SUMTER FIELD DESK
Backup or power plant?
What if it generates power on site?
Short answer
Occasional emergency backup has different effects from regular generation. Engines or turbines running for months because grid service is delayed or inadequate would function as an on-site power plant, even if described as “temporary” or “mobile.”
Three numbers officials need
- Normal facility demand - how much power the campus normally uses.
- Installed generating capacity - often larger because of redundancy.
- Allowed operating hours - the difference between rare backup and routine pollution.
Diesel scale scenario
A representative Caterpillar 3516B has a 1.64 MW continuous rating and uses about 119 gallons of diesel per hour at that rating. Scaling comparable engines to 100 MW of continuous output gives approximately:
| Measure | Approximate amount |
|---|---|
| Diesel per hour | 7,300 gallons |
| Diesel per day | 175,000 gallons |
| Diesel per year | 63.6 million gallons |
| Direct CO₂ per year | 650,000 metric tons |
| Passenger-car CO₂ equivalent | 140,000 typical cars |
This scenario assumes continuous operation and is not a forecast for the Americus project.
Natural-gas turbine scale scenario
A representative 16.53 MW turbine with a 9,630 Btu/kWh heat rate scales to approximately:
| Measure at 100 MW continuous output | Approximate amount |
|---|---|
| Gas per hour | 963,000 cubic feet |
| Gas per day | 23.1 million cubic feet |
| Gas per year | 8.44 billion cubic feet |
| Direct CO₂ per year | 450,000 metric tons |
| Passenger-car CO₂ equivalent | 98,000 typical cars |
Natural gas usually emits less direct CO₂, particulate matter, and sulfur pollution than diesel per unit of electricity, but it still emits NOx, CO, VOCs, hazardous pollutants, and CO₂. Upstream methane is outside the stack calculation.
Limits of the car comparison
The car comparison describes annual CO₂ scale only. Cars spread emissions over many roads; a generator plant concentrates emissions at one property. Local health analysis requires unit-specific emission rates, stack heights, operating hours, weather, and dispersion modeling for NO₂, particulate matter, CO, VOCs, and hazardous pollutants.
Questions that close the loopholes
The signed development agreement states that backup generators “shall be used only in emergency situations” and limits routine testing to 8:00 a.m. through 6:00 p.m., Monday through Friday (§10). It does not define “emergency,” cap annual testing days or identify the engines, fuel and emission controls. The following conditions would supply those details.
The draft ordinance passed by the Zoning Committee on August 18, 2026 says nothing about on-site generation either: no emergency definition, no hour limits, and nothing addressing "bring your own generation," a data center building or contracting its own dedicated generating capacity instead of waiting on utility interconnection. If the project goes that route, this draft would not regulate it as the power plant it would be.
- List every engine and turbine by model, rating, fuel, controls, and location.
- Separate hours for testing, outages, demand response, peak shaving, and delayed grid connection.
- Define “emergency” narrowly.
- Model simultaneous testing and credible outage operation.
- Aggregate temporary, mobile, phased, and commonly controlled equipment.
- Require public hour-meter, fuel, and emissions records.
- Do not allow occupancy before firm grid service without separate approval as a power plant.
The equipment schedule and any air-permit application are records held by the county and Georgia EPD. See how to obtain the records and reach the officials, and the contact page for the same roster with each official's published e-mail address.
Relevant precedent
An official Irish filing illustrates why residents should ask whether generation is truly for emergencies. It describes temporary gas engines followed by nine permanent dual-fuel engines, with seven serving normal load, selective catalytic reduction, and continuous emissions monitoring. This is an example from South Dublin Routing 4 No. 2 Limited, not evidence about the Sumter County proposal.