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Let's burn more sunshine 4

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fast4door

fast4door

Mechanical
May 29, 2012
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Climate change deniers, go away.

So let's say global warming is caused by pulling tightly-packed carbon out of the ground in solid/liquid form, then combining it with oxygen and creating more CO2 than there was previously. Let's also say we want to simply freeze the amount of CO2 in the atmosphere and dispense with this "sequestration" baloney. In that scenario, we would need a carbon-neutral course of energy. That leaves nuclear or solar or bio-fuels. I want to talk about bio-fuels.

Here's what I can't figure out. Nature has been capturing sunlight and turning it into carbohydrates and lipids for like a trillion years. There's tons of energy out there. We're really good at disassembling those hydrocarbon chains inside of cylinders, turbines, etc. We should be able get good old nature to make our fuel for us. Is there any hope to the people that want to make biodiesel from algae? Are the yields unrealistically low?
 
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My brother in-law is doing PhD research at a well known university on utilizing photosynthesis to create alternative energy. All I can say is its not simple.
 
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Biodiesel is plausible enough that there are now ASTM standards for it.

Algae biodiesel looks plausible, if they can keep the algae from clogging their mechanism, and low-oil competitor species from invading the growing media. Soy biodiesel is plausible, but uses food crop land. Jatropha can be grown for biodiesel oil in areas unsuitable for food crops (though with lower yield.)

Waste vegetable oil -> biodiesel makes sense at an individual/backyard/small co-op level, but there's not enough available to make a meaningful impact at city level, let alone nationally.

Ethanol makes sense in the tropics with sugar cane -> ethanol. Corn-> ethanol is little better than breakeven energy-wise. Subsidies make it profitable.

What would be really useful is a practical cellulose -> ethanol route. There are some promising studies and pilots. Lots of inedible waste cellulose - for example, the rice hulls which are burnt off every year. Grass clippings. Corn stalks.
 
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How about instead of Corn Ethanol something crazy like 'Beat Ethanol' for places that can't grow sugarcane?

However, back the OP... In principle algae bred or GM'd to have higher oil/fat seems interesting. The devil seems to be in the detail as TomDOT mentions.

I won't get into the usual discussions about whether bio fuel => liguid fuel really makes much sense on a large scales, or if we'd be better using simple biomass for stationary power generation and divert the saved fossil fuels (even NG) to mobile applications.

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Boatloads of excess NG being produced in the USA at the moment. Unfortunately, we don't yet have enough facilities to go from NG to LNG so that we can actually load it on the boats.... Check back in 5 years.

I don't know whether beets--> ethanol would be reasonable. We only have beet sugar at its current production level because of HUGE tariffs on imported sugar. World sugar prices are much lower than US sugar prices.
 
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What if, instead of trying to force nature to give us a uniform liquid we can inject into our cylinders, we just burn the cellulose we have? Grain elevators explode all the time because of suspended flour dust. Steam engines did this: they could be run on anything that burned. The problem was that it was an external combustion engine which is inherently less efficient than an internal combustion engine. Plus I think diesels really killed them because they didn't have to heat up a monstrous tank of water in order to get going.

So two alternatives: could we internally combust solids? Or, could we burn plant matter and generate electricity and have an all-electric economy?

One idea I had to get around the problem of long charging times was to have swappable battery modules at filling stations, much like the propane tanks outside gas stations. Each battery would be the size of a suitcase (or whatever didn't weigh too much), and you could swap out 5 modules or so when you go to "fill up".

You're welcome, car companies. I'll expect my royalty checks any day now.
 
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Tom, my heating bill has gone down by half over the last few years. I'm very thankful, but that is still carbon we're adding to the atmosphere. It's better energy per carbon emitted than coal or oil, but it's still adding.
 
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fast4door - exchangeable battery packs aren't a novel idea. They've been discusses on one of the previous 'global warming' or 'green engineering' threads before. In fact I think Greg Locock may have even directed us to some industry paper or similar on it.

Plus, I though my comment about burning biomass for stationary power generation pretty much covers your post about burning cellulose.

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KENAT, sorry, I didn't fully understand the implications of stationary power generation in your comment. So the reason we don't burn plants instead of coal is because coal is cheaper, right? Is that actually a true statement or do we just default to coal because it's more convenient (consistency, existing infrastructure, etc)?

