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That's a nice idea, but can you do some similar back of the envelope estimation for how much we'd have to grow the renewable/low-emissions energy grid to meet t

That's a nice idea, but can you do some similar back of the envelope estimation for how much we'd have to grow the renewable/low-emissions energy grid to meet those other demands? For example we'll need hydrogen fuel cells for any serious replacement of current oil since light trucks and beyond cannot run on lithium batteries (batteries become the cargo). But 95% of hydrogen production is currently based on fossil fuels[0]. So to come anywhere close to meeting the transport needs we would have to not only radically ramp up hydrogen production, but would need to even more extremely ramp up electrolysis. I'd really like an insight into how we're going to achieve carbon free concrete production as well... It's insane that HN downvotes aggressively any basic math of how dire the situation is, and always responds with hand wavy solutions that won't hold up to even the most basic back of the envelope estimates. 0. https://en.wikipedia.org/wiki/Hydrogen_production https://en.wikipedia.org/wiki/Hydrogen_production

hedora 5y ago
We’ll need to add carbon capture to the mix. Many promising atmospheric carbon capture technologies exist in the $17-70 per ton range. A gallon of gasoline emits 20 pounds of CO2, which is conveniently 1% of a ton. So, if we added a $1/gallon gas tax, and spent 100% of the proceeds on carbon capture, the vehicle fleet would be strongly carbon negative in 5-10 years (when some of the carbon capture technologies successfully ramped). We could add a similar tax to concrete, electricity production, etc. The trick is to make it proportional to actual carbon emissions so that incentives align. Once gross emissions fall off significantly, the tax would have to be increased, and/or levied against carbon neutral industries, since we’ve already completely screwed over future generations.
- baron_harkonnen 5y ago
  > Many promising atmospheric carbon capture technologies exist Do we have any at that scale? I mean self-driving cars were a promising technology a decade ago and that's a much easier problem to solve than large scale ccs and we still might never see that.
Robotbeat 5y ago
It’s blatantly false that light trucks and up can’t use lithium ion batteries. In fact, the business case is actually better than for electric commuter cars due to the much greater efficiency. Longer range trucks are a bit of a challenge due to total weight, but doable. (And battery electric freight trains make WAY more sense than hydrogen freight trains and are actually super easy to electrify due to ability to just use overhead lines for charging and the greater efficiency of rail.) Also, hydrogen fuel cell trucks (and cars) are worse (compared to battery) than you might think. (On the car side, the Model 3LR has more range, costs less to buy, costs far less to fuel, has a huge fast charging network, can be charged anywhere with an outlet, is much faster and actually weighs less than the hydrogen Mirai.) Hydrogen fuel cell trucks require a huge heat exchanger (with a fan), really heavy and bulky compressed hydrogen tanks, and the cost of motor hydrogen (ie distributed for dispensing to vehicles) is much, MUCH greater than that of electricity and the conversion efficiency is lower than batteries plus the fuel cells themselves have a limited lifetime and aren’t cheap, plus you need a lithium ion battery anyway and the cost of the dispensing stations is very large (even adjusted for fueling speed) due to need to cryogenically cool hydrogen before dispensing, the presence of big compressors, safety mitigations, etc. Electric trucks are pretty straightforward compared to fuel cell hydrogen trucks. You’re right that hydrogen production is generally from steam reforming of fossil fuels nowadays, but until the 1940s when steam reforming became available on an industrial scale, electrolysis was actually the most common industrial hydrogen source using (for instance) abundant hydroelectric power. This was used for making ammonia fertilizer, etc. (New iron plants in the US actually use a syngas mix of hydrogen and CO, although the mix can be adjusted to virtually all hydrogen without too much trouble.) So we absolutely CAN produce hydrogen using electricity, and there’s a long history of doing so, although battery electric vehicles are far more efficient than hydrogen vehicles. That, combined with heat pumps, should enable us to limit the amount of more electricity we’ll need. Our current electricity usage in the US is ~475GW average, and by efficient decarbonization of almost all energy usage, I calculate we’d need about 1000GW total average electricity, so just a bit more than double we have now… although about 40% of current electrical energy production in the US is already decarbonized, about half of it nuclear, so we already have a leg up). that means we need ~715 GW average of more clean electricity than we have now. The US produces over 5 billion bushels of corn per year for ethanol. At 170 bushels per acre yield, that’s about 30 million acres. At typical solar farm output of about 40000 Watts average per acre (ie multiplying nameplate times capacity factor divided by footprint), that’s 1200GW average, so even if all we did was use the existing footprint of biofuels and converted it to solar, we’d have more than enough clean electricity to decarbonize everything. (Not even counting biodiesel, etc.) So again, you claim that “won’t hold up to back of the envelope estimates” isn’t true. If you like, we can discuss this one on one and I’ll explain the calculations.

