The Michigan EnviroImpact Tool: A Supporting Tool to Help Farmers in Forecasting Manure Nutrient Runoff Risk

The purpose of the MI EnviroImpact Tool is to provide farmers with a daily runoff risk decision support tool that can aid in effectively planning short-term manure and nutrient application. This not only helps keep nutrients on the field and potentially saves money, but it also helps to protect our waterways in Michigan.

Lifecycle of manure nutrients
Figure 1. Livestock operations are a readily available source of manure nutrients. With effective nutrient application, farmers might be able to reduce the use of commercial fertilizers and save money.
With the MI EnviroImpact tool, farmers are able to plan for effective short-term manure application.
Figure 2. With the MI EnviroImpact tool, farmers are able to plan for effective short-term manure application.

What did we do?

Farmer interest groups were pulled together for initial piloting and testing of the MI EnviroImpact tool to hear what worked and what needed improvement. The goal was to make this a very user-friendly tool that everyone could use. Additionally, educational and outreach materials were created (factsheet, postcard, YouTube videos, and presentations) to help get the word out about this decision support tool. The ultimate goal of the MI EnviroImpact tool is for use as a decision support tool for short-term manure and nutrient application. The tool derives the runoff risk forecast from real-time precipitation and temperature forecasts. This information is then combined with snow melt, soil moisture and temperature, and other landscape characteristics  to forecast times when the risk of runoff will be higher. The MI EnviroImpact tool is applicable in all seasons and has a winter mode for times when the average daily snow depth is greater than 1 inch or the 3-day average soil temperature (top 2 inches) is below freezing.

The MI EnviroImpact tool displaying both winter and non-winter modes of daily runoff risk.
Figure 3. The MI EnviroImpact tool displaying both winter and non-winter modes of daily runoff risk.

What did we learn?

Through our work with the MI EnviroImpact Tool and those that helped to develop this tool, we were able to spread awareness of this user-friendly tool, so that more farmers would be likely to use it to help in nutrient application planning. Furthermore, those outside of the farming community have been very encouraged to see that agriculture is continuing to take steps in being environmentally friendly. Additionally, others have viewed this tool as a resource outside of farmers, showing that the MI EnviroImpact Tool has broader implications than just agriculture.

Future Plans

Future plans include continuing education about the MI EnviroImpact Tool as well as continued distribution of educational materials to help spread awareness of the tool itself.

Additional Information

Those who would like to learn more about the MI EnviroImpact Tool can visit the following links:

Acknowledgements

This project was prepared by MSU under award NA14OAR4170070 from the National Oceanic and Atmospheric Administration, U.S. Department of Commerce through the Regents of the University of Michigan. The statements, findings, conclusions, and recommendations are those of the author(s) and do not necessarily reflect the views of the National Oceanic and Atmospheric Administration, the Department of Commerce, or the Regents of the University of Michigan.

MSU is an affirmative-action, equal-opportunity employer, committed to achieving excellence through a diverse workforce and inclusive culture that encourages all people to reach their full potential. Michigan State University Extension programs and materials are open to all without regard to race, color, national origin, gender, gender identity, religion, age, height, weight, disability, political beliefs, sexual orientation, marital status, family status or veteran status. Issued in furtherance of MSU Extension work, acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture. Jeff Dwyer, Director, MSU Extension, East Lansing, MI 48824. This information is for educational purposes only. Reference to commercial products or trade names does not imply endorsement by MSU Extension or bias against those not mentioned.

Partners and funding sources involved in supporting, developing, and implementing the MI EnviroImpact tool.
Figure 4. Partners and funding sources involved in supporting, developing, and implementing the MI EnviroImpact tool.

Project Collaborators:

Heather A. Triezenberg, Ph.D.
Extension Specialist and Program Leader, Michigan Sea Grant
Michigan State University Extension
Community, Food and Environment Institute
Fisheries and Wildlife Department
Meaghan Gass
Sea Grant Extension Educator
Michigan State University Extension

Jason Piwarski
GIS Specialist
Michigan State University
Institute of Water Research

Dustin Goering
Senior Hydrologist
North Central River Forecast Center
NOAA National Weather Service

Cindy Hudson
Communications Manager, Michigan Sea Grant
Community, Food & Environment Institute
Michigan State University Extension

Jeremiah Asher
Assistant Director
Institute of Water Research
Michigan State University

