can you have too many coffee grounds?

I work for a big company that always throws their staff coffee grounds in the garbage. I'm wondering about asking if they can be put aside in a compost bin (grounds only) for me to take home once a week. I imagine this would fill up about a grocery sized bag every two weeks. I live on 0.3 acres (not a huge property), and have a regular sized compost pile behind my shed. Would it throw off things to be adding so many coffee grounds, or might it help?

Last year I built a compost tower from 400lb of used coffee grounds mixed with sawdust, and added some composting worms. I planted zucchini in the top and they were quite happy in there.

This year I'm collecting 5 gallons every 2 days and using it around the garden. As long as you don't use it as a mulch (it forms a crust that repels water and hinders seedling emergence) then I doubt you'll be overdoing it at the rate you're collecting it.

I use a lot of grounds - thousands of pounds per year.  We use the filters (browns) as well and they break down well with the coffee grounds (green).
I also just fling them in the yard like a monkey flinging poo.  I used to do this at night but the neighbors are used to me now
Warning - if you live in the southeast, you are almost guaranteed to get black soldier fly larvae (big maggots).
I don't have a problem with them but a lot of folks don't do well with the 'ick' factor.

Coffee grounds are a unique resource...they are after all a seed and therefore rich in nutrients, and because they are boiled or steamed to extract the coffee, they start out in a semi-sterile condition.  This combination makes them an ideal substrate for certain edible mushrooms.  And, as mentioned above, black soldier flies....which are wonderful feed for poultry and fish!  So there are at least two possible yields (both of which would be much more worth pursuing if the grounds are available in quantity!) before letting the residue from these processes go to compost.  As a compost or soil amendment, I've read that they encourage acidity in the soil....probably more so in an uncomposted state....this can be a problem or a benefit depending on what your native soil is like.  I have alkaline soil and so coffee grounds when I get them in any quantity (Starbucks, for instance, often bags their grounds and offers them for free) I use them around acid loving plants like blueberries.

Alder Burns wrote:Coffee grounds are a unique resource...they are after all a seed and therefore rich in nutrients, and because they are boiled or steamed to extract the coffee, they start out in a semi-sterile condition.  This combination makes them an ideal substrate for certain edible mushrooms.  And, as mentioned above, black soldier flies....which are wonderful feed for poultry and fish!  So there are at least two possible yields (both of which would be much more worth pursuing if the grounds are available in quantity!) before letting the residue from these processes go to compost.  As a compost or soil amendment, I've read that they encourage acidity in the soil....probably more so in an uncomposted state....this can be a problem or a benefit depending on what your native soil is like.  I have alkaline soil and so coffee grounds when I get them in any quantity (Starbucks, for instance, often bags their grounds and offers them for free) I use them around acid loving plants like blueberries.

Hi Alder,

I have lots of blueberries. Would you just sprinkle the grounds on them, or try to compost them first?

Sorry if this question takes things off topic...  Should we worry about if the coffee was organic or not?  I don't know how coffee trees or beans are "treated" and if in the process of brewing coffee the ick is removed.  

I would mulch the plants with them fresh and not composted.  I think composting will reduce the acidifying properties.

There is a company in the UK that makes fire logs using compressed waste coffee grinds. They're called "Bio Bean coffee logs". I have a bag of them (purchased on impulse), but have not yet tried them. They do appear to use some sort of waxy binder, so they're not 100% coffee grinds.

update - day 1 I found plastic cream containers in my compost bin marked "Coffee grounds and filters only" - I guess some people thought I was collecting anything related to coffee?
Day 2 - I left the bin here over the weekend but didn't think to notify the cleaning staff. They emptied out all my coffee grounds and took all my compostable bags I had underneath! I guess they thought it was all garbage.
Day 3 - cleaning staff have been notified. I'll buy new bags tomorrow. Hope I can start bringing some home soon.

Coffee residues are very high in nitrogen. Excellent for composting! You'll know you have "too much" when your compost pile starts wafting out ammonia; otherwise you're good to go. If you do get ammonia coming off, you'll want to add carbon material at that point if you want to keep adding coffee grounds

Mike Jay wrote:Sorry if this question takes things off topic...  Should we worry about if the coffee was organic or not?  I don't know how coffee trees or beans are "treated" and if in the process of brewing coffee the ick is removed.  

