Is Clean Coal on a very small scale possible?

Can a coal-fired pizza joint keep from polluting the air, at least partly?

Today’s USA Today Life Sunday in the Indianapolis Star had a splashy piece on various styles of pizza. The first American pizza style, writes Larry Olmstead, was Neapolitan-American, made by immigrants from Naples. In Naples the ovens were wood-fired, but it NYC it was much easier to get coal, which makes for a hotter oven than wood does. Back then, burning coal wasn’t seen as a villainous thing to do.

Today, coal-fired power plants employ some methods to reduce sulfur dioxide, soot and such. I don’t understand any of those methods, I’ll tell you up front. Can any of them be used on a scaled-down pizza oven size?

I tried, but failed, to provide a link to the article. Sorry.

IDK if they could be done to the standards that powerplants can, but certainly some aspects could be implemented such as particle capture, perhaps a liquid spray like used in diesel vehicles. However I don’t know if scaling down powerplant tech is the best solution instead of redesigning it for the application mentioned here.

Coal fired plants generally have a two-stage system for scrubbing exhaust gases. The first is an electrostatic precipitator which is used to remove fly ash. The fly ash is then collected and sold (at least in the plant that I worked in). They use it to make concrete and all sorts of stuff.

The second stage is used to remove sulfur compounds like sulfur dioxide. In this stage, they basically spray a mist of water droplets combined with something like calcium carbonate (crushed limestone). This reacts with the sulfur and produces gypsum, which can also be sold.

I’m not sure how well these methods would work when scaled down to something that small. You’d probably end up with a fairly finicky system that requires a lot of maintenance. You might also need something different like a filter to catch the ash, and that would definitely require more cleaning and maintenance.

Why would you think a coal-fired pizza oven would produce more emissions than a wood-fired pizza oven?

It’s true that coal burning power plants produce a lot of emissions, but that’s because they burn a truly staggering amount of coal every day. We just don’t have a comparable infrastructure of wood burning power plants, and if we did they’d be spewing soot just like coal plants.

While it’s not used on a huge scale, we do have some biomass power plants. Most of the ones that I am familiar with came from a need to get rid of waste materials like wood pulp from foresting operations and saw mills.

Generally speaking, biomass plants produce about the same amount of ash and particulates as coal plants. However, coal plants produce a lot more sulfur dioxide and sulfur compounds.

Nope. The cost of the secondary systems to eliminate pollution would make the energy produced too expensive.

To be precise you have define the size of the system, and what you mean by clean. Originally clean coal power was intended to be as clean as gas fired plants at the time the concept was originated. Since then standards are higher for gas generation, and the idea is to get to minimal emissions except for CO2 I assume. It’s not sounding good, and we have plenty of natural gas now making coal fired plants less economical in general.

Scale may be different though, I don’t know if we’re making the smallest clean coal plants we can now. Simply justifying the cost of a new power plant and justifying it’s existence politically requires a high potential power output. So maybe something big enough to power a small city is possible. A clean coal pizza oven definitely isn’t.

On top of the cleanliness of the power plant we still have to consider the costs, pollution, and politics involved with coal mining.

Sooner or later we’re going to have to choose our poison, there won’t be any truly clean efficient source of energy until 10-20 years from now when the fusion plants go online. And that ‘now’ will be valid for at least 10-20 more years from now.

Certainly more sulfer produced from burning bituminous coal.

I see your point, Lemur. If I remember right, Vail, Colorado had so many wood-heated houses that the little town developed a layer of something like L.A.'s smog. However, most of America’s pizza ovens are powered by electricity or natural gas.

When I was a kid, we heated with anthracite, which I think has far less emission than ordinary soft coal. Since we could get it in Philly, I assume you could get it in NYC.

A coal-fired pizza cookery sounds pretty awful, taste-wise.

I believe there were some occasional concerns about smoke, but related to exacerbating factors like thin air and temperature inversions at high altitudes. This is certainly not evidence for making the claim that “coal is no worse than wood”.

