Difference between fly ash and bottom ash?

To Powell River Legacy group:

I saw yesterdays viewpoint in the Peak, and once again I see a statement that the fly ash coming out of Catalyst is no worse than the ash left behind from a wood stove. This seems like a pretty straightforward empirical claim: either the mill's flay ash IS or IS NOT worse than wood stove residue.

Since I'm new to knowing about the landfill, can you point me to whatever you know about the dioxin content of wood stoves ashes, or about the dioxin content of fly ash from the mill's boilers? Or is this a red herring? Isn't it possible to settle this claim one way or another? It's clear that this line is being pushed by the mill as part of their PR campaign. -Along with the claim that demanding that Catalyst adhere to environmental regulations equates to demanding that the mill be closed -- what about following the guidelines AND doing their business? Have we all decided that we have to choose either a functioning mill or a non-toxic town?

Reply 1 from the PR Legacy group:

Yes it does seem to be a part of the Catalyst campaign to minimize any concerns we have.

Fly ash and "ash from a fire" are really two entirely separate products. Fly ash is actually the “smoke” that leaves the fire, and bottom ash is what remains after the fire is done.  So if you compare woodstoves to power boilers, the woodstove ash would be compared to the bottom ash, and flyash would be compared to the smoke-particles leaving your chimney. 

One major factor is the size of the particulates involved. The particles of  flyash are on the order of 1000 times smaller than that of the ash left at the end of a fire. And while they are in the air, these particles are generally not visible.  They only become easy to see when they are  gathered into a concentration of flyash, which allows them to be seen in their aggregate. 

A couple more things about the physical nature of fly ash. These particles can be inferred as being present when we see a ''shimmer'' or a ''dancing '' above the pavement or other solid surface on a hot day. What we are actually seeing is not the particles themselves, but the shadows of many particles being projected  onto other particles below them. It's  that interference with the light that we see, not the particles themselves.

This brings up the issue of what happens when these particles of a small size are breathed in the lungs.

Since they are so small, the particles tend not to be able to be dislodged by the mucus in the lungs. In fact, there are times when the particles actually directly enter the body tissue itself. So the makeup of the particles becomes an issue --and in the case of the fly ash, there is a high concentration of silica --and that is a major concern in and of itself.--By the way, the Golder report refers to these small particles as "Total Suspended Particles [TSP]" , and the report acknowledges that this was never tested at the site .And the report itself also quotes the MOE as they confirm that this is a factor in health.

Not only are the particles smaller than conventional dust, but the particles  tend to become
1] more easily airborne,
2] tend to stay in the air for longer periods of time,
3] travel much longer distances than dust.. 
because flyash dust is such a smaller particle size than is the ash left behind at the end of a fire ----and we haven't even mentioned dioxins and furans yet.

We get into the realm of dioxin and furans when we consider another factor associated with the small size of the fly ash particles. This is the physical nature of surface area  of all the particulates  when a certain volume is gathered. ---the smaller the particulate size, the greater the  surface area associated with the same volume of ash. A fairly easy way to show this is to visualize a box of volleyballs. If you measured the total surface area of all the volley balls in the box, and compared it to the results you would get from  computing the surface area if that same box were filled with ping-pong balls.---the result is that there is an exponential increase in the surface areas involved. This becomes a factor when we take into account that any dioxin or furan formed, will distribute itself in a manner which is fairly consistent throughout any surfaces available to it. This results in more dioxins and furans being in the  flyash,  just because there is more surface area to attach itself to. ---and when you consider the relative efficiencies of the flyash particles to be included into the body, then the potential for contamination from the fly ash becomes a very real danger.

Now to the question--is the flyash worse than the wood stove residue? Even if everything were the same as the ash left at the end of a fire in  a woodstove, since there is far more surface area to attach to in the fly ash, it is definitely more dangerous than bottom ash.--even if the ratings per unit area were the same.

But it isn't as simple as that ---The wood I burn in my stove has not  soaked in salt water before it is burned --as it is within the boiler at Catalyst. We know that at the temperatures in the boiler are enough to break down some or all of the Sodium  chloride [salt] and that the elemental chlorine will form to make dioxins and furans under certain conditions --the less oxygen available to it, the more likelihood of dioxin and furan formation.

This whole issue really is a bit of misdirection. It all  sounds so simple, but it isn't the same at all.

Hope this helps.
go well, Dave

P.S. You can do an internet search using the terms "Fly ash" and "silicosis" and dioxins" and "furans" and get some interesting reading. Here's something worth looking at right now regarding fly ash and bottom ash. Please notice what it says about silicosis.