An Introduction to Bioenergy: Feedstocks, Processes and Products

1. A project of the National Center for Appropriate Technology 1-800-346-9140 • www.attra.ncat.org
An Introduction to Bioenergy:
Feedstocks, Processes and Products
By Leif Kindberg, Bioenergy offers farmers an alternative to petroleum-based energy sources, and new market opportuni-
NCAT Farm Energy ties for farm products. When biomass feedstocks are burned, fermented or reacted through an energy
Specialist conversion process, they return some carbon dioxide and water and release the sun’s energy. Because
© 2010 NCAT plants have the capability to store and then release energy in this way, they act as a natural battery. This
introduction to bioenergy offers a brief and non-technical overview of bioenergy feedstock production
with discussion on how bioenergy is made.
Contents
Introduction ......................1 Introduction
Feedstock Basics..............1 Bioenergy uses renewable biomass feedstocks
Sugar and Oil
from many sources. Renewable biomass feed-
Feedstocks ....................1 stocks use the process of photosynthesis in plants
Sugar Feedstocks .......2 to capture the sun’s energy by converting carbon
Oilseed Feedstocks....2
dioxide (CO2) from the air and water (H2O)
into carbohydrates and complex oil and fiber
Cellulosic
Feedstocks ....................2 compounds made up of carbon, hydrogen and
Agricultural
oxygen. These energy-rich carbohydrates, oils
Residues .........................3 and fibers can be harvested and used for many
Animal Manure ............3 types of bioenergy. There are hundreds of ways
The Production
to turn biological materials into energy, although
of Bioenergy .....................3 currently only a few of them represent legitimate
Thermochemical short-term opportunities for the average farm or
Conversion ....................3 rural landowner.
Carbon cycling is the foundation of sustainable bio-
Biochemical energy. Source: BC Bioenergy Strategy.
Conversion ....................6
Bioenergy was used in industrial processes well
before petroleum and coal-fired electricity were
Conclusion .........................8
commonly available. Although a great deal of animal parts and many other biological materials.
Further Resources ...........9
attention goes to solar and wind energy, bioen- The benefits of one feedstock versus another are
Additional Online ergy BTUs (British thermal units of energy) gen- regionally specific. This makes feedstock selection
Resources ...........................9
erated from biomass make up 53 percent of all a key consideration in bioenergy production.
References .........................9
renewable energy in the United States, according Feedstocks may be dedicated to energy produc-
to the Energy Information Administration. That tion or non-dedicated. Feedstocks that are dedi-
is more than all other renewable sources com- cated are often called energy crops. Each feed-
bined (EIA, 2009). However, bioenergy presents stock has advantages and disadvantages that may
a complex set of energy topics. This publication include how much usable biomass they produce,
The National Sustainable will discuss many of these complex topics but soil types required, water and energy inputs,
Agriculture Information Service,
ATTRA (www.attra.ncat.org),
will only mention others. Topics that will not be energy density, air quality benefits, production
was developed and is managed discussed in any detail in this introductory pub- cost and other considerations.
by the National Center for
Appropriate Technology (NCAT). lication include most feedstock pre-processing
The project is funded through considerations such as transporting, sizing, dry-
a cooperative agreement with
the United States Department ing and storage.
Sugar and Oil Feedstocks
of Agriculture’s Rural Business- Sugar and oil feedstocks often include seeds,
Cooperative Service. Visit the
grains and plants that are made up of sugar,
NCAT website (www.ncat.org/
sarc_current.php) for
more information on
Feedstock Basics starch or oil, and animal fats or tallow. Today,
our other sustainable Bioenergy can be produced from feedstocks these feedstocks are often used to produce the
agriculture and
energy projects.
such as trees, agricultural crops, plant residues, biodiesel and ethanol fuels we are familiar with.

2. Sugar Feedstocks
The two most common bioen-
ergy feedstocks used for their
starch and sugar content are corn
and sugar cane. Over 90 percent
of ethanol (or bioethanol as it is
sometimes called) is still made
from corn in the United States.
The world’s largest producer of
ethanol is Brazil. Brazil uses sugar
cane as its primary feedstock.
Because fermentation produces
Related ATTRA alcohols, the higher the yield of
publications fermentable sugars in the feed-
Biochar and Sustain- stock, the higher the yield of alco-
able Agriculture hols. Since fermentation can pro-
cess almost any starch into sugar, The geographic range of some bioenergy crops. Source: ORNL.
