Recovering phosphorus as a coproduct from corn dry grind plants: A techno‐economic evaluation

Abstract

Background and objectives The coproduct of ethanol industry, dried distiller's grains with solubles (DDGS), has phosphorus content in excess of the animal diet requirement, which leads to excess P in manure and causes environmental concerns. The objective of this study is to determine the technical and economic feasibility of recovering this excess P as a coproduct. Findings The amount of P was observed to reduce from 9.26 to 3.25 mg/g (db) of DDGS, which is consistent with the animal diet requirement of 3–4 mg P/g animal diet. For an existing dry grind plant of 40 million gallon ethanol capacity, an additional fixed cost of $5.7 million was estimated, with an operating cost increase of $1.29 million/year. Conclusions The total phosphorus recovered from the plant was estimated as 1,676 kg P/day, with an estimated operating cost of $2.33/kg P recovered. Significance and novelty Approximately 37 million MT of DDGS is produced annually as animal food containing excess P, which is a serious concern for the environment. This study provides with an economically feasible solution to recover the excess P as a coproduct, which has a potential to be used as fertilizer on more than 56,000 acres of land annually, growing corn and soybean.

Mapping the National Phosphorus Recovery Potential from Centralized Wastewater and Corn Ethanol Infrastructure

“…P recovery from large WRRFs in the Midwest has a direct influence on the reduction of P discharge, while P recovery from the large corn biorefineries could reduce embedded P in livestock feed. In states like Iowa, Wisconsin, Minnesota, and Missouri with high livestock populations, the reduction of P at biorefineries could also decrease the risk of manure P losses to surface water due to the lower P content in biorefinery coproducts used in animal feeds. − The mismatch of manure N/P with crop N/P needs means that application of manure to meet crop N needs entails excessive application of P and thus aggravated P loss risk to surface waters . Decreasing the manure P content by reducing the amount of P fed to animals thereby stands to mitigate manure-based contributions to non-point source P losses, which in some watersheds of the US Corn Belt are thought to be the major driver …”

“…The process models for P recovery in wet milling and dry grind processes were developed using SuperPro Designer (Intelligen Inc., Scotch Plains, NJ, USA) and were based on previously developed models. , Models were run at varying grind rates to develop a linear relationship between the grind rate and rP potential for both wet milling and dry grind processes (Figure S1). A detailed description of the models is available in the existing literature. , For additional details on wet milling and dry grind process simulations, refer to the Supporting Information (SI) (Methods S1 and S2, respectively).…”

“…Although approximately 1.71 Gg of P as the fertilizer is applied annually to US croplands, nearly 0.54 Gg of P enters water bodies due to soluble and erosive losses . Recovery and agricultural reuse of P from wastewater and aqueous food processing streams can both reduce the amount of phosphate rock needed while also reducing the amount of P in livestock feed that would eventually be lost to water bodies from animal waste streams. − Outside of P recovery that is already done (e.g., land application of manure and wastewater sludge), human waste and animal manure present two main untapped pathways for renewable P (rP).…”

“…In contrast, most manuresthough highly variable in N/P based on species, diet, and manure storagegenerally have a lower N/P than crop needs, meaning that the typical use of manure to meet crop N needs will entail overapplication of P . Although there is work outlining the rP potential from corn biorefineries , and the technology for recovery does exist, they are often overlooked as a source of rP since they are upstream of P loss through animal waste, and the magnitude of recovery potential at the national scale is yet to be elucidated.…”

“…5 Recovering and concentrating P upstream at biorefineries allow for application of rP that meets, but does not exceed, crop needs. In contrast, most manuresthough highly variable in N/P based on species, diet, and manure storage 16 generally have a lower N/P than crop needs, 17 meaning that the typical use of manure to meet crop N needs will entail overapplication of P. 18 Although there is work outlining the rP potential from corn biorefineries 6,7 and the technology for recovery does exist, they are often overlooked as a source of rP since they are upstream of P loss through animal waste, and the magnitude of recovery potential at the national scale is yet to be elucidated. This work had two primary objectives: (i) to quantify US potential rP supply from centralized grain processing and waste handling infrastructure, specifically corn ethanol biorefineries and WRRFs, and map co-location with P consumption and (ii) to assess the impacts of rP transport and blending with synthetic P fertilizer on rP supply co-location with crop P consumption.…”