Performing Department
Environmental Resources Engineering
Non Technical Summary
• Objective: Dairy farms generate 138 L liquid manure/cow, which has high ammonia concentrations and contributes to air and water pollution due to free ammonia release to air and nitrogen export to water at their production sites and manure-applied land.Anaerobically digested dairy manure has even higher ammonia concentrations. Besides, ammonia accumulation in digesters may inhibit anaerobic digestion at higher organic loading rates. Dairy farms need cost-effective methods to upgrade their nutrient management plans. Traditional wastewater treatment methods are economically prohibitive to remove ammonia from dairy manure. Our goal is to develop an innovative technology coupling vacuum distillation and acid absorption for sustainable recovery of ammonia from anaerobically digested and undigested dairy manure. Ammonia in dairy manure can be distilled under a low vacuum at a temperature below the normal boilingpoint of water and absorbed in a sulfuric acid solution to produce ammonium sulfate as a value-added product. Specific objectives are to 1) evaluate effects of temperature, low vacuum, and solids on ammonia recovery from dairy manure; 2) design an ammonia distillation - acid absorption system to produce ammonium sulfate granules with dairy manure; 3) construct a pilot-scale vacuum distillation - acid absorption system and develop operational parameters; and 4) perform a farm-scale economic analysis of the developed technology across its life cycle. This project will fill a literature gap in the combined effects of temperature, low vacuum, and solids on ammonia distillation. Kinetic study with a pilotscale ammonia recovery system at different feed depth will support design for scale-up,broader applications. Coupling vacuum distillation - acid absorption with anaerobic digestion is anticipated to make ammonia recovery an economically viable technology. The technology to be developed is applicable to dairy farms without anaerobic digesters as well.• Description: Concentrated animal feeding operations need cost-effective technologies to upgrade their nutrient management plans as required by increasingly stringent federal and state regulations. This project will develop a technology to produce a marketable productfrom dairy manure (ammonium sulfate granules as a bio-fertilizer and chemical), thus generating revenues while meeting regulatory requirements for farm nutrient management. By coupling ammonia recovery with anaerobic digestion and biogas energyutilization, heat is recycled, inhibition of ammonia to anaerobic digestion prevented, and greenhouse gas emission reduced. Three graduate students in this P3 team will develop knowledge and skills of sustainable design for wastewater treatment and resource recovery.Undergraduate students and high school students in a Boy Scouts Engineering Camp will gain hands-on skills with the pilot-scale ammonia recovery system and be inspired of sustainable waste management.• Results: A laboratory vacuum distillation - acid absorption assembly will be used to evaluate the efficiency and energy consumption of ammonia distillation under different combinations of temperature and low vacuum with digested and undigested dairy manure that have different salinities as well as manure filtrate. A pilot-scale ammonia recovery system will be operated by batch modes to prove the design concept and determine operational parameters including feed depth and cycle length. The pilot system will include a vacuum still for ammonia vaporization at boiling points lowered by low vacuum, an ammonia absorption column to produce ammonium sulfate granules, and a vacuum pump to bridge the still and absorption column. Cost benefit assessment across life cycle will be performed, taking a large-size dairy farm as an example.Contribution to Pollution Prevention and Control: Animal manure has 0.04-0.88% (wet weight) ammonia, which exists in free ammonia (NH3} and ionized ammonium (NH/). Volatilization of free ammonia may cause air pollution and health risks. Land application of liquid manure may impact on aquatic ecosystems and groundwater resources. Oxidation of ammonia generates greenhouse gas. In combination with anaerobic digestion, the proposed technology will provide dairy farms with a sustainable solution to nutrient management, minimizing the risk of ammonia release and nitrogen export. Ammonia recovery from dairy manure makes productive use of agricultural waste, thus preventing pollution associated with natural gas- and coal-based production of ammonia. The developed technology could also be applied to ammonia recovery from other ammonia-rich wastewater and coupled with anaerobic digestion of other organic wastes such as food waste and municipal sludge.Supplemental Keywords: bio-based feedstock, resource recovery; waste to value; concentrated animal feeding operationsAwarded Start Date: 8/15/2014Sponsor: Environmental Protection Agency
