I've been trying to get my head around biofuels as I am deeply sceptical about the aircraft industries plans for expansion when they seem to have no credible plans in place to restrict let alone decrease GHG, with the great hope being SAF, and even that they plan in a 50% only mix for the foreseeable future.

There is this study of biofuels from lignin just out:
https://newenergyandfuel.com/http:/newenergyandfuel/com/2024/02/29/research-says-biomass-pretreatment-makes-biofuel-practical/

' According to the Department of Energy, up to a billion tons per year of biomass could be made available for the manufacture of biofuels and bioproducts in the US alone, capable of displacing 30% of our petroleum consumption while also creating new domestic jobs.

Because a CELF biorefinery can more fully utilize plant matter than earlier second-generation methods, the researchers found that a heavier, denser feedstock like hardwood poplar is preferable over less carbon-dense corn stover for yielding greater economic and environmental benefits.

Using poplar in a CELF biorefinery, the researchers demonstrate that sustainable aviation fuel could be made at a break-even price as low as $3.15 per gallon of gasoline equivalent. The current average cost for a gallon of jet fuel in the U.S. is $5.96.'

Looking through the linked paper, I could not spot whether this cost is factory gate or delivered, as the output of lots of refineries would be needed to provide fuel for one major international airport.

Having said that, once you have the liquid fuel, moving that is way cheaper than lugging around the initial trees etc, so the difference is not perhaps critical, as in theory at least there is quite a bit of headroom to be economic against jet fuel.

Remaining concerns are about sensible exploitation to retain soil fertility, instead of basically strip mining regardless.

Hi Jim:

There are others here who will know way more about biofuels than I, as in a reaction similar to that which some others on this blog have regarding fossil fuel extraction, where regardless of how it theoretically could be practise is so awful that it is tempting to dismiss it entirely, I looked at corn use, which however dubious in energy terms was a magnificent mechanismg for extracting and exploiting subsidies, and gave up.

The bottom line would appear to be that there is substantial room for production without overstepping the boundaries of what needs to be returned to the soil to retain fertility, but I have not got a handle on where those boundaries are in relation to the projected output of SAF.

Basically it seems to me to be insanity to allow long distance air travel, a luxury item to continue to grow, when there is no sort of control of emissions, so from that position it is difficult to make an even handed assessment of the best options if we are going to do that anyway.

Lignin, seaweed or some such would seem likely to have least impact on soil fertility, deprivation of the hungry to provide jet fuel and so on, but hopefully others with infinitely more knowlege of and grasp of what is going on in the use of biological resources for energy will share some of their insights, as I have not really either read up on it, or can claim to have any sort of impartial grasp as I thought what was actually going on was so yucky.

Regarding the use of forest resources as feedstock for methanol, the development of Coppice sylvicuture [felling one acre plots of trees young and regrowing them from the stumps] avoids exhausting the soil. This is due to the trees biological clocks being reset at harvest, with the root ball thriving if it carries less than 28 years of growth. The oldest such tree known is a coppice hazel near Ashford in Kent, UK, that has been regularly coppiced since it was germinated during the Roman occupation.

With no disruption of the soil by heavy machinery, by roots' extraction or even by replanting, and with routinely high biodiversity bringing nutrients to the coppice woodlands, the soils are not being degraded in well managed coppices.

Regarding the use of methanol as a feedstock for SAF, there are so many severe strikes against the latter's "sustainability" that its commercial proponents really should be indicted for greenwashing fraud. Moreover, I've yet to see any account of the final fuel costs showing methanol-based synthetic kerosene jet fuel to be cheaper than using methanol in "Methanol Reformer Fuel Cells" on planes to drive their electric motors.

Those with fleets of kerosene-burning jet planes may prefer the temporary illusion of keeping their assets' value . . . . .

After looking at the term carbon efficiency it has more to do with economics than chemistry it says I can emit a lot of fossil carbon but if I do a lot of good for the economy then it's more efficient that's a completely BS metric.

In this context carbon efficiency is phony accounting, it does not take into consideration the damage that fossil carbon does to the environment, droughts, floods, hail, crop failures, property damage are all unaccounted for. It may seem efficient to the GDP but they haven't considered all factors, thus it's bogus.

Just in a new analysis showing how unrealistic Direct Air Capture is using anything other than biological means:

https://techxplore.com/news/2024-03-air-carbon-capture-higher.html

' ETH researchers have developed a new method that provides a more accurate estimate of the future cost of various DAC technologies. As the technologies are scaled up, direct air capture will become significantly cheaper—though not as cheap as some stakeholders currently anticipate. Rather than the oft-cited figure of 100 to 300 U.S. dollars, the researchers suggest the costs are more likely to be between 230 and 540 dollars.'

This is quite simply complete cobblers, and a ploy to extract funds for a useless technology, useless that is apart from as a very flimsy cover story for the expansion of long distance GHG belching aircraft for instance.

DAC is not going to come to the rescue from this insanity.

By reusing fossil carbon you reduce the emission of fossil carbon to the atmosphere.

I think that biofuel production should be considered in the framework of the total human demand on the biosphere rather than simply in the narrow framework of how to preserve a "healthy" jet tourism industry with a minimum impact on the biosphere. Agriculture, cotton and other fiber crops, stock raising, lumber and paper production, are already putting large demands on the biosphere and with the human population still rising these demands could increase substantially over the next several decades unless we put a strong emphasis on lowering the per capita demand on the biosphere of the earth's most highly developed economies. Any new biofuel industry needs to be considered in this context. Coppicing may be less ecologically demanding than the cut and replant practices of the lumber and paper industries (any references?) but it still removes nutrients from the soil and it presumably has a negative impact on bio-diversity compared to natural forests.

'A key solution for carbon capture and storage is under our feet. We're investigating the interactions between plants, microbes, and geological features in soil with the goal of using healthy soil ecosystems to pull carbon from the atmosphere and stash it underground for a long time, at a low cost.'

https://phys.org/news/2024-03-video-stashing-carbon-haul-healthy.html

The video is well worth a look.

These guys are doing the grunt work of sorting out how carbon storage actually happens, so it is seminal to whatever we do in future.