In fact, coal is the worst and dirtiest of all the common fossil fuels for a number of reasons:

  • the dirty, dangerous, and often environmentally damaging work of extracting it

  • coal emits relatively high levels of sulfur dioxide, nitrogen oxides, and particulate matter which may or may not be effectively scrubbed (and typically cannot be economically scrubbed in small installations)

  • coal actually produces radioactivity because naturally occurring uranium and thorium and their chemical and decay byproducts become concentrated in the fly ash

  • and like all fossil fuels, coal releases large amounts of CO2. This is different from burning wood which only releases recently sequestered carbon, basically returning to the air that which was just recently removed from it. Coal returns to the air carbon that’s been sequestered for as much as hundreds of millions of years. There is also a very large abundance of it. Those two facts together mean that if we burn a significant amount of it, we will very quickly (in the blink of an eye, geologically speaking) push atmospheric carbon and global temperatures towards what they were in the distant geological past.

That is what I was thinking. Charcoal maybe, but coal?

Come to New Haven sometime. You’ll change your mind once you’ve eaten at Pepe’s or Sally’s.

A traditional oven where the fire is built inside the oven might end up making the pizza a little smelly, but I don’t know. When these ovens are hot enough, they can reach 1000F or more, the soot lining in the oven burns off, the carbon turns into CO and CO2 and is exhausted. I imagine the same thing would happen to other impurities in the coal. Many commercial brick and stone ovens are now heated externally so there would be no effect on the interior of the oven from the particular fuel used. And the coal used in the ovens described by the OP may have been anthracite, very close to pure carbon. They might even have used coke which is nearly pure carbon as well. There would have been a lot of it produced in coal gas plants, it’s essentially the equivalent of charcoal made from coal.

Musicat, and Ike Witt, unlike gas-fired ovens or charcoal grills, the smoke doesn’t pass through the baking box. It provides the heat, but the firebox and flue aren’t connected to the baking chamber.

Do they give the details in the article? The traditional pizza oven is a brick or stone bread baking oven where the fire is built inside the baking chamber and kept going until the entire oven is hot enough, then the ashes are swept out when it’s ready. Sometimes a small fire is kept going in the oven to maintain the heat. A properly designed oven can stay hot enough after the initial firing to keep on baking for 8 hours or more.

Right, except wood is not a common fossil fuel.

Nobody makes a big squawk about wood emissions because wood is a very small player in the energy budget. Coal, gas, fuel oil, and so on are much bigger, and so it makes a lot of sense to focus on producing those as cleanly as possible.

Wood is an especial problem because a typical wood burning setup is a fireplace in someone’s home, not a commercial power plant. And home fireplaces produce horrible pollution measured in terms of pollution per energy output rather than absolute amounts. Wood smoke is a significant source of urban air pollution.

My only point is that it makes a lot of sense to focus on getting a massive coal-fired powerplant as clean as possible because that one plant is producing millions of tons of emissions every year. A coal fired pizza oven is going to be in the same ballpark as a wood fired pizza oven, and possibly even better, except for sulfur. But sulfur is only one pollutant, and is only significant on a truly massive scale. The real worry for these small ovens and fireplaces is particulates and soot.

This article from Boston Magazine includes a photo showing the oven at the Frank Pepe Pizzeria Napoletana location in Boston. The small opening in the middle of the photo is where the pizzas go, while the larger opening on the left is where the coal goes. Note the extremely long (ten feet or so) handle on the pizza peel hanging from the ceiling. That’s because the oven is quite deep, so the cook has to manipulate the pizzas several feet into the oven.

For local air quality, I’d add NOx and other ozone formers and PM. We see regulation of wood burning stoves due to PM, IIRC in the form of catalyst beds.

Maybe I am a philistine, but for me it’s just a gimmick. On a barbeque the smoke alters the taste of whatever is being cooked. In an oven, there is only heat - how that heat is achieved is surely incidental to the taste and quality of the final product. If one pizza chain makes better pizza, it is surely more to do with preparation and recipe than the source of the heat.