Calling all juice bar waste composters...

...how on earth do you get the moisture level of your mixture correct without messing up the C:N ratio?

I'm loving how easy composting with juice bar waste is -- everything is so lovely and small, no chopping needed.  And it sure cooks!  I haven't yet seen 140°F, but I got close one day and I had 11 days at more than 120°.  However, I'm not loving how wet the mixture is.

I've been really trying to get the C:N ratio to 30:1, but even without getting there the result has been a wet, anaerobic mixture that I actually had to spread out on the lawn in the sun yesterday.  This was about the most unpleasant gardening task I've ever done -- darn heavy to shift to and from, and it actually smelled like vomit!

I've formed this mixture over the past few weeks, each week adding 12 litres (about 0.4 of a cubic foot) of juice bar waste, the same quantity of coffee grounds, and 2.5 litres (about 0.08 of a cubic foot) of sawdust.  According to my calcs, I get a ratio of 39:1...

    Juice bar waste: 12 litres x 0.7kg/litre x 35 = 294
    Coffee grounds: 12 litres x 0.6kg/litre x 20 = 144
    Sawdust: 2.5 litres x 0.15kg/litre x 500 = 187.5
    TOTAL CARBON: 625.5

    Juice bar waste: 12 litres x 0.7kg/litre x 1 = 8.4
    Coffee grounds: 12 litres x 0.6kg/litre x 1 = 7.2
    Sawdust: 2.5 litres x 0.15kg/litre x 1 = 0.375
    TOTAL NITROGEN: 15.975

    C:N = 39.15

So, the ratio is nearly right, which is borne out by the nice high temperatures I was seeing.  But the mixture is just so darn wet.  I can't risk having this result again; my tumbler is very close to the neighbour's back door, and my body can't handle having to dry it on the lawn.

So, what do you folks do with your juice bar waste to get it drier?  Mixing in lots of cardboard/paper/sawdust can't be a solution -- that'll destroy the C:N!  I'm at my wits' end here -- I need to figure out how to build the next mixture so it's actually a success....

Any advice, experience etc will be gratefully received!

Fantastic!  Nothing I can  say adds.

KiwiSFGnewbie wrote:So, what do you folks do with your juice bar waste to get it drier?  Mixing in lots of cardboard/paper/sawdust can't be a solution -- that'll destroy the C:N!  I'm at my wits' end here -- I need to figure out how to build the next mixture so it's actually a success....

I am apparently somewhat fortunate in that most of the juice bar pulp I get is not that wet, though some of it is very wet. A simple solution for me is installing a spigot in a 5-gallon food grade bucket, putting a car wash bucket grid guard in the bottom of the bucket. I put a paper towel over the grit guard, and then dump the wet pulp in the bucket to let it drain into the bottom couple inches of the bucket under the grit guard. After a few days of draining off the liquid there is no more liquid and the pulp is ready to add to compost.  A little extra work, but worth the effort.

I recently experienced a similar problem with coffee grounds. I had picked up several large bags of coffee grounds from Starbucks, and when I picked them up out of the jeep was surprised to find a large puddle of liquid coffee in the cargo tray the bags were setting on. Picking up the bag I noticed it had a large amount of liquid coffee under the grounds. I had to use a shovel to take out as much of the dry grounds as possible, then dump the rest of the grounds into the bucket to drain off the liquid - there was over a gallon of liquid in that bag that had not yet leaked out, and I did not want that in the compost tumbler.

OhioGardener wrote:I am apparently somewhat fortunate in that most of the juice bar pulp I get is not that wet, though some of it is very wet. A simple solution for me is installing a spigot in a 5-gallon food grade bucket, putting a car wash bucket grid guard in the bottom of the bucket. I put a paper towel over the grit guard, and then dump the wet pulp in the bucket to let it drain into the bottom couple inches of the bucket under the grit guard. After a few days of draining off the liquid there is no more liquid and the pulp is ready to add to compost.  A little extra work, but worth the effort.

Ah!  What a simple solution, indeed -- and for once, an item you folks have is easily and cheaply available here too!   I'm not sure about installing a spigot, but I'll look this week in my local plastics shop, maybe they have a food safe bucket with one.  I see they're used in home brewing.