Oilseed Processing for
other feedstocks may include bar-
Small-Scale Producers
ley, milo, wheat, potatoes, sugar beets, cheese information on the best rotations for soil-build-
Biodiesel Use, Han- whey, brewery and beverage waste and many ing, water needs and pest management. See the
dling, and Fuel Quality others. Many of these feedstocks serve multiple ATTRA publication Biodiesel: The Sustainability
functions as either food or fuel sources. Dimensions for more information about oilseed
Agriculture, Climate
feedstocks.
Change and Carbon
Sequestration Oilseed Feedstocks
Renewable Energy Plants that have oil-rich seeds, frequently
Cellulosic Feedstocks
Opportunities on referred to as oilseeds, can be a sustainable Feedstocks from cellulose (the primary com-
the Farm source of bioenergy. Common American oilseed ponent in the cell walls of plants) such as pop-
crops include soybeans, canola, sunflower, cam- lars, willows and switchgrass are creating a lot
Biodiesel: The
elina, and safflower and cottonseed. Camelina is of excitement among farmers, scientists and
Sustainability Dimen-
a short-season crop that is well-suited for dou- the public. These fibrous and generally ined-
sions
ble cropping and grows well in cooler climates ible parts of plants are abundant and can be col-
Biodiesel: Do-it-your- lected from diverse regions or grown directly by
such as the northern Midwest. In comparison,
self production basics farmers. Although there is currently a very lim-
many varieties of sunflower are well-suited for
Ethanol Opportunities warmer Southern climates. Canola (one cultivar ited market for cellulosic bioenergy feedstocks in
and Questions of rapeseed) is particularly well-suited for cooler the United States, some companies are currently
regions, with varieties that are adapted for both purchasing cellulosic biomass for pellets and
Switchgrass as a
spring and fall planting to achieve multiple oil- for cofiring (burning biomass with coal). A few
Bioenergy Crop
seed harvests. Your state agricultural experiment companies intend to begin commercial produc-
Micro-Scale Biogas station, Cooperative Extension Service or the tion of cellulosic ethanol. Demand for cellulosic
Production: A begin- biomass is expected to expand market opportu-
Natural Resources Conservation Service (NRCS)
ner’s guide nities in the near future.
may have information on specific oilseed crops
that are well-adapted to your location and Energy crops can be grown on farms using prac-
tices similar to those used with other agricul-
tural crops. Trees and grasses, particularly those
that are native to a region, can be sustainably
produced when grown with minimal inputs
such as water, fertilizer and chemicals. Trees
that will regrow after each harvest may be cop-
piced (repeatedly cut off at ground level), allow-
ing them to be harvested multiple times. Woody
Canola (rapeseed) being varieties that regrow quickly without being
harvested for oil. Photo replanted are called short-rotation woody crops.
courtesy NREL. Perennial varieties of grasses and legumes are
Page 2 ATTRA An Introduction to Bioenergy: Feedstocks, Processes and Products

3. also being tested and used as feedstocks. Many
energy crops are being researched for their bio-
The Production
energy potential. of Bioenergy
Feedstocks require a conver-
sion process in order to take
Agricultural Residues raw materials and turn them
Residues left over from forest products and farm- into useful bioenergy such as
ing may also be used as cellulosic feedstocks. The electricity, biodiesel, ethanol,
U.S. Department of Energy has estimated that biobutanol, methane, heat
between 581 and 998 million dry tons of agri- and other bioenergy products.
cultural residues such as corn stover and wheat Keep in mind that harvesting,
straw (the stalks and leaves left on a field after a drying to the correct moisture content, trans- Short-rotation hybrid
harvest) could be harvested for biofuels by the porting to the necessary location and supplying poplar trees. Photo cour-
middle of the 21st century (DOE, 2005). How- a sufficient quantity of biomass are important tesy NREL.
