Coal Ashes in the garden?

[Richard S.]

LsFarm asked in another post if putting coal ashes in the garden was OK. I figured that's a pretty good question so I started a new thread. It was discussed in another thread here, someone had chimed in that coal ashes contain trace heavy metals and other toxic agents.... so does dirt...

I know many of my customers use them in there garden and swear by them. As far as the toxic aspect I'm not a scientist so I really don't know. Really depends on the level, perhaps someone with a little more knowledge can help.

The previous post thread can be found here: http://nepacrossroads.com/viewtopic.php?t=291

[mjb]

I work at a DOE Laboratory on Long Island and one of the bldgs. there is a biology department. I e-mailed the guy who runs the greenhouses and this is his reply. More to follow.

Coal ash contains stuff, including trace elements, that is harmful to plants in high concentrations and I think it contains arsenic too. I'll try to find something in print rather than try to rely on my failing memory.
Rich

[Richard S.]

Another thing I had also pointed out was that I'd assume you'd have to consider the type of ash. I'm sure the composition of anthracite ash differs from bituminous ash... Information on bituminous ash should be fairly abundant, whether the same is true for anthracite ash I don't know.

What I'm really interested in is if using the ash can be hazardous to your health. The big question is are the levels of toxins enough to be harmful to human if they consume food grown in this ash or is just the same as if you used plain topsoil.

[Berlin]

Coal ash is best avoided for use in gardens; It does not contain much nutrient content nor does it really benefit the soil structure. Coal ash is not beneficial to a garden because its phosphorus and potassium content are low compared to wood ash, which can be quite beneficial. Some coal ash containes elevated levels of arsenic which is not good for plants; however, in the US and especially the eastern us, this is generally not the case; additionally coal ash contains mostly unburnt rock, silica and similar inert and unbenifical matter.

Now, having said all that, realize that if you were to add some coal ash to your garden, it generally wont hurt it, unless you add excessive amounts over possibly years; additionally with anthricite or bituminous coal, the % of ash that contains certain undesireable trace elements varies widely from coal seam to seam, region to region, and even different areas of the same coal seam. However, in the us eastern coals, bituminous or anthricite have very low levels of the worst trace elements and do not generally differ greatly from the soil in general. The main point of my post being that while the addition of ash to your garden will probably not hurt your garden or you, it would add no noticeable benifit either, so just dump your coal ash in the woods and save your wood ash for the garden.

[Yanche]

I also don't think adding coal ashes to a garden is a good idea. The questions are, "Why?", "What's the benefit?", "What's the risk?" If need to improve your garden soil you should first have a soil test done to find out what's needed. In my area the local county Agricultural Agents have low cost soil test kits available that are sent to the state University for analysis. The test report will tell you what soil amendments are needed. Ideally some organic product is available. In my area frequently crushed limestone in needed to correct for acidic soil.

Since you don't know the analysis of your coal ash it's just unknown that it might do. Power plant coal ash is certainly different that our residential ash because of the very high temperature combustion processes in the power plant boiler. This is the kind of fly ash we read about that has been recycled into cement or construction aggregate. It's the unknown that of concern. The coal burning combustion process burns the carbon, which combines with the air to make carbon dioxide and carbon monoxide. These are carried off by the chimney. But what about the other unknown elements in the coal that are not affected by the combustion process? They are concentrated in the ash. The many pounds of unburned coal that contained these trace elements, have now concentrated these elements in the much smaller volume of ash. Now we put the ash on a garden. Plants hopefully grow in it. Young plants take in these concentrated trace elements. We eat the food. Is it good? Who knows? It's not worth the risk. Limit ash use to filling pot holes or aggregate in concrete. It's like septic system sewage. We know it makes the grass grow but we wouldn't put on our gardens. It's the unknown in it.

[mikeandgerry]

No benefit to coal ashes in the garden. Could hurt over time. Wifey doesn't want them in our driveway (me neither). They would track in the house. No place on my suburban plot to dump them. I take them to a clean fill site when there is no snow, otherwise, it' off to the landfill.

The Lehigh Coal and Navigation website stated that the EPA doesn't consider the untreated effluent or ashes to be hazardous waste nor do they regulate it. Cant find the Lehigh Coal site. I think they lost their permits.

Certain coal ash is sought after to be mixed with concrete (after being processed). NYS requires a certain percentage of coal ash in any concrete that it buys. I tried to tell that to the one toothed woman who is the gate keeper at the local landfill. She was unimpressed and told me, while rolling her eyes, "it goes in the regular trash". "That'll be $2.50, buddy." I dump it loose from my ash pails once a week.

[lincolnmania]

we use coal ash in our garden, along with cow manure and compost.....every yr the garden gets better

[Richard S.]

