What to do with dead fish?

Not exactly sure where to put this topic but thought I'd start here...

We have the opportunity to accept several hundred pounds of dead, whole invasive carp weekly. Some of the carp are 30+ pounds...3 foot long, a belly the thickness of an average adult thigh. It could prove to be valuable fertilizer for our garden.

The first drop-off coincided with a barn clean out so we took the bedding...a lot of it, added the fish and now we wait. We don't generate anywhere near enough carbon to use this solution long term... If it even works. Our neighbors aren't super close, to us, but they're great neighbors, but stinking fish wouldn't go well.

Our primary concern besides smell is keeping any solution from attracting rodents. We have no control over when or how much shows up, so any expenses would preferably be minimal.

Trenching
We don't have any means to easily dig trenches and bury them... The thought of shoveling a trench large enough to bury a 55 gallon barrel worth of fish on a weekly basis exhausts me... And I don't shy away from hard work.

Emulsion
We did this on a small scale a couple years ago with our kitchen blender. The blender hasn't been the same since and any emulsion solution I'm aware of would be capital intensive.

Sealed container rot emulsion
With these parameters, the best idea I've been able to come up with is to get a "rain barrel" type container with locking lid (for smell, rodent proof) and let living things do what naturally occurs...rot. does anyone have experience or thoughts on this? Any inputs required? Maybe some soil micro organisms to simulate rot? Cover with water? Add yeast?? The goal would be a liquid slurry that might need minimal agitation to break up large remains, drain/filter, and apply to garden/pasture via spray or pour into a hoe'd-in trench.

If anyone has any tips, suggestions, new ideas all input is appreciated... Would hate to lose such an opportunity and have it go to a landfill or otherwise.

Are you located somewhere that you could source large volumes of woodchips from arborists?

There would still be a lot of work involved without equipment to move and mix.. but the fertility would be incredible!

How dead are you getting them? Have they began decomposing or are they fresh enough to dehydrate?  If you pull out all the water fish can be odourless preserved for a long time even without using salt by bleeding, deffating, and drying to full sun or with fire. If you’re getting them fresh enough can be used as protein feed for chickens simply by pulverizing or grinding once they’re dried. This could buy you some time and/or help controlling the decomposition process, matching all that nitrogen with carbon is essential tho.

Do you have a neighbour who keeps pigs? Maybe you could make a deal.

Douglas, I do have pig farmers in the area. I've let my contact know, but they don't seem interested.

Andres, I get them fairly fresh--within a day or two. To dehydrate them I'm guessing we need a rack system to hang them in the sun...any idea how long a 30 pound carp would take to dry like this? Ballpark...are we looking at a few weeks or more like 4 months? I'm located in PA so summers (when we'll be getting most fish) can get toasty.

D Nikolis, unfortunately, we don't have a source for wood chips anywhere near large enough to support a weekly delivery of fish.

Thanks for the thoughts and suggestions!

Black soldier flies..


I would feed these to chickens,  and I would feed these to black soldier flies..  then I would freeze sell the black soldier flies larva.


The Indians would put a fish under their corn  for fertilizer,   sounds like a great idea to me.

Mart, the flies is an interesting one. I've read about those systems here and there over the years, but I'm hesitant. From what I've read it seems you really have to keep after it--we've got full plates already, so a "KISS" solution is very much desired. Anything that needs to be tended to has a way of slipping through the cracks. Burying the fish under our plants would be great, but on this scale, it's just not feasible and we tend to err on the side of not disturbing soil if we can help it.

After I posted it, I noticed in the "similar threads" section at the bottom a thread about homemade fish fert and they linked here: https://www.unconventionalfarmsupply.com/homemade-fish-fertilizer

I'm leaning in that direction at the moment...cut up with a recip saw, blend with a drill attachment perhaps, and ferment in barrels.

I have a friend here in Idaho who commercially harvests carp just like the ones pictured. He sells them fresh and whole for I think about $1.30/lb to someone who trucks them directly to California to be sold in ethnic markets.
On a good day he loads 3000 lbs onto the truck.