ever, research has also shown that less than 25 considerations that are only briefly mentioned
percent of some agricultural residues could be in this introduction to bioenergy. Each type of
sustainably harvested under current agriculture feedstock may require a slightly different conver-
practices, because crop residues are critical to
E
sion process, but many feedstocks can be con-
soil fertility (Graham et al., 2007). Study results verted using similar processes and technologies. ach type of
vary widely on the quantity of agricultural resi- feedstock
dues that may be sustainably harvested. What is
certain is that when left in the field, agriculture Thermochemical Conversion may require a
residues help restore soil tilth, protect agricul- Heating biomass assists a chemical reaction (a slightly different con-
tural soils and sequester carbon. The removal of thermochemical process) and creates useful bio- version process, but
agricultural residues is unlikely to be sustainable energy products such as gases, liquids and heat. many feedstocks can
unless agricultural best management practices Electricity generated from biomass is referred to as
be converted using
such as cover crops, no-till production and better biopower, and the combination of both heat and
fertilizer management are fully adopted, among power is commonly referred to as cogeneration or similar processes and
other practices (Marshall and Zugg, 2008). combined heat and power (CHP). The overall effi- technologies.
ciency of these integrated systems is significantly
higher than either of the systems alone.
Animal Manure
Manure is used for feedstocks in anaerobic
digesters primarily to produce gas burned to Combustion in a Direct-fired or
generate electricity. Although there are substan- Conventional Steam Boiler
tial environmental and welfare issues associated The burning of feedstocks for energy has been
with confined animal feeding operations, these practiced for many years. One of the oldest
large operations are increasingly using manure commercial methods of producing electricity
digestion to control a variety of environmental is through the burning of wood or charcoal to
problems, reduce odors, generate bioenergy for produce steam. The steam is piped into a tur-
the farm and provide additional income through bine that spins a generator used to make elec-
the sale of power. tricity, or biopower. A problem with burning
feedstocks in a steam boiler is that that a great
deal of energy is lost in the conversion process.
Pre-processing biomass by pelletizing, torre-
faction (superheating in a low-oxygen environ-
ment) or making condensed biomass briquettes
has helped improve the efficiency of burning
woody biomass. These processes are expensive
and not always economical given current fossil
fuel prices.
This 21-megawatt direct-fired biopower plant uses
wood residues discarded from orchards and industrial
operations. Photo courtesy NREL.
www.attra.ncat.org ATTRA Page 3

4. Cofiring feedstocks into useful intermediates to be used
as energy later (Sadaka, 2010). Gasification
Cofiring woody biomass and high-fiber grasses
exposes the feedstock to some oxygen, but not
with coal can reduce carbon dioxide emissions
enough to allow the feedstock to burn. The con-
compared to burning coal alone. Many plant-
version efficiency of gasification systems is high,
based feedstocks have lower sulfur contents than
typically between 80 and 85 percent efficiency
coal, reducing sulfurous gases including sulfur
in taking a raw feedstock and converting it into
dioxide. Cofiring plant-based feedstocks has
producer gas (NREL, no date). Controlling the
been successfully demonstrated to replace up to
temperature, pressure, feedstock characteristics
20 percent of the coal used in the boiler, accord-
and other aspects changes the energy density
ing to the Federal Energy Management Program
and makeup of the producer gas.
(2004). However, the economics of cofiring have
generally not been favorable with historical fos- More on gasification can be found on the Sun
sil fuel prices. You should carefully consider the Grant BioWeb Web site at http://bioweb.sungrant.
market opportunities in your local area if you are org/General/Biopower/Technologies/Gasification/
planning to produce feedstocks for cofiring, and Default.htm.
you should pursue long-term supply contracts.
BioWeb is a non-commercial, educational Web
G
More information on cofiring and other bio- site that provides current information about bio-
asification power technologies can be found at the U.S. mass resources for bioenergy and bioproducts.
converts Department of Energy’s Distributed Energy
feedstocks Program’s website, www.eere.energy.gov/de/ Pyrolysis
into combustible biomass_power.html.
