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Most everything you need to know about Used Coffee Grounds

 
Bryant RedHawk
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Location: Vilonia, Arkansas - Zone 7B/8A stoney, sandy loam soil pH 6.5
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Having used spent coffee grounds since 1970 for a myrad of purposes in gardens, farms and for other growing purposes,
I thought it would be a good idea to build a reference thread for this wonderful amendment.
There are definitely pros and cons to using spent coffee grounds as well as several ways to utilize them in gardening/farming.

Here are some useful characteristics of used coffee grounds. They are:

•High in nitrogen (a very valuable nutrient for plants). Grounds have a C/N (carbon:nitrogen) ratio of 20/1.
•Almost neutral (although coffee is highly acidic, the pH level of the grounds are diminished significantly when brewed)
•Digestible by worms
•Good for improving soil tilth (structure)
•A natural pesticide (great for repelling slugs, flies, and other critters!)
•An agent for bacterial control. The natural mold and fungus on coffee can suppress pathogenic fungi, including fusarium, pythium, and sclerotinia species.
•Weed killers

The predominate fungals that are found in used coffee grounds are; Pseudomonas, Fusarium, Trichoderma and Mucorales.
These organisims are very effective in preventing pathogenic fungi and pathogenic bacteria from becoming established,
this includes; Fusarium, Pythium, Sclerotinia species, E.coli and Staphylococcus.

Nitrogen-rich proteins needed for seed germination and growth comprise
over 10% of coffee grounds. In fact, the carbon-to-nitrogen ratio of coffee
grounds can be as low as 11:1, an ideal ratio for plant and soil nutrition. Since
coffee is extracted in water, most of the hydrophobic compounds, including
oils, lipids, triglycerides, and fatty acids remain in the grounds, as do insoluble
carbohydrates like cellulose and various indigestible sugars. Structural lignin,
protective phenolics, and the wonderful aroma-producing essential oils are also left
over from the brewing process. It’s this last group of chemicals that are reported
to have antioxidant and antimicrobial properties.


Over the course of several months, specialized bacteria and fungi break down
the various chemical components of coffee grounds. Some larger consumers,
including earthworms, are also able to use this food source. The fact that earthworms
pull coffee grounds deep into the soil may,account for noted improvements in soil
structure such as increased aggregation.
Humic substances, which are important chemical and structural soil components,
are produced through coffee ground degradation. Carbon-to-nitrogen ratios
change as well, generally starting out a bit higher than ideal (e.g. 25-26) and
decreasing to 21, 13, 11, or even 9.4 in a year’s time.

Less straightforward are the changes in pH that occur during decomposition.
A commonly held assumption states that coffee grounds are acidic, but this does
not hold true experimentally. While two studies on coffee ground composting
reported mildly acidic pHs of 4.6 and 5.26, others have measured neutral (7.7)
to somewhat alkaline (8.4) pH levels.
More than one researcher found that the pH of soil treated with coffee compost increased
after 14 to 21 days of incubation, gradually decreasing thereafter. Obviously
the pH of decomposing coffee grounds is not stable and one shouldn’t assume that it will always, or ever, be acidic.

Not all plants get a jolt from coffee grounds:

Seed germination of alfalfa (Medicago sativa) and white and red clovers (Trifolium repens and T. pratense)
was inhibited by water leached through coffee grounds. Growth of crops such as Chinese mustard (Brassica juncea),
komatsuna (Brassica campestris) and Italian ryegrass (Lolium multiflorum) were all inhibited by coffee grounds, as
was that of ornamentals including inch plant (Tradescantia albiflora), geranium, and asparagus fern. One investigator
speculated that toxic substances released from decomposing coffee grounds were responsible for their inhibitory effect.
This effect also reduces weeds, and perhaps in a landscape dominated by large shrubs and trees, only germinating seeds
and seedlings would be injured. But there has been no experimental research on coffee grounds and woody plants published to date.

Percentages of 10 to 20 percent of total compost volume have been reported as optimal for compost quality and
effectiveness, while over 30 percent can be detrimental.

Only small amounts of coffee grounds are required for effective disease suppression. Therefore, it is recommended
using no more than 20% by volume of coffee grounds in a compost pile. A diverse feedstock will ensure a diversity
of microorganisms.

