# Used Coffee grounds.... **URL:** \ **Category:** Factual Questions\ **Created:** [May 31, 2005, 12:14am UTC](https://boards.straightdope.com/t/used-coffee-grounds/306149 "2005-05-31T00:14:27Z")\ **Posts on this page:** 12\ **Page:** 1
**Author:** ![Javajake3](https://avatars.discourse-cdn.com/v4/letter/j/ea5d25/32.png) [@Javajake3](https://boards.straightdope.com/u/Javajake3)\ **Post date:** [May 31, 2005, 12:14am UTC](https://boards.straightdope.com/t/used-coffee-grounds/306149/1 "2005-05-31T00:14:27Z")
I’m trying to confirm what a buddy told me recently…that pouring used Coffee grounds into the sink disposal is not only ok, but that it will actually help to sharpen the blades within the disposal??? fact or fiction?? thanks in advance ---
**Author:** ![WhyNot](https://avatars.discourse-cdn.com/v4/letter/w/c77e96/32.png) [@WhyNot](https://boards.straightdope.com/u/WhyNot)\ **Post date:** [May 31, 2005, 1:32am UTC](https://boards.straightdope.com/t/used-coffee-grounds/306149/2 "2005-05-31T01:32:13Z")
[In-Sink-Erator’s website says:](http://www.insinkerator.com/dodont.html) > [@](#): > > Do grind hard materials such as small bones, fruit pits, and ice. A scouring action is created by the particles inside the grind chamber. I doubt that used coffee grinds are as hard as bones or fruit pits, but they prob’ly scour some. Not sure about sharpening though. ---
**Author:** ![Reeder](https://avatars.discourse-cdn.com/v4/letter/r/c6cbf5/32.png) [@Reeder](https://boards.straightdope.com/u/Reeder)\ **Post date:** [May 31, 2005, 1:32am UTC](https://boards.straightdope.com/t/used-coffee-grounds/306149/3 "2005-05-31T01:32:43Z")
> [@](#): > > She told me that contrary to popular belief, all the plumbers actually encouraged people to put their coffee grounds down the disposal or kitchen sink drain. Oh sure, you skeptics out there (you know who you are) are thinking this was a powerful marketing technique put forth by the plumbers union to increase repairs and build up market share. However, consider their logic. These drains have a tendency to accumulate oils, grease, and other disgusting things we all wash down the sink from time to time. Coffee grinds actually will act as a sort of sandpaper or grit to help bind with these cloggers and help them flush down the drain. If you have a disposal the grinds will also help clean up the blades. At least that was the plumbers theory and you are not going to make a living trying to argue physics with a plumber. [http://www.coffeegeek.com/reviews/vacpots/bodumesantos/Grindaddy](http://www.coffeegeek.com/reviews/vacpots/bodumesantos/Grindaddy) ---
**Author:** ![Javajake3](https://avatars.discourse-cdn.com/v4/letter/j/ea5d25/32.png) [@Javajake3](https://boards.straightdope.com/u/Javajake3)\ **Post date:** [May 31, 2005, 2:17am UTC](https://boards.straightdope.com/t/used-coffee-grounds/306149/4 "2005-05-31T02:17:19Z")
good info…makes sense. 🙂 ---
**Author:** ![Peanuthead](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/peanuthead/32/360_2.png) [@Peanuthead](https://boards.straightdope.com/u/Peanuthead)\ **Post date:** [May 31, 2005, 5:01am UTC](https://boards.straightdope.com/t/used-coffee-grounds/306149/5 "2005-05-31T05:01:11Z")
It’s a good idea to keep some coffee grounds near the sink anyway. A little rubbed into your hands after peeling garlic will remove the odor. ---
