I have loaded a lot of mushroom bedding over the years, and would never have characterized its scent, odor, or aroma as that of tar. My suggestion would be to find out where it came from and go visit if it isn't very far away. If nothing else call the mushroom grower and ask some questions about the medium that they use to grow the product and any amendments that might be used.

Terran

I had another thought. Who hauled the Mushroom compost? If it was an independent hauler the previous material that was in the truck might have been asphalt.

Terran

Most likely it's not yet done composting.

Even mushroom compost that is finished should smell like good, rich earth. Even if the truck that delivered the compost had hauled asphalt for 100 years that odor would not permeate the compost in that short a time. I don't know what you got but it is not something I would use, right now anyway.

Bad news! It's more than a year later and there still is some of that smell, what's worse is that in areas where water has pooled a little, it is iridescent. Like oil from under a car.

There's no point in arguing with the supplier. What can Ido to counteract the problem?

"What can Ido to counteract the problem?"

I don't know if there's much you can do to "counteract" the problem as you don't know what it is. If it were me I would dig it all out, dispose of it, and start all over. I certainly wouldn't ever grow edibles in it, (not that you would).

Greg
Southern Nevada

The solution used to mitigate some contaminated soils elsewhere is to add organic matter, shredded leaves, straw, whatever you can get a lot of for not much cost.

"There's no point in arguing with the supplier."

You can report them to the Better Business Bureau, and write a spicy review on Yelp.

I just purchased some mushroom compost which smell likes tar or oil. After doing some searching it seems that one reason for the dreadful coal tar smell is cresol. Cresol is created when organic substances break down and some types of fungi also smell like coal tar as well.

At low levels there is no evidence it causes any problem but if you breath in high concentrations it can make your eyes and throat sore. At really high levels you can actually pass out. Not enough research has been done on this substance.

Some info on naturally occurring and manufactured cresols can be found in this PDF - http://www.atsdr.cdc.gov/toxguides/toxguide-34.pdf

It seems to break down readily in soil and via the action of microbes. It doesn't accumulate in the body and is excreted in urine. It can be absorbed orally, through the lungs and skin.

Can't say I am very happy about the smell. I previously purchase mushroom compost and it just had a musty earthy smell so this tar smell is quite unexpected. Won't be buying it again though unless I smell it first.

You have to uncover the pile to smell it because I was kicking it around with my boot prior to purchasing it and couldn't smell it until after it was scooped up and put into the trailer. Peeeuuuuw. I think for safety's sake it would be wiser not to use any compost that smells like this.

I've had a lot of mushroom compost smell that way. Still has the same wonderful results and I'm not dead yet. I'm sure it is known to cause cancer in the state of California, but I live in Washington so I'm safe ;-)

You shouldnt be landscaping over a septic field, grass cover is best for wastewater treatment

It sounds like a temporary condition and I suspect it's related to the substrate (what type of wood, etc. went into the mix) as well as the presence of certain types of fungi or other microbes. So it doesn't happen all the time, just when the conditions are right.

Sheen on the water can be organic matter from the composting process. I've seen rainbows on the water from sawdust piles, big mulch piles and decaying leaf piles. Without chemical analysis it's impossible to pin it on anything specific.