Don’t assume coffee grounds will make an acidic compost; pH levels will undoubtedly change over time.

The concept of "friendly microorganisms" was developed by Professor Teruo Higa,
from the University of the Ryukyus in Okinawa, Japan. He reported in the 1980s
that a combination of approximately 80 different microorganisms is capable of
positively influencing decomposing organic matter such that it reverts into a "life promoting" process.
Higa invoked a "dominance principle" to explain the effects of his "Effective Microorganisms".
He claimed that three groups of microorganisms exist: "positive microorganisms" (regeneration),
"negative microorganisms" (decomposition, degeneration), "opportunist microorganisms".
In every medium (soil, water, air, the human intestine), the ratio of "positive" and "negative"
microorganisms is critical, since the opportunist microorganisms follow the trend to regeneration or degeneration.
Therefore, Higa claimed that it is possible to positively influence the given media by supplementing with
"positive" microorganisms.

The concept has been challenged and no scientific studies support all of its claims.
This was acknowledged by Higa in a 1994 paper co-authored by Higa and soil microbiologist James F Parr.
They conclude "the main limitation...is the problem of reproducibility and lack of consistent results".

They did not look at spent coffee grounds specific but were looking into just organism combinations.

Lwini and Ranamukhaarachchi published in 2006 a paper that discusses biological
controls of bacterial wilt disease and showed that EM and EM Bokashi were most-effective as bio-control agents.
Yamada and Xu examined the use of EM in making organic fertilizers.
Hui-Lian Xu studied photosynthesis and yield of sweet corn, physiological characteristics in peanuts,
and fruit yield and quality of tomato plants. Daiss, et al., looked at pre-harvest and post-harvest applications of EM-1.

The use of EM in the bokashi-intensive composting process for home kitchen waste has been in use in Christchurch,
New Zealand for years, backed by the local city council.

Given the quantity of research that has been done on refuse of coffee production and the lack of research done on spent coffee grounds specifically,
there is much work to be done to discover all the best uses of spent coffee grounds.

One research that is currently underway (by myself) is in a method to increase the microbiology of soils through the use of spent grounds.
The model I am working through at this time calls for gathering the grounds and letting the normal fungi grow till they are spent.
From that point the grounds are stirred and dried completely before being incorporated into finished compost which is then used as a soil amendment in soil garden beds.
The subject beds are ground level, raised bed, and hugel mound topping along with a straw bale garden.
Results of this three year study will be posted here when completed.

I hope this information is useful to you.


 
Pete Hwan
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Location: Portland, OR
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Fantastic write up! Makes me inspired to want to hit up the local coffee shops for their spent grounds.

Any ideas for keeping the coffee grounds from "crusting over" (and becoming essentially waterproof) when you apply it as a weed suppressing mulch?
 
Bryant RedHawk
gardener
Posts: 1980
Location: Vilonia, Arkansas - Zone 7B/8A stoney, sandy loam soil pH 6.5
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That crust forms because of the slight amount of mucilage released from coffee beans when they are roasted and ground. If you have some wood ash, blending in about 2-3 tablespoons per 3 pounds of spent grounds should help with the crusting over.
 
Deb Stephens
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Location: SW Missouri, Zone 7a
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Bryant,
Thank you for this detailed report! We have been incorporating coffee grounds into our compost piles on a regular basis for years, as only one more organic substance to help create better soil structure -- without really knowing much about the specifics. One thing we have wondered about over the years though is whether the benefits (or negatives) of using spent grounds change according to whether the original beans are grown organically or with the "aid" of chemicals. When we relatively financially secure, we always buy green coffee beans grown organically and roast them ourselves. In lean times we are often reduced to buying pre-roasted and ground so-called coffee in cans from the grocery store.

My question is... do you know whether there have been any studies comparing the two types of coffee grounds (organic vs. non-organic) and do those include observations about the herbicidal/ pesticidal qualities of the grounds? We wonder whether at least some of the weed-killing, etc. properties of the grounds may come from herbicides picked up by the coffee plants in non-organic plantings. Might not those poisons remain in the plant system and pass on to the fruits (aka beans) and remain as trace amounts in the spent grounds? If so, I think we will be doing without when we can't afford organic beans in the future.
 
Keith Odell
Posts: 60
Location: Indiana
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Thanks Bryant.

