Low sulfur clean-burning diesel trucks are replacing gasoline trucks. But diesel and gasoline fuels are of environmental concern because burning the fuel emits carbon dioxide, nitrous oxide and methane. Alternative fuels are meant to reduce greenhouse gases, which include water vapor, carbon dioxide, methane, nitrous oxide and ozone.
Alternative fuels include hydrogen, biodiesel (B20 and above), ethanol (E85), electric, compressed natural gas (CNG), liquefied natural gas (LNG) and liquefied petroleum gas (propane).
There are more than 14,765 public alternative fuel stations in the continental United States. There are thousands of private stations. For example, companies that use propane often install their own fueling station.
The most common comment about hydrogen fuel is that, “it will always be the fuel of the future.”
Biodiesel B20 is a vegetable oil or animal fat-based fuel. Biodiesel may be blended with petro diesel in any proportions. Biodiesel is used in standard diesel engines. Availability, maintenance issues and weather-complicated starts have limited adoption of this fuel. Vigilant maintenance is required to avoid an increase in emissions of carbon monoxide, carbon dioxide and nitrous oxide.
E85 is an 85% ethanol and 15% gasoline or other hydrocarbon by volume. The fuel is produced from cellulosic fiber such as corn leaves, stalks and husks. Although some tail-pipe emissions are reduced, the fuel increases the emissions of acetaldehyde, a toxic chemical. Maintenance and operational issues have been identified. Studies have shown that the toll on the environment of current corn production for ethanol production has been serious, draining water supplies and degrading soils.
Electric road vehicles are powered by an on-board rechargeable electricity storage system and a direct continuous connection to land-based generation plants for purposes of on-highway recharging with unrestricted highway range (urban mass transit) or an on-board rechargeable electricity storage system and a fueled propulsion power source (internal combustion engine): plug-in hybrid.
The environmental impact of using energy generated by a coal-fired power plant is the biggest off-set to any environmental benefits of running these vehicles. Up scaling vehicles for the transport of commercial goods has been problematic.
A natural gas vehicle uses compressed natural gas (CNG) or liquefied natural gas (LNG). Most natural gas vehicles are buses. Fueling stations are mostly regional. Cold weather and maintenance issues have been concerns. The burning of natural gas produces lower carbon emissions than gasoline or diesel fuels.
According to a study funded by the Propane Council, at the point of use, propane emits fewer greenhouse gases than gasoline, diesel, heavy fuel oil or E85 ethanol per unit of energy. Natural gas (methane) generates fewer greenhouse gas emissions per British thermal unit than propane, but methane is chemically stable when released into the air and produces a global warming effect 25 times that of carbon dioxide. Propane is a good choice from an environmental perspective and also is an economically viable choice at this point in time.
Route scheduling is becoming increasing sophisticated with software that may add fueling stations as a variable. Trucks are better designed for weight and aerodynamics. Vehicle refrigeration systems are improving. All these changes will increase efficiencies in the face of increasing vehicle costs.
State and federal subsidies for the purchase of vehicles and the use of alternative fuels are available as tax credits and incentives (for more information, visit www.afdc.energy.gov and search for states of interest). States are required by the Environmental Protection Agency to reduce their carbon emissions and to meet the goals; some may convert their fleets to alternative fuels, thus encouraging more fueling stations.
In March 2015, the E.P.A. and the National Highway Traffic Safety Administration expect to issue a proposed rule for fuel efficiency and carbon pollution standards (i.e. tail-pipe emissions limits) for medium- and heavy-duty vehicles for model year 2019 and later. The first standards were released in August 2011.
The E.P.A. SmartWay Technology Program is a testing, verification and designation program to help freight companies identify equipment, technologies and strategies that save fuel and lower emissions. For information about vehicles that meet environmentally responsible standards go to www.epa.gov/smartway and www.fueleconomy.gov/feg/SmartWay.do.
At this time there is an increased cost to purchasing vehicles that use alternative fuels but the equation is not simple or static. Important variables include local fuel availability and cost; customer demands for reducing greenhouse gas emissions; public perception; and the negative impression left when standing next to a gas or diesel truck vs a propane truck.