Pyrolysis is derived from the Greek words pyro,
gases called syn- meaning fire, and lysys, meaning decomposi-
thesis gas (syngas)
Thermal Process Heat tion. Pyrolysis is a method of producing syngas
that can be used to
and Space Heat and biocrude, also known as bio-oil or pyroly-
Burning biomass directly can be used to produce sis oil. Pyrolysis uses thermal decomposition by
produce heat, motor heating biomass at temperatures usually greater
both process heat and space heat. Process heat
fuels, biopower, is vital to many manufacturing processes and than 400 degrees F (204 degrees C). Biocrude
chemicals and for is used in a variety of agricultural applications is formed when syngas produced during pyroly-
other purposes. including grain and crop drying. Space heat- sis is re-condensed into liquid biocrude. There
ing is the most common use. Both large boil- are few opportunities to use unrefined biocrude
ers in manufacturing facilities and small stoves in directly on the farm and a limited market. Bio-
shops are frequently used for space heat. Wood, crude can be refined into high-quality hydrocar-
wood chips and hay can be used for both process bon fuels such as diesel, gasoline and jet fuel.
heat and space heat, and are readily available on These liquid fuels can be used in internal com-
the farm. bustion engines as a chemically identical substi-
tute to petroleum fuels.
Thermal Gasification Pyrolysis is often the first process that occurs
Gasification converts feedstocks into combusti- during the burning of solid fuels including
ble gases called synthesis gas (syngas) that can wood. Pyrolysis releases gases that are visible
be used to produce heat, motor fuels, biopower, as yellowish and orange flames. If you were to
chemicals and for other purposes. Syngas is also stop burning these gases and condense them,
sometimes referred to as producer gas, wood you would have a form of biocrude. Next, the
gas and town gas. Synthesis gases are generally solids (charcoal) left behind are burned but
upgraded to other fuel products such as etha- have no visible flame. Instead of letting these
nol, methanol, hydrogen and ammonia using solids burn, they can be converted into bio-
char. Using modern pyrolysis for energy stops
processes such as the Fischer-Tropsch process.
the burning of both gases and solids short.
These fuels and process will be discussed later in
this publication. Gasification occurs at tempera-
tures generally between 1,202 and 1,832 degrees Pyrolysis variables such as temperature, pres-
Fahrenheit (650 to 1,000 degrees Celsius) and sure, reaction rates and other factors produce a
deliberately limits burning in order to convert wide variety of gas, liquid and solid intermedi-
ates. However, generally pyrolysis processes with
Page 4 ATTRA An Introduction to Bioenergy: Feedstocks, Processes and Products

5. higher temperatures and more rapid reaction Wind electricity may
rates are most efficient at producing biocrude. be used to electrolyze
water and produce
The pyrolysis process known as fast or high-
hydrogen, a key com-
temperature pyrolysis has higher reaction rates ponent of ammonia.
(greater than 1,000 degrees F or 538 degrees C). Photo courtesy Uni-
This process can be used to optimize biocrude versity of Minnesota
or char production. Low-temperature pyroly- Renewable Energy
sis processes are generally used to produce char. Center.
Pyrolysis and gasification are both complex pro-
cesses that require laboratory-like conditions to
consistently produce bioenergy products.
Biochar is a type of charcoal that is high in wind, solar, water, biomass and other renewable
organic carbon and is a coproduct of pyrolysis resources. Instead of using natural gas or coal to
of biomass. Char has many potential benefits in produce hydrogen, biopower is used to electro-
agriculture (International Biochar Initiative, no lyze water and produce hydrogen. This offers the
date). Biomass pyrolysis systems for biocrude benefit of releasing fewer carbon dioxide emis-
and biochar production are available in smaller sions, but has normally required large amounts
B
demonstration units at this time, but some of energy and remains cost-prohibitive because iochar is a
larger-scale facilities are being built. For more of low-cost natural gas and coal. type of char-
information on biochar, see the ATTRA publi-
cation Biochar and Sustainable Agriculture. coal that is
Ammonia high in organic
More on pyrolysis can be found on the Sun Ammonia produced during the Haber-Bosch
Grant BioWeb Web site at http://bioweb.sungrant carbon and is a
process can be run in modified internal com-
.org/General/Biopower/Technologies/Pyrolysis/ bustion engines as an alternative liquid fuel. coproduct of pyrolysis
Default.htm. Ammonia has about half the energy of gasoline of biomass.
and can be generated from a variety of renewable
Fischer-Tropsch Process energy sources. Farmers who have experience
The Fischer-Tropsch process converts syngas with ammonia application know there are many
usually produced during gasification into unre- hazards associated with the handling and use of
fined liquid fuels such as biocrude. The Fischer- ammonia. The broad use of ammonia as a liquid
Tropsch process usually takes place in a pres- fuel for vehicles will require substantial invest-
surized and high-temperature environment. ments in safe storage and handling, and require
This process chemically converts a gas generally improvements in transportation infrastructure.