Kraig Ehm
Multimedia Producer
ANR Communications and Marketing
College of Agriculture and Natural Resources
Michigan State University

Luke E. Reese
PhD, Associate Professor
Biosystems and Agricultural Engineering
Michigan State University

Marilyn L. Thelen
Associate Director, Agriculture and Agribusiness Institute
Michigan State University Extension

Todd Marsee
Senior Graphic Designer
Michigan Sea Grant
University of Michigan

Mindy Tape
Manager
ANR Communications & Marketing
Michigan State University Extension

 

 

The authors are solely responsible for the content of these proceedings. The technical information does not necessarily reflect the official position of the sponsoring agencies or institutions represented by planning committee members, and inclusion and distribution herein does not constitute an endorsement of views expressed by the same. Printed materials included herein are not refereed publications. Citations should appear as follows. EXAMPLE: Authors. 2019. Title of presentation. Waste to Worth. Minneapolis, MN. April 22-26, 2019. URL of this page. Accessed on: today’s date.

Cataloging and Evaluating Dairy Manure Treatment Technologies


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Purpose

To provide a forum for the introduction and evaluation of technologies that can treat dairy manure to the dairy farming community and the vendors that provide these technologies.

What Did We Do?

Newtrient has developed an on-line catalog of technologies that includes information on over 150 technologies and the companies that produce them as well as the Newtrient 9-Point scoring system and specific comments on each technology by the Newtrient Technology Advancement Team.

What Have We Learned?

Our interaction with both dairy farmers and technology vendors has taught us that there is a need for accurate information on the technologies that exist, where they are used, where are they effective and how they can help the modern dairy farm address serious issues in an economical and environmentally sustainable way.

Future Plans

Future plans include expansion of the catalog to include the impact of the technology types on key environmental areas and expansion to make the application of the technologies on-farm easier to conceptualize.

Corresponding author name, title, affiliation  

Mark Stoermann & Newtrient Technology Advancement Team

Corresponding author email address  

info@newtrient.com

Other Authors 

Garth Boyd, Context

Craig Frear, Regenis

Curt Gooch, Cornell University

Danna Kirk, Michigan State University

Mark Stoermann, Newtrient

Additional Information

http://www.newtrient.com/

Acknowledgements

All of the vendors and technology providers that have worked with us to make this effort a success need to be recognized for their sincere effort to help this to be a useful and informational resource.

The authors are solely responsible for the content of these proceedings. The technical information does not necessarily reflect the official position of the sponsoring agencies or institutions represented by planning committee members, and inclusion and distribution herein does not constitute an endorsement of views expressed by the same. Printed materials included herein are not refereed publications. Citations should appear as follows. EXAMPLE: Authors. 2017. Title of presentation. Waste to Worth: Spreading Science and Solutions. Cary, NC. April 18-21, 2017. URL of this page. Accessed on: today’s date.

USDA-NRCS and the National Air Quality Site Assessment Tool (NAQSAT) for Livestock and Poultry Operations

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Purpose

The National Air Quality Site Assessment Tool (NAQSAT) was developed as a first-of-its-kind tool to help producers and their advisors assess the impact of management on air emissions from livestock and poultry operations and identify areas for potential improvement related to those air emissions.

What did we do?

In 2007, several land-grant universities, with leadership from Michigan State University, began developing NAQSAT under a USDA-NRCS Conservation Innovation Grant (CIG). The initial tool included beef, dairy, swine, and poultry operations. A subsequent CIG project, with leadership from Colorado State University, made several enhancements to the tool, including adding horses to the species list. In 2015, USDA-NRCS officially adopted NAQSAT as an approved tool for evaluating air quality resource concerns at livestock and poultry operations. USDA-NRCS also contracted with Florida A&M University in 2015 to provide several regional training workshops on NAQSAT to NRCS employees. Six training workshops have been completed to date (Raleigh, NC; Modesto, CA; Elizabethtown, PA; Lincoln, NE; Richmond, VA; and Yakima, WA) with assistance from multiple NAQSAT development partners. Additionally, USDA-NRCS revised its comprehensive nutrient management plan (CNMP) policy in October 2015 to make the evaluation of air quality resource concerns mandatory as part of CNMP development.

Snippet from website of the National Air Quality Site Assessment Tool

Group photo of team in field

Zwicke in class lecturing

Zwicke and group in animal housing facility

What have we learned?

