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Comment by lifeonlars | Hacker News Reader

This seems suspicious. Converting land to be used for crops doesn't reduce the utility of that land as a carbon sink. It's generally the opposite. Most wilderness does not steadily accumulate carbon biomass, but stays at a steady mass in a cycle of plant growth and decay into the atmosphere. Crop land, on the other hand, has lots of the carbon removed each year to be used as fuel.

It seems that there's a clear anti-biofuel agenda when a few comments apart we get "biofuel is replacing food crops causing people to starve" and "biofuels should have land use change carbon emissions counted against them".

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> Converting land to be used for crops doesn't reduce the utility of that land as a carbon sink. It's generally the opposite.

You think so? How much carbon do you suppose is stored per hectare in a mature woodland versus tall grass prairie versus a corn field? Consider the cornfield after harvest or ploughing. How much carbon is stored aboveground? How much below? I don't know the numbers, but it's hard to believe that that rutted dirt and stubble is storing more carbon than the woodland or prairie it replaced.

Yea, prairie is burned converting some fraction of accumulated bio to char which stays in the soil more or less permanently.

Pretty sure that burning things generally leads to a lot of carbon emissions..

See your previous comment about carbon neutrality of that biomass, except less methane is produced through burning, which also produces long lasting char... Are you commenting in good faith?

Sorry, but this is a frustrating topic full of double-counting and apples-to-oranges comparisons (arguably on both sides).

Some praries burn regularly and some don't. Most (as I said above, most land types) do not have significant ongoing accumulation of carbon in the soil. Obviously there are some biomes that do. Citing the fact that prairies burn as proof that they aren't long-term carbon neutral just seems to me like a low-quality argument if you are trying to challenge what I have suggested here, that land use changes are a one-off carbon cost which is paid off by biomass being used in fuels which replace fossil carbon.

You're also replying to someone who completely ignored the difference between the amount of carbon biomass and the change over time of that amount.

If I am completely mistaken and land types which are plausibly converted from unmanaged to biofuel crops are in fact accumulating significant stored carbon on an ongoing basis then tell me so and I stand corrected.

From https://tallgrassontario.org/wp-site/carbon-sequestration/

> Various studies of the potential for tallgrass prairie carbon storage have shown that the storage rates vary between .30 and 1.7 metric tons per acre per year. This storage ability is cumulative over time

> Ironically and sadly, because they produce the best, deepest and richest soils, grasslands have been their own worst enemy as they have been rapidly converted to agriculture.

Pretty much at odds with your whole point of converting to farmland being net neutral.

> Some praries burn regularly and some don't.

Prairies in the Midwestern United States (where we grow most of the corn for Ethanol) do burn (or rather, did), and do have significant long term accumulation of carbon in the soil - it's literally why our soil is so good for farming (for now). Like, where on earth do you get the nonsense idea that they're carbon neutral ecosystems? Tallgrass prairie has crazy deep roots that over time can place a lot of carbon in the ground, not even accounting for the persistent char layers that accumulate after periodic burns. Thousands of years of accumulation adds up, and converting it to farming:

1. Removes that service 2. Has one off costs 3. Has ongoing costs, in that biofuels are not (currently) carbon neutral at all 4. Has other negative impacts.

Assuming that biofuels have a one-off cost and then become carbon neutral just isn't supported by the evidence - it's a simplistic argument that is so at odds with the literature that I have a hard time taking it seriously.

I accept your point about tallgrass prairies but you're back to the double-counting. The argument that 3 - biofuels are not carbon neutral, is established based on 1 and 2.

Also, it might be true that prairies do long term accumulation of carbon, but not true that this represents more carbon than that which is removed from the environment by biofuel crop growing and harvesting. That was my original claim and I don't think you've shown quantitative evidence that it should be dismissed.

Did you read the next sentence after the two you quoted? The point is not how much carbon is stored in the prairie but how much it changes by each year.

The prairie does not accumulate more carbon each year; it is roughly carbon neutral as decaying matter balances new photosynthesis. The corn field has a large part of the biomass carbon removed from it each year. Within a few years the destruction of the prairie has been cancelled out.

This is true even for most woodland, although of course the break-even is much much longer. I'm not arguing in favor of cutting down first-growth forest to grow ethanol though, and I don't think that is the typical case in the United States.

Plowing absolutely releases carbon, particularly as a source of methane.

Again, that's more or less a one-off effect of land use conversion, and further biofuels agriculture does not indefinitely continue to release carbon into the atmosphere.

It just (in its current form at least) uses a net positive amount of carbon to plant, fertilize, spray, harvest, dry, ship, process, and finally burn in our cars. In addition, the impacts on land use (and correspondingly on our water quality and topsoil) of things like the RFS are clear now.

It's not a rosy picture at all.

Sorry, but read literally what you are claiming is totally acceptable and does not indicate that we shouldn't be using biofuels. You seem to be saying that biofuel generation including burning as fuel using a net positive amount of carbon. There is no reason it shouldn't. It is a viable strategy if it uses less than the fossil fuel alternative. Note that the way to measure the alternative here is not the emissions from burning a unit of fossil fuels, but that plus all the emissions involved in extracting, refining and transporting the fossil fuel. For example, this includes flaring (~1% of all global C02 emissions).

It would even be viable if the total amount of carbon generated by the farming, processing and transportation of biofuels without including burning but subtracting the carbon taken from the air by plant growth, was a net positive by itself, as long as the excess was less than the corresponding total for fossil fuel production, including all the carbon involved in its production.

I accept the validity of what you said about land use in the sister thread, but I don't think you've established that this criterion isn't true (and making the much weaker claim above suggests that you aren't able to).

I also believe that many types of impact on the environment (for example what you mentioned about topsoil and water quality) should be treated with much lower priority than the greenhouse effect. If biofuels, or some other strategy for reducing emissions such as solar or wind power generation has a devastating but localized impact on some ecosystems, it might be worth it to forestall the wider effects of global warming. This is a matter of opinion though, and I do not live in an area which could be sacrificial in this sense.

> Sorry, but read literally what you are claiming is totally acceptable and does not indicate that we shouldn't be using biofuels. You seem to be saying that biofuel generation including burning as fuel using a net positive amount of carbon. There is no reason it shouldn't. It is a viable strategy if it uses less than the fossil fuel alternative.

No, I'm saying it's of dubious climate benefit (compared to fossil fuels), and has outsized environmental externalities besides.

https://www.reuters.com/business/environment/us-corn-based-e...

Not to mention that your goal posts are so incredibly, unbelievably far from where the industry started. Corn-based ethanol was pitched as a bridge fuel to get us to cellulosic, and was supposed to have real, tangible environmental benefits. This also doesn't touch on the fact that the subsidies involved have distorted several climate-relevant markets, most importantly the consumer market for inefficient vehicles in the US. When gas prices go up, demand for inefficient vehicles goes down - US biofuels are giving inefficient cars a huge boost.

> I also believe that many types of impact on the environment (for example what you mentioned about topsoil and water quality) should be treated with much lower priority than the greenhouse effect.

In some cases I agree - see mining of minerals for batteries. It just happens to turn out that if you look at the whole system, biofuels are a scam from a climate perspective, as well as an environmental disaster in their own right.

> This is a matter of opinion though, and I do not live in an area which could be sacrificial in this sense.

I live in Iowa, one of the most modified ecosystems on the planet, and ground zero for biofuels.

You also know they plow more than once, right? Like, they're doing no till a bunch now (by using more herbicide), but still plow when rotating crops.

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