Socratic biofuels | 34 comments (34 topical, editorial, 0 hidden)

Re: Socratic biofuels (none / 1)

Notimpossible but wholly unproven. You cannot buildan energy policy on unproven technology. Does anyone know an estimate of how much energy the EU could produce sustainably from second-generation biofuels?

We have met the enemy, and it is us — Pogo

by Migeru (migeru at eurotrib dot com) on Thu Oct 25th, 2007 at 03:33:41 AM EST
[ Parent ]

Re: Socratic biofuels (none / 1)

No freakign idea... but it would be really a lot ... after all it is unproven.

A pleasure

I therefore claim to show, not how men think in myths, but how myths operate in men's minds without their being aware of the fact. Levi-Strauss, Claude

by kcurie on Thu Oct 25th, 2007 at 03:40:14 AM EST
[ Parent ]

Re: Socratic biofuels (none / 0)

What is the maximum possible yield of second-generation biofuels? The most efficient photosynthesizers known are among the blue-green algae. For instance...

Chlorella - Wikipedia, the free encyclopedia

Chlorella is a genus of single-celled green algae, belonging to the phylum Chlorophyta. It is spherical in shape, about 2 to 10 μm in diameter, and is without flagella. Chlorella contains the green photosynthetic pigments chlorophyll-a and -b in its chloroplast. Through photosynthesis it multiplies rapidly requiring only carbon dioxide, water, sunlight, and a small amount of minerals to reproduce.

...
Many people believed Chlorella could serve as a potential source of food and energy because its photosynthetic efficiency can theoretically reach 8%,^[1] comparable with other highly efficient crops such as sugar cane. It is also an attractive food source because it is high in protein and other essential nutrients; when dried, it is about 45% protein, 20% fat, 20% carbohydrate, 5% fiber, and 10% minerals and vitamins. However, because it is a single-celled algae, harvest posed practical difficulties for its large-scale use as a food source. Mass production methods are now being used to cultivate it in large artificial circular ponds.

What does "8% efficiency" mean?

Photosynthetic efficiency - Wikipedia, the free encyclopedia

The photosynthetic efficiency is the fraction of light energy converted into other forms of energy for use. Trees convert light in to chemical energy through the process of photosynthesis with a photosynthetic efficiency of approximately 0.2-0.5%. Other numbers reported range up to 6%, a more detailed analysis is required. By comparison solar panels convert light into electric energy at a photosynthetic efficiency of approximately 10-20%. The photosynthetic efficiency varies with the frequency of the light being converted.

So, assume you cover a hectare of land with a pond full of chlorella and manage to capture 100% of the light and convert it at 8% efficiency into second-generation biofuel feedstock. How much area does Europe need to cover with chlorella in order to satisfy 10% of its liquid fuel demand? Note that this land use is compatible with, for instance, puttin it on the roofs of buildings though in urban environments it's probably more sensible to use solar panels to power the buildings themselves.

We have met the enemy, and it is us — Pogo

by Migeru (migeru at eurotrib dot com) on Thu Oct 25th, 2007 at 04:19:30 AM EST
[ Parent ]

Re: Socratic biofuels (none / 0)

Yes..c ertianly that number can be computed... I woudl try this weekend if I have time...

But you can certianly genetically modified it to make it five times bigger (why not... it is unproven)...

But I agree that ten times this number (efficiency of 50%) will be the most you can get..

SO you should do the fficiency number using 5% and 50%.... ther will give you a boundary of the unproven technology.

A pleasure

I therefore claim to show, not how men think in myths, but how myths operate in men's minds without their being aware of the fact. Levi-Strauss, Claude

by kcurie on Thu Oct 25th, 2007 at 04:53:03 AM EST
[ Parent ]

Re: Socratic biofuels (none / 0)

Hey, hey, "why not, it is unproven" is not valid in support of calculating on the assumption of genetically engineering an organism that doesn't even exist in concept. Stick to 8% efficiency, please.

The technology to grow algae on a massive scale, harvest them, and turn the green goo into liquid fuel is already unproven, but clearly feasible given what we know. The question is one of losses along the way, so let's ignore the losses and compute the theoretical capacity. After all, this 10% biofuels and 20% renewables is an EU goal for 2020, not for 2100 (at which point maybe postulating genetically engineered superalgae that can photosynthesize at the theoretical quantum efficiency of photosynthesis just might be legitimate).

We have met the enemy, and it is us — Pogo

by Migeru (migeru at eurotrib dot com) on Thu Oct 25th, 2007 at 05:18:28 AM EST
[ Parent ]

Re: Socratic biofuels (none / 0)

But regardign energy of the sun per sqaure meter cosnidering days of 12 hours all year through adn considering the Earth average is roughly 1000 kilocaries (real physicist kilocalories) per year.

http://curriculum.calstatela.edu/courses/builders/lessons/less/biomes/SunEnergy.html

A pleasure

I therefore claim to show, not how men think in myths, but how myths operate in men's minds without their being aware of the fact. Levi-Strauss, Claude

by kcurie on Thu Oct 25th, 2007 at 04:56:38 AM EST
[ Parent ]

Re: Socratic biofuels (none / 0)

So, throwing in a factor of 1/2 for latitude and a factor of 1/2 for weather you get 250 Kcal per year per square metre, or 2.5e6 Kcal per year per hectare. At 8% efficiency, that is 2e5 Kcal per year per hectare. That's about 8.4e5 KJ per year per hectare. For comparison, the energy density of diesel fuel is 11 KWh per litre, or approximately 4e4 KJ/l. So, a hectare of chlorella can at most produce the equivalent of 21 litres of diesel fuel per year.