composed of carbon monoxide and hydrogen
into liquid fuels or oils that can then be burned Methanol
in an internal combustion engine and used to Methanol or wood alcohol is usually produced
make other fuels. Fischer-Tropsch liquids can be from methane during steam-methane reform-
refined further into hydrocarbon fuels such as ing of natural gas and coal. Methane produced
gasoline and diesel and used as a direct replace- from anaerobic digestion of manure (discussed
ment for petroleum-derived fuels. next) may also be an option but is usually cost- Methanol and ethanol
prohibitive. Methanol can be used as a substi- pumps. Photo courtesy
Haber-Bosch Process tute for gasoline with some engine modifica- NREL.
The Haber-Bosch process is a synthesis reaction tions but has only about
between nitrogen gas, hydrogen gas and an iron half the energy density of
catalyst. The Haber-Bosch process is often used gasoline. Methanol can also
in sequence with steam reforming of natural gas be converted into synthetic
or coal into gaseous hydrogen to produce ammo- fuels such as dimethyl ether
nia. The entire process of producing ammonia (DME) to be used as a die-
is often referred to as the Haber-Bosch process. sel substitute with signifi-
cantly lower emissions and
Gaseous hydrogen for the Haber-Bosch pro- with about half the energy
cess can be produced using electricity from density of diesel. Methanol
www.attra.ncat.org ATTRA Page 5

6. is already commonly used in the transesterifi-
cation process of producing biodiesel, which we
will discuss later.
Biochemical Conversion
A
Bacteria, yeasts and other living enzymes fer-
naerobic
ment material such as sugars and proteins and
digesters convert them into useful alcohols or other liquid
break down fuels. These processes are known as biochemi-
(or digest) organic cal conversion processes. Corn ethanol and
matter without oxy- other grain alcohols are some of the most com- Anaerobic digestion creates a variety of nutrient-rich
mon fuels produced in this way. Other meth- liquids and solids that can be used on the farm. Photo
gen (anaerobic) to ods include capturing methane produced when courtesy USDA ERS.
produce methane bacteria break down manure from livestock and
and other gases and poultry production, human sewage and landfill natural gas (LNG) in automobiles, among other
waste to burn it for heat and biopower. uses. The byproducts from anaerobic digestion
coproducts that are
can be used as soil amendments and liquid fer-
useful on the farm. tilizers. For more information, see the ATTRA
Anaerobic Digestion publication Anaerobic Digestion of Animal Wastes:
Anaerobic digesters break down (or digest) Factors to Consider.
organic matter without oxygen (anaerobic) to
produce methane and other gases and coprod-
ucts that are useful on the farm. This gas mixture
Fermentation (for Ethanol)
is commonly referred to as biogas or digester gas. Ethanol, a fuel alcohol, is made from biologi-
Biogas is a combustible and normally consists of cal sources and usually is produced through the
50 to 60 percent methane. Biogas can be burned fermentation of plant starches and sugars. In the
in an engine to generate biopower and thermal United States, corn is the most common source
energy or processed further into other fuel types of starch converted into ethanol, while barley,
such as methanol. Refined biogas can be used milo, wheat starch, potatoes, cheese whey and
as compressed natural gas (CNG) and liquefied brewery and beverage waste make up a smaller
share of production. Ethanol can also be pro-
duced from sugarcane, which has a high content
of the sugars needed for fermentation. Accord-
ing to the Renewable Fuels Association, the
United States produced 9 billion gallons of eth-
Cellulosic biofuels anol in 2008 and 22 million metric tons of dis-
and the carbon cycle. tillers grains were sold from the ethanol making
Source: US DOE. process (2008). For more information, see the
ATTRA publication Ethanol Opportunities and
Questions.
Ethanol from corn and other grains can be made
using either a dry milling or wet milling process.
The dry milling process uses the whole corn ker-
nel, which is ground into a powder, mixed with
water to form a mash and then cooked with
added enzymes that turn the liquefied starch to
glucose (sugar). After cooling, the mash is fer-
mented with a second enzyme (yeast) and finally
distilled further to separate the alcohol from the
solids and water. Coproducts of the dry milling
process include distillers grain, which is used as
animal feed (also known as distillers dried grain
with solubles or DDGS) and carbon dioxide.
