Comment by voxleone | Hacker News Reader

Comment by voxleone | Hacker News Reader

While it's true that Big Ag in the U.S. has oversold corn ethanol as a climate-friendly alternative, it's important to distinguish between types of biofuels. Not all ethanol is created equal.

Take Brazil, for example. Their ethanol program is fundamentally different. It's based on sugarcane, not corn, and it has a spectacular EROI (Energy Return on Investment) of about 8:1. That means for every unit of energy put into producing it, eight units are returned. By contrast, U.S. corn ethanol barely breaks even, with an EROI around 1.3:1 to 1.8:1.

Brazilian ethanol also sidesteps many of the land use and food diversion issues that plague U.S. biofuels. Sugarcane is mostly grown on degraded pastureland far from the Amazon, and it doesn’t displace staple food crops. Plus, the leftover biomass (bagasse) is burned to power the refineries themselves, making the process close to energy self-sufficient.

The Brazilian model shows that biofuels can work—but only under the right agricultural, environmental, and economic conditions. The U.S. corn ethanol lobby essentially hijacked the "green energy" narrative to push something that mostly benefits Big Ag subsidies and corn states, with questionable climate gains.

So yeah, skepticism about biofuels is warranted—but we should be careful not to throw out the good examples with the bad.

Sugarcane requires a LOT of water - so you need around 2000-2860 litres of water for every litre of ethanol.

Is that a lot? We would need some other examples to compare--specifically corn.

Assuming all this about Brazilian ethanol is true, the real question for me is scale. The US consumes an enormous amount of gasoline every year compared to just about any other country. That’s what I’m curious about.

Brazilian current ethanol production is 2/3 of the US

At what rate do they produce degraded pasture land? Is it renewable?

Brazil is a big place, and growing sugarcane properly actually regenerates the soil, such as if no or low till techniques are used (which are popular in Brazil).

I don’t believe there’s any evidence to suggest sugarcane regenerates soil. In fact I can only find evidence to the contrary.

even a simple rotation like corn -> soybeans can aid some bacteria recover, thus a better soil lifespan (high productive areas with proper management (beyond rotation, like some rest and proper fertilization can last ~ 120 years being abused all the year long)

probably hundreds of years if erosion wasn't a thing [0]

but "regenerating" as the OP types is probably about actively managing land recover while planting some sugarcane in between the process. now. if the harvest will be profitable for making biofuel is probably another talk

[0] just a guess

the crux of ag soil "energy" is just nitrates and stuff. some plants like beans and lentils recharge nitrogen in the soil (hence the old native american trinity or whatever, corn, beans, and some other plant). fertilizer, that's just nitrates. poop and pee (natural fertilizer).. yup, nitrates.

Basic reason would tell us, unless we're using a nitrogen-fixing plant like beans, unless we're using fertilizer, the plant's gonna suck up nitrates from the soil, get harvested, and now there's less nitrates in the soil. Weakening the soil quality thusly. Pretty straightforward.

Biologically you could then go on to argue micronutrients along the same lines, with poop and pee more likely to contain those things, since aminals also are eurkaryotes so probably depend on some of the same

Indeed, but high intensity agriculture at a scale to feed earth's population consumes more nitrogen than can be obtained through crop rotation.

Farming basically never replenishes soil unless youre very carefully rotating mixed crops and animals through the area.

> Sugarcane is mostly grown on degraded pastureland far from the Amazon.

I vaguely recall campaigns against turning Amazon into pastureland via slash and burn.

blame meat.

highly productive areas on sugarcane aren't in Amazon [0]

[0] https://www.researchgate.net/profile/Bruno-Santos-52/publica...

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