Scientific community called upon to resolve debate on 'net energy' once and for all

Nov 07, 2008

"Net energy is a (mostly) irrelevant, misleading and dangerous metric," says Professor Bruce Dale, editor-in-chief of Biofuels, Bioresources and Biorefining (Biofpr) in the latest issue of the journal published today.

Net energy is a metric by which some scientists attempt to assess the sustainability and ability of alternative fuels to displace fossil fuel but recent debate in Biofpr shows that scientists are undecided on its merits as a tool.

Instead, in a series of corresponding articles clearly stating the case for and against net energy, Professor Dale calls for a more holistic approach which takes into consideration issues such as greenhouse gas emissions, petroleum displacement and economic growth, particularly in the developing world. He is calling on the scientific community to come together to help establish, once and for all, parameters by which to calculate fuel efficiency by using not just one, but several metrics that can be used in conjunction to give a fuller picture.

The articles – Net energy: still a (mostly) irrelevant, misleading and dangerous metric,
Bruce E. Dale; Net energy and strategic decision making: response to Professor Dale, Franzi Poldy; and Response to Dr. Poldy's questions in this issue, Bruce E. Dale – are the culmination of the ongoing heated exchange, which has already attracted a huge response, between those in favour and those against the use of 'net energy' as a metric.

Professor Dale says: "The election of the new USA president, Barack Obama, who is an open supporter of biofuels will put them very much on the agenda. We need to resolve this issue of appropriate metrics once and for all so we can concentrate on the real task at hand – to deliver viable alternative fuels and reduce our dependence on fossil fuels."

He adds: "Net energy is misleading because it does not give us the whole story of a fuel but instead asks us to make a judgement using a very small component of the decision making process, albeit an important piece of a large jigsaw. When trying to determine whether a fuel is viable or not, we not only need to consider energy in versus energy out but also the overall context such as petrol displacement, land usage and economic growth – this requires a balanced approach with several metrics."

However, in a corresponding article, Dr. Franzi Poldy, CSIRO Sustainable Ecosystems, Australia, disagrees, arguing that in order for policymakers and governments to make decisions about which fuels are best, they need to have numbers to work with to establish a way of calculating the benefits of potential fuels – net energy is the best way to do this.

He says: "Although net energy is not the whole story about any fuel, it is an important part of the story for those concerned with long-term energy supply at the whole-economy level."

Source: Wiley

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4 / 5 (1) Nov 07, 2008
No one thinks they are going about this the wrong way? If whatever the "net energy" is supposed to be doesn't rethink, first and foremost, mass transportation, which is a pressing need in any country and in any city, then what is it for? It's starting with an attempt to easily quantize... what, private profit?!

Maybe I misundestood it.
3 / 5 (2) Nov 07, 2008
You didn't misunderstand! "Greed", not "Need" has driven availability in all things for a long time!
3 / 5 (2) Nov 07, 2008
Didn't someone on the forums say just a few days ago that plants only absorb about 3% of the sunlight that hits them?

So then, in terms of electricity and fuels, etc, wouldn't it then be more efficient to cover an entire farm with solar panels, instead of plants? I hear Solar Panels are about 25% efficient at turning sunlight into electricity these days. That is 8x more efficient than crops, and you have almost no labor or upkeep costs once the "Solar Farm" is planted...

Solar farm...
expensive up front, but then...
Zero energy in, each year, 25% sunlight to electricity.

Biofuel farm...
expensive upfront (you need processing plants, etc.)
Expensive each year (you need to replant and reharvest every year...)
3% efficient...

Am I missing something, or is "biofuels" completely pathetic as an "alternative energy source"?
2 / 5 (1) Nov 08, 2008
I agree we should just take all the energy from the sun and turn it into electrity. Who cares if that means the sky is no longer bright by the sun we will have electrity to make the sky bright!
3 / 5 (1) Nov 08, 2008
The Solar Constant is 1350 Watts meter^-2 equivalent to 4 - 6 kWh day^-1 no matter how the greenies deny it.
not rated yet Nov 08, 2008
Net Energy Gain (NEG) is a concept important in energy economics, referring to a surplus condition in the difference between the energy required to harvest an energy source and the energy provided by that same source. (from Wikipedia)

So net energy takes into account how much energy we need to spend to get the final output. In the case of biofuels, this would include the fuel for the tractor and the harvest, processing etc.

It doesn't seem to me that net energy is unimportant when deciding about what kind of energy to use.

And ... by the way, if we make fuel from food crops, we should also look at the effect that has on food prices.

So let's go slow on biofuels. Direct sun energy harvesting as Quantum Conundrum says, is more efficient by far. And it can be done both direct conversion to electricity or harvesting the heat and using that to run a steam turbine/generator.

We're just too addicted to liquid fuels. Time to change.

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