Douglas Alpenstock wrote:Do you have a neighbour who keeps pigs? Maybe you could make a deal.

Farley Mowat recounts in The Dog Who Wouldn't Be a farmer in Saskatchewan who fed pigs the sucker fish from the river - his pigs were big and grew quickly!  But the farmer wouldn't sell them locally and sent all of them East to the large yards and butchers.  Why?  Because locally everyone would learn they didn't like fishy ham, but in the larger system they were untraceable.

Not sure if this is actually true but I would research the topic before raising hogs on carp.

Gray Day wrote:
Sealed container rot emulsion
With these parameters, the best idea I've been able to come up with is to get a "rain barrel" type container with locking lid (for smell, rodent proof) and let living things do what naturally occurs...rot. does anyone have experience or thoughts on this? Any inputs required? Maybe some soil micro organisms to simulate rot? Cover with water? Add yeast?? The goal would be a liquid slurry that might need minimal agitation to break up large remains, drain/filter, and apply to garden/pasture via spray or pour into a hoe'd-in trench.

You might be describing Bokashi here.  Place food waste - including meats - into an air tight container.  Add the starter cultures of bacteria and fungus.  Seal.  In a week or two use a drain to remove some fluid.  Wait a total of two to four weeks ... and you've got something which Chickens love, can be added to compost or buried in patches in your soil for further processing by the local biota.

It takes an airtight container.  There is some disagreement on the starter culture - there is a product called EM1 available, and others just talk about adding liquids from other ferments.

My starting point was this podcast: https://www.thepermaculturepodcast.com/2020/reducing-food-waste-an-introduction-to-bokashi-matt-arthur/

I've not done it yet : (
But I'm going to try with a 5 gallon bucket and then see if I can't find enough scraps to use a large 55 gallon drum.

Would you suppose that you could keep rodents out with tightly spaced electric fence? No guesses on how tall or what spacing would work.  A thick layer of mulch and some charcoal on top might help control the odor.... perhaps a bit of soil over that?  How much time is required for it to become usable compost? And does it need to be turned? That would be a dreadful task.

About trenching, could you hire someone with a digger for an hour to dig one long skinny trench? Then It might not be too much work to shovel the loose soil back over each addition.

Aside from wood chips, are there any lumberyards in your area? Where I live, wood chips are not a thing, but there are lumberyards, timber stores, and sawdust and shavings are free or cheap from them. From my experience with composting toilets, fine sawdust does a better job of preventing flies and smells, but a mix with shavings in also works okay. Shavings alone does let flies and smell out, as do autumn leaves. Soil works perhaps the best for that purpose, but doesn't make as good a compost.

That sounds pretty sad, that much fresh fish going to waste. Wow. Carp is delicious.

Eliot, the bokashi idea is interesting. Curious how much mass would shrink down as water weight since we're talking fish. The end result being something the chickens would like is favorable, still curious if there's a way to "liquify/emulsify" via a natural decomposition process without an abundant carbon source and traditional composting, but I suppose I'm getting into the realm of flesh eating bacteria... And for reasons I'll stop myself right there.

Another source of carbon, besides wood chips, would be autumn leaves. You could find landscaping companies that clean up leaves and have them deliver the leaves to your farm (a tipping fee could be a source of income). Combined with tree service chips, you could probably get enough, though you will need to plan ahead to stockpile since there's a seasonality to the leaves and the fish.

I like the idea of hiring out the trenching, it could be an excavator/backhoe job, or could be a tractor and moldboard plow job. If the leaves and wood chips were in a windrow beside the trench(es) it would be a lot less work to fork/shovel the carbon, soil, and fish together into the trench(es).
It might also be economical to get yourself a small tractor/loader to DIY. I've done some farm-scale composting both by hand, and by tractor, and sure enjoy not wearing out my back and shoulders!
Another thought might be a trade with a landscape company, for their equipment work to trench, in return for your leaf dump site, or finished compost for their use.