NAQSAT has proven to be a useful tool for bench-marking the air emissions impacts of current management on confinement-based livestock and poultry operations. In the training sessions, students have been able to complete NAQSAT runs on-site with the producer or producer representative via tablet or smartphone technologies. Further classroom discussion has helped to better understand the questions and answers and how the NAQSAT results can feed into the USDA-NRCS conservation planning process. Several needed enhancements and upgrades to the tool have been identified in order to more closely align the output of the tool to USDA-NRCS conservation planning needs. NAQSAT has also proven to be useful for evaluating the air quality resource concern status of an operation in relation to the CNMP development process.

Future Plans

It is anticipated that the identified needed enhancements and upgrades will be completed as funding for further NAQSAT development becomes available. Additionally, as use of NAQSAT by USDA-NRCS and our conservation planning and CNMP development partners expands, additional training and experience-building opportunities will be needed. The NAQSAT development team has great geographic coverage to assist in these additional opportunities.

Corresponding author, title, and affiliation

Greg Zwicke, Air Quality Engineer – Air Quality and Atmospheric Change Team, USDA-NRCS

Corresponding author email

greg.zwicke@ftc.usda.gov

Other authors

Greg Johnson, Air Quality and Atmospheric Change Team Leader, USDA-NRCS; Jeff Porter, Animal Nutrient and Manure Management Team Leader, USDA-NRCS; Sandy Means, Agricultural Engineer – Animal Nutrient and Manure Management Team, USDA-NRCS

Additional information

naqsat.tamu.edu

https://lpelc.org/naqsat-for-swine-and-poultry

https://lpelc.org/naqsat-for-beef-and-dairy/

Acknowledgements

C.E. Meadows Endowment, Michigan State University

Colorado Livestock Association

Colorado State University

Florida A&M University

Iowa Turkey Federation

Iowa Pork Producers

Iowa Pork Industry Center

Iowa State University

Iowa State University Experiment Station

Kansas State University

Michigan Milk Producers Association

Michigan Pork Producers Association

Michigan State University

Michigan State University Extension

National Pork Board

Nebraska Environmental Trust

Oregon State University

Penn State University

Purdue University

Texas A&M University

University of California, Davis

University of Georgia

University of Georgia Department of Poultry Science

University of Idaho

University of Maryland

University of Maryland Department of Animal and Avian Sciences

University of Minnesota

University of Missouri

University of Nebraska

USDA-ARS

Virginia Tech University

Washington State University

Western United Dairymen

Whatcom County (WA) Conservation District

The authors are solely responsible for the content of these proceedings. The technical information does not necessarily reflect the official position of the sponsoring agencies or institutions represented by planning committee members, and inclusion and distribution herein does not constitute an endorsement of views expressed by the same. Printed materials included herein are not refereed publications. Citations should appear as follows. EXAMPLE: Authors. 2017. Title of presentation. Waste to Worth: Spreading Science and Solutions. Cary, NC. April 18-21, 2017. URL of this page. Accessed on: today’s date.

Nitrogen and Phosphorus Cycling Efficiency in US Food Supply Chains – A National Mass-Balance Approach


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Purpose 

Assessing and improving the sustainability of livestock production systems is essential to secure future food production. Crop-livestock production systems continue to impact nitrogen (N) and phosphorus (P) cycles with repercussions for human health (e.g. secondary particle formation due to ammonia emission and drinking water contamination by nitrate) and the environment (e.g. eutrophication of lakes and coastal waters and exacerbation of hypoxic zones). Additionally, P is a limited resource, and sustaining an adequate P supply is a major emerging challenge. To develop strategies for a more sustainable use of N and P, it is essential to have a quantitative understanding of the flows and stocks of N and P within the society. In this study, we developed detailed national N and P budgets to assess nutrient cycling efficiency in US (livestock) food supply chains, to identify hotspots of nutrient loss and to indicate opportunities for improvement!

What did we do? 

1. National nutrient mass-balance

A mass-balance framework was developed to quantify nutrient flows within the US. In this framework, the national US system is represented by 9 major sectors are relevant in terms of nutrient flows: mining (relevant for P only), industrial production, agriculture, food & feed processing industry, retail, households and other consumers, energy and transport, humans, and waste treatment. These sectors can exist of several sub-sectors. For example, the agricultural sector consists of several secondary sub-systems including pasture, agricultural soil, livestock and manure management (WMS – waste management system).