I could easily be off by a factor of 1000 because of sloppy use of units, but otherwise this is a no-go.

We have met the enemy, and it is us — Pogo

by Migeru (migeru at eurotrib dot com) on Thu Oct 25th, 2007 at 05:31:37 AM EST
[ Parent ]

Re: Socratic biofuels (none / 0)

Biofuels & Petro-fuels = Liquid Fuels (Part Two) by afew on July 13th, 2006, has lots of data on first-generation biofuel yields. (3000 litres per hectare seems like a sensible estimate - I must be off by a few zeroes in my estimate for algae).

We have met the enemy, and it is us — Pogo

by Migeru (migeru at eurotrib dot com) on Thu Oct 25th, 2007 at 05:53:14 AM EST
[ Parent ]

Re: Socratic biofuels (4.00 / 3)

Using incident solar power numbers from wikipedia, puts Europe at something like 150W/m^2 average for the year.

At 8% conversion efficiency:
150*0.8*365*24*60*60 = 378,432,000 J/(year*m^2)
For disel, 11kWh/L = 11000*60*60 = 39,600,000 J/L
So, per square metre disel equivalent yield per year:
378,432,000/39,600,000=9.6L/(year*m^2)
or 96,000L/(year*hectare)[sounds like a lot more than 3000. Do I have an extra zero??]

The EU used 494616 kTOE in 2005
In joules: 494616*1000*42e9 = 2.0774e19 J
Which, converted to diesel litres is: 5.2459e11 L
Per percent replacement: 5.4645e8 m^2
or 54645 hectares per percent replacement of 2005 fossil fuel usage.

by someone (s0me1smail(a)gmail(d)com) on Thu Oct 25th, 2007 at 06:43:05 AM EST
[ Parent ]

Re: Socratic biofuels (none / 0)

I think either kcurie's solar energy figure or my interpretation of it were off by a factor of 1000, which is not entirely surprising given the ambiguity in the meaning of the word "calorie".

Calorie - Wikipedia, the free encyclopedia

The calorie was never an SI unit. Modern definitions for calorie fall into 3 classes:
The small calorie or gram calorie approximates the energy needed to increase the temperature of 1 gram of water by 1 °C. This is about 4.184 joules.
The large calorie or kilogram calorie approximates the energy needed to increase the temperature of 1 kg of water by 1 °C. This is about 4.184 kJ, and exactly 1000 small calories.
The megacalorie or ton calorie^{[citation needed]} approximates the energy needed to increase the temperature of 1 tonne of water by 1 °C. This is about 4.184 MJ, and exactly 1000 large calories.

Did I tell you I like TribExt?

We have met the enemy, and it is us — Pogo

by Migeru (migeru at eurotrib dot com) on Thu Oct 25th, 2007 at 06:12:08 PM EST
[ Parent ]

Re: Socratic biofuels (none / 0)

Are we discussing a solar driven fuel source that has a theoretical maximal effiency which is lower then what we today can get from either photovoltaic or thermal solar power?

What am I missing here?

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by A swedish kind of death on Sat Oct 27th, 2007 at 11:55:50 AM EST
[ Parent ]

Re: Socratic biofuels (none / 1)

For fuels, we need chemical energy whereas solar panels provide electrical energy, the conversion of which into chemical energy won't be 100% (or even 30%) efficient (that is true of batteries, too).

Un roi sans divertissement est un homme plein de misères

by linca (antonin POINT lucas AROBASE gmail.com) on Sat Oct 27th, 2007 at 09:12:47 PM EST
[ Parent ]

Re: Socratic biofuels (none / 1)

Thanks, I see.

Sweden's finest (and perhaps only) collaborative, leftist e-newspaper Synapze.se

by A swedish kind of death on Sun Oct 28th, 2007 at 12:50:05 PM EST
[ Parent ]

Re: Socratic biofuels (none / 1)

Liquid biofuels will be presumably used in explosion motors with a theoretical maximum efficiency of less that 50%.

Electrical energy (from solar panels) can be converted to work at a higher theoretical efficiency.

We have met the enemy, and it is us — Pogo

by Migeru (migeru at eurotrib dot com) on Mon Oct 29th, 2007 at 05:56:41 PM EST
[ Parent ]

Re: Socratic biofuels (none / 1)

Isn't starvid's signature that "Peak oil is not an energy crisis but a liquid fuel crisis"? It's all about the considerable technological convenience of using liquid fuels.

We have met the enemy, and it is us — Pogo

by Migeru (migeru at eurotrib dot com) on Mon Oct 29th, 2007 at 05:59:01 PM EST
[ Parent ]

Socratic biofuels | 34 comments (34 topical, 0 editorial, 0 hidden)

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