A different approach would be to build an anaerobic digester. Take a look here at Solar Cities Biogas You will still get a liquid fertilizer product, plus biogas which you could use for heating/cooking/etc...

Another approach that comes to mind, with the drying fish idea, is to make fish meal for aquaculture/aquaponics use. The sustainability of aquaculture is questionable when the fish meal for feed is made from wild ocean fish that are "bycatch" from commercial fishing, but if you could use fish that were part of a program of eradicating invasive fish, it seems like a win-win scenario, and a marketing/public-relations goldmine.

There might even be some combination of ideas such as: a portion of drying for fish meal--> feeds aquaponics, a portion made into fish emulsion, a portion sent to anaerobic digestion/biogas-->powers fish meal drying (summertime when fish are in) and also greenhouse operations (wintertime heating) for fish meal and aquaponics...
There'd be a usefulness of having a system in place for processing fish parts for dealing with the aquaponics raised fish.

Turning these fish into fish meal to make animal feed is a good idea. When using this meal to make feed for aquatic animals it will be necessary to heat the meal to a high temperature to kill pathogens. Wild fish can be a vector for disease for aquaculture animals.

Gray Day wrote:
Sealed container rot emulsion
With these parameters, the best idea I've been able to come up with is to get a "rain barrel" type container with locking lid (for smell, rodent proof) and let living things do what naturally occurs...rot. does anyone have experience or thoughts on this?  

I used to be a police officer.  On one occasion at an old abandoned home on the outskirts of the city I MADE THE MISTAKE of opening a refrigerator that had a bit of food inside.  I think the smell may have exceeded the worst, rotting dead body I ever encountered.  

I would strongly (very smelly strongly) recommend to not seal meat into a container to let it rot.   I can not emphasize this advice enough.

Boiling them and making a fertilizing tea would be an option, but you would need a very large kettle and a big burner to keep it boiling.  It's probably not a feasible option but it should work.

Last spring, my son and husband got into a big mess of crappie.  We fileted them, dug a trench, probably 30' long, put the scraps in, covered with shredded leaves, wood chips and topped with peat moss. I ended up putting some boards up to make a bed around the area. The results have been fantastic so far. Luckily, our garden is fenced off, so no scavengers came sniffing around.

Along with some other great recommendations here, if I had those fish - I would simply chop and bury them in beds /rows.

Gray Day wrote:Eliot, the bokashi idea is interesting. Curious how much mass would shrink down as water weight since we're talking fish. The end result being something the chickens would like is favorable, still curious if there's a way to "liquify/emulsify" via a natural decomposition process without an abundant carbon source and traditional composting, but I suppose I'm getting into the realm of flesh eating bacteria... And for reasons I'll stop myself right there.

I like Silver Bullet solutions too! The only problem is they always remain an idea and don't seem to actually happen!  I mean, if the fish would jump out of the bucket, dig a hole, jump into it, vomit up a bunch of wood chips and then die that would be great!  But they don't so we are left trying to figure out the best way given our constraints on time, labor, willingness to burn diesel, etc.

Addressing your questions based on my reading (and yeah, that's a plea for anyone with ACTUAL experience with Bokashi to chime in):
- The Bokashi process releases a lot of liquid from mixed food waste.  Even when adding the dry substrate/medium (often bran or oats that has been inoculated with the mix of EM) it seems like you get about a 50% reduction in volume at the end.  So the volume would definitely reduce.. can't say how much.
- Sources of Carbon: most everything I see written about Bokashi uses some additional inputs to introduce the mix of organisms.  Buying the packaged Bokashi medium doesn't seem particularly cheap, although if you have a source of bran then you can make it yourself.   You'll use a lot less bran than wood chips.
- Yep, the end product still needs to be composted before its good for plants.