Different livestock categories can have distinct environmental impacts and nutrient use efficiencies (e.g. (Hou et al. 2016), (Eshel et al. 2014), (Herrero et al. 2013)), we therefore distinguish six livestock categories (dairy cattle, beef cattle, poultry (meat), poultry (layers), sheep, hogs) and

 their associated food commodities (dairy products, beef from dairy cattle, beef, poultry, eggs, lamb, pork).

For each sub-system, we identify and quantify major flows to and from this compartment. All flows are expressed in a common unit, i.e. metric kiloton N per year (kt N/yr) for nitrogen and metric kiloton P per year (kt P/yr) for phosphorus. Quantified flows include nutrient related emissions to the environment and waste flows.

At present, the waste sectors and environmental compartment are outside the system boundaries, that is, we quantify flows to these compartments, but we do not attempt to balance these sectors. We do, however, keep track of the exact chemical species (e.g. emission of N2O-N to air instead of N to air) emitted as far as possible. The municipal waste treatment (MSW) and municipal waste water treatment (WWTP) are treated in more detail: major flows from and to these compartments are quantified. These sub-sectors are treated in more detail because of their role in nutrient recycling through e.g. sewage sludge application on agricultural soils.

Data were collected in priority from national statistics (e.g. USDA NASS for livestock population) and peer-reviewed literature, and were supplemented with information from industrial reports and extension files if needed. If available, data were collected for the years 2009 to 2012 and averaged, when unavailable, we collected data for the closest year.

2. Scenario analysis

In the scenario analysis, we test the opportunity for dairy livestock production systems to contribute to a more efficient nutrient use through anaerobic co-digestion of dairy manure and organic food waste. Recently, Informa Economics assessed the national

 market potential of anaerobic digester products for the dairy industry (Informa Economics 2013). Next to a reduction in greenhouse gas emissions, anaerobic co-digestion of dairy manure and organic food waste can contribute to improve nutrient cycling efficiency (Informa Economics 2013). Dairy manure contains high levels of nitrogen and phosphorus, which can be used as a natural crop fertilizer, if recuperated from manure. Presently, non-farm organic substrates such as food waste are typically disposed of in landfills, which causes greenhouse gas (GHG) emissions and also results in a permanent removal of valuable nutrients from the food supply chain (Informa Economics 2013). By anaerobic co-digestion, a part of the nutrien! ts contai ned in dairy manure and food waste can be recovered. These nutrients can be used to fertilize crops and substitute synthetic fertilizer application. In the scenario analysis, we test to what extent anaerobic co-digestion of dairy manure and food waste can contribute to improve nutrient cycling efficiency, particularly by substituting synthetic fertilizers. We develop the scenario based on data provided in the InformaEconomics report.

What have we learned? 

In general, our results show that livestock production is the least efficient part of the total food supply chain with large losses associated with manure management and manure and fertilizer application to crops. In absolute terms, the contribution of the household stage to total and N and P losses from the system is small, approximately 5 and 7% for N and P, respectively. However, households ‘waste’ a relatively large percentage of purchased products, (e.g. 16% and 18% of N and P in dairy products end up as food waste), which presents an opportunity for improvement. A scenario was developed to test to what extent anaerobic co-digestion of dairy manure and food waste can contribute to improving nutrient cycling efficiency on a national scale. Results suggest that 22% and 63% of N and P applied as synthetic fertilizer could potentially be avoided in dairy food supply chains by large scale implementation of anaerobic co-digestion o! f manure and food waste.

Future Plans     

Future research plans include a further development of scenarios that are known to reduce nutrient losses at the farm scale and to assess the impact of these scenarios on national nutrient flows and losses.

Corresponding author, title, and affiliation        

Karin Veltman, PhD, University of Michigan, Ann Arbor

Corresponding author email    

veltmank@umich.edu

Other authors    

Carolyn Mattick, Phd, Olivier Jolliet, Prof., Andrew Henderson, PhD.

Additional information                

Additional information can be obtained from the corresponding author: Karin Veltman, veltmank@umich.edu

Acknowledgements       

The authors wish to thank Ying Wang for her scientific support, particularly for her contribution in developing the anaerobic co-digestion scenario.

This work was financially supported by the US Dairy Research Institute.

