Farm Energy Analysis with Anaerobic Digestion (FEAAD) tool

Overview of the FEAAD Tool

The Farm Energy Analysis with Anaerobic Digestion (FEAAD) Tool is an Excel-based decision-support tool designed to assist a broad range of users, including farmers, stakeholders, students, and researchers, in evaluating and optimizing farm operations for energy use, greenhouse gas (GHG) emissions, nitrogen balance, and economic performance of farm-based anaerobic digestion (AD) systems.  Users can supply their own data on livestock, cropping systems, manure management, and an AD system. FEAAD offers both quick scenario comparisons and deeper evaluations tailored to specific farm operations. 

Users can:

• Compare on-farm energy use and emissions under different crop, livestock, manure, and digestate management systems;
• Estimate the potential energy output and GHG emissions changes from a farm without anaerobic digestion compared to one with anaerobic digestion;
• Track nutrient flows and assess changes in fertilizer requirements;
• Evaluate economic performance under different assumptions about feedstocks, energy values, tipping fees, and policy incentives.

The tool is available for free and built in Microsoft Excel. It is intended for use by farmers, advisors, educators, and researchers. While scenario inputs are fully editable, background data and assumptions are placed in clearly labeled, visible, but locked support sheets to maintain consistency. These sheets are accessible for transparency but protected from accidental edits.

If you require an unlocked version for advanced use or modification, please contact the tool developers.

The main functionalities of the FEAAD tool are:

• Energy Use Analysis: The FEAAD Tool allows users to input detailed information about their farm operations, including crop types, livestock numbers, and manure management practices. By analyzing this data, the tool estimates energy consumption over the year and highlights opportunities for energy savings. A user can examine the energy production potential of anaerobic digestion systems, which can be combined with a biogas generator to produce electricity and corresponding waste heat or renewable natural gas.
• Greenhouse Gas Emissions Assessment: The tool quantifies the greenhouse gas emissions associated with specified farm activities, including methane from livestock and manure management (e.g., storage lagoons), nitrous oxide from nutrient applications, and carbon dioxide from energy use associated with equipment operations (e.g., tractors to seed, till, etc.). Users can explore how changes in management practices, such as adopting anaerobic digestion or altering manure application methods, impact overall emissions. 
• Nitrogen Balance On-Farm: The tool estimates the amount of nitrogen that is plant-available from manure and/or digestate. This is compared to the crop nitrogen demand of the crops and crop management specified for the user-defined farm. assuming application rates outlined in the Penn State Agronomy Guide. Users can evaluate how the digestion of a mix of feedstocks affects the nitrogen balance on their farm. Note that phosphorus and potassium are also calculated but are not presented on the main user interface tabs.
• Economic Performance Evaluation: By inputting economic parameters, such as feedstock costs, bioenergy value, and discount rates, users can assess the financial viability of different farm management scenarios. The tool provides a detailed breakdown of costs and benefits, enabling farmers to evaluate the economic impact of integrating anaerobic digestion and other energy-saving technologies. The user may even alter various economic parameters for "what if" scenario analysis.
• Customized Farm System Analysis: The FEAAD Tool allows users to build a customized model of their farm by entering specific data on cropping systems, livestock types, manure management practices, and anaerobic digestion operations. This tailored approach helps farmers identify the best strategies for their unique circumstances, considering local conditions and market factors.
• Real-Time Graphical Outputs: The tool generates instant graphical representations of the farm's energy use, greenhouse gas emissions, nitrogen balance, and economic performance as data is entered or modified. This real-time feedback helps users visualize the impact of different management decisions, making it easier to explore various scenarios and outcomes.
• Scenario Exploration and Case Studies: Users can explore premade scenarios that demonstrate different farm setups, such as mixed crop-livestock systems or specialized dairy operations. These scenarios provide valuable insights into how different farm management practices affect energy use, emissions, and economic performance, offering practical examples that users can adapt to their own farms.

In summary, the FEAAD Tool is designed to provide farmers, agricultural professionals, and students with clear insights into farm energy use, GHG emissions, nitrogen balance, and economic outcomes related to anaerobic digestion. Its integrated analysis supports informed decision-making tailored to individual farm situations, helping users evaluate options appropriate to their specific needs.

