REP Sustainability Practices & Environmental Impact 2 — Questions and Answers
Question 1: Which greenhouse gas has the highest 100-year Global Warming Potential (GWP) among those commonly tracked in energy sector reporting?
- Carbon dioxide (CO2)
- Methane (CH4)
- Nitrous oxide (N2O)
- Sulfur hexafluoride (SF6) (Correct answer)
Correct answer: Sulfur hexafluoride (SF6)
SF6 has a 100-year GWP of approximately 23,500, far exceeding CO2 (1), CH4 (~27-30), and N2O (~273).
Question 2: What does a 'cradle-to-grave' lifecycle assessment (LCA) encompass?
- Raw material extraction through end-of-life disposal (Correct answer)
- Manufacturing through consumer use only
- Installation through decommissioning only
- Design through final product sale
Correct answer: Raw material extraction through end-of-life disposal
Cradle-to-grave LCA covers all stages from raw material extraction through manufacturing, use, and final disposal.
Question 3: Which metric measures the ratio of energy delivered by a renewable system over its lifetime to the energy required to build, operate, and decommission it?
- Capacity factor
- Energy Return on Energy Invested (EROI) (Correct answer)
- Net Present Value (NPV)
- Carbon intensity
Correct answer: Energy Return on Energy Invested (EROI)
EROI quantifies how much energy a system produces relative to the energy consumed across its entire lifecycle.
Question 4: Land use change associated with large-scale bioenergy crops can lead to which environmental concern?
- Increased albedo
- Carbon debt from displaced ecosystems (Correct answer)
- Reduced nitrogen deposition
- Higher water table levels
Correct answer: Carbon debt from displaced ecosystems
Converting forests or grasslands to bioenergy crops releases stored carbon, creating a 'carbon debt' that can take decades to repay.
Question 5: Under the US EPA's Renewable Fuel Standard (RFS), advanced biofuels must achieve what minimum lifecycle GHG reduction compared to the fossil fuel baseline?
- 20%
- 35%
- 50% (Correct answer)
- 60%
Correct answer: 50%
Advanced biofuels under the RFS must achieve at least a 50% lifecycle GHG reduction versus the petroleum baseline they displace.
Question 6: Which environmental impact is most directly associated with improper decommissioning of solar photovoltaic panels?
- Increased UV radiation at ground level
- Heavy metal leaching into soil and groundwater (Correct answer)
- Elevated electromagnetic field exposure
- Ground-level ozone formation
Correct answer: Heavy metal leaching into soil and groundwater
PV panels can contain lead, cadmium, and other heavy metals that leach into the environment if not properly recycled or disposed of.
Question 7: The concept of 'avoided emissions' in renewable energy project reporting refers to:
- Emissions captured and stored underground
- GHG reductions achieved by displacing fossil fuel generation (Correct answer)
- Emissions offset through reforestation credits
- Internal carbon pricing applied to project costs
Correct answer: GHG reductions achieved by displacing fossil fuel generation
Avoided emissions represent the GHG reductions attributable to a renewable project by replacing higher-emitting fossil fuel generation.
REP Sustainability Practices & Environmental Impact 2
Which greenhouse gas has the highest 100-year Global Warming Potential (GWP) among those commonly tracked in energy sector reporting?