Could engines be adapted to burn airesolized dust? What if I put 5 pound bags of flour in my fuel tank (yeah, okay, not acutally wheat, but powdered cellulose or something) and instead of fuel injectors we would have something like a carburator that uses high-velocity air to pick up dust to put it into the cylinder? If you controlled the fuel/air ratio you would minimize ash, right?

And just think: everybody's car would smell like the outside of a bakery!
 
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Well the fundamental problem with ANY bio-energy scheme is that....it's solar energy. So here in the middle US you're getting a year-round average of about 200 W/m^2 incident energy, if I remember correctly. To really scale up to replace most of the fossil fuels requires an area on the order of the entire US just to produce our transporation fuels. No food, no fibers, no flowers, etc.

Yes, some technologies are better than others, some have higher conversion efficiencies, and so on.

But the incident energy, the source of it all, is not very intense.

Regards,

Mike
 
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In the late middle ages in Europe my understanding is they started running out of suitable biomass for fuel use, and this may have been part of the reason for colonization of the new world etc. Similar has happened in other places leading to deforestation etc.

Ok, we have better technology now (not just on the combustion side but in agriculture etc.) but we also have higher population (so as well as more people needing energy, more demand on land resources for other use such as growing food or timber for housing) and higher energy demands for the current western lifestyle.

So it doesn't look overly promising for bio fuel to become the primary energy source any time soon.

Sure, we can make biomass production more efficient, make more use of different types of biomass, find ways to increase the amount of land available for generating biomass, better ways to turn biomass in to more readily usable energy...

Coal, by several definitions, is a more dense energy source than most biomass and I'd guess more consistent. May be easier to work with too than some biomass.

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Way to go Mike. You've just depressed the living heck out of me. I found another source, that concurs with you. Basically there's not enough solar energy reaching the surface to keep up with our energy needs.

Sigh.

So that leaves nuclear, right? Unless we can generate enough extra energy to sequester the carbon we produce. Or if nature reaches a new carbon consumption equilibrium to keep up with our production.

How's Gates's thorium reactor coming? Have the Chinese started any pilot projects yet?
 
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SnTMan - it's not nearly that bad for biofuels if we get cellulose in the game. I did a BoE calculation* awhile back. With an efficient cellulose -> liquid fuel method, a city could produce 10% of its transportation fuel purely form yard waste which is currently being landfilled. I didn't even count construction debris, or agricultural material which is currently being wasted (like the aforementioned rice waste burnoff.)

For incident energy, kWhr/m2-day is a more useful unit. Austin, TX gets roughly 4 kWhr/m2-day of solar energy on an average day (DNI). El Paso gets 7. Abilene gets 5-6.

*Using hard numbers for population, average fuel consumption, mass of waste going to the landfill, percent of waste as yard trimmings, etc. Austin, TX was my example calculation.
 
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Tom, I don't disagree with your numbers, but you can't capture ALL of the ground level solar power. You need big big chunks of it just to power things like "all the plants on earth" and "weather". Both of which we are already messing with.

Mr. Fusion it is.
 
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TomDOT, well the numbers can be done somewhat differently based on assumptions and so forth, but still, incident solar energy limits any really large scale replacement of fossil transportation fuels with bio-fuels. Everyplace ain't Austin:)

Regards,

Mike
 
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There are other options besides Nuclear.

Any individual one may not be able to replace all fossil fuels, and have pro's and cons, and many may be of dubious overall efficiency and many of them are indirect solar engerby but there are lots of them.

Geothermal is one that seems a bit underutilized.



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First, Better Place are building automated battery swapping stations for suitable electric vehicles. Having long been a proponent of that technology, I am a bit more dubious now that push has come to shove. The battery swap station either needs a lot of power, or a series of large trucks taking empty batteries to somewhere where there is a lot of power.

Secondly, I strongly recommend your read "Without Hot Air" as the author does a reasonable job of presenting the options in a sensible fashion. It is a full book, but is free.

Thirdly I am a CC sceptic, that is, I strongly doubt reducing CO2 produced by man will have much effect on the climate, and don't believe the /science/ (as in stuff that follows the scientific method as opposed to silly statistical curve fitting) has progressed much beyond Arhenius in the last 30 years. But I have no objection to increasing efficiency, and exploring alternatives to oil seems wise. At the same time displacing food crops with fuel crops seems unethical to me.

Cheers

Greg Locock


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