Certain coal ash is sought after to be mixed with concrete (after being processed). NYS requires a certain percentage of coal ash in any concrete that it buys.

It's my understanding concrete made with flyash is superior, longer life span. I wouldn't doubt if you examine the composition of many these older roads that were built back in the 20's, 30's out of crete that are still in half way decent shape considering their age you'd find that they have coal ash. That would certainly be the case around the coal region.

[coalstoves]

As far as gardens go the grass is still thick and green all around my ash pile in yard, I kid you not

[Richard S.]

I got plenty of grass/weeds growing in the driveway where ashes have been dumped, wish it did kill them.

[mikeandgerry]

No benefit to coal ashes in the garden. Could hurt over time.

To clarify: the downside of ashes over time is that the continued application of a non-beneficial mineral simply crowds out the access of the plant to beneficial minerals. The downside is minimal and the ashes are not detrimental in and of themselves except that they are alkaline which may not be good for some vegetation. Toxics are minimal but present in the form of heavy metals and sulphur.

The one good point of the ash is that it may sustain hydration in soil (hold water longer). The fine powdery ash does this, not the chunky stuff. But again, too much ash is not a good thing. Use it sparingly. Best bet is to have your soil analyzed and use only what the soil needs.

If you are mixing soil and ash for making an embankment or something similar, there are engineering standards for percentages used. I cannot recall exactly but once you approach certain levels the embankment becomes dangerously unstable, that is, it can slide or will fail to support a load. The research was done by some Japanese engineering school.

[mikeandgerry]

It's my understanding concrete made with flyash is superior, longer life span. I wouldn't doubt if you examine the composition of many these older roads that were built back in the 20's, 30's out of crete that are still in half way decent shape considering their age you'd find that they have coal ash. That would certainly be the case around the coal region.

You are right it is fly ash is what they really want. They sort and grind clinkers from the bottom ash and use that in concrete too as an aggregate.

Fly ash adds stability and self-adhesion characteristics (like clay) to soils and concrete up to a point. The mix proportions are critical (as is true for most mixtures).

[gaw]

No benefit to coal ashes in the garden. Could hurt over time.

To clarify: the downside of ashes over time is that the continued application of a non-beneficial mineral simply crowds out the access of the plant to beneficial minerals. The downside is minimal and the ashes are not detrimental in and of themselves except that they are alkaline which may not be good for some vegetation. Toxics are minimal but present in the form of heavy metals and sulphur.

I have heard that coal ash is acidic. This sounds like a good time for one of Matthaus's science experiments. I have soil that is mostly neutral to slightly acidic at best. I like growing blueberries, azaleas, and rhododendrons, as well as evergreens and some other plants that like acid. I heard in the past that coal ash lowers ph. If it contains sulphur it should because you add sulphur to soil to lower ph. Aluminum sulfate, iron sulfate are soil acidifiers and ammonium sulfate is a nitrogen fertilizer for acid loving plants.
This spring if time permits I think I will till a small plot of soil and test the ph and then over time incorporate coal ash into the soil and test to see if it has an effect on the ph. Many acid loving plants like soil ph as low as 4.5 and blueberries to 4.0. If I see a good effect on lowering ph I may consider it for that purpose.

[Matthaus]

I have heard that coal ash is acidic. This sounds like a good time for one of Matthaus's science experiments.

Sorry the lab is down at the moment. I do know that my entire yard is 80% coal ash, wherever you dig the stuff is anywhere from 6" to over 3' deep. Grass grows with no issues and the garden I used to have didn't seem to have an issue. My neighbor who has a garden uses my excess ash in his compost pile at a ratio of 1/3 ash, 1/3 leaves and other mulchings out of my mulcher, and 1/3 soil. I think his tomatoes in particular like that mix so I guess the whole thing about ash making the soil acidic could be at least partly true.

On another note when I was a lil one we used hydrated lime (calcium hydroxide) to treat the more acidic food wastes and lawn clippings in preparation for addition to the compost pile. We used biodynamic compost starter (info on this here http://www.attra.org/attra-pub/PDF/biodynam.pdf ) in the pile and it would get so hot in the winter no snow would ever even stay on it during a storm.I would think that could work with use of coal ash in the compost to reduce the acidity. If I hadn't paved my entire back yard I could have tried it out in the garden.

[mikeandgerry]

I have wide range litmus paper and a color chart. I took 6 ounces (avoir.) and about an ounce and a half of fine coal ash using a shot glass as the volume measure. My water tested in the 7 range. After stirring in the coal ash, I tested again. The mixture tested in the 8 range.

Solid ash, according to a paper I found, showed a dry pH in the range of 9.1 to 11.3

http://www.mcrcc.osmre.gov/PDF/Forums/CCB6/3-2.pdf