Biodiesel
Biodiesel is a domestically produced, renewable fuel that can be manufactured from vegetable oils, animal fats, or recycled restaurant grease for use in diesel vehicles. Biodiesel's physical properties are similar to those of petroleum diesel, but it is a cleaner-burning alternative. Using biodiesel in place of petroleum diesel, especially in older vehicles, can reduceemissions.
Basics
Biodiesel is a domestically produced, renewable fuel that can be manufactured from vegetable oils, animal fats, or recycled restaurant grease. It is a cleaner-burning replacement for petroleum diesel fuel. It is nontoxic and biodegradable.
Biodiesel is a liquid fuel often referred to as B100 or neat biodiesel in its pure, unblended form. Like petroleum diesel, biodiesel is used to fuel compression-ignition engines, which run on petroleum diesel. See the table for biodiesel's physical characteristics.
How well biodiesel performs in cold weather depends on the blend of biodiesel. The smaller the percentage of biodiesel in the blend, the better it performs in cold temperatures. Regular No. 2 diesel and B5 perform about the same in cold weather. Both biodiesel and No. 2 diesel have some compounds that crystallize in very cold temperatures. In winter weather, manufacturers combat crystallization in No. 2 diesel by adding a coldflow improver. For the best cold weather performance, drivers should use B20 made with No. 2 diesel manufactured for cold weather.
Biodiesel Blends
Biodiesel can be blended and used in many different concentrations, including B100 (pure biodiesel), B20 (20% biodiesel, 80% petroleum diesel), B5 (5% biodiesel, 95% petroleum diesel) and B2 (2% biodiesel, 98% petroleum diesel). B20 is a common biodiesel blend in the United States.
Low-Level Blends
ASTM International develops specifications for conventional diesel fuel (ASTM D975). These specifications allow for biodiesel concentrations of up to 5% (B5). Low-level biodiesel blends, such as B5 are ASTM approved for safe operation in any compression-ignition engine designed to be operated on petroleum diesel. This can includelight-dutyandheavy-dutydiesel cars and trucks, tractors, boats, and electrical generators.
B20
B20 (20% biodiesel, 80% petroleum diesel) is the most common biodiesel blend in the United States. B20 is popular because it represents a good balance of cost, emissions, cold-weather performance, materials compatibility, and ability to act as a solvent. Using B20 provides substantialbenefitsand avoids many of the cold-weather performance and material compatibility concerns associated with B100. Most biodiesel users purchase B20 or lower blends from their petroleum distributors or biodiesel marketers. Biodiesel blends of 20% (B20) or higher qualify for biodiesel fuel use credits under theEnergy Policy Act of 1992.
B20 and lower-level blends generally do not require engine modifications. Engines operating on B20 have similar fuel consumption, horsepower, and torque to engines running on petroleum diesel. B20 has a highercetane number(a measure of the ignition value of diesel fuel) andhigher lubricity(the ability to lubricate fuel pumps and fuel injectors) than petroleum diesel.
However, not all diesel engine manufacturers cover biodiesel use in their warranties (see theNational Biodiesel Board's OEM Informationfor those that do support the use of biodiesel blends). Because diesel engines are expensive, users should consult their vehicle and engine warranty statements before using biodiesel. Biodiesel blends between B6 and B20 must meet prescribed quality standards—ASTM D7467 (summary of requirements).
B100, or neat biodiesel, contains about 8% less energy per gallon than petroleum diesel. For B20, this could mean a 1% to 2% difference, but most B20 users report no noticeable difference in performance or fuel economy. Biodiesel has some emissions benefits, especially for engines manufactured before 2010. For engines equipped with selective catalytic reduction (SCR) systems, the air quality benefits are the same whether running on biodiesel or petroleum diesel. However, biodiesel still offers better greenhouse gas (GHG) benefits compared to conventional diesel fuel. The emissions benefit is roughly commensurate with the blend level; that is, B20 would have 20% of the GHG reduction benefit of B100.