hedora 5y ago

We’ll need to add carbon capture to the mix. Many promising atmospheric carbon capture technologies exist in the $17-70 per ton range. A gallon of gasoline emits 20 pounds of CO2, which is conveniently 1% of a ton. So, if we added a $1/gallon gas tax, and spent 100% of the proceeds on carbon capture, the vehicle fleet would be strongly carbon negative in 5-10 years (when some of the carbon capture technologies successfully ramped). We could add a similar tax to concrete, electricity production, etc. The trick is to make it proportional to actual carbon emissions so that incentives align. Once gross emissions fall off significantly, the tax would have to be increased, and/or levied against carbon neutral industries, since we’ve already completely screwed over future generations.

baron_harkonnen 5y ago
> Many promising atmospheric carbon capture technologies exist Do we have any at that scale? I mean self-driving cars were a promising technology a decade ago and that's a much easier problem to solve than large scale ccs and we still might never see that.

Robotbeat 5y ago

It’s blatantly false that light trucks and up can’t use lithium ion batteries. In fact, the business case is actually better than for electric commuter cars due to the much greater efficiency. Longer range trucks are a bit of a challenge due to total weight, but doable. (And battery electric freight trains make WAY more sense than hydrogen freight trains and are actually super easy to electrify due to ability to just use overhead lines for charging and the greater efficiency of rail.) Also, hydrogen fuel cell trucks (and cars) are worse (compared to battery) than you might think. (On the car side, the Model 3LR has more range, costs less to buy, costs far less to fuel, has a huge fast charging network, can be charged anywhere with an outlet, is much faster and actually weighs less than the hydrogen Mirai.) Hydrogen fuel cell trucks require a huge heat exchanger (with a fan), really heavy and bulky compressed hydrogen tanks, and the cost of motor hydrogen (ie distributed for dispensing to vehicles) is much, MUCH greater than that of electricity and the conversion efficiency is lower than batteries plus the fuel cells themselves have a limited lifetime and aren’t cheap, plus you need a lithium ion battery anyway and the cost of the dispensing stations is very large (even adjusted for fueling speed) due to need to cryogenically cool hydrogen before dispensing, the presence of big compressors, safety mitigations, etc. Electric trucks are pretty straightforward compared to fuel cell hydrogen trucks. You’re right that hydrogen production is generally from steam reforming of fossil fuels nowadays, but until the 1940s when steam reforming became available on an industrial scale, electrolysis was actually the most common industrial hydrogen source using (for instance) abundant hydroelectric power. This was used for making ammonia fertilizer, etc. (New iron plants in the US actually use a syngas mix of hydrogen and CO, although the mix can be adjusted to virtually all hydrogen without too much trouble.) So we absolutely CAN produce hydrogen using electricity, and there’s a long history of doing so, although battery electric vehicles are far more efficient than hydrogen vehicles. That, combined with heat pumps, should enable us to limit the amount of more electricity we’ll need. Our current electricity usage in the US is ~475GW average, and by efficient decarbonization of almost all energy usage, I calculate we’d need about 1000GW total average electricity, so just a bit more than double we have now… although about 40% of current electrical energy production in the US is already decarbonized, about half of it nuclear, so we already have a leg up). that means we need ~715 GW average of more clean electricity than we have now. The US produces over 5 billion bushels of corn per year for ethanol. At 170 bushels per acre yield, that’s about 30 million acres. At typical solar farm output of about 40000 Watts average per acre (ie multiplying nameplate times capacity factor divided by footprint), that’s 1200GW average, so even if all we did was use the existing footprint of biofuels and converted it to solar, we’d have more than enough clean electricity to decarbonize everything. (Not even counting biodiesel, etc.) So again, you claim that “won’t hold up to back of the envelope estimates” isn’t true. If you like, we can discuss this one on one and I’ll explain the calculations.