Net energy -- a useless, misleading and dangerous metric, says expert

Aug 09, 2007

As oil becomes scarce, the world needs new transportation fuels. As new fuel options develop we need means of assessing which are most effective at replacing petroleum. So far many scientists have used a measure called ‘net energy’.

However, Professor Bruce Dale from Michigan State University claims, “Net energy analysis is simple and has great intuitive appeal, but it is also dead wrong and dangerously misleading – net energy must be eliminated from our discourse.” Dale’s perspective is published in the first edition of Biofuels, Bioproducts and Biorefining.

Instead, Dale recommends comparing fuels by assessing how much petroleum fuel each can replace, or by calculating how much CO2 each produces per km driven.

A fuel’s ‘net energy’ is calculated by attempting to assess how much energy a new fuel supplies, and then subtracting the energy supplied by fossil fuels needed to create the new fuel. The calculation is often carried out in a way that leaves grain ethanol with a net energy of -29%, giving the impression that it uses more fossil fuels to produce it that the new fuel supplies. Dale claims that this figure is then used by opponents of biofuels to pour scorn on the new products.

The problem with net energy, says Dale, is that it makes an assumption that all sources of energy (oil, coal, gas etc) have equal value. “This assumption is completely wrong – all energy sources are not equal – one unit of energy from petrol is much more useful than the same amount of energy in coal…and that makes petrol much more valuable,” says Dale.

For evidence, he points to the markets, where a unit of energy from gas, petrol and electricity are worth 3.5, 5 and 12 times as much as a unit of energy from coal, respectively.

“Clear thinking shows that we value the services that energy can perform, not the energy per se, so it would be better to compare fuels by the services that each provides…not on a straight energy basis…which is likely to be irrelevant and misleading,” says Dale.

For example, biofuels could be rated on how much petroleum use they can displace or their greenhouse gas production compared with petroleum. His calculations indicate that every MJ of ethanol can displace 28 MJ of petroleum, in other words ethanol greatly extends our existing supplies of petroleum. Using corn ethanol provides an 18% reduction in greenhouse gasses compared with petrol, while fibre-produced ethanol gives a 88% reduction compared to petrol.

“As we embark on this brave new world of alternative fuels we need to develop metrics that provide proper and useful comparisons, rather than simply using analyses that are simple and intuitively appealing, but give either no meaningful information, or worse still, information that misleads us and misdirects our efforts to develop petroleum replacements,” says Dale.

Source: John Wiley & Sons, Inc.

Explore further: Study: Alcatraz inmates could have survived escape

add to favorites email to friend print save as pdf

Related Stories

Microbial 'signature' for sexual crimes

27 minutes ago

Bacterial communities living on an individual's pubic hairs could be used as a microbial 'signature' to trace their involvement in sexual assault cases, according to a study published in the open access journal Investigative Ge ...

Brazil: Google fined in Petrobras probe

1 hour ago

A Brazilian court says it has fined Google around $200,000 for refusing to intercept emails needed in a corruption investigation at state-run oil company Petrobras.

Atari's 'E.T.' game joins Smithsonian collection

2 hours ago

One of the "E.T." Atari game cartridges unearthed this year from a heap of garbage buried deep in the New Mexico desert has been added to the video game history collection at the Smithsonian.

Sony threatens to sue for publishing stolen emails

2 hours ago

A lawyer representing Sony Pictures Entertainment is warning news organizations not to publish details of company files leaked by hackers in one of the largest digital breaches ever against an American company.

Microsoft builds support over Ireland email case

2 hours ago

Microsoft said Monday it had secured broad support from a coalition of influential technology and media firms as it seeks to challenge a US ruling ordering it to hand over emails stored on a server in Ireland.

Recommended for you

Study: Alcatraz inmates could have survived escape

11 hours ago

The three prisoners who escaped from Alcatraz in one of the most famous and elaborate prison breaks in U.S. history could have survived and made it to land, scientists concluded in a recent study.

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.