 

The authors are solely responsible for the content of these proceedings. The technical information does not necessarily reflect the official position of the sponsoring agencies or institutions represented by planning committee members, and inclusion and distribution herein does not constitute an endorsement of views expressed by the same. Printed materials included herein are not refereed publications. Citations should appear as follows. EXAMPLE: Authors. 2017. Title of presentation. Waste to Worth: Spreading Science and Solutions. Cary, NC. April 18-21, 2017. URL of this page. Accessed on: today’s date.

Planning for Resilience: Using Scenarios to Address Potential Impacts of Climate Change for the Northern Plains Beef System

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Purpose

Resiliency to weather extremes is a topic that Northern Plains farmers and ranchers are already familiar with, but now climate change is adding new uncertainties that make it difficult to know the best practices for the future. Scenario planning is a method of needs assessment that will allow Extension and beef system stakeholders to come together using the latest climate science to discover robust management options, highlight key uncertainties, prioritize Extension programming needs, and provide an open forum for discussion for this sometimes controversial topic.

Overall objectives:

1. Determine a suite of key future scenarios based on climate science that are plausible, divergent, relevant, and challenging to the beef industry.

2. Determine robust management options that address the key scenario drivers.

3. Develop a plan for Extension programming to address determined educational needs.

What did we do?

A team of researchers, Extension specialists, and educators was formed with members from University of Nebraska and South Dakota State University. They gathered the current research information on historical climate trends, projections in future climate for the region, and anticipated impacts to the beef industry. These were summarized in a series of white papers.

Three locations were selected to host two half day focus groups, representing the major production regions. A diverse group representing the beef industry of each region including feedlot managers, cow calf ranchers, diversified producers, veterinarians, bankers, NRCS personnel, and other allied industries. The first focus group started with a discussion of the participants past experiences with weather impacts. The team then provided short presentations starting with historic climate trends and projection, anticipated impacts, and uncertainties. The participants then combined critical climate drivers as axis in a 2×2 grids, each generating a set of four scenarios. They then listed impacts for each combination. The impacts boundaries were feed production through transporting finished cattle off-farm.

Project personnel then combined the results of all three locations to prioritize the top scenarios, which were turned into a series of graphics and narratives. The participants were then brought together for a second focus group to brainstorm management and technology options that producers were already implementing or might consider implementing. These were then sorted based on their effectiveness across multiple climate scenarios, or robustness. The options where also sorted by the readiness of the known information: Extension materials already available, research data available but few Extension materials, and research needed.

Graphic depicting warm/dry, warm/wet, cold/dry, cold/wet conditions on the farm during winter-spring

Graphic depicting hot/dry, hot/wet, cool/dry, cool/wet conditions on the farm during summer-fall

What have we learned?

The key climate drivers were consistent across all focus groups: temperature and precipitation, ranging from below average to above average. In order to best capture the impacts, the participants separated winter/spring and summer/fall.

This method of using focus groups as our initial interaction with producers on climate change was well received. Most all farmers love to talk about the weather, so discussing historical trends and their experiences with it as well as being upfront with the uncertainties in future projections, while emphasizing the need for proactive planning seemed to resonate.

With so many competing interests for producers’ time, as well as a new programming area, it was critical to have trusted local educators to invite participants. Getting participants to the second round of focus groups was also more difficult, so future efforts should considering hosting a single, full day focus group, or allowing the participants to set the date for the second focus group, providing more motivation to attend.

Future Plans

The scenarios and related management options will be used to develop and enhance Extension programming and resources as well as inform new research efforts. The goal is to provide a suite of robust management options and tools to help producers make better decisions for their operation.

Corresponding author, title, and affiliation

Crystal Powers, Extension Engineer, University of Nebraska – Lincoln

Corresponding author email

cpowers2@unl.edu

Other authors

Rick Stowell, Associate Professor at University of Nebraska – Lincoln

Additional information

Crystal Powers

402-472-0888

155 Chase Hall, East Campus

Lincoln, NE 68583

Acknowledgements

Thank you to the project team:

University of Nebraska – Lincoln: Troy Walz, Daren Redfearn, Tyler Williams, Al Dutcher, Larry Howard, Steve Hu, Matthew Luebbe, Galen Erickson, Tonya Haigh

South Dakota State University: Erin Cortus, Joseph Darrington,

This project was supported by the USDA Northern Plains Regional Climate Hub and Agricultural and Food Research Initiative Competitive Grant No. 2011-67003-30206 from the USDA National Institute of Food and Agriculture.