I use the coffee grounds in my compost piles and in my worm bins but my favorite way to use them is on my lawn and garden.
I seperate the filters from the grounds and then fling 'em like a monkey flingin' poo. I add pond water to rinse the bucket and then pour that on the plants I like.
I used to do this at night to avoid the suburban neighbors watching. Now I do in broad daylight. They get a laugh, my wife sighs and I get a better lawn.
 
Suzanne Cornell
Posts: 53
Location: Chemung NY
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I have a coffee ground question. I spilled coffee grounds on the way to the compost pile, and the next day the pile of coffee was covered with honey bees. Is it the nitrogen they are after? Why would they love coffee grounds?
 
Bryant RedHawk
gardener
Posts: 1980
Location: Vilonia, Arkansas - Zone 7B/8A stoney, sandy loam soil pH 6.5
151
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Deb Stephens wrote:Bryant,
Thank you for this detailed report! We have been incorporating coffee grounds into our compost piles on a regular basis for years, as only one more organic substance to help create better soil structure -- without really knowing much about the specifics. One thing we have wondered about over the years though is whether the benefits (or negatives) of using spent grounds change according to whether the original beans are grown organically or with the "aid" of chemicals. When we relatively financially secure, we always buy green coffee beans grown organically and roast them ourselves. In lean times we are often reduced to buying pre-roasted and ground so-called coffee in cans from the grocery store.

My question is... do you know whether there have been any studies comparing the two types of coffee grounds (organic vs. non-organic) and do those include observations about the herbicidal/ pesticidal qualities of the grounds? We wonder whether at least some of the weed-killing, etc. properties of the grounds may come from herbicides picked up by the coffee plants in non-organic plantings. Might not those poisons remain in the plant system and pass on to the fruits (aka beans) and remain as trace amounts in the spent grounds? If so, I think we will be doing without when we can't afford organic beans in the future.


According to ECF, ICO and USDA there are some diseases and pests that need control. diseases are Leaf Rust and Black Rot, both are controlled by a Bordeaux spraying (1% or less).
pests are Coffee Berry Borer, White stem Borer, Shothole borer, Mealy Bugs and Green Scale. Most Borers are controlled with endosulfan while Mealy bugs and Green Scale are controlled with Fenitrothion

According to research available through the above three listed control organizations These sprays do not get into the healthy berries, all are sprayed after fruiting and the waxy coat of the developing berry apparently protects the fruits from contamination. There are no Herbicides used in coffee growing, the bushes require very healthy soil, full of organic material and undergrowth doesn't get a chance to grow since all orchards are mulched to a depth of around 6" minimum.

Organic guidelines allow these sprays to be used, more proof that the term Organic is not what most people think it means.
 
Bryant RedHawk
gardener
Posts: 1980
Location: Vilonia, Arkansas - Zone 7B/8A stoney, sandy loam soil pH 6.5
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Keith Odell wrote:Thanks Bryant.

I use the coffee grounds in my compost piles and in my worm bins but my favorite way to use them is on my lawn and garden.
I seperate the filters from the grounds and then fling 'em like a monkey flingin' poo. I add pond water to rinse the bucket and then pour that on the plants I like.
I used to do this at night to avoid the suburban neighbors watching. Now I do in broad daylight. They get a laugh, my wife sighs and I get a better lawn.


Good way to use them without composting! you are also feeding your worms by doing that type of spreading.
 
Bryant RedHawk
gardener
Posts: 1980
Location: Vilonia, Arkansas - Zone 7B/8A stoney, sandy loam soil pH 6.5
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Suzanne Cornell wrote:I have a coffee ground question. I spilled coffee grounds on the way to the compost pile, and the next day the pile of coffee was covered with honey bees. Is it the nitrogen they are after? Why would they love coffee grounds?


Coffee grounds contain at least three sugars, which are most likely to be what the bees are after. There are also many trace minerals that could be attracting bees. I wouldn't worry about spillage like you described, worms will take care of it in a short time, just spread them thinner with a rake or your foot.
 
