Energy content of biofuel


Energy content of biofuel

A Table of Energy Content and CO2 Output of Common Fuels

Energy is the ability to do work. Per kilogram of mass, different substances can do different amounts of work.cite web
url=http://bioenergy.ornl.gov/papers/misc/energy_conv.html
title=Bioenergy Conversion Factors
publisher=Oak Ridge National Laboratory
accessdate=2008-05-18
last=
first=
] In other words they have different energy contents. Of course to do work we usually use a machine of some type. These machines vary in efficiency, or useful work done, and none are 100% efficient. Thus the amount of useful work actually performed by these substances will never totally match these results. However this table gives us a relative measure of the amounts of these substances which could be equivalent in producing the required result (moving a car, heating a home, etc.).

In the example of the first two entries, Bagasse (Cane Stalks) has 9.6 MJ/kg (Mega Joules per kilogram) and Chaff (Seed Casings) has an energy content of 14.6 MJ/kg. In other words 1 kg of Chaff as a fuel would have 14.6-9.6, or 5 MJ more energy per kilogram energy content and potential work output than Bagasse.

The next column in the table (3) is the energy content per liter of volume, which is useful for liquid fuels.

The next column (4) contains the ratio of CO2 mass produced to the mass of the fuel. For example Bagasse has a ratio of 1.3 which means 1.3 kg of CO2 will be produced for every 1 kg of Bagasse used as fuel.

The last column (5), Energy in MJ per kg CO2 produced (MJ/kg) lists the energy produced per Kg of CO2 produced. This is a measure of the potential environmental impact of the use of the substance as a fuel with respect to the release of CO2. The more CO2 released the worse it is for the environment. Thus a higher number in this column is better for the environment because we get more energy per kg of CO2 produced. For example gasoline produces 13.64-14.64 MJ per kg of CO2 but methane produces 20.05-20.30 MJ of energy, or nearly 50% more energy for the same CO2 production.

Notes

*While all CO2 gas output ratios are calculated to within a less than 1% margin of error (assuming total oxidation of the carbon content of fuel), ratios preceded by a Tilde (~) indicate a margin of error of up to (but no greater than) 9%. Ratios listed do not include emissions from fuel Cultivation/Mining, Purification/Refining & Transportation. Fuel availability is typically 74-84.3% NET from source [http://www.mda.state.mn.us/ethanol/balance.html Energy Balance] .
*While Uranium-235 (235U) fission produces no CO2 gas directly, the indirect fossil fuel burning processes of Mining, Milling, Refining, Moving & Radioactive waste disposal, etc. of intermediate to low-grade uranium ore concentrations, produces the equivalent CO2 gas emissions per MJ of net-output-energy of a Natural Gas fired power station. [http://abc.net.au/4corners/special_eds/20050822/ Prof.Mark Diesendorf, Inst. of Environmental Studies, UNSW]

Yields of common crops associated with biofuels production

Oil per seeds = Typical oil extraction from 100 kg. of oil seeds
- Note: Chinese Tallow (Sapium sebiferum, or Tradica Sebifera) is also known as the "Popcorn Tree".
Source: Used with permission from the [http://www.globalpetroleumclub.com The Global Petroleum Club]

See also

*Conversion of units
*Energy density
*Heat of combustion

References


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