Page 6 ATTRA An Introduction to Bioenergy: Feedstocks, Processes and Products

7. The wet milling process involves soaking the energy density that is 10 to 20 per-
corn kernel in water and sulfurous acid before cent lower than gasoline and slightly
grinding the kernels into a mash. This soaking higher than ethanol. The Environ-
separates the germ (oil), fiber, gluten (protein) mental Protection Agency allows
and starch components. The starch is fermented biobutanol to be blended with gas-
into ethanol and then distilled further, corn oil oline up to 11.5 percent. Higher
is extracted from the germ and both fiber and blends have greater restrictions and
other starch components are separated. While may require modifications to inter-
dry milling provides valuable coproducts such nal combustion engines (DOE, no
as DDGS, the wet mill process is also used to date). Biobutanol can be delivered
produce corn oil, corn gluten and meal. to the end user with existing pipe-
line and storage infrastructure in
As with ethanol produced from starch grains,
many cases. However, biobutanol is
processing cellulosic feedstock for ethanol aims
toxic to humans and is water solu-
to extract fermentable starch from the feedstock.
ble, which means it may easily find
However, the starches found in cellulose are
its way into water sources.
hard to extract because they are locked in com-
plex carbohydrates called polysaccharides (long Biodiesel is blended with
chains of simple sugars). To produce ethanol Transesterification for Renew- petroleum-based die-
sel to produce B99 and
from cellulose efficiently, these chains of simple able Diesel Fuels lower blends. Photo by
sugars must be broken up prior to fermentation. Transesterification is a chemical process that Leif Kindberg.
Fermenting sugars from cellulose into ethanol reacts an alcohol with the triglycerides con-
is less efficient than fermenting sugars directly, tained in vegetable oils and animal fats to pro-
although ethanol from either source is chemi- duce biodiesel and glycerin. This process is
cally identical. commonly used to produce B100 biodiesel, or
The conversion of cellulose to sugar is gener- 100-percent biodiesel to be blended with petro-
ally accomplished through one of two processes. leum diesel. Biodiesel is essentially permanently
The first uses acid hydrolysis (a method of split- thinned plant oil or animal fat, with a viscos-
ting water molecules) to break complex carbo- ity approximating that of standard No. 2 petro-
hydrates into simple sugars. The second uses a leum-based diesel fuel. Biodiesel is chemically
combination of pre-treatment to break apart the different from petroleum-based diesel because it
B
feedstock cell structure and enzymatic hydro- contains oxygen atoms and is not a pure hydro- iobutanol is
lysis for the production of fermentable sugars. carbon. For more information about biodiesel,
very similar
Cellulosic ethanol may also be produced from see the ATTRA publication Biodiesel Use, Han-
gasification, which is a thermochemical process. dling and Fuel Quality. to gasoline
and is produced in
Another type of renewable diesel known as
Biobutanol green diesel or hydrogenation-derived renewable much the same way
Biobutanol is very similar to gasoline and is diesel is more like petroleum-based diesel, but as ethanol.
produced in much the same way as ethanol. uses many of the same plant oil and animal fat
Biobutanol is produced by Acetone-butanol- feedstocks used in making biodiesel. Green die-
ethanol (ABE) fermentation. Biobutanol has an sel is produced using a chemical reaction known
as hydrocracking or hydrotreating. Hydrocrack-
ing is a process in which hydrogen is added to
organic molecules under pressure and heat. An
important advantage of green diesel is that it can
be produced as a chemically identical replace-
ment to petroleum diesel.
A ButylFuel vehicle was driven across the United
States on 100 percent biobutanol. Photo courtesy
ButylFuel, LLC. July 18, 2005.
www.attra.ncat.org ATTRA Page 7

8. An important part of bioenergy production is the net energy balance (also referred to as the energy
balance). The energy balance is a lifecycle method of accounting for the amount of energy needed
to make a unit of bioenergy versus the amount of usable energy produced. Therefore, the lifecycle
energy balance of bioenergy will include inputs required to plant, cultivate, fertilize, harvest, trans-
port, dry and process the feedstock and convert it into a useful bioenergy form. Said another way,
the energy balance is the difference between the energy produced and the energy needed to pro-
duce that given unit of energy.
