[Community_garden] The Great Koffee Kontroversy

[Mike McGrath]

right--you sent that lab result before.
    And the Director of Wood's End, a highly respected soil lab (they have 
been testing composts for municipalities and organic production for decades) 
very recently told me that they've tested 30 some samples of grounds from 
production facilities over the years and always got an initial pH of around 
5. He ran a test on their break room's grounds for me this winter and got 
5.1. He also noted that some samples that tested neutral were later found to 
have been composted with other materials.
    So we're trying to figure it out--and not from one source (the more I 
think about it, the more I wonder if that Washington State one might have 
been my own original reason for believing the grounds to be neutral).
    I think Don is right on the money about the type of coffee and brewing 
process having an influence. Heck I'll even speculate that the time between 
brewing and testing may be a factor.
    So let's figure it all out; its fun and should make a great story.
    C'mon kids--break out those pH meters and send us some numbers!
                                        ----Mike McG

----- Original Message ----- 
From: "Ray Schutte" <rayschutte at comcast.net>
To: "'Mike McGrath'" <MikeMcG at PTD.net>; 
<community_garden at list.communitygarden.org>; <yarrow at sfo.com>
Sent: Tuesday, February 20, 2007 11:44 AM
Subject: Re: [Community_garden] coffee grounds are HIGHLY acidic


>I have been using coffee grounds along with selected browns as a mulch for
> years.  I have my soil tested regularly and have not found an acidity
> problem here in the Pacific Northwest know for a certain level of acidity.
> I have found the following to be trustworthy.
>
> Starbucks commissioned a study in 1995
> to better understand the make up of the
> organic matter we call coffee grounds. The
> following is the result of the analysis
> performed by the University of Washington,
> College of Forest Resources:
>
> Primary Nutrients
> Nitrogen 1.45%
> Phosphorus ND ug/g
> Potassium 1204 ug/g
> Secondary Nutrients
> Calcium 389 ug/g
> Magnesium 448 ug/g
> Sulfur high ug/g
> Terms: ND = indicates sample is below
> detection limit
> ug/g= microgram / gram
>
> Most of the acidity in coffee is removed
> during the brewing process. Used grounds
> have an average pH of 6.9. Use your
> grounds within 3 weeks to capture the
> most nutritional value.
>
>
> Ray Schutte
>
> "The truth of the matter is that the flower has cleverly manipulated the 
> bee
> into hauling its pollen from blossom to blossom." The Botany of Desire,
> Michael Pollan
>
>
> -----Original Message-----
> From: community_garden-bounces at list.communitygarden.org
> [mailto:community_garden-bounces at list.communitygarden.org] On Behalf Of 
> Mike
> McGrath
> Sent: Tuesday, February 20, 2007 6:42 AM
> To: community_garden at list.communitygarden.org; yarrow at sfo.com
> Subject: [Community_garden] coffee grounds are HIGHLY acidic
>
> My bad! I was one of the people guilty of spreading the 'coffee grounds 
> are
> neutral' news for several years; luckily, I eventually followed up with 
> more
>
> research.  Wood's End Lab has confirmed that coffee grounds are VERY 
> acidic;
>
> here's the very interesting details:
> http://www.gardensalive.com/article.asp?ai=793
>                                        Best to all, Mike McG
>
> ----- Original Message ----- 
> From: <yarrow at sfo.com>
> To: <community_garden at list.communitygarden.org>
> Sent: Monday, February 19, 2007 10:10 PM
> Subject: Re: [Community_garden] Lime, worms and flies
>
>
>> Don wrote:
>>>Interestingly, coffee grounds would do the opposite of
>>>lime chemically, making conditions too acidic. But
>>>worms don't like them, either - I did an experimental
>>>trial of large amounts of coffeegrounds as sole
>>>foodstock, with newspaper as bedding, in wormbins, and
>>>the results were a complete bust (small amounts of
>>>grounds are fine).
>>
>> Acidic coffee grounds? That's a common myth. In fact, although coffee
>> itself is acidic, used coffee grounds are neutral.
>>
>> _____
>> http://faq.gardenweb.com/faq/lists/soil/2002015354019975.html
>>
>> While it is widely thought that they are acidic it has been shown
>> that most of this acidity is removed in the brewing process. Used
>> grounds are essentialy neutral and composting them with other
>> materials will buffer any minor residual acidity.
>>
>> One of the forum regulars with a scientific background did some
>> controlled chemistry experiments on the acidity question and this is
>> what he had to say:
>>
>> "Roasted coffee is fairly acidic, but it appears that almost all of
>> the acid is water soluble and is extracted during brewing. Used
>> grounds have essentially neutral pH, although the coffee beverage
>> produced is rather acidic.
>>
>> The measured pH of used coffee grounds was 6.9, with a significant
>> amount of buffer capacity - adding the coffee to either acidic or
>> basic solutions drove both towards neutral pH. The exact pH of used
>> grounds will depend on the pH and alkalinity of the water used in
>> brewing, but with any potable water, used grounds will be close to
>> neutral pH."
>> _____
>>
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