pathogens and orange peels

Hi, I have a few questions about composting.
1. Hot composting: the temperature increases and this is good to kill pathogens, but doesn't it also kill other beneficial microorganisms? So this is what I think, but is it correct (?): during the hot stage of the compost the material breaks down because of the Heath and the thermofilic micro organisms and the pathogens (T sensitive) are killed, when compost cools off the mesofilic microorganisms that break down organic material come back (and not the pathogens because they prefer different conditions).

2. I hear often not to put in orange and onion peels in the compost. Is it OK to put these in a humanure hot composting heap or will they stop the process? We will have quite a lot of orange peels, is there anything else to do with them?

3. Can you compost sick plant material? The plant pathogens may also die during the hot stage but they might comeback after because these plant pathogens probably like decomposing plant material? Right?

Hi Marie -

My understanding of the microbial dynamics goes like this: During the high temperature phase all the mesophilic life moves out to the edges and down to escape the heat. As the pile cools down, they move back toward the core and reassert themselves. Pathogens starve, because they need the same feedstocks that the thermophiles are partying on, and can't live on the low-energy material that sustains the mesophiles. One exception: Legionella. This is a thermophile and can remain dormant after the heat dies down. This is why there are warnings on bagged potting mixes and we get the occasional death in NZ from gardeners working with compost.

Orange peels are fine. So are onion skins. I have no idea where this information germinated, but it's erroneous with respect to compost (worms do seem to hate citrus, though). You can put all sorts of stuff into a well-balanced aerobic compost pile, and it all breaks down. Pretty much all food waste works (although you might want to leave out the meaty or fatty stuff if you have opportunistic scavengers). I've put dead chickens, possums, and offal into compost and found nothing but a few bone fragments at "harvest time." The only exceptions I've noted over about four decades of intimate observation of compost are dog and cat poop. Don't put those in or you will be sorry.

Sick plants are a grey area...if the disease is fungal or bacterial, you probably want to make sure it's in the centre of a hot pile. Viral diseases usually require live tissue to survive, but they can insinuate themselves into seeds. When in doubt, burn it or put it into a barrel of water for at least a few months.

Hi Marie,
I put citrus peels in my pile when I need to, but I prefer to add them to vinegar for a citrus acidic cleaner. Every winter, I fill a five gallon bucket with 3-4 gallons of distilled vinegar and add citrus peels to it all season. I let it sit for the rest of the year, and then strain and use for cleaning greasy things. It's also a good weed killer.

Everyday we pick up free, day old produce from a major food store. We get ALOT of produce, including lots of oranges, peppers, ear corn, pineapples and limes. What doesn't get fed to the pigs and chickens, we compost. Our simple solution is to maintain two piles, a "normal" one that works fairly quickly, and another that receives all the citrus, woody stuff, much larger woody stemmed weeds, onions and such. The second pile is at a distance and behind a gated fence so it doesn't create a raccoon problem. The second pile we just let sit and wait usually for several years. Egg shells we wash, dry and grind, then store for summer use whenever the tomatoes show signs of needing them. This is not the best solution, but with the very large complicated farm and school we run, its the simplest thing to do. We heat several buildings with wood, so we spread some of the ashes during Winter on all the gardens, and spread the rest in Spring. The animals generate a large amount of manure and the excess goes on its own pile for use as needed. We get huge amounts of wood chips delivered for free, and we gather lots of grass clippings. We layer leaves, grass, chips and manure on the gardens as we collect them. So instead of digging up the ground to dig or till things in, we continuously build up layers of material over large areas, making top soil much as happens in the woods. None of this is the "best" composting technique, but its the most effective way to manage acres on a very busy farm.

I have no idea where this information germinated, but it's erroneous with respect to compost (worms do seem to hate citrus, though).

 seems funny to me, but it looks like you just answered your own question, Phil.  Worm bin aficionados tend to observe that onions and citrus do not get consumed by their worms, which are 'composting' worms, and since this is true, they assume that these items do not compost.  They do compost, but not via worms.  A half lime squeezed of liquids and added to a pile, might be in the pile for a while, or in several piles, before it composts fully, but it will compost as will onions.  If it didn't, my composts would be a shambles (which is not the case); at the moment the compost heap is about half onion tops, skins, and rejects from a massive harvest that is less than half way done.  I toss some citrus peels in with my urine bucket to aid with odors; this also seems to help the peels break down a lot faster.  But I wouldn't worry too much about oranges and onions.  Just make your heap, layered with enough carbon and nitrogen, and turn it when it cools a few times, and you will break most of anything down (as long as it's not too bulky).  I sift my compost, and get things like broccoli stalks, avocado pits, citrus peels, and such hard woody materials on the screen, and these are either used as mulch or added to a future compost process.  

Just to make a quick note to the point that things like citrus composting can do good for the environment, I saw this article the other day:

Juice Company Dumped Orange Peels In A National Park

Obviously too much of one thing can definitely throw things out of balance for a while, but when done appropriately it can work wonders to return unused produce back to the land. In this case, they added the orange peels to abused land and over time it rehabilitated much faster than other areas left alone.

I have 9 citrus trees and a lot of fruit falls to the ground.  It all gets picked up in 5-gal. buckets and dumped onto the compost pile.  Lemons in particular -- in June and July, the old lemons fall from the tree by the hundreds.  Never had a problem with it.

If it's carbon, it will compost.

As for diseased biomass from sick plants, I used to bag stuff that had powdery mildew fungus on it.  Now it all gets thrown on the pile.  It seems like the problem gets less and less every year.  Zuchini are still prone to it, but nothing else.  I don't know if by composting it, I'm increasing the presence of something that counters that fungus.  Anyhow, I compost everything and my garden/food forest gets healthier every passing year.

When you cut an onion, keep the bottom root part and plant it in the ground. It can grow into a new onion. You can also do this with the green stem that grows in old onions.

I dig all my kitchen scraps directly into the ground, including onions and citrus peels. After a few weeks they completely disappear.