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Opinion · Ammonia in broiler houses

Woodchip Biocharin poultry litter is notPoultry Litter Biochar

Woodchip char added to bedding litter is not the same as char that is made from litter.

Forged Innovation · October 2026 · 6 min read

Don't ask what absorbs ammonia

Ask what stops it forming

Two things · similar name · not the same
BIOCHAR IN POULTRY LITTER char goes into the house · litter plus char comes out Wood Char made off farm carbon credit stays there Heat wasted char Bought in · ≈ 1.7 t 10% of bedding · per crop Broiler house ≈ 250 t litter + char out ≈ 255 t litter hauled away POULTRY LITTER BIOCHAR litter goes out of the house · heat comes back · char is the product House · dry litter all crop reduced output ≈ 230 t Own litter ≈ 230 t in per crop ZEDE Pyrolysis on farm char Poultry litter biochar 230 t reduced to ≈ 75 t Heat back to the houses, whole crop · 0 t of litter to haul away
End-of-crop ammonia · lower is better

5 Approaches, 1 Outcome (that matters)

Heat for the full crop · lowest floor heating + heat exchanger, commercial houses, separate trial (HAFL 2024) Acidifier (PLT, sodium bisulphate) · lower Untreated control · base Doped / treated biochar · still above the untreated control (Cornell 2020) Untreated biochar in bedding, 30% v/v · 104 ppm · highest USDA bars: order is the published ranking; control and acidifier values are not given in the abstract, so those bars are not to scale. Heat and treated-char bars are from separate trials (HAFL two-house; Cornell compost), drawn against the control for comparison; indicative only.
Poultry litter biochar heat
9×less ammonia per cycle

Constant heat × drier litter
= 9× less ammonia

Bern University of Applied Sciences ran two identical 9,000-bird broiler houses through a cycle.

Total ammonia emitted over the cycle was about nine times lower in the heated house, and the end-of-cycle peak concentration about a third of the reference house.

The heated house's litter was "considerably drier".

Gfeller, Valach, Häni, Bowald & Kupper (2024), Floor heating and heat exchanger as an ammonia mitigation technique for broiler housing, EGU General Assembly, EGU24-19295.

Every bedding type emits more as moisture rises, with a one-to-two-week lag.

Miles, Rowe & Cathcart (2011), Poultry Science 90, 1162–1169; Liu, Wang, Beasley & Oviedo (2007), J. Atmos. Chem. 58, 41–53.

Wageningen found no gain from floor heating switched off before the litter gets wet; the gains come from heat through the whole crop.

Ellen, van Harn & Veldkamp (2005), Inventarisatie mogelijkheden reductie ammoniakemissie uit vleeskuikenstallen, PraktijkRapport Pluimvee 16, Wageningen.
Ammonia is under 1% of what the char takes up

Woodchip Char = Water Char

~97% water 1–2× the char's own weight in the bed ~2–3% organics, salts, microbes <1% ammonia and ammonium the only part it is sold for By mass, at 10% inclusion. Indicative proportions.

Woodchip char's fine-pore structure readily takes on water, and does not readily give it up.

That water is held by capillary force against house heating and ventilation.

Once waterlogged, gas can no longer reach the char's surfaces.

A broiler crop, day by day

Woodchip char is spent before the crop starts to produce

day 071421283542 5% 10% 20% Char still absorbing ammonia inclusion rate · median-to-best case capacity (4–25 mg N/g) Char full: wet, alkaline, colonised. Working against you. cumulative water into the litter Heating normally off

Capacity windows: day on which ammonium formed in the litter exceeds what the char can hold. Ross 308 as-hatched intake, 18 birds/m², CP 22/20/18%, 42% of dietary N excreted, only 20% of that hydrolysed to ammonium (generous to the char), 1.5 kg/m² bedding. Char capacity 0.4–7.5 g N/m²; ammonium formed in the litter passes that within the first week and ends the crop two orders of magnitude above it. Water curve from drinker figures in our broiler-house guide.

Where ammonia starts
2×moisture of litter around it

Wet Woodchip char = ammonia generation sites

Woodchip char sits at roughly 50–65% moisture in the litter bed while the litter around it runs at 25–35%.

The bedding as a whole need not be wetter; what changes is that the wet sites are now millions of alkaline, microbe-colonised particles spread through it, each one a nucleation zone for ammonia generation.

Litter moisture is measured on the bulk sample. The water sits inside the char, so the bulk reads drier while the particles stay wet and alkaline. That is how a biochar litter can be the driest in the house and still give the most ammonia.

Forged estimate from published water-holding capacity of wood biochar (1–2 g water per g char in a bedding environment).
Full-crop broiler trial · USDA 2025
104ppm ammonia, day 41

Woodchip biochar in the bedding finished with the driest litter and the most ammonia

USDA ARS and Mississippi State ran biochar at 30% by volume against a sodium bisulphate acidifier and an untreated control through a 42-day broiler grow-out.


The biochar litter was the driest of the three and had the highest ammonia on day 41.


