Compost in trunk of Mustang

My wife just came home and said she’d heard a woman on the show ask about what damage might happen from compost that had been stored in the trunk of her car for two months. The most likely impact would be a little surface rust on any unprotected metal from the moisture in the compost. The trunk rug will clean very easily. And, no, it’s not halfway between garbage and dirt. If it’s made properly, it is a rich soil conditioner that resembles nothing like what it was started from (grass, brush, food scraps, etc.). Compost is an important component of a healthy soil, and healthy soils mean healthy plants. Anyway, she can drive over here and I’ll take her compost!


I don’t think she’d giveit to you. I mean she shoveled it into her trunk when her husband forgot shewanted the truck and droveit to work. She REALLY wanted the compost! I have a girl crush on this lady.

If she wanted it so bad, why did she say that she might just leave it in the trunk when she gets her new Mustang in about six weeks?

There was no mention of the quality or composition of the compost. Compost creates compost tea which will cause the trunk pan to rust. Vehicle trunks are usually closed off on one side by the seat back of the rear seat which is generally some type of hard cardboard covered in felt or fabric of some sort. The tea may seep into the seat back and might cause mold, and/or pool under the passenger seat and start rusting the floor pan. On the sides of the trunk are generally wells that trap the liquids and eventually rust out (common in cars with leaking trunks). Moisture may also get into the materials covering the rear deck causing mold there also. As the compost heats up it will cause condensation which can get into the electrical connections located in the trunk and cause rust and electrical issues. =o)

Compost is decaying/decayed vegetable matter, which may or may not have some worms crawling around in it. Great stuff for the garden, not so great for the trunk of a Mustang. I wouldn’t do it, but then I take care of my cars better than this.

I think this was the funniest segment in a long while. After saying she couldn’t name her husband’s employer and went on to say a Mustang a year, my partner and I had laugh and I said GM and he said Chrysler. Anyway, compost happens because it generates heat, which is why people often say it is cooking. Well, my neighbor once took her husband’s truck to get a load of compost and then didn’t unload it for awhile and the compost started a fire in the back of his truck. On side note, that is why one should not store wet hay because it can start a fire as it heats up.

compost usually has a large amount of fungus in it… it may cause a fungus problem in the rug.

Finished compost is the stuff they give away. There is no tea in finished compost. There may be worms, true, just as there are worms in regular dirt. The point is that click and clack were wrong: its the same as dirt. I know this because I make my own and I sometimes have a truckload delivered. I cant believe I’m the only person who admires this woman. Free compost is certainly worth getting your trunk dirty.

Also finished compost doesn’t generate heat, so there’s no safety issue. You can buy compost in hardware stores.

Ok, for the record compost is not dirt, however given they way it is made it may contain significant quaitities of dirt. Compost is largely organic matter in an advanced state of decay. Yummy! Dirt, or more appropriately “soil”, means mineral soil. For the non-math/science kids in the room that is to be read “very small rocks”. Yup you got it, the grass in your front yard and the tomatoes in the garden are rooted in “very small rocks”. As for the compost in the trunk, bad idea. Unless cooked, dried, and vacuum sealed, compost will likely contain lots of fungus and bacteria. Not exactly a hypoallergenic driving experience! Finally and probably most importantly, the reason people love compost is because it contains nutrients necessary for plant growth. Elements like nitrogen, potassium & phosphorus. The water soluble salts of these elements tend to be corrosive to metal. As an upstate New Yorker I prefer to have my vehicles rust from the outside in rather vice versa. Starting in 2012, used car value estimators like Kelly Blue Book or Edmunds will be asking, “Has compost or other large quantities of dead stuff been stored in the trunk of this vehicle”?

Um, yeah, filed under “S” for “Sez you”. A lot of the grass in my front yard is rooted in previous generations of grass in addition to all the rocky stuff. Plus squirrel carcasses, etc. N.B. none of this will ever be converted into petroleum by migrating thousands of feet down into the Earth.

If you don’t want fungi or bacteria in your car, you should never, ever let human beings into it. We’re covered in that stuff.

“Has compost or other large quantities of dead stuff been stored in the trunk of this vehicle”?

“Why, yes, I HAVE been to the grocery store!”

Not to worry, she’s getting a new one. The next question…how much will it affect trade in ?

It won’t. Both this car and the next one are free.

My sources tell that compost weighs between 38 and 70 pounds per cubic foot. The Mustang has a 13 cu ft trunk so at the low end (40 lb per cu ft) theres between 520 and 900 pounds of weight sitting above and behind the rear wheels. The 2011 Mustang is rated for a maximum load of 700 pounds, the average woman weighs 165 while the average male weighs 194 so with 520 pounds of compost the vehicle is already at the weight limits recomended by the manufacturer. Then theres the location of the added weight, having it well behind the rear wheels adds leverage so the 520 pound load would be magnified by how far behind the wheels its sitting. Then theres the problem with an unrestrained cargo in the case of an emergency stop, that extra weight moving forwards could smash through the opening between the rear seat and trunk possibly smothering the driver. And one final comment, if the compost was worth shoveling into the car wouldn`t it be worth unloading so it could be used for the purpose you got it to begin with?

“The 2011 Mustang is rated for a maximum load of 700 pounds”

So a Mustang can’t carry four average sized men? That assertion makes me call bogus on your entire post.

Have you ever tried to fit 4 “average sized men” in that car? Can’t be done. Well, it can, but only if they’re willing to be intimate. :slight_smile:


With regards to the weight of compost in trunk. I work part time for a friend who owns a nursery delivering mulch, compost and gravel by the truck load. I’m by no means an expert but can only say that it can be heavy if stored outside, though not as heavy as gravel. But if one compact tractor bucket full of compost were dropped in a Mustang trunk, it would definitely be a big issue weight wise…and not for the betterment of the Mustang. Though I can’t vouch for your numbers, your concern is well taken.

Compost can be a lot lighter than 38 lbs/cu ft. It depends on the moisture content. If it was outside in dry weather for awhile, it can get very light, but one rain will make it very heavy. Once it has settled, it won’t move around.

I would get it out of there though, its only good in the garden, not in the trunk of a car.

My mother used to throw a bale of hay into the back of her mustang convertible. I came home from college and she was clipping the grass growing in her back seat. Compost contains seeds, not all seeds are killed by composting!

Littlemouse, The source of my post was, "Consumer Reports Best and Worst New Cars 2012, page 84…the factory specs allow a maximum load of 700 pounds. Even the lowly Ford Focus is rated for a maximum load of 825 pounds, which I have to admit is surpassed by many, many drivers who have eaten themselves into those precious handicapped parking spots at the mall. You want to cry bogus before you did your research. The weight of compost I used was at the low end of the scale I found when I Googled “weight of compost per cu ft” so crossreferencing sources prove this is still a realistic estimated weight. You have to take into consideration that the front wheels need traction to steer, therefore adding excess weight behind the fulcrum that is the rear axle removes weight from the steering wheels. I hold firm that compost in a Mustang cant be good for the car nor the safety of the driver. All I could add is that I hope she doesnt need manure for her garden.