The authors are solely responsible for the content of these proceedings. The technical information does not necessarily reflect the official position of the sponsoring agencies or institutions represented by planning committee members, and inclusion and distribution herein does not constitute an endorsement of views expressed by the same. Printed materials included herein are not refereed publications. Citations should appear as follows. EXAMPLE: Authors. 2017. Title of presentation. Waste to Worth: Spreading Science and Solutions. Cary, NC. April 18-21, 2017. URL of this page. Accessed on: today’s date.

Early Stage Economic Modeling of Gas-permeable Membrane Technology Applied to Swine Manure after Anaerobic Digestion

 

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Purpose

The objective of this study was to conduct cost versus design analysis for a gas-permeable membrane system using data from a small pilot scale experiment and projection of cost versus design to farm scale.

What did we do?

This reported work includes two major steps. First, the design of a small pilot scale batch gas-permeable membrane system was scaled to process effluent volumes from a commercial pig farm. The scaling design maintained critical process operating parameters of the experimental membrane system and introduced assumed features to characterize effluent flows from a working pig farm with an anaerobic digester. The scaled up design was characterized in a spreadsheet model. The second step was economic analysis of the scaled-up model of the membrane system. The objective of the economic analysis was to create information to guide subsequent experiments towards commercial development of the technology. The economic analysis was performed by introducing market prices for components, inputs, and products and then calculating effects on costs and on performance of changes in design parameters.

What have we learned?

First, baseline costs and revenues were calculated for the scaled up experimental design. The commercial scale design of a modular gas-permeable membrane system was modeled to treat 6 days accumulation of digester effluent at 16,300 gallons per day resulting in a batch capacity of 97,800 gallons. The modeled large scale system is 19,485 times the capacity of the 5.02 gallon experimental pilot system. The installation cost of the commercial scale system was estimated to be $903,333 for a system treating 97,800 gallon batches over a 6 day period.

At $1/linear ft. and 7.9 ft./gallon of batch capacity, membrane material makes up 86% of the estimated installation cost. Other installation costs include PVC pipes, pumps, aerators, tanks, and other parts and equipment used to assemble the system, as well as water to dilute the concentrated acid prior to initiating circulation. The annual operating cost of the system includes concentrated sulfuric acid consumed in the process. Using limited experimental data on this point, we assume a rate of 0.009 gallons (0.133 pounds) of acid per gallon of digester effluent treated. At a price of $1.11 per gallon ($0.073/lb) of acid, acid cost per gallon of effluent treated is $0.010. Other operating costs include electric power, labor, and repairs and maintenance of the membrane and other parts of the system estimated at 2% of investment cost for non-moving parts and 6% of investment for moving parts. Potential annual revenue from the system includes the value of ammonium sulfate produced. Over the 6 day treatment period, if 85% of the TAN-N in the digester effluent is removed by the process, and if 100% of the TAN-N removed is recovered as ammonium sulfate, and given the TAN-N concentration in digester effluent was 0.012 pounds per gallon (1401 mg/l), then 0.01 pounds of TAN-N are captured per gallon of effluent treated. At an ammonium sulfate fertilizer price of $588/ton or $0.294/pound and ammonium sulfate production of 0.047 pounds (0.01 pounds TAN-N equivalent), potential revenue is $0.014 per gallon of effluent treated. No price is attached here for the elimination of internal and external costs associated with potential release to the environment of 0.01 pounds TAN-N per gallon of digester effluent or 59,073 pounds TAN-N per year from the system modeled here.

Several findings and questions, reported here, are relevant to next steps in experimental evaluation and commercial development of this technology.

1. Membrane price and/or performance can be improved to substantially reduce installation cost. Membrane material makes up 86% of the current estimated installation cost. Each 10% reduction in the product of membrane price and length of membrane tube required per gallon capacity reduces estimated installation cost per gallon capacity by 8.6%.

2. The longevity and maintenance requirements of the membrane in this system were not examined in the experiment. Installation cost recovery per gallon of effluent decreases at a declining rate with longevity. For example, Cost Recovery Factors (percentage of initial investment charged as an annual cost) at 6% annual interest rate vary with economic life of the investment as follows: 1 year life CRF = 106%, 5 year life CRF = 24%, 10 year life CRF = 14% . Repair costs are often estimated as 2% of initial investment in non-moving parts. In the case of the membrane, annual repair and maintenance costs may increase with increased longevity. Longevity and maintenance requirements of membranes are important factors in determining total cost per gallon treated.