Also -- I realise that you folks aren't used to dealing in metrics, but do my ingredient proportions look about right?  12 fruit pulp, 12 coffee, and 2.5 sawdust?  I'm still not certain I'm calculating correctly.
Thanks so much, OG 

KiwiSFGnewbie wrote: I'm not sure about installing a spigot, but I'll look this week in my local plastics shop, maybe they have a food safe bucket with one.  I see they're used in home brewing.

Also -- I realise that you folks aren't used to dealing in metrics, but do my ingredient proportions look about right?  12 fruit pulp, 12 coffee, and 2.5 sawdust?  I'm still not certain I'm calculating correctly.

Don't know about your area, but here all of the big box stores, such as Lowe's, Home Depot, Menards, Tractor Supply, etc., sell food grade buckets. They will have hundreds of non-food-grade buckets, but they will also sell one food grade. Putting a spigot in it is easier than you think. The first one I ever made was thanks to a thrift store - I saw a used water cooler for sale of $1, and it had a nice plastic spigot on it that was in good condition.  I bought the water cooler, took the spigot out, and donated the cooler back to the thrift store. I then put the spigot in a bucket and was ready to go.

Yes, your calculations are about right, with one exception. The weight/liter is relative (isn't everything?). How wet are the grounds or vegetables? For example, I frequently pick up small bags of coffee grounds from Starbucks at our grocery store. One time the bag may way two pounds, but another time it might weigh seven pounds. Another condition is how dry is the sawdust? Did it pick up moisture from the air? For example, I use pine pellets which are sold for horse bedding. They are compressed pine sawdust, and the instant they come in contact with moisture they swell and expand, pulling moisture out of the compost.

Best advice I can give regarding composting is to experiment to find what works for you.  Remember, in gardening there are no failures, only experiments that did not work.

Thanks for confirming the proportions are about right, it's good to know I'm on the right track.  I'm investigating spiggots (which are surprisingly hard to find here, -:sigh:-) and looking forward to building the next batch in a few weeks' time.  I did weigh the ingredients several times and got what I thought were representative figures, but this is a good reminder to check periodically at least.  (It's not the easiest thing to do with my kitchen scales!)

Thank you also for the encouragement

Yay, my bucket is nearly ready -- just waiting overnight to make sure there aren't any leaks.  Can't wait to use it!

You were right, OG, it wasn't that hard to make 

I used the draining bucket for the first time last week -- put the juice bar waste into it on Monday afternoon, and ~96 hours later opened the lid.  I was surprised how wet it still was to the touch, especially since there wasn't a lot that had drained into the bottom of the bucket.

I didn't know how moist it should be, so put it into the tumbler with an equal quantity of shredded leaves and coffee grounds (i.e. equal quantities of all three ingredients), and a tiny amount of sawdust, weighing everything as I went.  Calculated C:N was 33:1.

I'm wondering if I should have let the juice bar waste drain a few more days?  The tumbler is smelling a bit "fermenty" although over the weekend that has reduced in intensity a little.  I'm pretty anxious about another anaerobic mess! -- but the compartment is only about 1/3 full, so I can amend.  Squeeze test on the first morning had a couple of drops coming out of my fistful.

So far I haven't seen any Black Soldier Flies

KiwiSFGnewbie wrote:
I'm wondering if I should have let the juice bar waste drain a few more days?  The tumbler is smelling a bit "fermenty" although over the weekend that has reduced in intensity a little.

Remember that as microbial life begins activity the compost creates some moisture of its own. Based on the above comment, it would appear that you need to add a little more shredded newspaper or sawdust to give it more dry carbon. My experience has been that while leaves are a carbon, they do not absorb a lot of moisture.

OhioGardener wrote:Remember that as microbial life begins activity the compost creates some moisture of its own. Based on the above comment, it would appear that you need to add a little more shredded newspaper or sawdust to give it more dry carbon. My experience has been that while leaves are a carbon, they do not absorb a lot of moisture.

OK -- that explains what I saw in the previous batch.  I kept wondering if the larvae were peeing heaps, actually!   It seemed to get wetter no matter what I did.

What a pity dry leaves won't be too helpful -- I was enjoying the feeling that I could soak up moisture without affecting the C:N too much!

BTW the following arrived yesterday:


I finished the library one (finally), and decided this was not a book that I should scan little bits of, it was one I needed to have on-hand permanently.  Thanks for the recommendation