Energy Impacts

What are the energy impacts of biodiesel?

Biodiesel has a positive energy balance, meaning that more energy is produced with the fuel than is used to create a fuel.

Biodiesel fuel can also be used in combination with heating oil to heat residential and industrial buildings. This can reduce dependence on non-renewable and increasingly expensive heating oil

Energy Balance

(According to the National Biodiesel Board)

Biodiesel helps preserve and protect natural resources. For every one unit of energy needed to produce biodiesel, 3.24 units of energy are gained. This is the highest energy balance of any fuel. Because of this high energy balance and since it is domestically produced, biodiesel use can greatly contribute to domestic energy security.

Energy Security Benefits

With agricultural commodity prices approaching record lows, and petroleum prices approaching record highs, it is clear that more can be done to utilize domestic surpluses of vegetable oils while enhancing our energy security. Because biodiesel can be manufactured using existing industrial production capacity, and used with conventional equipment, it provides substantial opportunity for immediately addressing our energy security issues.

If the true cost of using foreign oil were imposed on the price of imported fuel, renewable fuels, such as biodiesel, probably would be the most viable option. For instance, in 1996, it was estimated that the military costs of securing foreign oil was $57 billion annually. Foreign tax credits accounted for another estimated $4 billion annually and environmental costs were estimated at $45 per barrel. For every billion dollars spent on foreign oil, America lost 10,000 – 25,000 jobs.

Energy Content

The energy content (also referred to as heating value) of diesel fuel is its heat of combustion; the heat released when a known quantity of fuel is burned under specific conditions.

In the U.S., the heating value is usually expressed as British thermal units (Btu) per pound or per gallon at 60°F (International metric [SI] units are kilojoules per kilogram or per cubic meter at 15°C). For gross (high) heating value, the water produced by the combustion is assumed to be recondensed to a liquid. For the net (lower) heating value, the water remains as a gas. Since engines exhaust water as a gas, the net heating value is the appropriate value for comparing fuels.

The three main factors that affect vehicle fuel economy, torque, and horsepower are the type of engine (i.e. gasoline or diesel), the efficiency of the engine turning energy in the fuel into usable work, and the fuel’s volumetric energy content or heating value.

The energy content of conventional diesel can vary up to 15% from supplier to supplier or from summer to winter. This variability in conventional diesel is due to changes in its composition which are determined by refining and blending practices. Number 2 diesel fuel usually has higher energy content than Number 1 diesel fuel, with blends of Number 1 and Number 2 varying between the two parent fuel values.

The efficiency of diesel engines is the same whether using biodiesel, diesel, or biodiesel blends so differences in horsepower, torque or fuel economy are due entirely to volumetric energy content1. The energy content of biodiesel is much less variable than that of petrodiesel, and with biodiesel meeting D 6751 standards the energy content is more dependent upon the feedstock’s used than the particular process. Blends of biodiesel and diesel fuel fall between the parent fuels.

The values below represent those of energy content of average No. 2 diesel fuel and average biodiesel in the US.2 While BTU changes of 1-2% can be picked up in lab tests for horsepower, torque, and fuel economy, in practice it is difficult to detect any differences with a 1-2% change in fuel BTU content outside normal variability experienced from day to day operations, even in closely monitored fleets.