout
Virginia. Obviously high quality portions of trees used for
veneer, sawtimber, ties, poles and other
valuable products will continue to be used in their
appropriate category. In addition to this relatively small
proportion of valuable material, there are vast quantities
of lower-value limbs, tops, cull, and small diameter
material that can be chipped and used for everything from
engineered wood products, to pulp and paper, to specialty
products, to energy.
There are also many other residues generated from wood
products industries, landfills and loggers in Virginia that
could be available for use as bio-energy or other
applications. A study by Parhizkar and Smith (2007) surveyed
primary and secondary wood manufacturers, landfills, loggers
across Virginia and incorporated these data into a GIS for
spatial analysis. This study estimates that 10 million green
tons of wood residues are produced per year, most of which
is produced by primary manufacturers and used for pulp and
paper. However there are still 1.9 million tons of solid
wood biomass, primarily from construction debris and woody
brush, disposed of each year. Using woody debris and
residues will reduce wildfire risk and wood waste while
providing management opportunities to improve the health and
sustainability of the forests in Virginia.
Solids Combustion—Tried and True
Wood has been combusted for home heating and cooking from
time immemorial. The combustion process itself has evolved
from burning whole logs and branches in a open-air fire, to
charcoal creation for efficient transport and
high-temperature applications, to mechanical processing such
as chips, pellets, and compressed logs for various stoves
and utilities. Beyond local or niche applications pellets
and chips will likely be the products of interest when it
comes to industrial-scale heat or electricity production for
transportation and air-quality purposes.
The machinery for creating wood chips is readily available
and can convert large quantities of material very rapidly
with minimal maintenance. The chips can be made to be fairly
uniform in size and moisture content for a consistent and
thorough burn. There are an increasing number of business,
college, and industrial electricity generation facilities
that are utilizing wood chips in their boilers.
The wood pellet process originated in Germany some 200 years
ago, therefore it cannot be viewed as a new technology. Like
the alcohol industry, it is an old industry with a new life
resulting from economic and environmental changes.
The rejuvenation of the wood pellet industry began with the
oil embargo of 1974. At this time sawmills and kilns in
Oregon and Washington were looking for help with reliable
energy. Shavings and sawdust were recognized, but storage
was a problem as was fuel efficiency. These problems were
overcome with the redevelopment of the wood pellet process.
Recent interest in this industry has resulted in the
development of high efficiency wood stoves and furnaces
resulting in 1.2 million tons of bagged pellets sold in
2006.
Europe is the main consumer of wood pellets largely due to
the high carbon taxes imposed for the burning of fossil
fuels. This market should increase in the U.S. at a local,
if not national level, as there is more emphasis placed on
green energy and low emissions.
Wood waste from manufacturing plants, harvesting
operations and landfills can be utilized to produce clean,
carbon neutral energy while increasing revenue for wood
producers. (Photo courtsey of Dan Georlich)
|
Wood Gases and Liquids
Combustion is an easy way to convert wood to energy
for direct heat or conversion to electricity, but
not very convenient for the needs of our
transportation industry which is a major contributor
to greenhouse gas emissions. For this purpose the
fuel needs to be transformed into a liquid (some
popular forms being ethanol, methanol, propanol,
butanol, etc.), with ethanol being one of the more
popular forms due to relatively efficient conversion
and the availability of government subsidies.
Currently, it is easier and cheaper to create
ethanol from corn, cane sugar, or sugar beets than
it is from wood or cellulose. The cost of production
for corn is in the range of $1.00-$1.15 per gallon
with $1.26 per gallon per year capital expenditure
required to build and maintain the facility (Shapouri
et al. 2006). Hydrolyzing wood to
sugars, which is currently quite challenging, costs
approximately $2.35 per gallon and greater than $4
per gallon per year of capital expenditure is
required to build and maintain the facility.
However, many research agencies and private
companies are working hard to lower these costs to
make this fuel competitive with ethanol from corn. |
 |
| Cofiring plants like
the Dominion Power plant in Pittsylvania can
provide some of the nearest term and lowest
cost options for reducing air pollutant
emissions from electric power generation.
(photo courtsey of Dan Georlich) |
|
There are no cellulose-to-ethanol plants
currently in operation in the U.S., but a number of plants
are under development. In general, the processes used fall
into two categories: gasification of the feedstock, and
pretreatment and fermentation of the feedstock.
There are several ethanol plants under development using
gasification processes. One recently announced is the 100
million gallon per year Range Fuels project slated to be
built in Soperton, Ga. In this two-staged process the gas
will be passed through a proprietary catalytic process which
will result in the production of liquid ethanol and
methanol.
There are also several plants under development using enzyme
and fermentation processes. One promising project is being
developed by a startup company in Georgia with the
cooperation of Georgia Tech and University of Georgia
researchers. This company (C2 Biofuels) plans to license
several pine to ethanol plants in the southeast, each
capable of producing 50 million gallons per year (Touchstone
2006).