Animal Health Component
(N/A)
Research Effort Categories
Basic
100%
Applied
(N/A)
Developmental
(N/A)
Goals / Objectives
Dairy farms generate 138 L liquid manure/cow, which has high ammonia concentrations and contributes to air and water pollution due to free ammonia release to air and nitrogen export to water at their production sites and manure-applied land.Anaerobically digested dairy manure has even higher ammonia concentrations. Besides, ammonia accumulation in digesters may inhibit anaerobic digestion at higher organic loading rates. Dairy farms need cost-effective methods to upgrade their nutrient management plans. Traditional wastewater treatment methods are economically prohibitive to remove ammonia from dairy manure. Our goal is to develop an innovative technology coupling vacuum distillation and acid absorption for sustainable recovery of ammonia from anaerobically digested and undigested dairy manure. Ammonia in dairy manure can be distilled under a low vacuum at a temperature below the normal boiling point of water and absorbed in a sulfuric acid solution to produce ammonium sulfate as a value-added product. Specific objectives are to 1) evaluate effects of temperature, low vacuum, and solids on ammonia recovery from dairy manure; 2) design an ammoniadistillation - acid absorption system to produce ammonium sulfate granules with dairy manure; 3) construct a pilot-scale vacuum distillation - acid absorption system and develop operational parameters; and 4) perform a farm-scale economic analysis of the developedtechnology across its life cycle. This project will fill a literature gap in the combined effects of temperature, low vacuum, and solids on ammonia distillation. Kinetic study with a pilotscale ammonia recovery system at different feed depth will support design for scale-up,broader applications. Coupling vacuum distillation - acid absorption with anaerobic digestion is anticipated to make ammonia recovery an economically viable technology. The technology to be developed is applicable to dairy farms without anaerobic digesters as well.
Project Methods
Animal feeding operations generate significant volumes of liquid manure, consisting of feces, urine, and milking washwater. Liquid manure is typically applied to cropland directly or after storage in lagoons (ASABE, 2010; USDA, 2009}. One of the major pollutants of animal manure is ammonia. As-removed animal manure has 0.04-0.88% (w/w) ammonia {ASABE, 2010), which exists in free ammonia {NH3} and ionized ammonium (NH/). Concentrated animal feeding operations {CAFOs} often do not have adequate land to absorb all of their manure, resulting in over-application of manure {USDA, 2009; U.S. EPA, 2002}. Animal manure contributes to air pollution through volatilization of free ammonia in animal housing, manure storage and treatment facilities, and manure-applied fields. CAFOs are a major source of ammonia emission (Mukhtar and Samani Maj, 2012). U.S. EPA {2004} estimated stable emission of free ammonia from animal feeding operations at 2.5 million tons per year in 2010-2030. Animal manure also adds pollutant loading to nearby surface water and groundwater due to leakage of manure storage facilities and land application of liquid manure. Large and new CAFOs are required to assure the no-discharge requirement {NVSDEC, 2013; U.S. EPA, 2012, 2008, 2003). Increasingly stringent federal and state regulations compel CAFOs to upgrade their nutrient management plans. CAFOs have to consider on-farm manure treatment.Anaerobic digestion is increasingly applied to liquid manure to stabilize organic matter, reduce pathogens, eliminate offensive odors, and recover energy from biogas {U.S. EPA, 2010; USDA, 2009}. As of April 2010, there are 124 anaerobic digester systems operating at dairy farms in the U.S. {U.S. EPA, 2010}. However, anaerobic digestion converts organic nitrogen and phosphorus to ammonia and phosphate, making nutrient export from manure applied land even riskier (Gungor et al., 2007}. The Pl has been developing a sustainable dairy manure management scheme {Figure 1). The Pl's team, in collaboration with Twin Birch Dairy, separates solids from liquid of anaerobically digested dairy manure with a passive filtration system (Xia et al., 2012}. Orthophosphate, ammonium, and magnesium in the manure filtrate (liquid portion) could be recovered as a compound fertilizer, magnesium ammonium phosphate hexahydrate, commonly known as struvite (Huchzermeier and Tao, 2012). Even with more than 95% of phosphorus removal, struvite recovery removes