Getting Started with the FEAAD Tool

The FEAAD Tool is built to work seamlessly with most versions of Microsoft Excel on a PC. It has been tested for compatibility with Excel in Office 365. While it may function in earlier versions of Excel, some features may not perform optimally.

Setting Up the File for Use

Once you've downloaded the FEAAD Tool, follow these simple steps to ensure it functions correctly on your computer:

1. Enable Editing: After opening the Excel file, a security warning may appear at the top of the spreadsheet, indicating that editing is disabled. To interact with the tool, click the "Enable Editing" button.
2. Enable Content: The tool contains automated calculations and macros designed to help you input and analyze your farm data. You may see a second prompt, asking you to enable content for the workbook. Click "Enable Content" to activate the necessary macros and calculations.
3. Save the File: Before beginning, save the file to your computer to ensure you do not lose any work. Use the Save As feature to rename the file according to your project (e.g., "FEAAD Analysis - Dairy Farm PA").

Overview of FEAAD Tool Sheets and Workflow

When users begin interacting with the Farm Energy Analysis with Anaerobic Digestion (FEAAD) Tool, they will encounter three main sheets:

1. Welcome: Introduces users to FEAAD's purpose and capabilities and directs the user to next steps, including quick-start instructions to help users navigate smoothly to the detailed inputs and outputs tab. 
2. FEAAD: Core interactive space for users to enter farm-specific data to define scenarios, including livestock system details, manure management, cropping systems, anaerobic digester configurations, economic parameters, and policy incentives. This sheet also includes real-time graphical outputs to see changes that result from selections made in the FEEAD Tool. 
3. FEAAD - Summary: Consolidates results from user inputs into a clear, detailed summary of the scenario analysis, ready for reporting and decision-making.

In addition to these main sheets, users may notice tabs beginning with DATA_ and shaded in light green. These support tabs contain the underlying source-linked data and default values used in calculations. They are view-only to maintain tool integrity, but references are included for transparency. Users with advanced needs can request an unlocked version.

After reviewing the Welcome tab, navigate to the FEAAD Tool tab. This tab is the main working space where you'll input your farm's specific details to evaluate energy production, greenhouse gas (GHG) emissions, and economic outcomes associated with anaerobic digestion (AD). You can navigate between these sheets using the bottom bar in Excel.

Step-by-Step Instructions

This section guides you through using the FEAAD Tool to analyze farm energy use, greenhouse gas emissions, and economic outcomes. Each step is designed to help you input data specific to your farm and receive real-time feedback through dynamic outputs. For each step, you'll find explanations, example scenarios, and tips to guide you through the process.

Input Fields, Color-Coding Guide, and Helpful Comments

The FEAAD Tool uses a color-coded system for user inputs:

• Yellow Cells: These cells are drop-down menus where users must select an option from a pre-set list. Choose the appropriate selection that best matches your farm's practices or conditions.
• Green Cells: These cells are for manual data entry. Users can input values specific to their farm's operations or keep the suggested default values if applicable. It's important to review these cells and adjust the data to reflect your farm's actual conditions.
• Red Triangles: If you see a red triangle in the upper right corner of a cell, it means there is additional information available. Simply hover your cursor over the cell to display a tooltip with more details or guidance on how to complete the entry.

Step 1: Select Your Representative State

Choose your state: Choose your state from the dropdown menu. This will update the tool with data specific to your area. Currently, FEAAD supports data specifically for Pennsylvania (PA) and Iowa (IA). If your farm is located outside these states, please select the state whose climate and agricultural practices most closely match your own.

Why this matters: Selecting your state ensures that the analysis is tailored with regional data, which is important for accurately assessing energy usage, crop inputs (e.g., fertilizer, gasoline for equipment), livestock feed, GHG emissions, and crop yields based on your location. 

Explore premade scenarios: If you are unsure where to start, you can use the premade scenarios. These are designed to showcase example setups for various farm types based on partnering farms with Iowa State University and Penn State University. To access this, click on one of the buttons to simulate common configurations from Pennsylvania and Iowa. 

Reset formulas: If you select any of the pre-made scenarios, or manually change any of the crop yields, the pre-existing formulas for crop yield will be removed. If you would like to bring them back, you can select the "Reset Formulas" tab to auto-populate the crop yield cells with the original formulas. Note: This feature is only available in the macro-enabled version of the tool (.xlsm).
Tip: Using state-specific or premade scenarios can simplify initial exploration and familiarization with the tool.