Good question Mike, the process of getting coffee beans ready to become coffee renders any "treatments" terminated, the beans are first sun dried then they are roasted then ground since the pulp is the first thing removed, the actual beans have very little if any pesticide residues on them to start with.
The sun drying process exposes all beans to lots of UV radiation then there is the roasting process which would break down any residuals so at that point the beans would not contain any herbicide residues.

Does that set your mind at ease?

Redhawk

hau Danille,  I have not found any detrimental amount of coffee grounds in three years of studying if there is a saturation point for soil with only coffee grounds used as an amendment.

I did find that composted grounds will not acidify soil more than 0.2 pH, while you can expect a 0.5 to 1.2 pH change with freshly collected coffee grounds use as a mulch around plants.

I regularly add coffee grounds both to my compost piles and garden beds, around fruit trees and I pile them onto fire ant mounds.

Redhawk

Bryant RedHawk wrote:Does that set your mind at ease? Redhawk

Yes it does, thanks Bryant!

One of the greatest things about spent coffee grounds is the plethora of bacteria and molds that the grounds attract and feed.
This makes them a great breeding ground for microorganisms that we want in our soil and earthworms and the red wiggler worms love to eat the bacteria that grow on the grounds.
This means that the garden that gets lots of coffee grounds will be a microbiological rich soil that attracts worms like a magnet does steel shavings.
Which is a Woo-Hoo factor for any garden.

Redhawk

Mike Jay wrote:Sorry if this question takes things off topic...  Should we worry about if the coffee was organic or not?  I don't know how coffee trees or beans are "treated" and if in the process of brewing coffee the ick is removed.  

I spent a couple of years living in Africa in coffee country (up at about 4000 ft. above sea level).  I don't remember anyone ever spraying anything.  At best, they might use some granular fertilizer to aid in growing, but I have no memory of any of the local farmers even doing that.  Coffee is an understory plant, so often they would grow banana or plaintains in the coffee fields.  

The beans are picked but have a husk around them.  People soak the beans, often in a burlap bag down in the river.  It ferments the bean a little bit so that the husk gets slimy and kind of pops off easily when you squeeze it with your fingers.  Then the raw bean is laid out on mats in the sun to dry for a week or so.  

That's it.   That's how coffee beans are treated.  Nothing nasty added along the way.

Decaf beans, on the other hand, are treated with methylene chloride or ethyl acetate.  Both are solvents that take away the caffeine.  But no traces of those solvents remain—it's tested pretty thoroughly.  After roasting, and then brewing, nothing bad remains.

I'd take 5 gal. of coffee grounds a day if I had a source.  I love them in my compost pile.  I love the smell, the instant nitrogen boost, and fine texture. . .  everything about them.

Alder Burns wrote:I would mulch the plants with them fresh and not composted.  I think composting will reduce the acidifying properties.

The acid comes out with the coffee, the leftover coffee grounds are typically close to neutral PH.  Sometimes higher, sometimes lower but in general pretty close to neutral.

https://s3.wp.wsu.edu/uploads/sites/403/2015/03/coffee-grounds.pdf

That is a good link Peter,
However in her article she mentions that some grounds are at a 4.7 pH, that is not neutral, some are 7.0, leading to the conclusion that coffee grounds are variable in pH which is a true statement based on many peoples research.
She then states that one researcher determined that this acidity decreases over time.
She also mentions she, herself did none of this research but gathered her information from other's reports.

I have been doing coffee grounds research for the past 10 year or so, I use them in many ways both composted and not composted and I also use fresh grounds for a few things.
What I have found, I put up on this site several years ago It was called, everything you want to know about spent coffee grounds, I can't locate the thread right now but it is on this site, somewhere.

Marco Banks wrote:

Mike Jay wrote:Sorry if this question takes things off topic...  Should we worry about if the coffee was organic or not?  I don't know how coffee trees or beans are "treated" and if in the process of brewing coffee the ick is removed.  

