# Glossary of Terms

Find definitions of terms related to the economic feasibility for carbon dioxide (CO₂) utilization.

**Capacity/onstream factor** –The percentage of assumed uptime for a process. For example, a process operating
329 days per year would have 329/365 = 90% capacity/onstream factor.

**Carbon efficiency** – Ratio of carbon mass in the product stream to the carbon mass input into the system.

**Chemical oxygen demand** – Amount of oxygen consumed during the oxidation of aqueous contaminants in wastewater
streams.

**Current case** – Published results in the open literature with electricity priced at $0.068/kilowatt-hour
and a CO_{2} cost of $40/metric ton.

**Current density** – The electron flux per unit area of an electrode. Typically represented in terms
of milliamps per square centimeter (mA/cm^{2}).

**Energy efficiency** – Ratio of the intrinsic energy contained in the product stream (lower heating value
basis) to the total energy input into the system. Input energy considers all forms
of energy including heat, electricity, and inherent chemical energy in feedstocks
(e.g., hydrogen) on a lower heating value basis.

**Faradaic efficiency** – The ratio of electrons utilized in product formation to the total electrons input
to an electrolyzer.

**Future case** – Attainable process improvements with electricity priced at $0.03/kilowatt-hour
and a CO_{2} cost of $20/metric ton.

**Kilowatt-hour (kWh)** – A measure of electrical energy equivalent to a power consumption of 1,000 watts
for 1 hour.

**Mass yield** – Ratio of product mass to the mass input into the system. Input mass can be calculated
both on total mass basis or CO_{2} basis.

**Metric ton (MT)** – A unit of weight equal to 1,000 kilograms or 2,205 pounds.

**Minimum selling price** – The calculated breakeven price of a product represented as $/kilogram product.

**Microbial productivity** – Intrinsic rate by which microorganisms convert feedstocks into products. Typically
represented in terms of mass of product per volume of reactor per unit time (e.g.,
g L-1 d-1).

**Product titer** – Concentration of a species in solution. Typically represented in terms of grams/liter
(g/L).

**Scale** – Percent change in the modeled volumetric flow rate of the incoming feedstock stream.
For example, +50% scale represents a 50% increase in the incoming volumetric flow
rate of CO_{2} (and hydrogen if applicable) relative to the baseline model.

**Theoretical case** – Thermodynamic limitations with electricity priced at $0.02/kilowatt-hour and a
CO_{2} cost of $0/metric ton.

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