There appears to be a growing consensus here that halting the increase of atmospheric CO2 concentration would require reducing global annual CO2 emissions to zero. There also appears to be a growing consensus that this emissions reduction should occur by 2050. There is no global plan to achieve this result. There is also no US plan to achieve this result in the US. However, this conceptual plan may be of use in scoping the challenge.

The US currently consumes approximately 95 quads of energy each year, according to the US EIA Annual Energy Review 2009. EIA shows fossil fuels providing approximately 78 quads, or ~80% of this energy. Therefore, to achieve zero CO2 emissions in the US, ~80% of US energy consumption would have to be shifted to non-fossil sources or supplied by fossil sources operating with 100% CCS.

US populationis expected to grow to ~450 million by 2050, assuming continuation of recent population trends. Therefore, US energy consumption in 2050 would be estimated to be ~140 quads, assuming continuation of recent per capita energy consumption trends. A combination of population controls, efficiency improvements, voluntary conservation and forced deprivation could cause that energy consumption to be less than this projection.

The US annual energy consumption currently includes ~10% revewables of all types, more than half of which is large scale hydro and geothermal, and ~10% nuclear.

Current US electric generating capacity is ~1,000 GW. This capacity would be required to increase to ~1,500 GW by 2050 just to satisfy existing electricity end uses, again assuming continuation of current trends. However, only ~39 quads is currently consumed to produce electricity. This would be expected to increase to ~60 quads by 2050 to meet the growth of current electricity use.

However, to achieve zero CO2 emissions in the US, all existing fossil fuel end uses would have to be replaced by alternative fuels or equipped for 100% CCS.

Let us assume, for this exercise, that all current fossil fuel end uses in all sectors would be replaced by nuclear generated electricity by 2050. For simplicity, let us also assume that all current fossil fuel end uses could be replaced by electric end uses using the same quantity of energy as those end uses currently require. Further, let us assume that all current US nuclear power plants would reach end-of-life by 2050 and would have to be replaced.

Therefore, satisfying projected US electricity consumption for current electric end uses in 2050 would require construction of new nuclear generating capacity of ~1,400 GW. Satisfying all current non-electric end uses would require additional generating capacity of ~2,100 GW. Assuming an average plant generating capacity of 1,400 MW (1.4 GW) and an average design, regulatory review and construction process of 10 years, the US would be required to commission 2,500 nuclear generators beginning in 2020, or approximately 80 new power plants each year.

Assuming an average installed cost of ~$6,000 per kW (~$6 billion per GW), this effort would require investment of ~$21 trillion by 2050 in new nuclear generating capacity alone. Further investments would be required in extraction, fuel processing and reprocessing, etc. Massive investments would also be required by all non-electricity generating energy consumers in electric end use facilities and equipment, including electric vehicles of all types. Total investment in all sectors to accomplish this conversion is estimated at ~$30 trillion, or ~$700 billion per year over the period.

Current US GDP is ~$14.6 trillion. Therefore, this effort would require investment of ~5% of GDP per year over the period.

NOTE: This estimate does not include any US investment in infrastructure in the developing countries to support their conversion to zero CO2 emissions economies.

NOTE: A GW of nuclear generation could be replaced by 2-5 GW of solar and/or wind generation capacity, assuming that adequate supply/demand matching could be achieved.

NOTE: Surplus generation capacity during off-peak periods could be used to produce hydrogen for use as vehicle fuel and/or to produce potable water from brackish or salt water for a variety of uses.