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New Chemical Process Can Convert Nearly a Quarter of All Plastic Waste Into Fuel (vice.com)
"Researchers at Purdue University have developed a new chemical process that they say can convert approximately one-quarter of the world's plastic waste into gasoline and diesel-like fuels," writes Slashdot reader dmoberhaus. Motherboard explains how it works: As detailed in a paper published this week in Sustainable Chemistry and Engineering, the chemists discovered a way to convert polypropylene -- a type of plastic commonly used in toys, medical devices, and product packaging like potato chip bags -- into gasoline and diesel-like fuel. The researchers said that this fuel is pure enough to be used as blendstock, a main component of fuel used in motorized vehicles. Polypropylene waste accounts for just under a quarter of the estimated 5 billion tons of plastic that have amassed in the world's landfills in the last 50 years.
To turn polypropylene into fuel, the researchers used supercritical water, a phase of water that demonstrates characteristics of both a liquid and a gas depending on the pressure and temperature conditions. Purdue chemist Linda Wang and her colleagues heated water to between 716 and 932 degrees Fahrenheit at pressures approximately 2300 times greater than the atmospheric pressure at sea level. When purified polypropylene waste was added to the supercritical water, it was converted into oil within in a few hours, depending on the temperature. At around 850 degrees Fahrenheit, the conversion time was lowered to under an hour. The byproducts of this process include gasoline and diesel-like oils. According to the researchers, their conversion process could be used to convert roughly 90 percent of the world's polypropylene waste each year into fuel.
To turn polypropylene into fuel, the researchers used supercritical water, a phase of water that demonstrates characteristics of both a liquid and a gas depending on the pressure and temperature conditions. Purdue chemist Linda Wang and her colleagues heated water to between 716 and 932 degrees Fahrenheit at pressures approximately 2300 times greater than the atmospheric pressure at sea level. When purified polypropylene waste was added to the supercritical water, it was converted into oil within in a few hours, depending on the temperature. At around 850 degrees Fahrenheit, the conversion time was lowered to under an hour. The byproducts of this process include gasoline and diesel-like oils. According to the researchers, their conversion process could be used to convert roughly 90 percent of the world's polypropylene waste each year into fuel.
So, they have discovered a method to convert millions of tons of plastic into fossil fuels that can be burned to release yet more sequestered carbon into the atmosphere. That's sure to solve our ongoing problem with carbon emissions causing climate change.
Their conversion process could be used to convert roughly 90 percent of the world's polypropylene waste each year into fuel.
Then we can put this fuel into our cars and burn, dumping all that carbon into the atmosphere, where it can no longer be any harm to our planet.
Oh wait...
At high enough pressures and temperatures, anything with carbon will turn into light hydrocarbons.
But if it turns out that the math means this is practical, then this would be very cool.
Plastics containing just H and C can probably be burned without much processing. The problem is that most recycled plastic is a mix of all sorts, including a lot of popular Cl containing plastics that are really nasty to burn.
If there are sources of sufficiently pure hydrocarbon plastics (polyethylene, polypropylene and the like) and if this is more cost effective and energy effective than other methods, its fine. I expect the bigger problem is the initial purification. Maybe there is a solution to separating out the other plastics?
Scientific writing should always be in celsius, with farenheit in parentheses.
between 716 and 932 degrees Fahrenheit = 380C to 500C. Looks like the author already took the perfectly workable celsius and obfuscated it by turning it into farenheit, which is stupid since no human would have an appreciation of what 716 farenheit is like compared to the normal temperature ranges they're familiar with anyway.
around 850 farenheit = around 450C.
isoenergetic conversion has to be better.
Some drink at the fountain of knowledge. Others just gargle.
Now, if they're going to convert plastic into fuel, which plastic do you think they're going to use? Obviously the former. Meaning (1) it will have zero effect on plastic pollution in the environment, and (2) you're just spending extra energy and money to convert petroleum byproducts into fuel, instead of just using new petroleum as fuel. You're just paying extra to swap carbon sequestered underground as plastics, for carbon sequestered underground as natural petroleum.
Any solution to address environmental plastic pollution must address the non-collection problem. That means either enforcing proper disposal of plastic waste, designing plastic waste to degrade more quickly in the environment, or reducing the use of plastics entirely. This plastic to fuel idea does none of these things. The only thing it does is reduce the space taken up in landfills.
I remember my chemistry professor talking about how stupid it was to recycle plastics. He said we should just burn them for electricity instead of sorting, transporting, and otherwise expending all kinds of energy and effort in recycling. I'm guessing he brought this up in class because the city was debating a waste to energy plant and that burning plastics was part of that debate.
What I'm wondering is where the energy would come from to reach these intense temperatures and pressures for this process. Not many things burn this hot. Would this be a kind of coal blast furnace like that used to make steel? That seems like a rather silly idea if the goal is to reduce the production of waste and CO2.
There is a technology that can reach these temperatures. This technology also produces very little carbon, and theoretically none. That is the molten salt reactor, nuclear power. The US Navy is developing a technology much like this, only they use carbon sourced from CO2 dissolved in seawater. They want high temperature reactors too. Although the high pressures like this process uses might turn them off. They want to get away from the use of high pressure steam as that created inherent hazards to the crew on a ship. High temperatures are also a hazard but a ship at sea is surrounded by a huge heat sink, and any steam from that hot stuff meeting the water would be at atmospheric pressures.
This plastic to fuel process is a nice idea but hardly new. I believe that gentlemen named Fischer and Tropsch developed this same process nearly a century ago in Germany. All they are doing is limiting the feedstock for the process to plastics, but the process would work on most any carbon based material.
I am armed because I am free. I am free because I am armed.
Ugh, I had to call the fire department to give a fine in order to stop my neighbor illegally burning toxic plastic in their wood designed fireplace.
It's not just a bad smell, it triggered illness in multiple people in the neighborhood when they did it, and they just wouldn't stop when asked.
That would be interesting.
The abstract, though, says: "supercritical water at 380–500 C and 23 MPa" which is 230 bar, which is still a respectable pressure (3300 psi) but the sort of "reasonable" pressure encountered in modern steam turbine power generation, etc.
You shouldn't need high temperature or pressure to burn these in a trash-to-smoke power plant. (I think the fancy term now is "co-generation" but I'm a bit behind on the latest buzz words). If you burn *just* plastic, you may need to be creative but if you mix it with other things that burn easily (such as paperboard), it should all just burn and generate heat. If not just add something that burns hotter to the mix. If you can *separate* the plastic, I suggested in a previous post just to mix it with your coal stream at existing coal-fired plants. They do this with wood pellets already.
Holy fuck people...
From the linked journal:
temperature: 450 C
pressure: 23 Mpa
It is not 2300 bar, it's 230 bar.
Standard propane burns at 1980 C in air and thats the same pressure as a scuba tank. So temperature and pressure are easy to achieve. This can reduce solid plastics waste and potentially reduce the consuption of crude oil.
And maybe we can stop dumping plastics in the ocean and killing all the damned sea life.
Oh yeah, stop burning plastics. The extraneous chemicals in there are going to kill you and the surrounding environment.
How many more will there be? Turning CORN into fuel was a wasteful enterprise, that benefits only the "farm industry". Many other things can be turned into fuel.