Combined AD + NCS
Although capable of treating any variety of organic wastes, PFED’s combined AD and NCS was initially designed and developed specifically to address the issue of poultry litter management in Maryland and the greater Chesapeake Bay region.
Present Day Poultry Litter Management
Poultry litter is managed differently throughout the U.S., but the state of Maryland provides a blueprint for best practices. Currently, poultry litter produced in any one of the Delmarva Peninsula’s 4,700 commercial poultry houses1 is cleaned out after each flock grow-out, at which time it is stockpiled in covered storage barns, where it remains until seasonal field application is allowed. During this time, it undergoes varying degrees of composting, including the release of greenhouse gases2,3.
Once regulations permit, the litter is removed from storage and field applied as a crop nutrient amendment, where it again can serve as a potential source of greenhouse gas emission and nutrient contamination, affecting the surrounding surface waters and the Chesapeake Bay. Most states' manure management practices are more lenient than Marylands and, as a result, the potential environmental ramifications are even more significant.
PFED’s Patent-Pending Combined AD + NCS Process
Introduction of Material
PFED’s Combined AD + NCS fundamentally alters traditional manure management practices after the poultry litter is delivered to covered storage. As opposed to allowing a slow composting process, PFED’s system undertakes daily removal, energy production, and nutrient capture on the stockpiled litter.
A skid-steer loader removes the daily allotment of manure and introduces it into a mixing tank, where water is added to create a slurry. Dilution is necessary for three primary reasons: 1) to encourage greater homogeneity in the waste; 2) to provide a means of efficient handling and mixing; and 3) to protect the downstream anaerobic digestion process from the elevated levels of ammonia associated with poultry litter.
Anaerobic Digestion (AD)
From the mixing tank, the poultry litter slurry either undergoes microbial pretreatment or is pumped directly to the AD system, where the anaerobic digestion treatment process is maintained in a controlled, heated (35 ºC/95 °F) environment in order to break down organic matter, solubilize nutrients, remove grit, and create biogas. Biogas is a methane (CH4) containing fuel (50-70% CH4 content) that PFED cleans, meters, and then uses to power combined heat and power (CHP) generators, boilers, and to offset energy use at client facilities. Any excess gas is flared.
The Nutrient Capture System (NCS)
Field Amendment: Following digestion, the treated slurry flows to the computer-automated NCS unit, where it undergoes physical and chemical treatment to remove organically complexed and soluble phosphorus (P) and selectively remove the largest solids. These solids dried for use as a stable, low-odor, high N:P (5:1) agricultural field amendment, suitable for application on most of the Chesapeake Bay Region’s farmland.
Potting Soil & Fertilizer: The finer particulates and P-laden waste water are fed back into the NCS, where the remaining materials undergo dewatering and chemical treatment, removing approximately 75% of the remaining phosphorus and 50% of the remaining total ammoniacal nitrogen. Two products result from this process:
PFED’s Potting Soil: A product with an elemental N:P:K:S ratio of roughly 9:1:2:4
PFED’s P-Based Fertilizer: A phosphorus-based fertilizer containing 6% elemental phosphorus and a combination of ammonium, potassium, sulfur, calcium, magnesium and other nutrients, depending on the original manure composition).
In PFED’s Pilot facility, these products are stockpiled in bulk for sale, with the phosphorus-based fertilizer prepared for transport and sale outside of the Chesapeake Bay Watershed.
Waste Water Recycling: The resulting, cleaned water is polished and recycled back into the AD system.
Automation & Verification
All system tasks apart from the initial loading, fertilizer unloading, and routine operation and maintenance are entirely automated, and each major component of the system in electronically monitored to provide feedback on operation status, process stability, and process efficiency, alerting operators to take any required action before any interruption to the process can occur.
The data collected serve to validate the process and verify the attainment of reporting standards such as those detailed by EPA’s AgSTAR program4.
1 Delmarva Poultry Industry, 2016. A Visual Summary of Historic Data about Delmarva’s Chicken Industry. DPI.
2 Ritz, C. W. & Merka, W. C., 2009. Maximizing Poultry Manure Use Through Nutrient Management Planning. University of Georgia Cooperative Extension.
3 Thorman, R. E. et al., 2006. Nitrous oxide emissions during storage of broiler litter and following application to arable land. Updated Proc. 2nd Int. Conf. Greenh. Gases Anim. Agric.
4 EPA AgSTAR, 2011. Protocol for Quantifying and Reporting the Performance of Anaerobic Digestion Systems for Livestock Manures. Eastern Research Group.
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