Final answer:
The nonrenewable energy resource with the historically highest EROEI is conventional oil, with ratios as high as 100:1, but modern conventional oil resources often have EROEIs of about 10-15:1. These values are approximations and should be seen as guidelines.
Step-by-step explanation:
The question asks about the nonrenewable energy resource with the highest Energy Return on Energy Invested (EROEI). The EROEI is a crucial metric used to evaluate the profitability of an energy source in terms of the ratio of energy output over the lifetime of the resource to the energy input needed to secure it initially. Most of the energy input for resources like hydroelectric dams, nuclear plants, wind turbines, or solar panels happens before any energy is produced. However, the nonrenewable energy source with the highest EROEI has been conventional oil, with EROEI ratios historically cited as high as 100:1, although more recent conventional oil resources have lower EROEIs, approximately 10-15:1. Tar sands, another type of nonrenewable oil, have an even lower EROEI of around 3:1.
These numbers are not precise but should be considered as approximate guidelines since it is challenging to account for all the energy inputs accurately. It is also crucial to note that while EROEI is an essential factor in assessing energy sources, it is not the only determining factor, and a lower EROEI may be acceptable if the resource is abundant.