Mohammadi-Aragh, Norris, Chesser, Lowe, Evans, Purswell & Linhoss (2025), Journal of Applied Poultry Research 34(1) 100499. Open access.
Five numbers that explain it
4 mg/gAmmonium an unmodified biochar can hold. Median of the published data.Weldon et al., NIBIO 2022
Day 1–7When that capacity is used up in a broiler house at 5–20% inclusion.Forged calculation, below
pH 8–10Typical wood biochar. Each pH unit up to ~9 frees roughly ten times more ammonia as gas.Khater et al. 2024; EBC/IBI
6×Ammonia loss from poultry manure with untreated wood biochar vs none.Hestrin, Enders & Lehmann, Cornell 2020
<3%Share of a crop's ammonia the char can hold at 10% inclusion.Forged calculation, below
Side by side

Poultry litter biochar vs biochar in poultry litter

Property
Biochar in poultry litter
Poultry litter biochar
Feedstock
Wood chip
Broiler litter from the farm's own houses
Made where
Off farm
On farm
Goes where
Into the bedding, then out with the litter
Bagged as product; never enters the house
Ammonia measure
Sorbent, full in days; alkaline after
Heat back to the house keeps litter dry all crop
Fixed carbon
70–85% (typical, prior to mix)
52–55%
N-P-K
<1 · trace · ~1
≈ 5-7-9
pH
8–10
10.5
Litter leaving the farm
Unchanged, plus the weight of the char
Leaves as heat and char: debulked, mass reduced
Carbon accounted to
The char producer
The farm

Wood figures are typical EBC/IBI ranges. Forged figures from our broiler litter char; full analysis on request. Poultry litter biochar is capital plant, needs an animal by-product approval, and the route for a pyrolysis plant inside those rules is still being settled with the regulators; ZEDE is designed around the on-farm conditions in the regulations and we do not claim a stamp we do not yet hold.

Don't ask what absorbs ammonia.
Ask what stops it forming.

Name the feedstock. Name the direction. Biochar in poultry litter and poultry litter biochar are different products with different chemistry, and the paperwork, the trials and the headlines should say which.

See ZEDEOur poultry litter biocharTalk to us

Poultry litter biochar · questions we get asked

What is poultry litter biochar?

Char made by pyrolysing poultry litter at high temperature with little or no oxygen. The litter's minerals stay in it, so it carries N, P and K that wood biochar does not, at a lower fixed-carbon content. Also called broiler litter biochar or chicken litter biochar.

Is adding biochar to poultry litter the same thing?

No. That is wood biochar, made elsewhere, mixed into the bedding at placement. It is bought in, it raises litter pH, and it leaves with the litter at clean-out.

How long does biochar in bedding keep absorbing ammonia?

Days. At a median 4 mg/g and 5–20% inclusion it is loaded within the first week, even allowing for low chick excretion, and holds a few per cent of the crop's ammonia.

Does biochar in bedding reduce ammonia?

Early in the crop it can. It is also alkaline; poultry-manure measurements found six times the ammonia loss with untreated wood biochar, and the one 42-day broiler trial found the highest day-41 ammonia over the biochar litter.

What stops ammonia forming in poultry litter?

Litter kept below the moisture microbes need for the whole crop, and pH kept down. Consistent heat and ventilation does the first; acidifiers the second. Adding an alkaline material does neither.

Can poultry litter biochar earn carbon credits?

Biochar removal methodologies credit the dry mass and stable carbon of the char produced, with measured evidence. Made on the farm from its own litter, the carbon is the farm's to account for; eligibility is decided by the registry and the plant's approval.

References

  1. Mohammadi-Aragh M.K. et al. (2025), J. Appl. Poultry Res. 34(1) 100499.
  2. Hestrin R., Enders A., Lehmann J. (2020), J. Environ. Qual., doi:10.1002/jeq2.20154.
  3. Weldon S.M. et al. (2022), A re-analysis of NH₄⁺ sorption on biochar, NIBIO.
  4. Khater E.-S. et al. (2024), Sci. Rep., doi:10.1038/s41598-024-52336-5; EBC and IBI guidelines.
  5. Gfeller S., Valach A.C., Häni C., Bowald S., Kupper T. (2024), EGU24-19295, Bern University of Applied Sciences HAFL.
  6. Liu Z., Wang L., Beasley D., Oviedo E. (2007), J. Atmos. Chem. 58, 41–53.
  7. Miles D.M., Rowe D.E., Cathcart T.C. (2011), Litter ammonia generation: moisture content and organic versus inorganic bedding materials, Poultry Science 90, 1162–1169.
  8. Ellen H.H., van Harn J., Veldkamp T. (2005), Inventarisatie mogelijkheden reductie ammoniakemissie uit vleeskuikenstallen, PraktijkRapport Pluimvee 16, Animal Sciences Group, Wageningen.
  9. Forged Innovation, How to defeat ammonia with water management (2026); saturation calculation from Aviagen Ross 308 performance objectives.

Further reading

  1. Natural Resources Wales, Emission factors for poultry for modelling and reporting; Mulvenna C., Ball E. (2024), Atmospheric Environment: X 23 (AFBI, two NI broiler houses).
  2. Rav emission factors for broiler housing with heat exchangers and floor heating (E 5.100, E 5.11, E 5.15), Netherlands.