Step 2: Build Your Farm 

Building your farm system allows the tool to generate outputs based on your specific livestock, cropping systems, and manure management practices. This will create a more accurate energy, greenhouse gas, and economic analysis.
The tool is currently configured for dairy, beef, and swine operations.

A. Enter Livestock Information

Livestock: Enter the type of animals on your farm, the head count, and how manure is managed. 

Why this matters: Accurate data on livestock and manure management is essential for predicting the digester's biogas production, emissions reduction, and the availability of nutrients for crop fertilization.

B. Manure and Fertilizer Application

Manure/Digestate Application: Inputting details on the amount, timing, and method of manure or digestate application helps determine nutrient availability (especially nitrogen) and environmental impacts such as potential nitrogen volatilization and GHG emissions. These insights are critical for optimizing nutrient use while reducing emissions.

Synthetic Fertilizer Application: By specifying the types and timing of manure, digestate, and synthetic fertilizers applied to your fields, the tool can assess total nitrogen input and potential reductions in synthetic fertilizer. This information also plays a role in evaluating the overall GHG emissions associated with fertilizer use on your farm.

Why this matters: Providing correct data on manure/digestate and synthetic fertilizer use is essential for understanding nutrient cycling on your farm. This data also allows the tool to assess how anaerobic digestion affects nutrient availability and GHG emissions, particularly in comparison to raw manure and synthetic fertilizers.

C. Crop Information

Crop Information: For each crop type, enter acreage, previous rotations, fertilizer application, manure application, and expected yield. Expected yields are automatically calculated based on state averages and published literature estimates for certain rotations (e.g. double cropping).

Additional Considerations: Soil carbon sequestration and livestock feed options can be set under the "Other considerations" section. The user has the option to select between low, medium, or high estimates for soil carbon sequestration, depending on whether they want to make pessimistic, average, or optimistic assumptions, respectively.

For livestock feed, the tool automatically assumes that crops grown on-farm will be used to feed livestock, when appropriate (e.g. corn will count as feed for pigs, but forages will not). The default option should be to select "I only purchase what's needed." However, if the user would like to explore what would happen if the farm did not purchase any feed, they may choose to do so.

Why this matters: Accurate crop data ensures that the tool can correctly model greenhouse gas emissions, farm energy analysis, and nutrient management practices. 
Tip: Accurate inputs here significantly improve model precision, ensuring results closely match your real-world conditions.

Step 3: Evaluate Anaerobic Digestion for Your Farm

Anaerobic digestion can reduce greenhouse gas emissions and provide renewable energy. This section allows you to explore if adding a digester to your farm would be beneficial and to assess the current setup if you already have one.

A. Specify Feedstocks for Anaerobic Digestion

On-farm Feedstocks: Input the types of feedstocks produced on your farm that could be used in the anaerobic digester. This includes manure, crop residues, and perennial grasses. If there's a cost for handling or transport, enter it in dollars per dry ton. If there's no cost, leave it at zero.

Imported Feedstocks: Enter the amount of imported feedstocks (e.g., manure, food waste) in the appropriate units like head (for manure) or trucks per week (for food waste). Also, enter the cost in dollars per wet or dry ton. If there's a payment for accepting the feedstock (e.g., food waste), enter a negative value (e.g., -$40 per wet ton). 

Why this matters: Choosing feedstocks for your anaerobic digester is important because each type of feedstock has different biogas production potentials and nutrient composition. Some feedstocks, like food waste or certain crop residues, might otherwise be wasted or incur disposal costs, but when used in a digester, they can become valuable inputs for energy production. Additionally, different feedstocks can qualify for various Renewable Identification Numbers (RINs), which can provide substantial revenue depending on the biogas generated and its end use. By carefully selecting and managing feedstocks, you can optimize biogas yield, reduce waste, and maximize the profitability of your anaerobic digestion system. 

B. Digester Operations and Assumptions

Digester Setup: Input details about the digester's operation, including biogas usage, efficiency, methane leakage, and whether the digestate is separated for further use.