B100
B100 and other high-level biodiesel blends are less common than B5 or B20 due to a lack of regulatory incentives and pricing. B100 can be used in some engines built since 1994 with biodiesel-compatible material for parts, such as hoses and gaskets. B100 has a solvent effect and it can clean a vehicle's fuel system and release deposits accumulated from previous petroleum diesel use. The release of these deposits may initially clog filters and require filter replacement in the first few tanks of high-level blends.
When using high-level blends, a number of issues can come into play. The higher the percentage of biodiesel above 20%, the lower the energy content per gallon. High-level biodiesel blends can also impact engine warranties, gel in cold temperatures, and suffer from microbial contamination in tanks. B100 use could also increase nitrogen oxides emissions, although it greatly reduces other toxic emissions.
B100 requires special handling and may require equipment modifications. To avoid engine operational problems, B100 must meet the requirements ofASTM D6751, Standard Specification for Biodiesel Fuel (B100) Blend Stock for Distillate Fuels (summary of requirements). ASTM Specification D6751 now includes a No.1-B and a No.2-B grade. The No.1-B grade has stricter limits on monoglycerides and filterability than the No.2-B grade. The No.1-B grade is a special purpose biodiesel grade for use in applications where low temperature operability is needed.
Biodiesel Production and Distribution
Biodiesel is a legally registered fuel and fuel additive with the U.S. Environmental Protection Agency (EPA). EPA registration includes all biodiesel that meetsASTM D6751and is feedstock neutral. The federalRenewable Fuel Standardrequires at least 1 billion gallons of biomass-based diesel consumption in the U.S. (at this time, biodiesel comprises the vast majority of biomass-based diesel in the US). The RFS requires 1.3 billion gallons of biomass-based diesel in 2013.
Production
Biodiesel is produced from vegetable oils, yellow grease, used cooking oils, and tallow. The production process converts oils and fats into chemicals called long-chain mono alkyl esters, or biodiesel. These chemicals are also referred to as fatty acid methyl esters, and the process is referred to as transesterification. Roughly speaking, 100 pounds of oil or fat are reacted with 10 pounds of a short-chain alcohol (usually methanol) in the presence of a catalyst (usually sodium hydroxide [NaOH] or rarely, potassium hydroxide [KOH]) to form 100 pounds of biodiesel and 10 pounds of glycerin. Glycerin, which is used in pharmaceuticals and cosmetics, among other markets, is a co-product. Although the process is relatively simple, homemade biodiesel is not recommended. Diesel engines are expensive and risking damage, loss of warranty, and operational problems from fuel that does not meet rigorousASTM D6751specifications is not wise.
Raw or refined plant oil, or recycled greases that have not been processed into biodiesel, are not biodiesel and should be avoided. Fats and oils (triglycerides) are much more viscous than biodiesel, and low-level vegetable oil blends can cause long-term engine deposits, ring sticking, lube-oil gelling, and other maintenance problems that can reduce engine life. (SeeStraight Vegetable Oil as a Diesel Fuel?(PDF)).
Research is currently focused on developing algae as a potential biodiesel feedstock, because it's expected to produce high yields from a smaller area of land than vegetable oils.
Biodiesel Benefits and Considerations
Biodiesel is a domestically produced, clean-burning, renewable substitute for petroleum diesel. Using biodiesel as a vehicle fuel increases energy security, improves public health and the environment, and provides safety benefits.
Energy Security and Balance
The United States imports about half of its petroleum, two-thirds of which is used to fuel vehicles in the form of gasoline and diesel. Depending heavily on foreign petroleum supplies puts the United States at risk for trade deficits, supply disruption, and price changes. Biodiesel can beproducedin the U.S. and used in conventional diesel engines, directly substituting for or extending supplies of traditional petroleum diesel.