The complexity involved in accurately calculating the energy balance of bioenergy makes the calcu-
lations almost impossible to conduct at this point. The methods used to produce an energy crop on
one farm, for example, may be somewhat or significantly different on the next. An example of this
could be intercropping nitrogen fixers and perennial grasses without the use of herbicides on one
farm versus using alternative nutrient and weed management practices on the next farm.
Straight Vegetable Oil (SVO) to consider when thinking about biomass and
bioenergy production on the farm.
The viscosity (thickness) of straight vegetable oil
W
hen may cause buildup when burned in an unmodi- Some things to consider include:
biodie- fied engine. However, engines that burn straight • Is there a local market for my feedstock
sel from vegetable oil are available and modification kits or fuel or can I use it on the farm to off-
oilseeds is burned, are available as well. With the correct filter- set energy costs?
carbon dioxide and ing, heating and conversion of a diesel engine,
straight vegetable oil offers a partial alternative to • Will the quantity of fertilizer and energy
other emissions are
bio-based or No. 2 petroleum-based diesel fuel. used during the production of my
released back into feedstock be positive or negative for the
the air and are taken For more information about straight vegetable
oil, see the ATTRA publication Biodiesel Use, environment?
up again by next
year’s energy crop, Handling and Fuel Quality. • Will converting my land, once out of
thus completing the agricultural production, into production
carbon cycle. Conclusion (indirect land use change) create addi-
tional greenhouse gases?
Through its role in the carbon cycle, bioen-
• How much energy will be consumed
ergy can reduce direct emissions such as car-
during transportation of feedstocks?
bon dioxide (CO2) when compared with petro-
leum-based energy. For example, when biomass • How much energy will be used during
feedstocks are grown, they pull carbon dioxide feedstock conversion?
from the air and make stems, roots, leaves and • Will bioenergy provide net positive ben-
seeds. When biodiesel from oilseeds is burned, efits to my farm and the environment
carbon dioxide and other emissions are released when all the economic, energy and envi-
back into the air and are taken up again by next ronmental costs are added up?
year’s energy crop, thus completing the carbon This publication did not provide answers to all
cycle. In comparison, when fossil fuels such as these questions and is meant as a starting point
coal or petroleum-based fuels are burned, all of for learning about bioenergy. It is not a com-
the carbon dioxide released adds additional car- plete reference guide and we encourage you to
bon dioxide into the air (NREL, 2008). How- explore all of the additional publications and
ever, not all bioenergy is equally good at reduc- resources provided by ATTRA and in the Fur-
ing emissions. There are many complex factors ther Resources that follow.
Page 8 ATTRA An Introduction to Bioenergy: Feedstocks, Processes and Products

9. Further Resources Additional Online Resources
National Biodiesel Board
Bioenergy Feedstock www.biodiesel.org
and Production Resources Renewable Fuels Association
For an extensive list of bioenergy equipment, designers, and www.ethanolrfa.org
technical assistance please visit the ATTRA Directory of
The Ammonia Fuel Network
Energy Alternatives at www.attra.ncat.org/dea.
www.ammoniafuelnetwork.org/why.html
For a glossary of bioenergy terms see the National Renew-
International Biochar Initiative
able Energy Laboratory at www.nrel.gov/biomass/glossary.
www.biochar-international.org
html.
U.S. Department of Energy
The Alternative Fuels and Advance Vehicles Data Center
Energy Efficiency and Renewable Energy
provides information on the production, distribution and
www1.eere.energy.gov/biomass
benefits of biobutanol, biodiesel, ethanol, hydrogen, metha-
nol, natural gas, propane, ultra-low sulfur diesel, biogas, Sun Grant Initiative
p-series fuels and much more. www.sungrant.org
www.afdc.energy.gov/afdc/fuels/emerging.html
The AgSTAR Program
Journey to Forever is a small, non-government organization www.epa.gov/agstar
based in Japan and involved in Third World rural develop-
ment work. The Web site also offers a lot of information BioCycle Magazine
about biofuels and other appropriate technologies. www.biocycle.net
http://journeytoforever.org/biodiesel.html Home Power Magazine
The Sun Grant BioWeb provides both non-technical and www.homepower.com
technical information on biomass, bioenergy conversion Roundtable on Sustainable Biofuels
technologies, biomass economics, and related policy. http://cgse.epfl.ch/page65660-en.html
http://bioweb.sungrant.org
The Bioenergy Feedstock Information Network (BFIN) is a References
helpful gateway to biomass resources from the U.S. Depart- Bergman, Patrick C.A and Jacob H.A Kiel. 2005. Torrefac-
ment of Energy, Oak Ridge National Laboratory, Idaho tion for biomass upgrading. 14th European Biomass Con-
National Laboratory, National Renewable Energy Labora- ference & Exhibition. Accessed July 2009.