Deb Stephens
Posts: 375
Location: SW Missouri, Zone 7a
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Bryant RedHawk wrote:
According to ECF, ICO and USDA there are some diseases and pests that need control. diseases are Leaf Rust and Black Rot, both are controlled by a Bordeaux spraying (1% or less). pests are Coffee Berry Borer, White stem Borer, Shothole borer, Mealy Bugs and Green Scale. Most Borers are controlled with endosulfan while Mealy bugs and Green Scale are controlled with Fenitrothion

According to research available through the above three listed control organizations These sprays do not get into the healthy berries, all are sprayed after fruiting and the waxy coat of the developing berry apparently protects the fruits from contamination. There are no Herbicides used in coffee growing, the bushes require very healthy soil, full of organic material and undergrowth doesn't get a chance to grow since all orchards are mulched to a depth of around 6" minimum.

Organic guidelines allow these sprays to be used, more proof that the term Organic is not what most people think it means.


Okay, so no herbicides -- although I question whether this is actually true in all situations or just a "recommendation" that many U.S. growers follow; but what about pesticide residue in non-organically grown coffee beans? Those you cited were used to control pests "organically". (I really disagree with allowing pesticides and still calling it organic. That sort of under the radar game truly pisses me off, because we use nothing on our crops and still can't sell them as organic because we can't afford certification!) What do the non-organic growers use?

Also, you mentioned "healthy berries"... it is my understanding that in coffee production, it really is not possible to individually inspect every berry -- which means a cut or hole in even a single berry could lead to contamination of a test sample. (Juan Valdez and his donkey don't really exist, so even those beautiful trees growing on the mountain sides in South America probably get a bug hole or two. ) So my question remains. Could the insecticidal qualities of the coffee be partially accounted for by pesticides used in growing crops? If you know, I mean. I'm not trying to put you on the spot or anything.

Also, we get our coffee from organic farms in South America, so the organizations allowing those pesticides may not have the same regulations as we do here in the USA. (That is an assumption, of course. I could be wrong.)
 
Mike Feddersen
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My cousin Troy was headed out to weed eat one day, upon asking if he wanted some more coffee, he declined. "I noticed I heat up more when I overdue it on the coffee." I sort of thought to myself, "okayyyy" then I was watching a compost video where they were adding coffee grounds from a five gallon bucket to "increase the heat" of the compost pile.
Huh...I guess ol' Troy was right, and now if I'll be wotking oudide I too keep the coffee to a minimum.
 
Mike Feddersen
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M.U.D.
Missoula Urban Demonstration https://m.youtube.com/watch?v=L-PyECLbHzo
 
Bryant RedHawk
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Posts: 1980
Location: Vilonia, Arkansas - Zone 7B/8A stoney, sandy loam soil pH 6.5
151
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Hau, Deb, I hate to be the bearer of bad news but Organic does not mean what most people think.
There is only one area of the USA that can produce coffee and that is Hawaii.
Most all coffee comes to the USA as Green Beans and they are roasted and packaged here.
Civet is the most expensive coffee on the planet since it passes through the digestive system of the civet cat first, "Kopi luwak, or civet coffee, refers to the seeds of coffee berries once they have been eaten and defecated by the Asian palm civet"
(it is very smooth and tasty as it should be because of the 100+ dollar cost for a pound of whole beans).

Most of the effects you see herbicide wise come from compounds in the coffee, Nitrogen in large quantities can actually act as a herbicide, killing plants with over nutrition which burns the roots and thus kills the plants.
I understand your concerns and worries. In the end it is, as always, a personal decision of what to use and how to use any item(s).
I personally, having been a chemist since 1971, and a coffee guy, don't have any qualms about using used grounds from my coffee drinking habit in my gardens and worm beds.

This is what the USDA Publishes about their USDA ORGANIC Label

Organic is a labeling term that indicates that the food or other agricultural product has been produced through approved methods that integrate cultural, biological, and mechanical practices that foster cycling of resources, promote ecological balance, and conserve biodiversity.
Synthetic fertilizers, sewage sludge, irradiation, and genetic engineering may not be used.

Consumer Information: Our Mission Ensuring the integrity of USDA organic products in the U.S. and throughout the world. About Us + Reports | USDA Organic Seal

Organic Standards : Regulations and guidance on certification, production, handling, and labeling of USDA organic products.

Organic Regulations : The organic standards describe the specific requirements that must be verified by a USDA-accredited certifying agent before products can be labeled USDA organic. Overall, organic operations must demonstrate that they are protecting natural resources, conserving biodiversity, and using only approved substances.