Air Quality
Compared with using petroleum diesel, using biodiesel in a conventional petroleum diesel engine substantially reduces tailpipe emissions of unburned hydrocarbons (HC), carbon monoxide (CO), sulfates, polycyclic aromatic hydrocarbons, nitrated polycyclic aromatic hydrocarbons, and particulate matter (PM). The reductions increase as the amount of biodiesel blended into diesel fuel increasesfor engines manufactured before 2010. Engines manufactured in 2010 and later have to meet the same emissions standards, whether running on biodiesel, diesel, or even natural gas.Selective catalytic reduction (SCR)technology, which reduces nitrogen oxide (NOx) emissions to near zero levels, makes this possible. For these new technology engines, the emissions from diesel fuel are comparable to those from biodiesel and are very, very low. These new technology engines are some of the cleanest engines on the road. B100 provides the best emission reductions, but lower-level blends also provide benefits. B20 has been shown to reduce PM emissions 10%, CO 11%, and unburned HC 21% (see graph) in older engines Learn more aboutBiodiesel Emissions.
Using biodiesel reduces greenhouse gas emissions because carbon dioxide released from biodiesel combustion is offset by the carbon dioxide sequestered while growing the soybeans or other feedstock. B100 use reduces carbon dioxide emissions by more than 75% compared with petroleum diesel. Using B20 reduces carbon dioxide emissions by 15%.
Greenhouse gas and air-quality benefits of biodiesel are roughly commensurate with the blend. B20 use provides about 20% of the benefit of B100 use. B100 use could increase nitrogen oxides emissions, although it greatly reduces other emissions.
Engine Operation
Biodiesel improves fuel lubricity and raises the cetane number of the fuel. Diesel engines depend on the lubricity of the fuel to keep moving parts from wearing prematurely. One unintended side effect of the federal regulations, which have gradually reduced allowable fuel sulfur to only 15 ppm and lowered aromatics content, has been to reduce the lubricity of petroleum diesel. To address this, theASTM D975diesel fuel specification was modified to add a lubricity requirement (a maximum wear scar diameter on the high-frequency reciprocating rig [HFRR] test of 520 microns). Biodiesel can increase lubricity to diesel fuels at blend levels as low as 1%.
Before using biodiesel, be sure to check your engine warranty to ensure that higher-level blends of this alternative fuel don't void or affect it. High-level biodiesel blends can also have a solvency effect in engines that previously used petroleum diesel.
Safety
Biodiesel is nontoxic. It causes far less damage than petroleum diesel if spilled or released to the environment. It is safer than petroleum diesel because it is less combustible. The flashpoint for biodiesel is higher than 130°C, compared with about 52°C for petroleum diesel. Biodiesel is safe to handle, store, and transport.
Electricity
Electricity can be used to powerall-electric vehiclesandplug-in hybrid electric vehicles. These vehicles can draw electricity directly from the grid and other off-board electrical power sources and store it in batteries. Hybrid electric vehicles use electricity to boost fuel efficiency. Using electricity to power vehicles can have significant energy security and emissions benefits.
Electricity Fuel Basics
Electricity is considered an alternative fuel under the Energy Policy Act of 1992. Electricity can be produced from a variety of primary energy sources, including oil, coal, nuclear energy, moving water, natural gas, wind energy, and solar energy.Plug-in vehiclesare capable of drawing electricity from off-board electrical power sources (generally the electricity grid) and storing it in batteries. Though not yet widely available,fuel cell vehiclesuse hydrogen to cleanly generate electricity onboard the vehicle.
Powering Vehicles with Electricity
In plug-inelectric vehicles, onboard rechargeable batteries store energy to power electric motors. Vehicles that run only on electricity produce no tailpipe emissions. But there areemissionsassociated with theproduction of most of the country's electricity.
Fueling plug-in vehicles with electricity is currently cost effective compared to gasoline, especially if drivers take advantage of off-peak rates offered by many utilities. Electricity costs can vary by region, type of generation, time of use, and access point. Learn aboutfactors affecting electricity pricesfrom the U.S. Energy Information Administration.
Electric Charging Stations
Many plug-in vehicle owners will do the majority of their charging at home (or at fleet facilities, in the case of fleets). Some employers offer access to charging at the workplace. In many states, plug-in vehicle drivers also have access topublic charging stationsat libraries, shopping centers, hospitals, and businesses. Charging infrastructure is rapidly expanding, providing drivers with the convenience, range, and confidence to meet more of their transportation needs with plug-in vehicles.
