Assessing Feasibility of Bio-acidification to Reduce On-farm Ammonia Volatilization from Dairy Manure, Digestate and Urine

Project Overview

Project Type: Partnership
Funds awarded in 2021: $29,939.00
Projected End Date: 09/30/2023
Grant Recipient: Rich Earth Institute
Region: Northeast
State: Vermont
Project Leader:
Abraham Noe-Hays
Rich Earth Institute

Information Products


  • Animals: bovine, swine
  • Animal Products: dairy


  • Animal Production: manure management
  • Crop Production: fertilizers, nutrient management, organic fertilizers
  • Education and Training: other
  • Energy: anaerobic digestion, byproduct utilization
  • Farm Business Management: budgets/cost and returns, feasibility study
  • Production Systems: integrated crop and livestock systems

    Proposal abstract:

    Ammonia volatilization from manure is a major source of nitrogen pollution in the environment, and also reduces the fertilizer value of manure on the farm. Bio-acidification via fermentation is a novel method of reducing ammonia loss by adding carbon-rich waste products to liquid manures. Fermentation produces organic acids, lowering manure pH. Like conventional manure acidification, this practice has the potential to reduce ammonia and methane emissions and retain available nitrogen, but without handling dangerous concentrated inorganic acids.

    This project will evaluate whether bio-acidification of manures, using free or negative-cost waste materials readily available in the Northeast, has the potential to reduce ammonia emissions. This project will evaluate three waste materials: acid whey, sweet whey, and short paper fibers (pulp sludge), all of which present disposal challenges to their respective industries. Testing will be done on liquid dairy manure, digestate, and pasteurized human urine, which is currently collected via Rich Earth Institute's Urine Nutrient Reclamation Program.  

    Lab trials will identify and test optimal recipes by monitoring pH change over time at different temperatures, and measuring potential ammonia loss following surface application. 

    The project is in close partnership with two farmer-partners and two farm advisor collaborators, to assess on-farm feasibility of this practice with regard to handling, storage, and equipment/infrastructure needs. These partners will be involved in lab trial design, interpretation of results, evaluation of implementation costs, and planning next steps including on-farm trials in a subsequent project. We will also interview 10-15 farmers in Vermont who manage liquid manure.

    Project objectives from proposal:

    This project will assess whether bio-acidification of manures using high-carbon substrates is a potentially feasible method for reducing ammonia emissions on Northeast farms. If successful, the method could generate increased farm revenue through whey or short paper fiber disposal fees, as well as reduced fertilizer purchases and/or higher yields from retained manure N. 


    We will address the following questions: 

    Lab research questions:

    1. Does the addition of whey and/or paper fibers induce fermentation in liquid dairy manure, digestate, and/or human urine?
      1. What pH changes are achieved by different volume ratios?
      2. Is there any benefit from adding starter cultures?
      3. How long do the pH changes of different mixtures last at different temperatures? 
    2. Does bio-acidification reduce ammonia volatilization when manure, digestate, or urine are applied to soil? 


    Farmer research questions:

    1. What challenges do farmers have managing ammonia loss from manure? How feasible would bio-acidification be on farms with liquid manure? 
      1. We will interview 10-15 farmers managing liquid manure to understand their concerns around manure N content and loss, and manure storage / management capacity
      2. Using lab trial results, we will conduct a detailed analysis with two farmer-partners of whether and how bio-acidification could be added to their operations, and additional research needs.
    Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.