I spent a couple of years living in Africa in coffee country (up at about 4000 ft. above sea level).  I don't remember anyone ever spraying anything.  At best, they might use some granular fertilizer to aid in growing, but I have no memory of any of the local farmers even doing that.  Coffee is an understory plant, so often they would grow banana or plaintains in the coffee fields.  

The beans are picked but have a husk around them.  People soak the beans, often in a burlap bag down in the river.  It ferments the bean a little bit so that the husk gets slimy and kind of pops off easily when you squeeze it with your fingers.  Then the raw bean is laid out on mats in the sun to dry for a week or so.  

That's it.   That's how coffee beans are treated.  Nothing nasty added along the way.

Decaf beans, on the other hand, are treated with methylene chloride or ethyl acetate.  Both are solvents that take away the caffeine.  But no traces of those solvents remain—it's tested pretty thoroughly.  After roasting, and then brewing, nothing bad remains.

I'd take 5 gal. of coffee grounds a day if I had a source.  I love them in my compost pile.  I love the smell, the instant nitrogen boost, and fine texture. . .  everything about them.

Yeah the organic thing is not much more than a marketing ploy. The vast majority of areas where coffee is grown commercially are too poor to afford chemicals and spraying equipment. The profit margins are so slim for the grower that they live in abject poverty. Any extra cash goes to food. And like you say, it grows in mountainous regions on steep land so it would have to be applied manually.

Organic coffee is akin to plutonium free blueberries.

The only coffee regions I have ever found that used spraying for insects is Brazil and Columbia, the sprays are insecticides and fungicides, used prior to flowering. That means that the fruits will not have any direct sprays on them.
Currently the "In" coffee regions are in Africa, no sprays used and manures are the normal fertilizer, they are the "In" coffees because of price, flavor profiles and availability of quantity.
My personal favorite coffee comes from the Jamaica Blue Mountain region. It is donkey and chicken manure fertilizer, spray free and the grower is a friend I first met in 1974.

I have no idea where all the urban legends about coffee having toxic sprays started, but I would imagine it is from the Brazil / Columbia regions use of sprays. (Folgers, and lots of the other big brands use beans from these areas)

Redhawk

Bryant RedHawk wrote:That is a good link Peter,
However in her article she mentions that some grounds are at a 4.7 pH, that is not neutral, some are 7.0,

And she mentions that some studies showed it around 8.4.  I recall reading somewhere that the type of coffee, the way it was roasted and the way the coffee is made all has an effect on the pH of the grounds.  If you're making your coffee at home and always make it the same way, then it will probably always have the same pH.   But when you are getting coffee grounds from Starbucks, etc.  then you'll end up with a mix of coffees made in many different ways and the average pH will likely be close to neutral.

However,this is all based on some limited research I did online.  I've never bothered to actually measure the pH from any coffee house, so perhaps I'm wrong.

Still, even if the coffee ground were acid, I don't see that it would have much effect on soil pH due to buffering action and lmited amount of coffee grounds applied vs the amount of soil in typical uses.  I know from my own experience and a bit of online research that it is very difficult to change the pH of soil and even harder to make the changes persist.  It's much easier to build soil of the proper pH to begin with.

Coffee grounds can change the pH for a very short time only, not a "permanent" solution, but then there is no permanent state in nature, anywhere.
I've tested spent grounds that registered 5.5  all the way up to 8.7 from samples provided by starbucks locations, that is a lot of variance, enough to not worry about the "acidity" of grounds, the effect would be quite temporary since one good rain would leach it beyond the application site.
There are so many variances in coffee grounds, it's like you state, differences are from batch to batch and brand to brand.

The benefits of coffee grounds far outweigh the singular pH factor, there are esters, keytones and even enzymes within spent coffee grounds that are difficult to obtain any other way, so this and the high nitrogen content that comes out slowly are the real benefits.
For pH adjustments it is better to use sulfur and lime than to try and rely on coffee grounds, but once you have the pH into the range you want, minor, temporary adjustments can be done with coffee grounds, you just experiment to find how they work in your soil.