only 15% of total ammonia in the manure filtrate. Our long-term goal is to develop a vacuum distillation - acid absorption system for sustainable recovery of ammonia from anaerobically digested dairy manure, undigested dairy manure, and manure filtrate. Coupling ammonia and struvite recovery with anaerobic digestion presents an integrated, closed-cycle solution to manure management.This P3 project is designed to meet CAFOs' need for cost-effective technologies to upgrade their nutrient management plans. Anaerobic digesters are typically installed with a combined heat and power system to utilize biogas, which can be used to heat manure from digester temperature (35 or 55 °C) to distillation temperatures and maintain a low vacuum for ammonia recovery. The ammonia-recovered hot manure is returned to digesters for heat recycling. For CAFOs without anaerobic digesters, photovoltaics is a promising source of renewable energy to power ammonia distillation - acid absorption systems because the space to install photovoltaic modules could be easily found at farms· (Chow, 2010}. Besides, this ammonia recovery technology can be coupled with anaerobic digestion of food waste, municipal sludge, and other similar agricultural wastes. Anaerobic digestion of protein-rich organic wastes faces process instability issue at higher organic loading rates, especially under thermophilic conditions, due to accumulation of ammonia and subsequent inhibition to methanogens (Agyeman and Tao, 2014; Pitk et al., 2013; Yenigun and Demirel, 2013; Zhang et al., 2013; Banks et al., 2012; Zhang et al., 2012). When anaerobic digestion is coupled with ammonia recovery, anaerobic digestion could be loaded at a higher rate while maintaining stable operation.The objectives of this P3 project are:1. To evaluate the effects of temperature and low vacuum on ammonia recovery from anaerobically digested dairy manure, undigested dairy manure, filtrate of digested dairy manure, and filtrate of undigested dairy manure, respectively.2. To design a vacuum distillation - acid absorption system for recovery of ammonia as ammonium sulfate at dairy farms.3. To construct a pilot-scale vacuum distillation - acid absorption system and develop operational parameters for ammonia recovery from dairy manure.4. To perform an economic life cycle assessment to evaluate ammonia recovery options with different types of feedstock at a large-size dairy farm.Cost-effective treatment of liquid manure has been a challenge for many dairy farms. Wastewater treatment methods such as air stripping, nitrification-denitrification, partial nitrification-anammox, and membrane distillation remove ammonia out of water (Wen et al.,2013; Xie et al., 2009; EL-Bourawi et al., 2007; Metcalf & Eddy, 2003}, but there are no value added products. Rather, ammonia recovery extracts ammonia from waste and produces marketable products. Ammonia recovery from dairy and swine manure has been investigatedusing methods such as coupled membrane permeation and acid absorption (Mukhtar and Samani Maj, 2012; Sato et al., 2006), electrodialysis and reverse osmosis (Mondor et al., 2008), production of algae and duckweed (Cheng et al., 2002; Wilkie and Mulbry, 2002}, coupled airstripping and acid absorption (Rulkens et al., 1998}, and struvite precipitation (Huchzermeier and Tao, 2012; Rico et al., 2011; Uludag-Demirer et al., 2008; Zeng and Li, 2006}. Nevertheless, the research has not resulted in industry adoption due to technical challenges, economic constraints, limited efficiency, or complex operation and maintenance requirements.Distillation is a method of separating substances based on differences in volatility of the components in a boiling liquid mixture. Although ammonia distillation is used as a method to concentrate ammonia for analysis (APHA et al., 1998}, it has rarely been addressed as anengineered process to recover ammonia. When a low vacuum is applied to an enclosed still, boiling point is reduced. Uchida et al. (1997) introduced steam to a Kjeldahl distillation assembly for ammonia distillation from 100 ml of 0.1-2.0 N ammonium nitrate solutions andobtained up to 91% ammonia recovery in 0.25-2 hours at 100 °C. In contrast, Udert and Wachter (2012) recovered only 1.5-3.0% ammonia as ammonium nitrate by drying 200 ml of nitrified urine in a Buchi rotavapor under reduced pressure at 78 °C for 1 h. This low ammonia recovery percentage was attributed to the low pH (6.0-7.2). Beyond these two laboratory studies, little is reported on distillation for ammonia recovery at scales beyond lab glassware.Unlike ammonia recovery through water vaporization, ammonia distillation may make advantage of the lower boiling point of ammonia {-3334 °C) relative to water, thus requiring much less energy for heating.