I like the assorted ideas presented here that involve some sort of dirt, shovel and (maybe wood chips).  Those are sort of one-step processes and they don't require more time or thought.  But rotting fish is time sensitive and digging holes every week can be a problem - and do you run out of room to dig holes?  The Bokashi idea is neat because with a 55 gallon drum you could just fill a drum each week, set it aside for a while and then empty it at a convenient time.  Assuming you have a good space for 4+ drums to hang around...

I didn't read all previous posts but that's one of the absolute best fertilizers there is. period
fish planted in the garden with the three sisters, corn, beans and squash, sustained native Americans for eons.

Andrés Bernal wrote:If you’re getting them fresh enough can be used as protein feed for chickens simply by pulverizing or grinding once they’re dried.

In my experience (feeding Yukon River salmon offal to chickens, 40 years ago) any significant amount of fish products fed to chickens flavors the eggs and flesh quite distinctively.  

My mother used 55-gallon drums to ferment salmon offal (heads, tails, entrails) into liquid fertilizer.  Sometimes open-ish (covered with a piece of plywood held down with a rock) and sometimes sealed-ish (snap ring lid).  Stench from the undisturbed barrels was distinct but tolerable; stench when attempting to distribute the resulting liquid was epic, tragic, penetrating, and lingering.  Mom retreated into a cloud of cigarette smoke (upwind) and made her children do the dirty work, but we were sufficiently rebellious that she eventually gave up her experiments.  

Eliot Mason wrote:Bokashi .....:
- The Bokashi process releases a lot of liquid from mixed food waste.... seems like you get about a 50% reduction in volume at the end....

- Sources of Carbon: uses some additional inputs.... doesn't seem cheap... you can make it yourself...

- the end product still needs to be composted before its good for plants.

I can give a bit of info about bokashi.
It does indeed break down, but I've been surprised when I've thrown, uh, vermin (rats I trapped in the garden) in the bin. When I dumped the barrel to bury the contents, I saw the rats and they were kinda "pickled" and hadn't lost much volume. I drain out a good amount of liquid from my kitchen waste bokashi, which is full of rotten tomatoes, tea leaves, bad spots from pineapples, etc., but I'm not sure you would drain anything out of fish.
I am also not entirely convinced that taking the time to make serums, mix with your medium, mix with the fish, ferment, and then have to bury it (I bury mine for two weeks to a month) is going to give you a better product than if you were to simply bury the dead fish in a hole, wood chips or no wood chips. You don't need to introduce microorganisms, I don't think-- dead fish come with that installed.
Another thing is that those fish look big. you're talking about a lot of mess and lots of barrels. I take a month or so to fill up my 5 gal bokashi barrel, with maybe another week of pressing everything down trying to delay the inevitable. Large volumes of smelly fish can't be cajoled into waiting another week, this just seems like an awful lot of kerfuffle and I'm not sure it would be worth it.

(that said, I do love bokashi and will happily talk to everyone about it. This may be the first time I have ever discouraged anyone from bokashi-ing. I make my own stuff because I am the queen of cheap. I use rice wash water, whatever cheap milk I can find, local molasses, a bit of bran for horses, and then sawdust I get from the mill for free. It works great.)

Dan Boone wrote:Stench from the undisturbed barrels was distinct but tolerable; stench when attempting to distribute the resulting liquid was epic, tragic, penetrating, and lingering.  

This is also true for bokashi, without the inclusion of fish. My husband refuses to come outside when the liquid is or has been applied-- and he's a mechanic with no sense of smell left after 20+ years of huffing petrogick. Then again, he's never cleaned out a stable or a pigpen so I assume he doesn't know from REAL stench!

My mom once buried a bunch of rotten pike under a tree she wanted to give a boost, and it grew like crazy. She'd also do the same with chicken carcasses and rotten eggs (while she kept chickens). I doubt there is a single (planted) tree in her garden that doesn't have some animal or another under it. But then again, if it's too much for you to bury... One possibility, if you also have some wood that you don't mind burning, is to cremate the fish (possibly after drying it a bit, to save fuel) and then use the ash as fertilizer. I suppose you'd lose most of the nitrogen, but the phosphorus, calcium, potassium etc would still be there. On the upside: No rodent issues. On the downside: maybe too big of an expense in fuel, plus it might not be good for the mycorrhizal fungi to dump a shitload of readily available phosphorus in the soil. But maybe you could get around that issue by using it in inoculating biochar? No idea if it would work.

