Hey everybody, it's Mr. Smeeds, and welcome to APE's video notes for topic 7.6, which is the reduction of air pollutants. Our objective for today is to be able to explain how air pollutants can be reduced at the source, and the skill that we'll practice at the end of today's video will involve using data to justify a solution to an environmental problem. So the first air pollution reduction method we'll talk about is just reducing emissions.
So these are common sense steps that we can take that just reduce the total amount of pollution that we're actually putting into the atmosphere. Things like riding our bikes instead of driving our cars or trying to walk or take public transit more, conserving electricity. So whether that's being mindful about turning off lights or just using smart appliances that draw less total electricity.
And remember, that's because most of our electricity in developed nations is coming from coal-fired power plants or other forms of fossil fuel. And so that is combusted and then that releases NOx, SOx, FOx, and a whole host of other air pollutants. Other things that we can do is eat. less meat.
And so for eating less meat, our food is requiring less total energy to be produced. That's requiring less agriculture. So it's putting less particulates into the air. And then we can also try to push for a change to more renewable energy sources that are non pollution emitting. So these would be things like hydro, hydroelectric, that is solar power and wind power.
Now we'll talk about some different laws and regulations that can be used to reduce emissions as well. So the first one is the Clean Air Act. Now remember that the Clean Air Act gives the EPA the ability to set acceptable levels of six different criteria air pollutants. They can monitor these levels and they can tax or levy penalties against institutions, corporations, companies, factories that release more emissions than are acceptable. So this is a really powerful law and one of the most important in terms of limiting air pollution in the United States.
We also have the CAFE vehicle standards. And so these stand for Corporate Average Fuel Economy Standards. So they're basically an average that all of the vehicles or the fleet of vehicles, we call it in the United States, has to meet.
And so by raising these standards or setting the average fuel economy or miles per gallon that cars have to achieve higher and higher, we travel the same amount of distance while releasing fewer air pollutants because the vehicles can burn less gasoline. So this is a really important way to reduce air pollution especially from transportation and then finally we have pollution credits so pollution credits are similar to itqs or individual transferable quotas that we learned about in the fishing unit or fishing topic but they're for pollution and so companies that bring their emissions far below the epa's you know acceptable levels voluntarily can earn credits companies that earn or that pollute a lot more than their acceptable levels have to buy these credits then from these less polluting companies so you're almost buying the rights to release air pollutants and so it tries to incentivize companies to release fewer and fewer emissions to earn these credits and one thing that i find really interesting is this is actually how tesla is profitable the tesla is this of course electric car maker that everyone is kind of enamored with but if you look at their business model, it's kind of interesting that they would not be a profitable business without all of this money that comes in from pollution credits. So car companies that do not make enough electric vehicles or do not lower their emissions of their fleet enough to comply with EPA law actually have to buy these pollution credits from Tesla. And that's how they are, you know, such a profitable business.
Now we'll talk about some specific pieces of technology that enable the reduction of air pollutants from vehicle emissions. So the first one is called a vapor recovery nozzle. This is a pretty common standard issue at gas stations in the United States and it's going to capture some of the volatile organic compounds that are released from the fumes of gasoline. So think about when you're at the gas station, the smell of gasoline is pretty strong.
That's because it's a volatile organic compound or it contains many volatile organic compounds. These are things like hydrocarbons and when they vaporize they enter the atmosphere and that's why you can smell them. That's why the smell is so potent.
Remember that they contribute to photochemical smog, their respiratory irritants. And so a vapor recovery nozzle is a really important piece of technology that reduces these emissions. What it does is basically captures some of the fumes that are volatilizing when you're putting that nozzle inside your vehicle's fuel tank or your fuel tube that goes down your tank. And it's going to capture those fumes and basically return them back to a tank underneath the ground.
so it can actually save gas stations a little money it can make them more efficient but it also limits the amount of volatile organic compounds released when you're refueling your vehicle This is a good thing because we know that gasoline contains benzene, which is a chemical that's a known carcinogen. And so it's also going to reduce your exposure to that. Another piece of technology that is standard issue now on vehicles in the U.S. is a catalytic converter.
So after 1975, this was mandated to be added to all new vehicles being produced. And it's a metal kind of box that fits underneath your car. And it basically filters the exhaust coming from your engine. It has some metals inside the converter or this box that are going to bind to carbon monoxide and NOx. And they're going to basically reduce them and convert them into, you know, harmless substances like water vapor or nitrogen gas.
They are going to convert the carbon monoxide into carbon dioxide. So carbon dioxide is still a greenhouse gas. But remember, it's not an air pollutant from a human health standpoint, at least directly.
So the carbon dioxide being released. is much better than having carbon monoxide released. Remember, that's an asphyxiant. It can be toxic to people.
