What Is Bioenergy?
The term “bioenergy” refers to renewable energy fuels and feedstocks derived from biological sources; agricultural biomass, liquid biofuels and biogas to be used for heat, electricity or vehicle fuel. The term is often used synonymously with “biofuels”.
Some examples of bioenergy feedstocks and fuels being developed in Vermont include switchgrass, hay and other agricultural biomass for heat and power; oilseeds (like canola, sunflower and soybean) and algae for biodiesel; animal waste and food scraps for anaerobic digesters and captured landfill gas to create electricity and biomethane.
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.
VSJF is a member of the Sustainable Biodiesel Alliance.
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. 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 reports that microalgae oil content ranges from 20-80% depending on the species (Chisti, Yusuf. 2007. “Biodiesel from Microalgae.” Biotechnology Advances. 25: 294-306).
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.
Switchgrass and big bluestem are native, perennial, warm season grasses that have high moisture and nutrient use efficiency. Grasses can be pelletized for thermal applications. Vermont farms are well suited for grass biomass production, with over 100,000 acres in pasture or cover crops and an additional 100,000 acres of former cropland not currently in production. The Vermont Grass Energy Partnership is working to evaluate the possibilities of grass as a fuel feedstock by studying the agronomy, chemical analysis, combustion performance and emissions of grass-derived pelletized fuels.
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.
Cellulosic ethanol is widely touted as the holy grail of renewable liquid fuels. While corn-based 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.