General > General Technical Chat
Confused about PHEV, Hybrids, etc...
nctnico:
--- Quote from: tom66 on August 04, 2022, 10:19:35 pm ---I'm quite sceptical you can produce enough road fuel (let's just assume this is for passenger cars for now) from just agricultural waste.
--- End quote ---
I ran some numbers based on yield per area information from Poet-DSM. Based on their numbers and just taking the amount of farm land, countries where farming is widespread should have enough agricultural waste to get to 50% to 75% of the fuel needed based on current consumption.
@Someone: the claims in that book are horribly outdated. Nowadays nobody involved in bio-fuel development is suggesting to grow crops to make bio-fuel or burn agricultural waste / plant based material (wood) for electricity production.
Someone:
--- Quote from: nctnico on August 04, 2022, 10:37:52 pm ---
--- Quote from: tom66 on August 04, 2022, 10:19:35 pm ---I'm quite sceptical you can produce enough road fuel (let's just assume this is for passenger cars for now) from just agricultural waste.
--- End quote ---
I ran some numbers based on yield per area information from Poet-DSM. Based on their numbers and just taking the amount of farm land, countries where farming is widespread should have enough agricultural waste to get to 50% to 75% of the fuel needed based on current consumption.
@Someone: the claims in that book are horribly outdated. Nowadays nobody involved in bio-fuel development is suggesting to grow crops to make bio-fuel.
--- End quote ---
The numbers in that book start with specific/replacement crops as you say, waste from another crop is never going to exceed the bio-fuel production of a dedicated crop (or people would just grow that instead). Its the land area use that is telling, the figures in W/m2. Agricultural waste energy production is too low to support the current energy demands.
Worldwide agricultural land use? About 50x10^12 m2 (world bank)
Energy output of pure biofuel crop in excellent conditions? 1 W/m2
Nice round number 50 TW
400 PWh annually
Worldwide transport fuel use? 110 exajoules (IEA) 30 PWh
sounds doable if you cut it that way, except thats for high efficiency (sugarcane) crops on excellent (limited) land. The link I provided was for the first page of a chapter which does have an explicit heading and paragraphs addressing your point of only using waste:
https://www.withouthotair.com/cD/page_286.shtml
When you start scrounging in the agricultural byproducts, there isnt much left. Most farmers are already pretty good at reducing their operating expenses and reusing any "waste". Trying to pull more than 10% of the agricultural output out of thin air (without reducing something else) sounds pretty extraordinary. Show us how it adds up! Because the reference you poo-poo says it doesn't.
But hey you'll just keep throwing out unreferenced unworked and unjustiified opinions as if they are fact that disprove others well researched and considered work. That might work on the lazy, but it wont work here.
tom66:
That's a good point about using biofuels in general. I was a big 'fan' of algae a while ago but the numbers don't add up.
A 1m^2 solar cell at 30% efficiency might generate about 1kWh per day, whereas photosynthesis has an efficiency of at most 5%. So you need a much larger collector area to make it work. You also need a way to recycle the 'waste' that the algae produce - most biofuel algae produce more than the desired fuel which requires a further distillation process.
More land take, more equivalent CO2 emissions if the land has other useful purposes already. Solar farms can be built on top of existing meadows without harming the meadow too much, as long as the panels have a bit of space between them. Wind turbines have even better kWh per m^2 equivalent, and have almost zero impact on the land surrounding them.
There may be something in it for specialist applications that can't move away from hydrocarbons but I don't see it being a major energy source. Although I think synthetic fuels produced from electricity and CO2 will ultimately win out here, e.g. Fischer-Tropsch producing jet fuels (and shorter flights will eventually be pure electric or at least hybrid electric.)
nctnico:
--- Quote from: Someone on August 04, 2022, 11:26:46 pm ---
--- Quote from: nctnico on August 04, 2022, 10:37:52 pm ---
--- Quote from: tom66 on August 04, 2022, 10:19:35 pm ---I'm quite sceptical you can produce enough road fuel (let's just assume this is for passenger cars for now) from just agricultural waste.