Research is continuing to develop more efficient ways of
utilizing wood and other biological feedstocks in the
production of energy. Chevron together with the Georgia
Institute of Technology are conducting research in:
identification of high impact technologies which will result
in the commercialization of cellulosic biofuels;
understanding the characteristics of biofuel feedstocks;
development of regenerative sorbents; and improvement of
sorbents used to produce high-purity hydrogen.
Biorefineries
The pulp and paper industry is critical for sustainable
forest management, and is a current leader in the use of
biomass and cogeneration utilizing wood wastes. Pulp mills
are already well-versed in the extraction and manufacturing
of multiple products. This can be expanded into a
bio-refinery, much in the same way that petroleum refineries
produce value-added byproducts with the leftovers from
gasoline production. Pulp mills can add energy to the
rosins, terpenes, lignins and activated carbon value-added
products gleaned in the paper making process. Wood
derivatives can be used in the manufacture of plastics,
adhesives, surfactants, etc. The threats of the petroleum
industry can become the opportunities of the bio-based
sector. Disruptive markets are ripe for entry of new
innovative technologies and improvements in quality.
Under the current model of a paper mill, the pulp mill is
the cost center and paper mill is the profit center making
the paper mill the center for innovation. A bio-refinery
model allows more valuable products to be derived from
earlier processes. Biofuel production, gasification,
bio-chemicals and bio-materials refining offer some great
opportunities. Currently 99 percent of lignins are used for
fuel at a value of $50-$500 per ton. Higher value products
can be derived netting 10 times that value if sufficient
demand exists. If nothing is done U.S. pulp and paper mills
are sure to experience lost opportunities and a decline in
global competitiveness.
Conclusion
Wood has an increasing place in the bio-energy market as
cellulose is the most abundant renewable resource. Wood, or
any existing biofuel, can not currently compete directly
with fossil fuels in a completely market-based economy.
Approximately 60 percent of the electricity produced in the
U.S. comes from plants fueled with coal, but this resource
is under great pressure from concerns about global warming,
renewable portfolio standards and potential carbon taxes.
Nuclear energy is experiencing much renewed interest, but
questions remain to be answered on standardized plant
designs, safe operating standards, waste fuel disposal and
actual construction costs. However in situations where
renewable or carbon neutral energy is mandated; biofuels
will be a component. And wood fiber will be a strong
competitor among competing biofuels due to its abundance,
low input cost, high transportation density, steady supply
rates and non-competitive usage.
If 30 percent of our energy resource is mandated to be
renewable, representing the equivalent of more than 1.5
billion kWh of electricity and over 45 billion gallons of
gasoline, there is quite a long ways to go considering only
six percent of our energy currently is produced from
renewable sources. Already some partnerships are being
created between petroleum-based and wood-based industries.
With so many energy possibilities, it seems to be a
footrace. Energy demand continues to increase, while costs
and restrictions also increase on just about every energy
generation solution from nuclear to coal. There is room for
a diversified energy portfolio and in fact it may well take
all of the solutions we can find to meet our future energy
needs.
References
- 25x’25. 2007. 25x’25 Action Plan:
Charting America’s Energy Future.
http://www.25x25.org/storage/25x25/documents/
IP%20Documents/ActionPlanFinalWEB_04-19-07.pdf
- Energy Information Administration.
2007. United States Spot Price FOB Weighted by Estimated
Import Volume (Dollars per Barrel) http://tonto.eia.doe.gov/dnav/pet/hist/
wtotusaw.htm
Loyd, E. & Valetkevitch, H. 2006. USDA News Release No.
0138.06
Parhizkar, O., Smith, R. 2007. A Geographic Perspective
on the Current Biomass Residue Availability in Virginia.
- Perlack, R. et al. 2005. Biomass as
feedstock for a bioenergy and bioproducts industry: the
technical feasibility of a billion-ton annual supply.
DOE/GO-102005-2135 ORNL/TM-2005/66.
Shapouri, H., OEPNU/OCE, USDA, and Salassi, M. 2006. The
economic feasibility of ethanol production from sugar in
the United States. http://www.usda.gov/oce/EthanolSugar
FeasibilityReport3. 69 pp.
- Touchstone, V. 2006. Alternative Fuel
Technology Company Locates in Georgia. The Georgia
Centers of Innovation: Agriculture: The Big Picture -
6/27/2006. http://agriculture.
georgiainnovation.org/news/details/3
Neil Clark is Associate Extension
Agent, ANR, Forestry and Natural Resources—Southeast
District, Tidewater Agricultural Reserach and Extention
center. Terence Cooper is a member of the VFA Magazine
Editorial Committee.
|
