Biodiesel from algae may not be as green as it seems

Biodiesel from algae may not be as green as it seems

www.newscientist.com

When algae are farmed in perspex tubes, she says, the energy needed to pump the algae around to ensure adequate exposure to sunlight results in a carbon footprint of 320 grams per megajoule equivalent of fuel. This compares with 86 g/MJ to extract, refine and burn regular diesel (Energy and Fuels, DOI: 10.1021/ef1003123).

"If you use tubular bioreactors, frictional losses mean the energy required to pump the culture around is so high that the biodiesel would have a much greater greenhouse gas emission than fossil diesel," she says.

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Related AboveTopSecret.com Discussion Threads:
Biodiesel a possible replacement for oil.

There are 2 methods of producing biodiesel, open ponds and growing tubes. Each has advantages and disadvantages.

Open tubes are more efficient but produce more CO2 and are more cost intensive. Open ponds are less costly but use much more water resources.

Her model shows that growing algae in open ponds offers "a lot more potential to produce an environmentally sustainable fuel" - the footprint of biodiesel produced this way is only 19 g/MJ. But open ponds have one major drawback, namely that the water tends to evaporate, making them potentially more water-hungry than biofuel crops. What's more, the yield of diesel from open ponds tends to be lower than from growing tubes, where the algae have better exposure to sunlight.

So algae production using ponds is far more efficient in both environmental and cost aspects but it uses much more valuable water resources.

Most likely algae production would occur in places like the southwest US in open areas, but in those areas water availability is always an issue.

Water is a valuable resource comparable to fuel. So the cost of water must be considered!

www.newscientist.com
(visit the link for the full news article)

[edit on 28/7/10 by plumranch]

Just an idea, why not have the ponds set up like a green house? The water that evaporated would be contained and captured to return to the pond. Thus reducing the loss and need for high water usage. Of course we can't have any system that might work now can we. Or did I miss the point as in carbon foot print and CO2 tax.

Another one bites the dust.

If you look at every one of the alternative fuel proposals they cost more in money and CO2 out put then they save.
The only alternative fuel systems that work and are cost effective are trash to biofuel using the Fischer–Tropsch Synthesis.
And that is because trash is a waste product and cost money to dispose of and its a major source of pollution.

The Fischer–Tropsch Synthesis makes money disposing of trash and the fuel cost is less then oil from the ground.
Also you no longer will need land for landfills.

And it can also make fresh water and fuel from sewage. so that it needs not outside water resources.

Our answers will not be found in slime. I am certain it WILL BE found here :

janus.mtsu.edu...

frank.mtsu.edu...

First one is a short comment by the creator. Second one is the Abstract.
Good reading and keep your jaws on your head.

There are ways around these problems. It just takes real people working on them instead of scientists for a while.

Scientists tend to look for the "WOW!" factor. People that need to fuel their car to get to work without going broke will tend ot look for the "Doable" factor. Perhaps not as fast, or as cool, but something that simply gets the job done.

The big thing here though, for now is this: It is cheaper to cut use of energy intensive methods than it is to develop new ones at this time.

No one want to hear the we need to cut our energy use, become more efficient or sacrifice pleasures. (Well, nearly seven billion people, there is probably SOMEONE who wants to hear that...)

But it is the soundest policy for now.

So for now it is about sacrifice and scrambling to find something better as soon as possible.

Pre Industrial revolution,we had these things called "water wheels."

Surely these could be adapted/re designed to ciculate the water needed for the algae?

Use the energy from the river,not a power station!

Sometimes the old ideas are the best ones

reply to post by plumranch


No joke.

Everything we do poisons Earth somehow. So really the best solution is to build a big spaceship and half of us leave.

There's no such thing as green technology. Just less polluting technology.

reply to post by Gorman91


I disagree mate-Although I love the spaceship idea

There ARE ways of generating big power in harmony with our earth-the motion is all there,waves can be used to generate a form of power which does not harm our planet.

Low orbital solar could also utilise massive amounts of energy,beamed to the earth by satellites.

There are ways.

But lets build the spaceship at the same time-no harm in a back up plan.

reply to post by pstrron

Just an idea, why not have the ponds set up like a green house? The water that evaporated would be contained and captured to return to the pond. Thus reducing the loss and need for high water usage.

Having built and worked with several greenhouses from simple to high end varieties, greenhouses are expensive, vulnerable to weather and the elements and concentrate all your disease, and other problems and they have a relatively short useful life.

The advantage of ponds is they can be large, out in the open air, on cheap land useless otherwise, etc.

You'd need a superdome type structure, I would think which is $$$$.

reply to post by ANNED

If you look at every one of the alternative fuel proposals they cost more in money and CO2 out put then they save.

Agreed.

Although I like alternative fuels and systems, etc. and I think the ground source heat pump system I use for my house and shop/ greenhouse is great, efficient, etc. I frankly question the need for alternative systems unless they are clearly cost effective.

I think our assumptions that we are running out of fossil fuel, that burning fossil fuels is doing permanent damage to the earth and that greenhouse gasses are bad and are not beneficial in some respects all needs to be questioned more than it is and these aspects need to be reexamined with a clear mind.

We all seem to jump on a bandwagon and sing the same tune when it comes to the environment and it is not necessarily good.

For example this $40,000 GM electric car, I think, is an obvious boondoggle and will in the end do nothing good for the environment. It's all "feel good" environmentalism.