Why this matters: Each of these factors impacts the overall performance of the anaerobic digester. Methane leakage, for example, can reduce the environmental benefits, while digestate separation can improve nutrient management.
Tip: Digester parameters significantly influence efficiency, biogas yields, and economic outcomes.

C. Economic Parameters

Economic Assumptions 

• Discount Rate: Reflects how you value money today compared to future earnings. A lower rate favors long-term investments, while a higher rate emphasizes immediate returns. 
• Bioenergy Values: How much money you earn per unit of energy (electricity or gas) produced by your anaerobic digester, measured in $/kWh or $/MMBTU. RIN credits are calculated separately and should not be included here.
• Digestate Value: Specify if digestate generates value as fertilizer ($/lb available nitrogen relative to manure) or bedding ($/ton bedding).
• Grants/Subsidies: Indicate the amount of external financial support.
• RIN credits and values: Income earned from Renewable Identification Numbers (RINs), which are credits for producing renewable natural gas. The tool separates D3 and D5 RINS based on feedstock type. D5 RINS are provided for any methane generated from food wastes, and are valued at $0.75/RIN.

Why this matters: Accurate economic inputs help you realistically evaluate your digester's financial viability. By clearly defining these values, you can better understand potential revenues, reduce financial risk, and make informed decisions about adopting anaerobic digestion. 

Step 4: View Instant Graphical Output

As you input data in Steps 1 through 3, the tool generates dynamic graphical outputs on the right-hand side of the FEAAD Tool sheet. These visuals summarize key insights, such as greenhouse gas emissions, energy production, nitrogen balance, and economic performance. These graphs help visualize the impact of anaerobic digestion and other farm management practices.

What to do: Review the graphs and charts generated by the tool. These visuals will update in real-time as you adjust your inputs, allowing you to experiment with different scenarios and see the immediate results.

Upon completing these steps and reviewing dynamic outputs, proceed to the FEAAD - Summary sheet to view a comprehensive analysis and generate printable reports for stakeholders. To access it, either click the "View Summary" button located beneath the Graphical Output section or use the sheet tabs at the bottom of the Excel workbook. 

Step 5: Printable Summary

The printable summary tab offers an in-depth report of your farm's energy use, greenhouse gas emissions, nitrogen balance, and economic outcomes, based on the FEAAD tool's analysis. This report is essential for interpreting the impacts of anaerobic digestion (AD) on your farm's operations and understanding the key trade-offs involved.

What to do: Navigate to the summary tab to view the results, which can be printed or exported for record-keeping or sharing with stakeholders such as farm managers, investors, or regulatory bodies.

Interpreting the Results: This summary highlights the outputs of the FEAAD tool, showing how AD systems can reduce methane emissions, produce renewable energy, alter nutrient availability compared to non-digested manure, and whether the project is profitable given the user-defined economic assumptions. The results help to illustrate the complex interactions between feedstock choices, biogas production, and nutrient management. It emphasizes the need for strategic decision-making to maximize both economic and environmental benefits, while addressing the complexities associated with integrating a digester into the farm system.

FAQS

Find answers to common questions about using the FEAAD Tool.

1. What if my farm isn't in Pennsylvania or Iowa?

FEAAD currently supports only PA and IA. If you're outside these states, choose the one that most closely matches your climate, cropping systems, and manure management practices.

2. Do I need all my farm data to get started?

No. You can start with estimates or use the example scenarios. More accurate data will improve the precision of results, but rough inputs can still help explore general trends and feasibility.

3. Will this tool tell me if I should build a digester?

FEAAD is not a prescriptive tool-it doesn't give yes/no answers. It helps you evaluate how a digester might perform on your farm under various scenarios so you can make informed decisions.

4. Can I save and share my results?

Yes. You can print or save your analysis from the FEAAD - Summary tab as an Adobe PDF. The summary is formatted to print cleanly as a 3-page document, making it easy to share.

This user guide was prepared by Siobhan Fathel, Elmin Rahic, Jim Jordahl and Christine Costello.

Grant Acknowledgements: This work is supported by the Agriculture and Food Research Initiative Sustainable Agricultural Systems program, project award no. 2020-68012-31824, from the U.S. Department of Agriculture's National Institute of Food and Agriculture.

Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and should not be construed to represent any official USDA or U.S. Government determination or policy.