> Substituting our empirically derived domestic emissions for those modeled in the RFS RIA would raise ethanol’s projected life cycle GHG emissions for 2022 to 115.7 g CO2e MJ−1—a value 24% above baseline gasoline (93.1 g CO2e MJ−1). The RIA estimate, however, includes improvements in feedstock and ethanol production efficiency that were projected to occur by 2022, such that the GHG intensity of ethanol produced at earlier time periods and over the life of the RFS to date is likely much higher [...].
My understanding is that they took the model used in the RFS RIA (when the RFS was first introduced), and plugged in what they've seen over the past few years to that model. Take that with what you will.
> And we're to assume that, without the production of fuel ethanol, the same land wouldn't be tilled and used for other crops?
With the increase in demand for corn for fuel usage, more fields are needed to plant the corn. Because the corn is for fuel, not food, food wouldn't have been planted in place of the corn had there not been fuel demand.
Spent corn used in ethanol production becomes livestock feed. Good quality feed, actually. Even with a surplus of spent corn, it can be dried and kept around until needed. Point being that it actually is food, just by proxy. More fields may be needed to scale for demand, but it wouldn't be linear. For all we know, the scale of corn production has a modest relationship with ethanol or is correlative and weakly causative.
The above is also why GMO crops are so great for the environment: by using a little roundup (just a little - not only is it a mist sprayed, but that mist is mostly water) much less fuel is used vs cultivating (think mechanical hoe).
Thats just not true. Plenty of farmers still plough. There has been some movement to lower disturbance low-till/ minimum-till systems for commodity crops, but we're still seeing soil carbon losses in agricultural soils in general. Number isn't going up and to the right, its still going down and to the left. I appreciate the importance of these kinds of systems, but I also appreciate that its not nearly as well adopted as one would think based on a survey of youtube videos. There is a very real departure from the Internets vision of farming and real-life farming in terms of practice.
I do agree however that carbon in the soils is the answer to most problems. The closest thing I came to witnessing a fist fight at work was between two 50+ yo scientists regarding aluminium/ alumina ions and their relationship with soil carbon. If geriatric scientsits are willing to raise fisticuffs over it, you should wonder why they care so much.
> Can't imagine there's any conflict of interest there.
Pro-nuclear bias you figure? Does the DoE have another reason to dislike corn?
I was doing reviews of at least a half dozen studies of this that dated back to the mid '00s, back then the most optimistic studies were around 1.3 joules of ethanol for 1 joule for extraction (which excludes the sunlight). Meaning you're burning 1 joule of gasoline to farm and transport and manufacture 1.3 joules of ethanol. But the pessimistic estimates from then were also below 1, meaning that you literally use more petrochemicals to support growing the crop than the crop produces in finished fuel.
Whether it's breakeven, a little positive, or a little negative we've known for a long time that it's marginal at best, thus the interest in cellulosic ethanol. Whether it's 0.7 joules out or 1.3 joules out per joule in depends on assumptions like how far you need to transport things and how dry the crops start. There's no way to avoid that uncertainty.
That whether it's positive, unity, or negative is sensitive to these variables is a statement of just how marginal it is. It should just be positive, always, or what are we doing? Confusingly, some oil wells are barely breakeven because they use so much energy to build the well and process the fuel.
You can follow the citations inside this article, but, for instance:
> Resulting EROI is typically around 1.4-1.5 [for shale oil].
So every 1.4-1.5 joules of shale oil you burn required 1 joule of other energy to extract. Net it produces only 0.4-0.5 joules of free energy after extraction, and that's... well, arguably not actually enough to operate a civilization but let's not go there.
https://en.wikipedia.org/wiki/Energy_return_on_investment#Sh...
Corn ethanol has been a scam and known to be one for a very long time. Shale oil is marginally less of a scam, but is truly hard to justify compared to PV solar or wind which both easily exceed 4 and 34 depending on the details.
But no, variation in the estimated EROEI is entirely normal and expected because different sites have different details.
Can't imagine there's any conflict of interest there.
> ethanol is likely at least 24% more carbon-intensive than gasoline due to emissions resulting from land use changes to grow corn, along with processing and combustion.
The nice thing about words like "likely" is that it leaves the door open for the other thing. Did the study find that ethanol is more carbon-intensive, or is it someone's opinion that it's more intensive?
I don't see how this adds up. As the article mentions, the carbon atoms in ethanol came from the atmosphere to which it returns. Yet not all of the carbon even makes it back. But the mere tilling of the soil puts ethanol somewhere worse than fossil fuels?
By that logic, we'd better stop farming crops all together.
> Tilling fields releases carbon stored in soil, while other farming activities, like applying nitrogen fertilizers, also produce emissions.
And we're to assume that, without the production of fuel ethanol, the same land wouldn't be tilled and used for other crops?
What is the nature of the carbon in that soil? Is it carbon that is constantly making its way up through the soil and into the atmosphere? Does stable isotope testing corroborate that it's a meaningful contributor to the global increase in atmospheric CO2?