Organic crops: The USDA organic seal verifies that irradiation, sewage sludge, synthetic fertilizers, prohibited pesticides, and genetically modified organisms were not used.

Organic livestock: The USDA organic seal verifies that producers met animal health and welfare standards, did not use antibiotics or growth hormones, used 100% organic feed, and provided animals with access to the outdoors.

Organic multi-ingredient foods: The USDA organic seal verifies that the product has 95% or more certified organic content. If the label claims that it was made with specified organic ingredients, you can be sure that those specific ingredients are certified organic.

Regulatory Process:
The NOP develops the laws that regulate the creation, production, handling, labeling, trade, and enforcement of all USDA organic products.
This process, commonly referred to as rulemaking, involves input from the National Organic Standards Board (a Federal Advisory Committee made up of fifteen members of the public) and the public.

National List & Petitioned Substances
The National List of Allowed and Prohibited Substances identifies substances that may and may not be used in organic crop and livestock production.
It also lists the substances that may be used in or on processed organic products.
In general, synthetic substances are prohibited unless specifically allowed and non-synthetic substances are allowed unless specifically prohibited.
For example, a vaccine used to prevent pinkeye in livestock is an allowed synthetic substance and arsenic is an example of a prohibited natural substance.
Some substances on the National List may only be used in specific situations, e.g. only for certain crops or up to a maximum amount.
The list of these approved substances is here: Organic approved substances

This is the USDA's Organic program web site, where you can learn exactly what they do and how to get the USDA Organic label :National Organic Program
 
Christopher Horton
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I have been collecting used coffee grounds for years, instinctively aware they must have a use.  About two years ago I started putting a handful on top of the milking cow's feed while I milked her. The result is that we no longer have to spray for ticks or other parasites, but any more than a fortnight without the coffee grounds they do get reinfested.  Initially I fermented the grounds before applying along the backbone but have found this unnecessary as a handful in the ration is sufficient.  My inspiration was the Japanese Starbucks for fed the grounds to their dairy herd to improve nutrition and lower waste costs.  I imagine goats and sheep would enjoy the same benefits.
 
Anne Miller
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Suzanne Cornell wrote:I have a coffee ground question. I spilled coffee grounds on the way to the compost pile, and the next day the pile of coffee was covered with honey bees. Is it the nitrogen they are after? Why would they love coffee grounds?


If the coffee grounds were damp the bees might have been after the moisture (water) in the coffee grounds.  We live in a very dry climate and bees and butterflies will try to find any moisture wherever they can find it.

We had cutworms cutting off the young corn stalks and used coffee ground to stop them.
 
Trevor Stewart
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Thank you!
 
Tom Casten
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Location: Hinsdale, Illinois
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In fall, I shred the leaves my neighbors gather and top up all the raised beds, giving garlic more time to root, but worry about tying up the soil nitrogen.  I vermicompost and have a strong worm population in the raised beds.  But I still worry about nitrogen, so this year, I am adding coffee grounds and contents of a few large tea bags from Einstein's, using a broom rake to mix into the shredded leaves.  In theory, this will add nitrogen, probably not decay much until temperatures warm, but then largely decompose the leaves by planting time.  I see from post a recommendation to keep the ration of leaves and coffee grounds 10 to 20% max coffee.

Two questions:
First, any experience or knowledge to share on this method of topping up the raised beds?

Second, an Einstein's district manager was fascinated, told me of a friend who used a mixture of coffee grounds and some other ingredients to save a large ash tree, says something in the mixture that is taken up by the tree repels the ash borers.  Anyone have information on this?

Thanks, Tom Casten
 
Alder Burns
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Coffee grounds are capable of producing at least two valuable yields before going to compost of any sort....black soldier flies and/or edible mushrooms.  There are other threads here and elsewhere about both.  With mushrooms the advantage is that the coffee grounds are essentially sterilized in the process of making the coffee, so if mushroom spawn is added as soon as the grounds are cool enough, it will easily predominate.  BSF can eat quite a lot of them, even if they should not be their sole diet.  I kept a colony going quite a long time basically on coffee grounds and humanure.  The resulting grubs are valuable poultry or fish food.
 
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