Manure methane, ammonia and odour cut by anaerobic digestion with covered storage, low-protein diets balanced with fermentation amino acids, and biological air treatment of livestock houses — instead of open lagoons, sulfuric-acid slurry acidification and masking agents

Replaces: open lagoons, sulfuric-acid acidification, masking agents · Scope: pig, dairy, poultry · Evidence: high (digestion, diet, covers), low (most manure additives)

The chemical problem#

• Liquid manure stored in open lagoons emits methane; slurry and litter emit ammonia, a fine-particle precursor and the main driver of nitrogen deposition in livestock regions.
• One chemical fix, slurry acidification with concentrated sulfuric acid (used in Denmark), cuts ammonia strongly but brings acid handling risks and adds sulfur to soils.
• Odour complaints are often met with masking chemicals that do not reduce emissions.
• EU rules are tightening: the revised Industrial Emissions Directive extends to more pig and poultry farms, and national ammonia ceilings apply.

Product overview#

1. Anaerobic digestion of manure with gas-tight digestate storage — captures methane as biogas (see EN01); small-farm digesters for smallholders.
2. Covered storage and low-emission spreading (trailing shoe, injection) of digestate.
3. Low-protein diets balanced with fermentation-made amino acids (lysine, methionine, threonine, valine — see FD01) → less N excreted, less ammonia formed.
4. Biological air treatment of livestock-house exhaust — biotrickling filters and biofilters (see RM03).

Active ingredient / Composition#

• Digestion: anaerobic microbial consortia; biogas ~55–65 % methane.
• Diet: crude protein reduced by 1–3 percentage points with crystalline amino acids from fermentation.
• Air treatment: nitrifying biofilm on packing material.

Key facts#

Advantages#

• Digestion turns a methane liability into energy and income (and carbon credits).
• Low-protein diets act at the source and save expensive protein feed.
• Biological air treatment needs no acid and reduces both ammonia and odour.
• Smallholder digesters replace firewood and charcoal (EN01).

Mode of action#

• Anaerobic digestion converts manure organic matter to methane in a closed vessel, so it is captured rather than released from the lagoon.
• Less dietary N → less urea in urine → less ammonia formed by urease in the slurry.
• Nitrifying bacteria in biofilters oxidize ammonia to nitrite/nitrate in the trickling water.

Application#

Limitations#

• Digesters need scale, capital and operating skill; leaks erase the methane benefit.
• Low-protein diets need accurate amino-acid balancing to keep performance.
• Air treatment is costly for naturally ventilated barns.
• Do not rely on unproven microbial manure additives.

Evidence of displacement — D1: works, adoption not proven#

Assessment (hand-reviewed): Mismatch: Danish slurry acidification (4% → 14%, 2011–2015) is a chemical (sulfuric acid) treatment, not digestion or biofilters.

Figures found (verified as quoted, but the assessment above explains why they do not count as displacement evidence for this substitution):

• displacement — The share of Danish slurry acidified using the SyreN technology grew from approximately 4% in 2011 to 14% in 2015. (Denmark, 2011-2015; peer-reviewed: exa.ai)
• displacement — In 2012, approximately 10% of Danish slurry was acidified, and by 2015, this figure had increased to 20%. (Denmark, 2012-2015; weak: biocover.dk)
• economics — Field acidification is estimated to cost 0.86 Euro per cubic meter of slurry, compared to 1.06 Euro per cubic meter for barn and storage acidification. (—, 2019; peer-reviewed: exa.ai)

Suppliers — real products and services (from the vendor index)#

Active vendors whose own card shows manure digestion or livestock-waste treatment.

Fermentation amino-acid producers for low-protein diets are listed in FD01; biofilter suppliers in RM03.

Government funding signals#

Scanned 2026-10-01 (OpenAIRE + NSF); candidates reviewed by hand.

Signal: Moderate. “Manure ammonia” returned 30 candidates, including NWO NWA.1228.192.182 (recycling ammonia from manure), Czech MZE QK23020011 (strategies to reduce GHG and ammonia from livestock), MSM 9B23002 (on-farm ammonia and GHG quantification) and Innovate UK 10079459 (stabilising manure N with an enzyme-based product, £58 k).

Scientific evidence#

• Montes F, Meinen R, Dell C, et al. (2013). Mitigation of methane and nitrous oxide emissions from animal operations: II. A review of manure management mitigation options. Journal of Animal Science 91: 5070–5094.
• Sommer SG, Hutchings NJ (2001). Ammonia emission from field applied manure and its reduction—invited paper. European Journal of Agronomy 15: 1–15.
• Holm-Nielsen JB, Al Seadi T, Oleskowicz-Popiel P (2009). The future of anaerobic digestion and biogas utilization. Bioresource Technology 100: 5478–5484.
• Fangueiro D, Hjorth M, Gioelli F (2015). Acidification of animal slurry – a review. Journal of Environmental Management 149: 46–56.

Bioeconomy value#

Manure is the one emission source that can pay for its own mitigation through biogas. Fermentation amino acids, digesters and biofilters are all bioeconomy products that already have suppliers in this index.

Cross-links: EN01 biogas; FD01 amino acids; RM03 biofilters; NU03 digestate as fertilizer; LE01 enteric methane.