Community Digester Assessment Tool

This spreadsheet has been designed to assist stakeholders to evaluate the economics of supplying manure to a community anaerobic digester that is operated by a separate digester company.  Income sources and cost savings include the payment from the digester operator for the manure along with potentially increased fertilizer nutrients and livestock bedding.  It contains default data loosely based on a real Pennsylvania farm situation as a starting point for other users.

There are 15 visible sheets.  The tabs are color-coded.  Yellow tabs are for data entry.  Green tabs are for data entry for the switchgrass calculations.  Grey tabs contain calculations.  The sheets are:

Welcome  (gives this overview)

Background - authorship, version number, and related information

Key inputs & outputs - starting point for a digester generating electricity from manure alone or with food wastes

Financial inputs - see the extra inputs in this sheet to finetune the analysis

Nutrient Inputs- see the extra inputs in this sheet to finetune the analysis

Winter Biomass Crop Budget - crop input quantities and prices related to the rye winter biomass crop

Switchgrass_Key_Inputs - extra inputs for the cost of growing switchgrass as an extra feedstock

Switchgrass_Budget - crop input quantities and prices related to growing and harvesting switchgrass

Sensitivity Analysis - graphs and a few tables showing the sensitivity to key inputs

Saved Scenarios - manually copy and paste the results into the additional columns for side-by-side comparisons

N_Availability - Table 1.2-12 from the 2023-24 Penn State Agronomy Guide with N availability default values

Condensed Cash Flow - inflows and outflows with graphs

Detailed Cash Flow - inflows and outflows with supporting operational and financial information

Nutrient Chart - flow chart of the nutrient flows, and table showing the nutrient valuation calculations

Nutrient Calculations - looks at the impact of digestion and solids separation on the fertilizer nutrient value of the digestate, and contains the calculations for the numbers shown in the Nutrient_chart sheet

Some parts of this spreadsheet are repurposed from the Cost of Renewable Energy Spreadsheet Tool (CREST) version 1.4 by Sustainable Energy Advantage, LLC under contract to the National Renewable Energy Laboratory.  The model output has been changed to investment criteria such as net present value and internal rate of return at a user-entered electricity sale price and other inputs, rather than a cost of energy as in that model.  Some of the switchgrass enterprise budget format is from the To Grow or Not Grow switchgrass budget spreadsheet by Jacobs, Mitchell and Hart.

The work that went into this tool is part of a regional collaborative project supported by the USDA-NIFA, Award No. 2020-68012-31824, Consortium for Cultivating Human And Naturally reGenerative Enterprises.  Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture.