I am not the biggest fan of corn ethanol. But I am the biggest fan of cogeneration, also known as combined heat and power, or CHP (well, maybe the second-biggest fan). It is probably the single most overlooked strategy for sharply cutting greenhouse-gas emissions while reducing overall energy costs.
Now a new EPA report finds that running an ethanol plant on natural gas CHP can, with the right design, result in negative net CO2 emissions (click on figure to enlarge).
Important caveat: "Impact of Combined Heat and Power on Energy Use and Carbon Emissions in the Dry Mill Ethanol Process" (PDF) does not examine the energy consumed (or emissions generated) from growing and harvesting the corn or from transporting the corn or ethanol. Still, with CHP, corn ethanol can actually generate significant CO2 reductions compared to gasoline.
If Congress is serious about promoting ethanol in a manner that actually reduces GHGs, they should require all new ethanol plants to cogenerate.
This post was created for ClimateProgress.org, a project of the Center for American Progress Action Fund.
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Comments
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caisteger Posted 8:29 am
03 Jan 2008
http://invisiblegreenhand.blogspot.com/2007/12/making-eth ...
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Sean Casten Posted 8:33 am
03 Jan 2008
For what it's worth, if you do a full field-to-tank analysis, you're not quite negative, primarily because of the natural gas that goes into make the fertilizer for corn farming. (And this # would be vastly lower for less fertilzer intensive crops). But relative to the ~76,000 Btus/gallon you have in a gallon of ethanol, you can essentially displace about 51,000 of them through thermally matched cogen, exporting the balance to the grid. For math, see here.
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drocto Posted 10:13 am
03 Jan 2008
If we want energy independence, reduced net GHG emissions, and a cleaner environment lets take whatever set of solutions deliver results as they are developed.
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GreyFlcn Posted 11:56 am
03 Jan 2008
The problem being that it's still based off of Michael Wang's / Argonne Lab's GHG projections.
http://greyfalcon.net/lca.png
The same Michael Wang that cuts out most emissions from land use, nitrogen, and soil disruption.
http://greyfalcon.net/n2o.png
http://greyfalcon.net/n2ostudy
http://greyfalcon.net/landuse
http://greyfalcon.net/soy2
http://www.treehugger.com/files/2007/12/ocean_bacteria_ni ...
The same Michael Wang which makes some really crazy off the wall comments like "Oil produces less energy than Corn Ethanol"
http://i-r-squared.blogspot.com/2006/09/postscript-with-w ...
The same Michael Wang, that after he was found to be bullshitting his study's inputs, and their impacts skyrocketed, he miraculously made the emissions from ethanol go down even further than the previous study.
http://i-r-squared.blogspot.com/2006/03/how-reliable-are- ...
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Certainly we could demand mandates for greener electricity use, but I think the Energy Bill is clear evidence of how that would go.
Besides which, they've been clearing the way for Coal to be the primary source of on-site electricity for these ethanol plants.
http://greyfalcon.net/ethanol4
http://greyfalcon.net/ethanol5
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GreyFlcn Posted 12:33 pm
03 Jan 2008
UCLA Researchers Modify E. Coli to Produce Efficiently Higher-Chain Alcohols for Advanced Biofuels
Dongfeng investigating hydrous ethanol
^ (Whats the deal with Hydrous Ethanol)
If Corn is King of Biofuels, Tropical Maize May Be Emperor
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But really I highly doubt any of this is going to qualify as "carbon negative".
Also last "combined cycle" corn ethanol plant I remember went bankrupt.
Responsible Ethanol Goes Bankrupt
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But then again, "Better" doesn't neccisary mean it's beneficial.
IGCC Coal is better than normal Coal.
But it's still coal.
I feel the same way about biofuels.
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Biodiversivist Posted 2:33 pm
03 Jan 2008
Accounting for the latest nitrogen oxide data and crops being grown elsewhere on the planet to make up for the shortfall in the human food chain by the 35,000 square miles diverted to our gas tanks (leakage effects) one would find the process much worse for global warming than gasoline and worse for the environment overall, as the many studies referenced here all did.
I can just picture it now; the biofuel forums all abuzz with links to the Gristmill article discussing how a corn ethanol plant, if properly designed, can actually suck greenhouse gases from the atmosphere! There is no such thing as a carbon negative corn ethanol plant. All the report says is that the refinery's natural gas fired electrical turbines displace grid power generated mostly by coal and that this displacement can exceed the CO2 being generated by the other processes in the plant, also fueled by natural gas.
As ridiculous as this sounds, if our goal is CO2 reduction, we really should be burning corn instead of trying to turn it into a liquid fuel for cars. Directly burning the corn in place of coal in an existing coal fired power plant would produce far, far fewer CO2 emissions per ear of corn than the case 3 refinery. We don't need another liquid fuel to displace that which is in our SUVs, we need efficiency and less CO2.
The report ignored all energy expenditures outside of the refinery except for electricity generation. Generating electricity with natural gas inside the refinery is going to compare pretty positively with the grid average outside the plant.
To summarize the report in one long sentence:
If a CHP corn ethanol refinery uses natural gas for its energy needs and makes enough electricity with waste heat using a gas turbine combined cycle to sell some back to the grid, you do not get to call the plant carbon negative just because a natural gas fired turbine releases less CO2 than the electric grid average, which mostly uses coal (i.e., displace a small amount of electricity generated by coal with electricity generated by natural gas).
Using this logic, any electrical power plant that comes on line in the future using natural gas can be called carbon negative because it is displacing electricity that would otherwise have been generated by a grid average heavily weighted by coal.
In the end, it all comes down to biodiversity. Poison Darts--Protecting the biodiversity of our world
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naught101 Posted 3:35 pm
03 Jan 2008
Consumption reduction first. THEN you tech heads can look at making things move fast along flat ground.
check out http://www.envirowiki.info, the knowledge database for environmentalists and activists.
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Pangolin Posted 4:13 pm
03 Jan 2008
At the end of the day if you start with a field in spring and add up all the inputs and outputs from that field, the transport fuel and to the plant that produces the ethanol there will be no net carbon increase in the soil. Burning less somewhere else really isn't the same as putting atmospheric carbon back into a mineral sink.
So it's all bullshit.
The only verified carbon negative energy source isn't even in production and that's biofuel pyrolysis with return of char to soils aka Terra Preta nova. The fine folks over at Eprida are one of several projects working on this. A lot of other people who are really working on carbon negative agriculture can be found here.
The most amazing thing about ethanol is the amount of pure fiction that is used to justify it's subsidy bandwagon. There are better ways to reduce the fossil fuel use of the existing fleet that would probably be cheaper reinstating the 55 mph speed limit tops on the list. There has to be some serious graft money being siphoned out of these projects to keep the BS flying at this rate.
Just for starters sugar beets or potatoes will give you more ethanol per acre than corn right off the bat. Sweet potatoes or sorghum significantly more and sorghum would probably give you enough leftover biomass that you could pyrolize it and get even more ethanol from a Fischer-Tropsch process.
The reason that the US focuses on corn ethanol has far more to do with the electoral college and the legalized bribery of campaign contributions than scientific efficiency. It's simply the easiest way to harvest US government subsidies without resorting to outright theft.
The atmosphere doesn't give a crap who got paid to promote corn prices and harvest subsidies. Unless NOX emissions from fertilizers stop and the carbon loaded into the atmosphere returns to the ground we're screwed.
Put the Carbon Back
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amazingdrx Posted 9:34 pm
03 Jan 2008
Or you could use heat pumps (running on solar and wind electricity) and solar heat to do the distillation. And even use organic fertilizer and plugin tractors (also running on renewable kwh) to grow the corn.
Wow. Clean fuel farming?
But you still are left with the internal combustion gas guzzler in the end. Using .06% of the energy in the liquid fuel (ethanol or gasoline) to actually move the weight of the passengers.
Plugin a plugin hybrid vehicle to renewable energy and you can use GHG free energy directly, without destroying the carbon sink effect of soil with agrichem farming, releasing millenia of stored cO2. 1000s of times the cO2 trapped by the corn crop or as with most ethanol, the sugar cane crop. Grown on burned down rain forest. Releasing even more CO2 than corn cropland.
Using manure and farm waste to generate clean kwhs with biogas, that's the efficient biofuel. Compressing the gas to use in tractors, the alternative to the rapidly approaching 5 dollar per gallon tractor fuel.
If you want to live like a russian peasant, penshioned off with rubles, keep supporting ethanol. Food and energy price inflation is destroying the dollar. What most of us will be payed in when we reach retirement.
Corporate boondoggles like ethanol keep adding to the corporate bottomline, raising prices for food and fuel. Fueling inflation, robbing us of the the right to pursue financial security, which depends upon a stable currency.
http://amazngdrx.blogharbor.com/blog
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Sean Casten Posted 11:32 pm
03 Jan 2008
All the report says is that the refinery's natural gas fired electrical turbines displace grid power generated mostly by coal and that this displacement can exceed the CO2 being generated by the other processes in the plant, also fueled by natural gas.
As ridiculous as this sounds, if our goal is CO2 reduction, we really should be burning corn instead of trying to turn it into a liquid fuel for cars. Directly burning the corn in place of coal in an existing coal fired power plant would produce far, far fewer CO2 emissions per ear of corn than the case 3 refinery. We don't need another liquid fuel to displace that which is in our SUVs, we need efficiency and less CO2.
This is not quite right without factoring in efficiency. The reason why there is such a substantial carbon gain from producing power onsite with cogen is partially because of the coal/natural gas switch, but equally because you're swapping a ~33% delivered efficiency source (the grid) with an ~80% delivered efficiency source (the on-site cogen). Thus, even coal-fired cogen on site would lead to a substantial carbon reduction relative to the current approach.
Your idea of burning corn to make power helps on the fuel side of the equation (to the extent that one can treat the corn as a zero-carbon fuel, which given fertilizer consumption isn't quite right), but not the efficiency unless there is a local thermal load - such as is presented by the ethanol facility.
Thus, it's not that the carbon goes back into the ground, as later commenters have asked, but that we slow the rate of it's extraction from the ground in inefficient coal plants. This is, at core, much larger than ethanol - it is about an energy efficiency society. Ethanol has its warts, to be sure, but it also has the great advantage of providing wonderful cogen sites, which can be leveraged to massively increase the efficiency of the power grid - which is, after all, the single biggest GHG source in the country. Simply deploying the technical potential for cogen and waste heat recovery in the country would cut GHG emissions by 20% - as compared to 19% if we took every single passenger car off the road (or alternatively, replaced every single passenger car with a truly zero-carbon fuel). This isn't to dismiss the need to also look at the transportation fuel side, but simply to point out that this particular baby is more important than the bathwater.
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Biodiversivist Posted 7:02 am
04 Jan 2008
I don't think you have fully grasped yet the damage being done to the planet by this fuel. One day your company may well install a cogen system in a corn ethanol refinery, or a mountain top removal mine, or a palm oil biodiesel plant, which would make for an interesting discussion for reasons other than technical ones. I have a similar dilemma when people ask me to design "green" second homes where forests presently sit.
This is, at core, much larger than ethanol - it is about an energy efficiency society.
I believe I covered that when I said, "We don't need another liquid fuel to displace that which is in our SUVs, we need efficiency and less CO2."
Cogeneration is great stuff. We need to see a lot more of it and as the rising price of energy creates economic incentives, I'm sure we will. However, using a corn ethanol refinery as an example is not the best way to do that, to put it mildly.
You seem to have misconstrued my post as a critique of cogeneration, or even of energy efficiency. Either that or you have built a strawman to knock down.
I had and have two main critiques of the article. First, the title is misleading. The comments document that. It suggests that a corn ethanol refinery can actually sequester CO2 emissions when in reality, it is creating them. In other words, the case 3 corn ethanol plant will add CO2 to the atmosphere that would not have been there had the plant never been built assuming it could not generate enough extra electricity to sell to the grid. Do you agree so far? Now, lets look at the case where it is able to sell extra electricity to the grid.
Ethanol has its warts, to be sure, but it also has the great advantage of providing wonderful cogen sites, which can be leveraged to massively increase the efficiency of the power grid - which is, after all, the single biggest GHG source in the country
Your conclusion that corn ethanol plants if properly designed would massively increase the efficiency of the power grid has a missing link or two. Like I said in the first post, you would get as much or more CO2 reduction just by building a natural gas fired power plant without the refinery and here is why.
Your conclusion assumes that efficiency imparted by the co-located power plant to the refinery will be transported to the grid, but it won't. It is true that the power used in the plant has insignificant transmission losses because the machine using that power may only be a few hundred feet away. However, the power sold to the grid by the refinery has the same transmission line losses and even lower efficiency (due to the small size of the refinery's turbine) than a grid gas turbine power plant. Power plants use a few giant turbines instead of many small ones (ditto for Jet airliners) to avoid the losses associated with each one. The case 3 plant is not carbon negative. It is simply less carbon intensive than a less efficient refinery, and less carbon intensive than a coal fired power plant. As far as grid power is concerned, it is equivalent to building a small natural gas fired power plant, nothing more.
My second critique is the use of a corn ethanol plant to demonstrate the benefits of cogeneration. Your typical mountain top removal process and palm oil biodiesel refinery can also put cogeneration to good use to lower the cost of the product and thus increase its consumption. The environmental destructiveness of corn ethanol gallon for gallon is in all likely hood just as bad or worse than those processes. It is clearly worse gallon for gallon than oil and I would not be surprised to see it is worse than coal although I have not yet seen any studies trying to compare it with coal, yet.
This is not quite right without factoring in efficiency. The reason why there is such a substantial carbon gain from producing power onsite with cogen is partially because of the coal/natural gas switch, but equally because you're swapping a ~33% delivered efficiency source (the grid) with an ~80% delivered efficiency source (the on-site cogen). Thus, even coal-fired cogen on site would lead to a substantial carbon reduction relative to the current approach.
I'd make that 33-45% versus 60-80 % respectively, not 45% verses 60% or 33% versus 80%. I didn't mention that efficiency gain because I was trying to keep my response short and simple (but failed anyway). That efficiency gain is covered by the concept of cogeneration, which is all about efficiency gains.
Thus, even coal-fired cogen on site would lead to a substantial carbon reduction relative to the current approach.
I honestly don't know what the average is for existing refineries (the current approach), but using coal did not create a refinery that produced less CO2 than the natural gas baseline refinery in the study as shown in case 4 below:
http://home.comcast.net/~russ676/Graphics/chp1.gif
Your idea of burning corn to make power helps on the fuel side of the equation (to the extent that one can treat the corn as a zero-carbon fuel, which given fertilizer consumption isn't quite right), but not the efficiency unless there is a local thermal load - such as is presented by the ethanol facility.
I didn't say that corn combustion would be a zero carbon fuel, so suggesting I didn't quite get that right is not quite right and my point is still valid. If you take the corn going into refineries, and instead mixed it with the coal in a coal fired plant, you put far less CO2 into the atmosphere than sending that corn to the case 3 plant. We can compare spreadsheets.
Simply deploying the technical potential for cogen and waste heat recovery in the country would cut GHG emissions by 20% - as compared to 19% if we took every single passenger car off the road (or alternatively, replaced every single passenger car with a truly zero-carbon fuel). This isn't to dismiss the need to also look at the transportation fuel side, but simply to point out that this particular baby is more important than the bathwater.
By "simply deploying" you mean convincing businesses to spend more money up front, hoping to remain fiscally solvent and competitive at the same time. It is all a numbers game, as you know. If a competitor makes more profit than me by not using cogen, he may well eventually drive me to bankruptcy, accomplishing nothing in the end. It is all about cost and profit. If the government were able to make laws requiring cogeneration, that law would have to be applied to all competitors equally (a level playing field) or the law will simply drive businesses who spend more up front out of business before they can recoup expenses. That level playing field would have to be global. What are the odds of that working? So, maybe it isn't all that simple.
And that's not a baby floating in the bath water, that's corn ethanol and it should be thrown out.
I'm a big fan of energy efficiency, as you well know. I use cogeneration in my home on cold winter days when the relative humidity is low. I have a valve on our dryer that dumps the exhaust into our home instead of outdoors. Morning showers can also be used to cut heating bills if you put a plug in the tub until the water cools to room temperature and by leaving a door cracked to let the steam heat the rest of the house. Imagine how long it would take to heat enough teapots to fill a bath tub.
Admittedly, the monetary incentive for doing those things is insignificant to me, but it feels good to do them and costs nothing, so why not?
The Prius is a rolling cogen machine (although, with a Prius, sometimes the engine has to turn on just to generate waste heat for the heater).
In the end, it all comes down to biodiversity. Poison Darts--Protecting the biodiversity of our world
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