Coffee grounds are also good for getting the fungi hyphae diversity in the soil a little higher, there are not only compounds in the grounds that feed the fungi but usually a few strains will propagate from the airborne spores that land on exposed grounds.
springtails appear to have a liking for some of the compounds as well, numbers have been found to increase when grounds are introduced to the soil.

It is usually non productive to focus on something like pH with any amendment that you use, unless it is an acidifier like sulfur and sulfur compounds, the same for raising pH, lime and other base pH compounds will tend to have longer effects.

The coolest thing about my research into this part of soil is that the plants will make some adjustments through exudates in the area immediately around the root (this can be as large as 2mm from the root but usually is within 1mm of the root).

There is opportunity for a lot more study of this one item, in a sea of amendment possibilities.
I like to use "discards" to find out ways to use them that doesn't include a landfill.

Redhawk

I put maybe 15 five gallon buckets of coffee grounds on my veggie garden starting in late February and early March.   Since my garden is on a drip irrigation system I put small piles around each emitter.  

I went to plant my veggies last Sunday.  I found several huge earthworms. I have never seen them this big before.  Almost as thick as a number 2 pencil.  

I will add some bacterial Compost tea this next weekend.  Great hopes and expectations at my first Organic Garden.

There are so many ways to use coffee grounds in the garden, I don't think there will never be too much of it. We are discouraged to use manure in the city, so coffee grounds (roughly 80kg/175lb each week from starbucks- thanks ) constitute a big portion of inputs.
We use it to fertilize and mulch (after seeding) lawn, as green material for compost, as deterrent of carpenter ants, while building hugelbeds, to soften hard soil, as mulch for raised beds, instead of sand when planting carrots (carrot-radish-grounds) and so on. It is an amazing material and does every wonderful thing that Redhawk said. If I were able to get 800 kg instead of 80 kg, life would be much better.
So pictures:
1- My raised beds settle a lot each year, so I put layers of a 2inch of brown material (wood chips or leaves) and 1 inch of grounds each fall. It boosts the worm population and dramatically reduces the amount of soil/compost I would need to add each spring before planting. Pictures taken yesterday.

2- to soften soil. I am trying to get life back into soil in this heavily shaded compacted section. Explosion of worm population and mycelium. Yeay :p

3- while building hugelbeds. I read many posts about coffee grounds being used in hugelbeds while Redhawk is strongly advocating it. New beds with a lot of coffee grounds. It will be something like buried wood bed with a raised garden bed on top, something like that. I waited for 1 month for it to cool down so that I can add worms this weekend(and soil from other beds and garden to inoculate). I made a mistake previously, adding worms too soon. It was a weird scene when worms and all those soil critters running away from hot - hugelbed at night.

I am really enjoying everyone's comments.

I love how coffee grounds are turning my gray caliche into brown soil.  I don't think I can have too many.  I bury all mine as I don't want the wind to blow them away.

About 5 years ago I collected leaves during the city fall garden pickup. At the time I remembered what Geoff Lawton says about mulch - put down as much as you dare, and then triple it.

Well I put down over 150 garbage bags full of leaves both as a mulch and also buried in the grow beds. I was freaking out because it appeared there was more leaves than soil in my garden.

I have no idea where they all went but I can no longer find a trace of them anywhere. And my soil is still very sandy loam.

My take away lesson from this exercise is that we massively underestimate how much organic matter can be added to a degraded soil. If you're looking to bust clay, or re-mediate over-tilled garden soil then applying crazy amounts of organic matter is probably not putting in enough.

Recent research suggests coffee is detrimental to seed germination and growing seedlings. For the past few weeks I’ve been growing seedlings from seed in pine needle compost. One section has added coffee grounds, the other doesn’t, and all are watered with worm tea almost daily. So far there’s been no difference in growth.

Another free coffee resource, if you live near/know any small roasters, the roasting machines gather chaff during the roasting process (i guess it's like residue of the shell of the seed?) and it is a waste product to the roaster. The person I go to will happily give me a contractor bag full of the stuff. It is super light and papery and I have used it to make bokashi but he told me that he has composted it and used it as mulch and used it in thick layers under woodchip pathways. It's another potential free source of organic material and has interesting physical properties that folks might find good uses for (mushroom substrate?)