**Author:** ![LSLGuy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lslguy/32/5813_2.png) [@LSLGuy](https://boards.straightdope.com/u/LSLGuy)\ **Post date:** [May 31, 2005, 12:11pm UTC](https://boards.straightdope.com/t/used-coffee-grounds/306149/6 "2005-05-31T12:11:27Z")
Coffee grounds, or any other foreign object, could not possibly sharpen blades. Sharpening is a process of organizing the edge, undoing the random dents and dings casued by the blades striking the stuff they’re grinding. Sharpening is the reduction of entropy in the blade edge. Meanwhile, blades plowing through a cloud of grounds is a random process, and will increase local entropy, not decrease it. Coffee grounds are much softer than steel, so I’d bet the net effect is small, but it will definitely be in the direction of duller, not sharper, blades. ---
**Author:** ![Turek](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/turek/32/18782_2.png) [@Turek](https://boards.straightdope.com/u/Turek)\ **Post date:** [May 31, 2005, 12:21pm UTC](https://boards.straightdope.com/t/used-coffee-grounds/306149/7 "2005-05-31T12:21:04Z")
> [@Peanuthead](#): > > It’s a good idea to keep some coffee grounds near the sink anyway. A little rubbed into your hands after peeling garlic will remove the odor. Or, you could just rub your hands on stainless steel under running water. Gets rid of the garlic smell without imparting coffee-stink on you. ---
**Author:** ![archmichael](https://avatars.discourse-cdn.com/v4/letter/a/bb73d2/32.png) [@archmichael](https://boards.straightdope.com/u/archmichael)\ **Post date:** [May 31, 2005, 2:01pm UTC](https://boards.straightdope.com/t/used-coffee-grounds/306149/8 "2005-05-31T14:01:26Z")
I thought the point of the coffee grounds in the garbage disposal, was odor control ---
**Author:** ![daffyduck](https://avatars.discourse-cdn.com/v4/letter/d/ec9cab/32.png) [@daffyduck](https://boards.straightdope.com/u/daffyduck)\ **Post date:** [May 31, 2005, 3:39pm UTC](https://boards.straightdope.com/t/used-coffee-grounds/306149/9 "2005-05-31T15:39:05Z")
Garbage disposals act more like hammer mills that beat the food to a pulp than they do like knives that cut it up. The “blades” in my garbage disposal have never been sharp and I hope never will be. Sometimes I stick my hand in there to retrieve things that shouldn’t go down the sink (like a ring) and the last thing I want is sharp blades that would cut me. I think this whole “shapeneing the blades” business was started by someone who had never actually looked at the “blades” in a disposal. ---
**Author:** ![redtail23](https://avatars.discourse-cdn.com/v4/letter/r/3e96dc/32.png) [@redtail23](https://boards.straightdope.com/u/redtail23)\ **Post date:** [May 31, 2005, 3:52pm UTC](https://boards.straightdope.com/t/used-coffee-grounds/306149/10 "2005-05-31T15:52:08Z")
The last plumber that mentioned coffee grounds to me told me NOT to put them in the disposal. He said lots of people had heard that grounds would clean out the disposal, but in fact they just jam it up. YMMV. ---
**Author:** ![sj2](https://avatars.discourse-cdn.com/v4/letter/s/65b543/32.png) [@sj2](https://boards.straightdope.com/u/sj2)\ **Post date:** [May 31, 2005, 7:08pm UTC](https://boards.straightdope.com/t/used-coffee-grounds/306149/11 "2005-05-31T19:08:12Z")
Wait, I have a septic system–which I was told not to put the grounds in. I’m so confused! I don’t think the grounds would damage the tank, just decrease the pumping interval due to solids build up…I live near Seattle–we have a lot of coffee grounds around here 😉 Hmmm… ---
**Author:** ![Anne\_Neville](https://avatars.discourse-cdn.com/v4/letter/a/b9e5f3/32.png) [@Anne\_Neville](https://boards.straightdope.com/u/Anne_Neville)\ **Post date:** [May 31, 2005, 7:32pm UTC](https://boards.straightdope.com/t/used-coffee-grounds/306149/12 "2005-05-31T19:32:52Z")
> [@](#): > > Do grind hard materials such as small bones Emphasis on the word “small”, and you should probably only grind bones that you think of as tiny. I tried grinding some of what _I_ thought were small bones, and then I had to call maintenance to come and fix the garbage disposal.