The Calculator for Anaerobic Digestion Economic feasibility (CADE), was developed by the four undergraduates: Hansen Tjo, Josh McGee, Nicholas Sbalbi, and Kieran Tay. It was officially published on the website in December 2020 and has since been undergoing continuous improvement. The calculator takes in variables for physical inputs and outputs as well as the economic environment, and generates the Net Present Value (NPV) which is representative of the theoretical digester's economic feasibility. A digester with a positive NPV is considered economically viable while one with a negative NPV is considered economically unviable. Results from this calculator are meant to be a rough estimate of scale of magnitude so that further studies can be done to refine the NPV.

Revenue Variables

Natural Gas Energy Value (MJ/m^3): Energy generated per cubic meter of biogas

Electricity Price ($/kWh): Price of electricity, used to calculate
savings due to biogas generated electricity

Renewable Energy Credit Value ($/credit): Value of one energy credit, equal to one
megawatt-hour. Government incentive dependent

SSO Tipping Fee 1 ($/ton): Per ton savings or revenue from SSO waste removal

SSO Tipping Fee 2 ($/ton): Optional second price to change to after transition year

SSO Tip Transition Year (17 for None): Transition year between SSO tip price changes.
The second price is used for and after the entered year

Salvage Percent (Decimal < 1): Fraction of salvagable initial capital cost

Depreciation Time (yrs, 16 Max): Duration of depreciation write off.
Straight line depreciation is used

System Variables

WB Processing (gal/day): Daily SB processing amount

SSO Processing (gal/day): Daily SSO processing amount

Operating Days (days/yr): Number of days in operation per year

Expenses Variables

Total Capital Cost ($): Intial machinery and construction costs

Total O&M Costs ($/yr): Yearly operation and management costs

Annual Town Taxes ($/yr): Annual taxes for reactor/generator operation

Number of Workers: Number of full-time workers for the reactor/generator

Cost Per Worker ($/yr): Worker salary, adjusted by 3% yearly in
the book to account for cost of living

Advanced Variables

Working Capital ($): ??? TO ADD ???

Discount Rate (Decimal < 1): ??? TO ADD ???

Calculate

System Outputs

Revenue Items

Year	Labor -(number of workers * cost per worker)*1.03^(year-1)	O&M Costs constant directly from input	Taxes constant directly from input	SSO Tipping Revenues tipping fee $/ton * SSO processing gal/day * days of operation per yr * 1.084 lb/gal * 0.0005 ton/lb * 3.33 to dilute to 30%	Electricity Savings electricity price * kWh generation per year	Renewable Energy Credits kWh generation per year * (1 MWh / 1000 kWh) * credit value per MWh	Depreciation capital cost * (1 - salvage percent) / depreciation time	Salvage salvage percent * capital cost	Total Capital from input	Sum sum of columns to left	Present Value sum / (1 + discount rate)^year

Sensitivity Analysis (Impact on NPV)

	WB Processing	SSO Processing	Electricity Price	Renewable Energy Credit Value	SSO Tipping Fees	O&M Costs	Town Taxes	Cost Per Worker
+10%
-10%