What are Biofuels?
Biofuels are biologically-based fuels such as biodiesel, ethanol, and methane that can be used to run vehicles, heat buildings, or generate electricity. More broadly, biofuels also include biomass fuels such as wood chips, wood pellets, and a variety of fast growing trees, shrubs, and grasses such as miscanthus and switchgrass.
Biodiesel is a domestically produced renewable fuel derived from virgin seed oils (e.g. canola, soybean, mustard, or sunflower) pressed from crops that can be grown in Vermont. It can also be produced from reclaimed vegetable oil, animal fat and, most promising of all, from algae. Biodiesel is known to have less of an impact on human health and the environment than petrodiesel—such as reduced greenhouse gas emissions—while containing a similar energy (Btu) content. Since it can be used in any compression ignition (“diesel”) engine without significant modification, biodiesel is being used today in farm equipment and other applications, including transportation and heating (“bioheat”).
Biodiesel blends easily with refined petroleum products and can be added to or replace No.2 heating oil or low sulfur (“on-road”) diesel. The word biodiesel here refers to the pure fuel - B100 (ASTM D 6751-03), while biodiesel blend refers to a percentage of biodiesel--usually between 2% (B2) and 20% (B20)--mixed with petrodiesel. .
Biodiesel is made through a process called transesterification whereby alcohol (either methanol or ethanol) and lye (sodium hydroxide or potassium hydroxide) are combined to separate the alkyl esters (biodiesel) from the glycerin that occurs naturally in the seed oil.
- Where can you get biodiesel in Vermont? (PDF: 715 KB)
- Where can farmers interested in biodiesel production find more information? (PDF: 1,657 KB)
Algal Biodiesel: From 1978 to 1996, the U.S. Department of Energy’s Office of Fuels Development funded an Aquatic Species Program (ASP) to develop renewable fuels, mainly biodiesel, from microalgae grown in ponds (Sheehan et al., 1998). Unlike other oil seed crops, microalgae grow very fast and are very rich in oil. “Waste” carbon dioxide from coal fired power plants was used to encourage algal growth. Research to date suggests that algal biodiesel is the only type of biofuel that theoretically can completely displace diesel for heating and transportation (Chisti, 2007: 304). Chisti reports that microalgae oil content ranges from 20-80% depending on the species.
The beauty of algae is that its production does not compete with food production and it is highly productive, doubling in biomass every day. According to National Renewable Energy Laboratory scientist Eric Jarvis, several hurdles need to be addressed before algal biodiesel becomes commercialized:
- Algal strains for continuous high-level oil production need to be developed: the right starting species need to be selected; strains need to be improved (e.g., genetic engineering); nutrient, temperature, pH, and salinity requirements need to be established; water and CO2 sources need to be identified; and protection from outside organisms needs to be maintained.
- Cultivation facility design and operation: reactor system engineering & optimization; harvesting and extraction technology development; algae co-products development.
- Fuel production: development of conversion technology; optimization of pre/post processing.
Anaerobic digesters transform cow manure, corn silage, haylage, and other biological material into “biogas” or methane. Anaerobic digesters are basically covered tanks that heat up as the biological material decomposes in the absence of oxygen. Bacteria in the digester turn the biological material into biogas that can then be piped to a generator to create electricity and heat for the farm and/or be sold to the grid. The remaining solids
can be used for a variety of uses, including animal bedding (e.g., Blue Spruce Farm used to pay $60,000 for bedding and they can now create their own) and compost (e.g., Foster Farm’s “Moo Doo”), and the liquid can be used as fertilizer. Anaerobic digesters also considerably reduce manure odor, eliminate pathogens, and can play a role in an integrated manure management system.
Biomass (e.g., organic matter such as wood chips, manure, pellets, crops and crop residues) can be burned in a boiler to produce steam which then causes a turbine to rotate and generate electricity. Biomass applications include co-firing (burning organic matter and coal), combined heat and power systems, and gasification (heating biomass in a low or no oxygen environment until it becomes a gas). Biomass is currently the largest source of renewable energy in the United States. According to Adam Sherman of the Biomass Energy Resource Center (BERC), biomass may make sense for any farm application that has a high heat load (e.g., greenhouses, sugarhouses, or other large farm facilities).
- BERC: Vermont Wood Chip Suppliers (PDF: 103 KB)
Cellulosic ethanol is widely touted as the holy grail of renewable liquid fuels. While cornbased ethanol produced in the Midwest and Brazilian ethanol made from sugarcane are derived from plant starch or sugar, cellulosic ethanol is made from the abundant cellulose in plant walls.
- What about cellulosic ethanol? (PDF: 213 KB)
Photo Credits: Canola Field (left), Netaka White; Seed press with sunflower seeds (middle), Ed Delhagen; Biodiesel flask (right), Netaka White.
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