To get accurate hog waste statistics is surprisingly difficult. It's generally measured in gallons of waste water, so this includes the water needed to wash the actual feces and urine into pipes (see Does hog size impact manure production?)

let's go down the rabbit hole!

This website says 2.3 lbs to 13.1 lbs which feels way too high. Swine Manure To Biomethane | BioCycle

But then you have this website saying a 400 lbs breeder pig can produce 75 lbs of waste, not including wash water? how is that even possible? osei.us/wp-content/uploads/Manure-Brochure-Horses-Cows-Pigs-and-Chickens-XXXXZZZ-1.pdf
apparently they're eating 13.2 lbs of corn per day for energy maintenance...
Formulating farm-specific swine diets | UMN Extension
and a lot of waste is water and urine i guess
urine can be heavy. even humans produce 2-4lbs per day.
still though. this is a mystery.

This site has done a lot of investigating and arrives at 1.3 gallons of manure per hog The Manure Scoop: Bigger Pigs: More Manure and Impact on Facility Design
according to hog manure and urine - Ask Extension (i think the answerer is extension school staff?) estimate for gallons to pounds is 8.3lbs/gal of manure
so that's 10.8/day
but again, does it include wash water?

UMD extension says 63-65 lbs? lbs/manure/AU/day?
au is animal unit (1000 lbs of live animal)
at 250 lbs / pig that's 16 lbs / day
but they don't specify actual feces vs feces with wash water
extension.umd.edu/sites/extension.umd.edu/files/2021-05/FTC_Table_4-1.pdf

Iowa DNR splits it up based on liquid lagoons and solid waste. iowadnr.gov/media/6179/download?inline
the numbers are confusing. why do gestation pigs have less liquid lagoon waste but more solid waste?
looks like 2.05 tons for a finisher and 6.16 tons per year for a gestation
that would be 12.5 lbs per day of solid waste!
farrow-finish per "breeding sow" is 67 lbs of solid waste per day? that checks out with UMD. what is happening with these sows? how are they producing so much waste? and is this averaged over their lifetime?

alright we're looking at clemson extension now clemson.edu/extension/camm/manuals/swine/sch3a_03.pdf
much clearer
they define an "animal unit" as 1000 pounds of "live animal"...
I want farrow to finish. these are grown pigs. i don't know why they keep switching from pigs to sows to hogs.
1,417 lbs / sow. That's 3.88 lbs of solid waste per day.
that is 1/3rd of what iowa dnr said... i double checked iowa dnr is not using animal units. its per animal.

sows can be 300 to 700 pounds. so if these sows are on the lighter side, the numbers could check out.
9.3solids per au/3.88 solids per sow= 2.39 sows per animal unit
so if we want manure production, that's
77lbs/2.39 = 32 lbs per day per sow
9.28/2.39 = 3.88 gallons per day per sow

minnesota ag extension has the nicest looking table mda.state.mn.us/sites/default/files/2018-05/nutmantables.pdf
finishing swine: 9 tons / year of solid waste, 2166 gal per year of liquid
in AU
let's assume 3 swine per AU
so 16.4 lbs / day of solid waste. still wild...

so the clemson pdf is an outlier. looks like hogs produce a ton of waste. i dont know how

watching videos of pigs pooping rn to corroborate.
this seems very lightweight: gigantic pig poops but maybe it's a perspective thing
disgusting but i'm doing it for a good cause, i hope a pig pooping
found this weird, weird, weird part of youtube Giant Mummy Pig poop??! Peppa Try Not To Laugh (Part 6) - YouTube

this has gone too far. i'm trusting minnesota state ag, iowa dnr, umd extension
11 - 13lbs / day. including wash water.
Does hog size impact manure production? this site confirms 1.3gals / 11lbs but "including any wash water used on site". it seems not much wash water is used, so the manure is mostly feces. is this true?

wash water is apparently not the water used to clean the barns daily, but water used to clean the barn between pig batches? are they using the term incorrectly?

ok wash water use is highly efficient according to this very detailed paper on the 5th page of google! porkcheckoff.org/wp-content/uploads/2021/02/09-128-BURNS-ISU.pdf
see page 16. .02 gallons / pigspace per day for finished pigs. that's nothing! it's all actually feces and urine! how do they use so little water? i use more than that washing my dishes. i can't be reading this right. it must be between batches? and they just let the hogs step in their own feces otherwise? and push it into the slats naturally over time? is it really that horrible? do they ever wash them? what about the flush systems from earlier?

Washing Pig Barns & Moving Feeding Mats for Growing Pigs - YouTube video of the cleaning. they use a power washer. that must be what the previous guys meant by wash water. yes confirmed they also talk about power washer flow rate in their paper, they say wash water is used twice a year, so does power washing only happen twice a year???

ars.usda.gov/ARSUserFiles/np212/LivestockGRACEnet/manureScraper.pdf
ok here's how barn "flushing" works
flushing is how you get all the manure to fall down the slats
they use the RECYCLED LAGOON WATER to do the flushing! so they wash poop with poop water...

Research has shown that flushing with odorous recycled anaerobic lagoon wastewater can result in unfavorable odor emissions

lmao at "research has shown... unfavorable odor emissions"
it seems difficult to get the exact clean water to waste ratio

so how much flushing water is used??? not fair to say 1-2 gallons of waste per day if most of it is water used to wash the barn!

sraproject.org/wp-content/uploads/2017/10/cafosandtheeconomicsofefficiency.pdf
problem solved i think. this makes much more sense. separates flushing water from power washing. flushing water is 15 gallons per pig per day! which means it's definitely not included in the manure calculations!

i think it's reasonable to go with the "1-2 gallons" of manure statistic since hog farmers use that themselves...

aside: these guys are turning manure lagoons into "drinkable" water??? wow Manure to Clean Water