--- End quote ---
I ran some numbers based on yield per area information from Poet-DSM. Based on their numbers and just taking the amount of farm land, countries where farming is widespread should have enough agricultural waste to get to 50% to 75% of the fuel needed based on current consumption.
@Someone: the claims in that book are horribly outdated. Nowadays nobody involved in bio-fuel development is suggesting to grow crops to make bio-fuel.
--- End quote ---
The numbers in that book start with specific/replacement crops as you say, waste from another crop is never going to exceed the bio-fuel production of a dedicated crop (or people would just grow that instead). Its the land area use that is telling, the figures in W/m2. Agricultural waste energy production is too low to support the current energy demands.
But hey you'll just keep throwing out unreferenced unworked and unjustiified opinions as if they are fact that disprove others well researched and considered work. That might work on the lazy, but it wont work here.
--- End quote ---
If you cared to do some actual research you'd be better informed. Go look at yield number from Poet-DSM and other companies that actually process agricultural waste into bio-fuels. These companies have numbers that come from running industrial scale factories instead of assumptions. In addition to that, there is a wealth of up-to-date information on ethanolproducer.com .
--- Quote from: tom66 on August 05, 2022, 08:53:58 am ---I was a big 'fan' of algae a while ago but the numbers don't add up.
--- End quote ---
Algae looked very good for a while but it seems scaling up to industrial production is far more difficult than expected. It looks like the idea of using algae has been largely abandoned (for now).
Someone:
--- Quote from: nctnico on August 05, 2022, 10:27:22 am ---
--- Quote from: Someone on August 04, 2022, 11:26:46 pm ---
--- Quote from: nctnico on August 04, 2022, 10:37:52 pm ---
--- Quote from: tom66 on August 04, 2022, 10:19:35 pm ---I'm quite sceptical you can produce enough road fuel (let's just assume this is for passenger cars for now) from just agricultural waste.
--- End quote ---
I ran some numbers based on yield per area information from Poet-DSM. Based on their numbers and just taking the amount of farm land, countries where farming is widespread should have enough agricultural waste to get to 50% to 75% of the fuel needed based on current consumption.
@Someone: the claims in that book are horribly outdated. Nowadays nobody involved in bio-fuel development is suggesting to grow crops to make bio-fuel.
--- End quote ---
The numbers in that book start with specific/replacement crops as you say, waste from another crop is never going to exceed the bio-fuel production of a dedicated crop (or people would just grow that instead). Its the land area use that is telling, the figures in W/m2. Agricultural waste energy production is too low to support the current energy demands.
The link I provided was for the first page of a chapter which does have an explicit heading and paragraphs addressing your point of only using waste:
https://www.withouthotair.com/cD/page_286.shtml
But hey you'll just keep throwing out unreferenced unworked and unjustiified opinions as if they are fact that disprove others well researched and considered work. That might work on the lazy, but it wont work here.
--- End quote ---
If you cared to do some actual research you'd be better informed. Go look at yield number from Poet-DSM and other companies that actually process agricultural waste into bio-fuels. These companies have numbers that come from running industrial scale factories instead of assumptions. In addition to that, there is a wealth of up-to-date information on ethanolproducer.com
--- End quote ---
Oh look replying to figures that can be checked and referenced with... more unreferenced and unworked opinion.
Even if the ambitious claims of "sustainable" yield for Poet-DSM has zero impact on the existing cropping its 130PWh should those claimed rates (from rich US corn land, also a crop with significant input fertiliser) prove possible in 100% of all agricultural land worldwide. Against world oil use of 80PWh. Most of the world's agricultural land is not as productive as the US corn industry, its hard to believe bio-fuels will ever be more than a small part of the future energy mix. tom66 puts it really simply:
--- Quote from: tom66 on August 05, 2022, 08:53:58 am ---A 1m^2 solar cell at 30% efficiency might generate about 1kWh per day, whereas photosynthesis has an efficiency of at most 5%. So you need a much larger collector area to make it work.
--- End quote ---
Synthetic hydrocarbons and hydrogen are more likely as they can "store" the predicted excess electricity from the land efficient solar/wind generators.
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