And so converting it to carbon dioxide is a really helpful thing from a human health standpoint. And so both of these methods are great ways to reduce NOx, VOx, and nitrogen oxides that are released from vehicles. Next, we'll talk about some specific pieces of technology for reducing the amount of SOx and NOx emissions in coal-fired power plants. So the first method involves using crushed limestone.
and so this crushed limestone can be combined with coal before it's sent into the boiler to be burned to create electricity so if we take a look at this diagram we can see how we have a pulverizer here that will basically crush up the coal in the limestone and mix them together now why do we do this well limestone is largely made up of calcium carbonate and when coal is burned in the presence of this limestone a lot of the sulfur dioxide that's produced mixes and combines with this calcium carbonate and instead of being emitted out of the smokestacks of these factories, gets trapped as a solid, and that's calcium sulfate. So again, instead of all of this SO2 being emitted, much of it is trapped in a solid form, which is calcium sulfate. We can use this calcium sulfate then for something productive. It can be turned into gypsum wall boards, so it can go into homes, or it can be used in the sheetrock of foundations for buildings. So again, rather than emitting high levels of sulfur dioxide, we can reduce that to some extent.
and create something useful with this calcium sulfate. We can also use something called fluidized bed combustion to reduce the level of NOx. So what this involves doing is basically blasting in jets of air at the bottom of your boiler, and it turns the mixture of coal and limestone into almost like this bubbling fluid bed, which is where it gets its name. Now this oxygen mixing in is going to basically make the burning of this coal far more efficient. It's going to mix...
the coal around so that the so2 being produced comes into more contact with the calcium carbonate and we capture more of the so2 but it's also going to make the reaction just so much more efficient that we can burn it under lower temperatures and reducing the temperatures of combustion is a great way to also reduce the nitrogen oxide emissions again fluidized bed combustion can make the crushed limestone method of capturing so2 more effective by more efficiently mixing the coal that's being burned but it can also allow for temperatures to be lowered which then reduces the amount of NOx being released. Next, we'll talk about two pieces of technology that can clean the emissions of numerous different types of facilities. So these are called wet and dry scrubbers.
So a wet scrubber is gonna be a great way to reduce NOx, SOx, and VOx. And the way that this works is it's basically a big column or tube that goes beneath your smokestack so that the emissions being produced by any sort of facility are passing through this column. Now what happens is it's typically filled with some sort of chemical agent, and that chemical agent is going to react with the air pollutants and basically convert them into a different form or trap them in this filter of sorts. A common example of this is using calcium oxide inside one of these dry scrubbers, and that calcium oxide will react with SO2 to form calcium sulfite, and again we trap it as a solid rather than releasing that sulfur dioxide as a gas.
and then it can be disposed of in a way that doesn't release it into the atmosphere. We can take a look inside of a dry scrubber here and you can see that it's basically just a tube that's packed with some sort of media. Again, calcium oxide is a great example. You don't have to memorize these different chemical agents, but it's just nice to know examples of how they actually reduce sulfur dioxide emissions. Then we have a wet scrubber, which is a very similar concept and it's a great way to reduce NOx, SOx, and VOx, but it also traps particulate matter a little bit more effectively.
And so similarly, it will often involve some sort of chemical agent that will bind to and trap or convert these air pollutants, but it also features sort of a misting apparatus inside. And so mist droplets, as you can see in the diagram, will kind of be released at different levels of this scrubber, and then those droplets will grab onto particulate matter in the air. And this is great because a lot of times air pollutants are actually attached to the particulate matter.
And so when it grabs those particles, They then fall down to the bottom of this device with the mist, or they hit this thing at the top called the mist eliminator, which basically traps the mist droplet so that it doesn't leave with the emissions. And then there's a sludge collection tank at the bottom, and that will concentrate all of this, you know, dirty polluted water with all of these pollutants in it and kind of forms this sludge-like material that can then be taken to a landfill. And finally, we'll wrap up today by talking about two specific ways to reduce particulate matter from emission streams. So the first way is called an electrostatic precipitator. And what happens here is the waste stream or the emission stream from a power plant or a factory passes through this device where we have a negatively charged electrode at the beginning of the device.
What it does is it gives all of the particles in the air passing that electrode a negative charge. Then we have positively charged plates, which you can see in red here on the screen, and they are going to grab onto those particles because the particles now have a negative charge. and it basically causes them to stick to the plates instead of leaving out the exhaust stream that comes out the end.
Then periodically the device can be discharged so that the particles just fall down and are collected in a hopper and can be disposed of. Next we have a bag house filter which is a really simple method that's been used for a long time to try to reduce particulate matter. It's basically just a large plastic bag or a bunch of plastic bags that are put inside a column like you can see here on the screen.
and then they will just trap the particles that are moving up with the waste stream. And then you have something called a shaker or a collection hopper, and that will kind of shake the bags out periodically so that the particles fall down into this hopper, where they can be collected, and then they can be disposed in a landfill instead of entering the atmosphere. So for practice FRQ 7.6 today, I want you to take a look at this graph, which shows different potential CAFE standards for the future. And I want you to make a claim about the effectiveness of the Obama Cafe standards as an effort to reduce the levels of NOx in urban areas. And then I want you to justify your claim with data from Figure 1, which is this graph here you can see on the screen.