What is F30 biofuel oil?

Here, “F30” means that the mixture contains 30% VOME and 70% domestic heating oil. So for F10 and F50 biofuel oils, the share of VOME in the mixture is 10% and 50% respectively. F100 biofuel oil, meanwhile, isn’t a mixture: it contains 100% VOME.

The VOME used in biofuel oil is produced from various plants such as sunflower, soya or rapeseed. In France, rapeseed tends to be used because it’s particularly well-adapted to the local soil and climate. In the United States, meanwhile, VOME is generally derived from soya.

What is rapeseed methyl ester?

Rapeseed methyl ester belongs to a group of compounds known as fatty acid methyl esters (FAMEs). More specifically, it’s a vegetable oil methyl ester (VOME), which is different from animal oil methyl esters (AOMEs) and waste oil methyl esters (WOMEs).

Rapeseed methyl ester is treated as a renewable energy source because it’s produced from a crop (in this case, rapeseed). It’s also considered to have a neutral carbon footprint because the CO2 emitted when it’s burned was absorbed from the atmosphere by the rapeseed as it grew.

Nevertheless, rapeseed VOME isn’t environmentally harmless because it’s produced by transesterification, a chemical conversion process that requires energy and other substances:

Rapeseed VOME also has another drawback: the potential for poor harvests means that the crop itself is unreliable. It also monopolises land that could be used to grow food crops. What’s more, if a plot of land has to be converted to grow rapeseed (a process known as “land-use change”), this generates a lot of CO2 emissions.

That’s why estimates of the total carbon footprint of VOMEs can range from 18 to 220 grams of CO2 equivalent per megajoule (MJ), depending on how they’re produced.

What does “CO2 equivalent” mean?

The units “gCO2e” and “gCO2eq” stand for “grams of CO2 equivalent”. These are known as “emission factors” because they represent an estimate of total greenhouse gas (GHG) emissions. In many cases, these values combine emissions from the two major stages of a fuel’s life cycle:

• Production: all energy expended in the production of the fuel (harvesting, fertiliser, extraction, processing, transport, etc.)
• Combustion: the sum of all gases released when the fuel is burned (carbon dioxide (CO2), carbon monoxide (CO), sulphur dioxide (SO2), nitrous oxide (N2O), methane (CH4), etc.)

Emissions from the production and combustion stages are expressed in “CO2 equivalent”: because different gases have more or less powerful greenhouse effects, total emissions for each gas are weighted relative to the specific greenhouse effect of CO2, which serves as the common denominator. /p>

This CO2 equivalent value is always expressed relative to another unit, such as the volume or weight of the fuel (gCO2e per kilogram or litre), the distance travelled by a vehicle (gCO2e per kilometre), or the amount of energy generated (gCO2e per joule or watt-hour).
 

How do fuels differ in terms of power and emissions?

We’ve put together a table comparing different fuels by energy density and carbon emissions relative to the amount of energy provided. Energy is the most common metric for comparing and ranking the performance of fuels. But energy density (also known as “energy content”) is also an important value, since it determines the size and weight of the tanks needed to store a fuel – a key detail that can’t be overlooked!

¹ CO2 emissions from combustion, excluding all other gases.
²CO2 emissions are offset by the CO2 absorbed by the rapeseed during growth.
³Theoretical CO2 emissions based on total combustion of the rapeseed VOME, ignoring the absorption of CO2 during growth.
⁴ Total emissions of all greenhouse gases across the entire life cycle of the fuel (source: ADEME carbon database).
⁵ Most optimistic CO2 emissions scenario: without land-use change for rapeseed cultivation.
⁶ Assumption of CO2 emissions with gas being transported by pipeline.

Notes: The values in the table are rounded for convenience. These values may differ slightly depending on the source. Most of our values come from the French Environment and Energy Management Agency (ADEME) and other government bodies. Since no official information is available, the values for F10, F30, F50 and F100 biofuel oils are extrapolations from the figures for heating oil and rapeseed VOME, based on their respective shares in the mixture.