tory and other research organizations. www.techtp.com/recent%20papers/ECN-Torrefaction
http://bioenergy.ornl.gov %20for%20biomas%20upgrading%20-2005.pdf
The Agricultural Marketing Resource Center provides Department of Energy. 2005. Biomass as Feedstock for a
resources on value-added agriculture including bioenergy Bioenergy and Bioproducts Industry: The Technical Feasi-
feedstocks. bility of a Billion-Ton Annual Supply. p. 23. Accessed May
www.agmrc.org/renewable_energy 2009.
The National Renewable Energy Lab (NREL) is a learning http://feedstockreview.ornl.gov/pdf/billion_ton_vision.pdf
resource covering biofuels, biopower, bioproducts and other Department of Energy (DOE). No Date. What is Biobuta-
energy technologies for farms and ranches. nol? Alternative Fuels & Advanced Vehicles Data Center.
www.nrel.gov/learning/fr_biopower.html Accessed June 2009.
www.afdc.energy.gov/afdc/fuels/emerging_biobutanol_what_
is.html
www.attra.ncat.org ATTRA Page 9

10. Energy Information Administration (EIA). 2009. Renew- National Renewable Energy Laboratory. 2008. Biodiesel
able Energy Consumption and Electricity Preliminary 2008 Handling and Use Guide. 4th Ed. p. 7. Accessed July 2009.
Statistics. Accessed October 2009. www.nrel.gov/vehiclesandfuels/pdfs/43672.pdf
www.eia.doe.gov/cneaf/alternate/page/renew_energy_consump/
National Renewable Energy Laboratory (NREL). No Date.
rea_prereport.html
An Overview of Biomass Gasification. p. 2. Accessed May
Federal Energy Management Program (FEMP). 2004. Bio- 2009. http://arkansasenergy.org/media/143168/
mass Cofiring in coal-fired boilers. DOE/EE-0288. Wash- overview_biomass_gasification.pdf
ington, D.C. U.S. Department of Energy. Accessed May
Persson, Kristoffer et al. No date. Biomass Refinement by
2009.
Torrefaction. Energy Technology and Thermal Process
www1.eere.energy.gov/femp/pdfs/fta_biomass_cofiring.pdf
Chemistry. Umea University. Accessed August 2009.
Graham, R. L. et al. 2007. Current and Potential U.S. Corn www.techtp.com/Biomass%20Refinement%20by%20
Stover Supplies. American Society of Agronomy - Agron- Torrefaction.pdf
omy Journal. p. 10
Renewable Fuels Association. 2008. Ethanol Industry Sta-
International Biochar Initiative. No Date. Biochar: A Soil tistics. Accessed May 2009.
Amendment that Combats Global Warming and Improves www.ethanolrfa.org/pages/statistics
Agricultural Sustainability and Environmental Impacts. p. 2.
Sadaka, Samy. 2010. Potential Bioenergy Production via
www.biochar-international.org/aboutbiochar/
Thermochemical Processes. Webinar for Energy Training
informationaboutbiochar.html
for Agriculture Professionals. September.
Marshall, Liz and Zugg, Zachary. 2008. Finding Balance:
Agricultural Residues, Ethanol, and the Environment.
World Resources Institute. WRI Policy Note. No. 3. p. 1.
Notes
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11. Notes
www.attra.ncat.org ATTRA Page 11

12. An Introduction to Bioenergy: Feedstocks, Processes
and Products
By Leif Kindberg
NCAT Farm Energy Specialist
© 2010 NCAT
Holly Michels, Editor
Robyn Metzger, Production
This publication is available on the Web at:
www.attra.ncat.org/attra-pub/bioenergy.html
or
www.attra.ncat.org/attra-pub/PDF/bioenergy.pdf
IP359
Slot 357
Version 102010
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