Otherwise, I agree with Rebecca. The best way to use all this fish would be for someone to eat it. But maybe by the time it reaches you, it's not so appetizing anymore?

Thanks Tereza for sharing actual experience instead of just expectations!

Interesting to hear that rodents don't lose as much liquid as vegetables ... and yeah, there's a lot of pre and post fermentation work that has to happen.  

Depends how fresh they are through a mincer and making frozen fish cakes bulk sale.

Otherwise of cause shredding and dry to make fish meal.
If you are looking at the amount you can get, find out how sustainable the delivery is and compare the price of fish meal per metric ton.

alibaba has fish meal production lines that pay themselves after a few deliveries.
Touching the 10000$ it will even make pellets for feed.

Digging such a mass into your garden you will definitely pollute your grounds and ground water over the time being.

I’ve had a 5 gallon bucket that had fish remains in water to make a slurry to put on my plants. I forgot about being there, I got sick. It has been sealed for two years. I’m afraid to open the bucket. What will I find when I open it?

Vickie Moore wrote:I’ve had a 5 gallon bucket that had fish remains in water to make a slurry to put on my plants. I forgot about being there, I got sick. It has been sealed for two years. I’m afraid to open the bucket. What will I find when I open it?

That sounds terrifying. Good luck!

I'm sure it will be a nosebreaker -- advanced decomp in an enclosed space. A little Tiger Balm on the nostrils is known to reduce the gag reflex.

It's still a resource though. Personally I would have a good amount of dry biochar at the ready and immediately dump it in the pail. The odour reduction will be amazing, and you can poke it with a stick over a number of days to encourage the char to soak up the nutrients.

If the bucket is sealed it should not have any solids remaining and should not have a bad smell. If it wasn’t sealed good you probably have some sort of maggot like soldier fly or something in it. It might be pretty nasty but good fertilizer either way. Use at about 20/1 water or so. I do this with weeds or fish sometimes. Mostly weeds. It’s only horrible smell if I leave for a couple of months instead of a year and use it.

Rubber gloves just in case because if it does smell it will stay with you a day or two no matter how much you wash. I don’t want to think about why I know lol.

Needed would be the great outdoors, rubber gloves as Joe suggested and a close pin.

Instead of the close pin a face mask might work.

Slowly open the lid and be prepared to run far away.

Then dig a deep hole and pour the contents into the hole and bury the contents.

Wait a few years and plant a tree in that spot.

Best wishes for great results.

Old thread, but we make plenty of fish compost by layering charcoal and carp remains in plastic 55 gallon drums with locking lids.  I drilled  1/4” drain holes around the out side of the bottom of the barrel.  The lid gets a few 1/8” holes to let some rain in, but exclude blow flies.  There is some smell for a few days, but it is tolerable.  My wife sits on the deck 50 ft away and doesn’t complain.  You could roll the barrel around a bit if you want, but we don’t.  It could probably be used after 5-6 months, but we wait closer to a year.

Since I started working with the OKK small farm food project (I’m posting our progress in the Small Farm forum for anyone who is interested), I  have been eagerly soliciting fish and fish waste in order to make fish emulsion fertilizer. We make it by the multiple trashcanfuls loads. And it works fantastically great. BUT it stinks, which makes little difference in a farm situation. Our volunteer workers simply put Vicks vapor rub up their noses before bucketing out the fertilizer. It helps a bit.

I could use a trashcanful of fish waste a week for a 3 acre food production garden.

If I wasn’t going to make fish emulsion, then I would trench the fish. I trench coffee pulp waste and it’s a quick and easy way to deal with volume.