Anaerobic Digestion Systems

Integrating Emerging Technologies to Improve Environmental and Economic Impact

The US Dairy Adoption Of Anaerobic Digestion Systems Integrating Multiple Emerging Clean Technologies:  Climate, Environmental, And Economic Impacts project aims to quantify the climate, air, water, nutrient and economic impacts of integrating emerging, next-generation technologies within AD systems on U.S. dairies. Existing evidence suggests that addressing nutrient concerns and improving project returns on investment could enhance AD adoption rates in the U.S., and generate additional environmental benefits. The project focuses on three technologies that are being developed by the project team through leveraged research.

Figure 1) AD System with Multiple Integrations

Project Objectives:

  1. Enhancement of pyrolysis through modification of biochar for nutrient recovery (NR), with exploration of nitrogen (N), phosphorus (P), and hydrogen sulfide (H2S) capture
  2. Agronomic evaluation of AD-derived fertilizers at greenhouse scale: surface-modified biochar, organic P-enriched solids, ammonium sulfate solution, and struvite crystals
  3. Modeling of various adoption scenarios for AD systems technologies, and the impacts on greenhouse gas (GHG) emissions, nutrient flows, and crop yields
  4. Techno-economic analysis of adoption scenarios
  5. Extension of research to key stakeholders positioned to facilitate adoption of AD systems (e.g. industry, regulatory agencies, and private carbon market entities)

Figure 2: Various manure-derived soil amendments: (1) anaerobically digested liquid manure; (2) ammonium sulfate solution from WSU AIRTRAP systems (USPTO 2011); (3) phosphorus-rich solids from AIRTRAP; (4) slow release ammonium and phosphorus containing struvite crystals from both dairy and municipal waste-water systems (USPTO 2010), and (5) phosphorus-enriched bio-char (Streuble et al. 2011)

Emerging Technologies Included in the Project

Two pyrolysis processes for AD fiber will be studied:

  • Pyrolysis optimized to produce process heat and biochar. The surface of the biochar will be modified so it can be used as media for biogas scrubbing (H2S) filters or for removal of N and P from lagoon wastewaters.
  • Pyrolysis optimized to produce a crude bio-oil for use as liquid fuel and a water‑soluble fraction containing small chain organics, which can be digested for methane production.

Three nutrient recovery (NR) technologies will be investigated:

  • Physical screening system to remove suspended P as an organic solid
  • A high temperature aeration treatment with physical screening to remove ammonium as an ammonium salt and suspended P as a separate organic solid
  • Combined ammonia and soluble P recovery as a single salt (struvite) product

Two water recovery pathways will be explored:

  • Returning NR-treated wastewater to the digester to dilute high solids wastes (such as “dry” poultry or feedlot manures), enabling digestion in slurry-based digesters (the most widely adopted technology)
  • Additional wastewater treatment approaches to achieve the purity required for animal drinking water


USDAFunding for this project is provided by USDA National Institute for Food and Agriculture

2012-2015 USDA NIFA AFRI Agriculture and Natural Resources Science for Climate Variability And Change Grant #WNP02012-00881