3. Based on experimental performance data (TAN removal in Table 1) and projected installation cost for various design treatment periods ( HRT = 2, 3, 4, 5, or 6 days), installation cost per unit mass of TAN removal decreases and then increases with the length of treatment period. The minimum occurs at HRT = 4 days when 68% reduction of TAN-N in the effluent has been achieved.

Table 1. Comparison of installation cost and days of treatment capacity

4. Cost of acid relative to TAN removal from the effluent and relative to fertilizer value of ammonium sulfate produced per gallon of effluent treated are important to operating cost of the membrane system. These coefficients were beyond the scope of the experiment although some pertinent data were generated. Questions are raised about the fate of acid in circulation. What fraction of acid remains in circulation after a batch is completed? What fraction of acid reacts with other constituents of the effluent to create other products in the circulating acid solution? What fraction of acid escapes through the membrane into the effluent? Increased efficiency of TAN removal from the effluent per unit of acid consumed will reduce the cost per unit TAN removed. Increased efficiency of converting acid to ammonium sulfate will reduce the net cost of acid per gallon treated.

5. Several operating parameters that remain to be explored affect costs and revenues per unit of effluent treated. Among those are parameters that potentially affect TAN movement through the membrane such as: a) pH of the effluent and pH of the acid solution in circulation, b) velocity of liquids on both sides of the membrane, and c) surface area of the membrane per volume of liquids; effluent and acid solution, in the reactor. Similarly, the most profitable or cost effective method of raising pH of the digester effluent remains to be determined, as it was beyond the scope of the current study. Aeration was used in this experiment and in the cost modeling. Aeration may or may not be the optimum method of raising pH and the optimum is contingent on relative prices of alternatives as well as their effect on overall system performance. Optimization of design to maximize profit or minimize cost requires knowledge of these performance response functions and associated cost functions.

6. Management of ammonium sulfate is a question to be addressed in future development of this technology. Questions that arise include: a) how does ammonium sulfate concentration in the acid solution affect rates of TAN removal and additional ammonia sulfate production, b) how can ammonium sulfate be removed from, or further concentrated in, the acid solution, c) can the acid solution containing ammonium sulfate be used without further modification and in which processes, d) what are possible uses for the acid solution after removal of ammonium sulfate, e) what are the possible uses for the effluent after removal of some TAN, and f) what are the costs and revenues associated with each of the alternatives. Answers to these questions are important to designing the membrane system and associated logistics and markets for used acid solution and ammonium sulfate. The realized value of ammonium sulfate and the cost (and revenue) of used acid solution are derived from optimization of this p art of the system.

7. LCA work on various configurations and operating parameters of the membrane system remains to be done. Concurrent with measurement of performance response functions for various parts of the membrane system, LCA work will quantify associated use of resources and emissions to the environment. Revenues may arise where external benefits are created and markets for those benefits exist. Where revenues are not available, marginal costs per unit of emission reduction or resource extraction reduction can be calculated to enable optimization of design across both profit and external factors.

Future Plans

A series of subsequent experiments and analyses are suggested in the previous section. Suggested work is aimed at improving knowledge of performance response to marginal changes in operating parameters and improving knowledge of the performance of various membranes. Profit maximization, cost minimization, and design optimization across both financial and external criteria require knowledge of performance response functions over a substantial number of variables. The economic analysis presented here addresses the challenge of projecting commercial scale costs and returns with data from an early stage experimental small pilot; and illustrates use of such preliminary costs and returns projections to inform subsequent experimentation and development of the technology. We will continue to refine this economic approach and describe it in future publications.

Corresponding author, title, and affiliation

Kelly Zering, Professor, Agricultural and Resource Economics, North Carolina State University

Corresponding author email

kzering@ncsu.edu

Other authors

Yijia Zhao, Graduate Student at BAE, NCSU; Shannon Banner, Graduate Student at BAE, NCSU; Mark Rice, Extension Specialist at BAE, NCSU; John Classen, Associate Professor and Director of Graduate Programs at BAE, NCSU

Acknowledgements

This project was supported by NRCS CIG Award 69-3A75-12-183.