top of page

Manure Storage: Lagoon Acidification

alternative practice names:

Acidifying Manure; N2 Applied

Acidifying manure is an effective manure management strategy aimed at reducing greenhouse gas emissions and ammonia volatilization from stored livestock waste. The process involves lowering the pH of manure using acids such as sulfuric or nitric acid, which inhibits microbial activities responsible for methane and ammonia emissions. Alternatively farms can use plasma technology to create create nitrogen from the air and use it to acidify manure without chemicals. By reducing the pH to around 5.5, acidification has the following impacts:


  • Reduced methane emissions: Acidification inhibits methanogenic bacteria that thrive in neutral to alkaline conditions, leading to reductions in methane emissions by up to 96%.

  • Decreases ammonia emissions: At pH 5, virtually all ammoniacal nitrogen in aqueous solution is nonvolatile ammonium. By stabilizing nitrogen in a nonvolatile, plant-available form as ammonium, acidification reduces ammonia emissions by up to 85%.

  • Enhanced phosphorus availability: Acidification increases the solubility and availability of phosphorus in manure by dissolving phosphorus compounds, making them more accessible for plant uptake. Acidification of manure slurry to pH 5.5 with sulfuric acid increases water-extractable phosphorus (20-61%) and phosphorus uptake by maize (47-49%)


One effective approach is to target the acidification of residual manure, also known as inoculum, which remains in storage after emptying. This residual manure can accelerate methane emissions when fresh manure is added, due to microbial activity. By treating only the inoculum with acid, farms can achieve significant reductions in methane emissions without needing to acidify all incoming fresh manure. This method not only curtails GHG emissions but also lessens the need for frequent acidification, thereby reducing costs.


While not currently used by U.S. dairy farmers, this has been an accepted practice in Europe for a number of years and is gaining interest here in the U.S.

When used, in what regions in the U.S. is the practice found: 

Northwest, West, Upper Midwest, Southwest, Northeast, Southeast

FARM SIZE 

When used, typically found on farms of the following sizes:

100 to 2500 cows

Case Studies.png

Practice Benefits 

Lower odors: By minimizing ammonia emissions, acidification reduces the risk of nuisance odors.


Enhanced nutrient retention: Acidified manure retains more nitrogen in the form of ammonium, reducing nitrogen losses and enhancing its value as a fertilizer. This process also increases phosphorus availability, making the manure more beneficial for crop growth.

Practical Insights.png

Implementation Insights

Site-specific or Farm-specific requirements 

farm-icon.png
  • Liquid manure storage: This technology is only applicable to farms that handle manure as a liquid or slurry.

  • No biogas collection: Manure acidification is well suited to smaller farms for which anaerobic digestion is not economically feasible. There is little incentive to use this practice in combination with anaerobic digestion. 

Required Capital Expenditures (CapEx)

red-dollar-0.png
  • Separation system: A coarse solid separation system may be installed to reduce the amount of acid required to lower the pH to the desired level.  

  • Acid storage and dosing system: A secure area should be constructed to store the acid. Acid is added directly to the manure in the animal housing or collection channels or directly to the manure tank/lagoon. A dosing pump and a mixing/agitation mechanism are typically used to maintain uniform pH levels and prevent foaming.

  • Plasma reactor: Some farms also opt to purchase specialized equipment that uses plasma to generate reactive nitrogen from the air to form nitric acid in manure. 

Required Operational Expenditures (OpEx)

orange-dollar-0.png
  • Labor: Implementing manure acidification can increase labor requirements due to the need for regular pH monitoring, equipment maintenance, and adherence to safety protocols for handling corrosive substances.

  • Chemicals: Manure acidification is achieved using strong acids like sulfuric acid, nitric acid, and hydrochloric acid, which lower the pH to inhibit methane and ammonia production. Sulfuric acid is the most commonly used due to its effectiveness and cost-efficiency, while organic acids like citric and lactic acid offer a less corrosive but more expensive alternative.

  • Electricity: Farms using plasma technology to acidify manure will not have to purchase and handle chemicals but will use significantly more energy. 

Implementation Considerations

implementation-complexity-1.png
  • Nitrogen nutrient management: If using nitric acid to lower slurry pH, the amount of nitric acid required to lower slurry pH to around five roughly doubles the amount of nitrogen in the slurry, and all the added nitric acid nitrogen is soluble and doesn’t have to mineralize before becoming available to plants. Furthermore, if ammonia loss during slurry storage is also substantially lowered, a much lower volume of slurry needs to be applied to meet crop needs for nitrogen. The surplus nitrogen may necessitate farms to export manure to avoid over-applying nitrogen.