Electricity Production and Distribution
Plug-in hybrid electric vehicles (PHEVs) and all-electric vehicles (EVs) store electricity in batteries to power one or more electric motors. The batteries are charged primarily by plugging into off-board sources of electricity, produced from fossil fuels, nuclear energy, and renewable energy sources.
EVs and PHEVs in all-electric mode do not produce tailpipe emissions. However, there are emissions associated with the majority of electricity production in the United States. See theemissions sectionfor more information.
Production
Most of the electricity in the United States is produced by steam turbine generators at power plants from primary resources such as coal, natural gas, and nuclear energy. According to the U.S. Energy Information Administration, in 2012, 37% of the nation's electricity was generated by coal, 30% by natural gas, 19% by nuclear energy, and 1% by petroleum.
Electricity is also produced from renewable sources of energy, including hydropower, biomass, wind, geothermal, and solar power. Together, renewable energy sources generated about 12% of the country's electricity in 2012. Production capacity from renewable sources (excluding hydropower) has been increasing steadily over the last decade.
With the exception of photovoltaic (PV) generation, most of the primary sources of energy are used directly or indirectly to move the blades of a turbine connected to an electric generator. The turbine generator set converts mechanical energy to electrical energy. In the cases of coal, oil, natural gas, nuclear fission, biomass, geothermal and solar thermal, the heat produced by these primary resources is used to create steam, which moves the blades of the turbine. In the cases of hydro and wind power, turbine blades are acted upon directly by flowing water and wind, respectively. PV panels convert sunlight directly to electricity using semiconductors that exhibit the photovoltaic effect.
The sources of energy used to produce electricity vary from one geographic region to the next. To find out about the mix of fuels and other energy sources used in your area, see theemissions section. Learn more about electricity production from the U.S. Department of Energy'sEnergy Information Administration.
Electricity Transmission and Distribution
Electricity in the United States travels long distances from generating facilities to local distribution substations through a transmission grid of nearly 160,000 miles of high-voltage transmission lines. Generating facilities provide power to the grid at low voltage, from 480V in small generating facilities to 22 kV in larger power plants. Once electricity leaves a generating facility, the voltage is increased, or "stepped up," by a transformer to minimize the power losses over long distances. As electricity is transmitted through the grid and arrives in the load areas, voltage is stepped down by transformers at distribution substations (ranges of 69 kV to 4.16 kV), and finally further lowered for use by customers (residential customers use 120V and 240V; commercial and industrial customers typically use 120V, 208V, and 480V).
Plug-In Vehicles and Electricity Infrastructure Capacity
EVs and PHEVs represent a new source of demand for electricity. However, they are unlikely to strain much of our existing electricity infrastructure in the near term. Large increases in the number of these vehicles in the United States will not necessarily require the addition of new electricity-generation capacity or substantial upgrades to transmission and distribution infrastructure.
Demand for electricity rises and falls, depending on time of day and time of year. Electricity production, transmission, and distribution capacity must be able to meet demand during times of peak use; but most of the time, the electricity infrastructure is not operating at its full capacity. In the United States, roughly 50% of the generation capacity is used 100% of the time, while only 5% of the time (about 400 hours per year) generation greater than 90% of the capacity is used. Usually the most costly and inefficient generation is used during these peak periods. As a result, EVs and PHEVs have the potential to create little or no need for additional capacity, as long as they charge predominantly during off-peak times, such as late at night, when the electric load on the system is at a minimum.
According to a study by Pacific Northwest National Laboratory, existing U.S. electricity infrastructure has sufficient capacity to meet about 73% of the energy needs of the country's light-duty vehicles. According to deployment models developed by researchers at the National Renewable Energy Laboratory (NREL), the diversity of household electricity loads and electric vehicle loads should allow introduction and growth of the plug-in vehicle market while "smart grid" networks expand. These networks will provide the capability to monitor and protect residential distribution transformers from future vehicle impacts, ensure that charging occurs during off-peak periods, and reduce costs to utilities, grid operators, and consumers. The NREL analysis also demonstrated the potential for synergies between plug-in vehicles and distributed sources of renewable energy. For example, small-scale renewables, like solar panels on a rooftop, can both provide clean energy for vehicles and reduce demand on distribution infrastructure by generating electricity near the point of use.