  • Phosphorous nutrient management: Acidification of manure slurry to pH 5.5 with sulfuric acid increased water extractable phosphorus. This is desirable re-crop production but has the potential to increase phosphorus runoff, especially from surface applications; injected applications should minimize increases in phosphorus runoff due to acidification.

  • Safety: The use of acids requires careful handling and appropriate safety measures to protect farm workers and prevent environmental contamination.

  • Removal of coarse solids from the waste stream can reduce the amount of acid required to lower the pH, but the acid's impact may not last as long due to the reduced buffering capacity of the coarse solids.

  • Impact on soil and crop yield: While acidified manure can improve nutrient availability, the long-term effects on soil health and crop yield need further investigation. It is important to monitor soil pH and nutrient levels to ensure optimal crop performance.

  • Corrosive impacts: Due to the acid's corrosive nature, piping and other fixtures will require inspection and replacement to ensure the system is operating properly.

  • Cost optimization: The cost of acids, infrastructure, and equipment for acidification can be substantial, which may limit its adoption by smaller farms. However, treating only the residual manure (inoculum) instead of the entire manure volume can reduce costs while still achieving significant emission reductions.

Financial Considerations and Revenue Streams

There are no federal cost-share programs or conservation funding for this practice.

Research Results.png

Environmental Impacts

REDUCES FARM GREENHOUSE GAS FOOTPRINT

Manure acidification offers several environmental benefits by significantly reducing greenhouse gas (GHG) emissions and improving nutrient management. By lowering the pH of manure, acidification inhibits the activity of methanogens, which are responsible for methane production. This results in a reduction of methane emissions by up to 96%, which is a potent GHG contributing to climate change. Additionally, acidification stabilizes nitrogen in a plant-available form, reducing ammonia emissions by up to 85%. This decrease in ammonia emissions not only improves air quality but also minimizes the risk of nitrous oxide emission associated with nitrogen deposition.


IMPROVES WATER QUALITY

Acidification increases the solubility and availability of phosphorus, making it more accessible for plant uptake. This reduces the potential for phosphorus runoff into nearby water bodies. Conserving nitrogen in manure aligns the nitrogen-to-phosphorus ratio more closely with crop nutrient requirements, allowing farmers to reduce the total amount of manure applied based on nitrogen needs. This practice minimizes phosphorus overapplication, preventing excess phosphorus buildup in the soil and reducing phosphorous buildup and runoff.

REFerences

farm-assessment.png

Alignment with FARM Program

This practice is not included in the FARM program.

Contents

farm-icon.png
farm-icon.png
farm-icon.png
farm-icon.png
farm-icon.png
farm-icon.png
farm-icon.png

We're always eager to update the website with the latest research, implementation insights, financial case studies, and emerging practices. Use the link above to share your insights. 

We're always eager to update the website with the latest research, implementation insights, financial case studies, and emerging practices. Use the link above to share your insights. 

Contents

farm-icon.png

Practice Overview

Case Studies.png
Practical Insights.png
dollar.png
reference,png
Research Results.png
farm-assessment.png

Acidifying manure is an effective manure management strategy aimed at reducing greenhouse gas emissions and ammonia volatilization from stored livestock waste. The process involves lowering the pH of manure using acids such as sulfuric or nitric acid, which inhibits microbial activities responsible for methane and ammonia emissions. Alternatively farms can use plasma technology to create create nitrogen from the air and use it to acidify manure without chemicals. By reducing the pH to around 5.5, acidification has the following impacts:


  • Reduced methane emissions: Acidification inhibits methanogenic bacteria that thrive in neutral to alkaline conditions, leading to reductions in methane emissions by up to 96%.

  • Decreases ammonia emissions: At pH 5, virtually all ammoniacal nitrogen in aqueous solution is nonvolatile ammonium. By stabilizing nitrogen in a nonvolatile, plant-available form as ammonium, acidification reduces ammonia emissions by up to 85%.

  • Enhanced phosphorus availability: Acidification increases the solubility and availability of phosphorus in manure by dissolving phosphorus compounds, making them more accessible for plant uptake. Acidification of manure slurry to pH 5.5 with sulfuric acid increases water-extractable phosphorus (20-61%) and phosphorus uptake by maize (47-49%)


One effective approach is to target the acidification of residual manure, also known as inoculum, which remains in storage after emptying. This residual manure can accelerate methane emissions when fresh manure is added, due to microbial activity. By treating only the inoculum with acid, farms can achieve significant reductions in methane emissions without needing to acidify all incoming fresh manure. This method not only curtails GHG emissions but also lessens the need for frequent acidification, thereby reducing costs.


While not currently used by U.S. dairy farmers, this has been an accepted practice in Europe for a number of years and is gaining interest here in the U.S.

Practices and technologies

Manure Storage: Lagoon Acidification

alternative practice name:

Acidifying Manure; N2 Applied