10. Evaluation of Climate Change: Achieving Zero CO2 by 2050

10 Evaluation of a Strategy for US Achievement of Zero Net Emissions by 2050

The Democratic Presidential candidates have proposed the US achieve zero net emissions by at least 2050. Candidate proposals include

• Ms. Warren’s plan to eliminate planet-warming emissions from power plants, vehicles and buildings over 10 years, and adds an additional $1 trillion in spending to subsidize that transition. Her plan would set regulations aimed at 100 percent zero-emission energy in electric generation by 2035

• Sanders - Reaching 100 percent renewable energy for electricity and transportation by no later than 2030 and complete decarbonization by at least 2050

• Yang has proposed investing $4.9 trillion over 20 years to deal with climate change. To meet his goal of net zero emissions across the economy by 2050, Yang would issue aggressive new federal rules that would require all new buildings to be net zero emissions by 2025, and all new car models to be zero emissions by 2030. Yang is alone among the Democrats in backing investment in new nuclear technologies—$50 billion in research and development for thorium-based molten salt reactors and nuclear fusion reactors. He also would put $11.5 billion over 15 years into carbon capture research and development. He sees this as particularly important for offsetting carbon emissions from aviation, which he believes will be tied to fossil fuels longer than ground transport.

• Biden foresees $1.7 trillion in spending over the next 10 years, and $3.3 trillion in investments by the private sector and state and local governments.

What impact would be having the US reduce CO2 emissions to zero by 2050

To assess the change on global temperature by reducing US emissions, the Kaya model discussed in Section 11.1 was used to calculate CO2 emissions. Assuming the US reduces its CO2 carbon intensity to 90% of its 2018 value in five years and maintains this rate of reduction such that CO2 emission is 1% of the 2018 value in 2050. The US reduction alone would reduce world CO2 emissions to about 90% of the EIA IEO baseline emissions.

This reduction in emissions would reduce global temperature rise by about 0.5oC in 2100. Such a reduction would have a significant impact as discussed in Why Half a Degree of Global Warming Is a Big Deal(https://www.nytimes.com/interactive/2018/10/07/climate/ipcc-report-half-degree.html).

10.1 Means to implement zero net emissions by 2050

To reduce to zero CO2 emissions by 2050 is a monumental and expensive task. In 2019 the EIA estimates the US will use about 100 quads of energy (Quadrillion Btu), the equivalent of ~40% of the annual global oil usage, of which about 83 quads come from CO2 emitting fuels.

These CO2 emitting fuels are used in five economic sectors (although the agriculture sector is responsible for 9% of the US CO2 emissions it is not addressed here).

Using a Sankey diagram, we can follow these fuels into each sector

Renewables principally flow into the electric sector although a portion of solar flows into the energy consumer sectors.

10.2 Expanded Generation of Carbon-Free Electricity

Because electricity is technically easier and less costly to decarbonize than other sectors, this study relies upon expanded generation of carbon-free electricity to meet greater shares of energy demand for heating, industry, and transportation. This study excludes a strategy of replacing coal and petroleum with natural gas since a previous study addressed the question of natural gas as a bridge to a more sustainable electricity sector (https://www.nrel.gov/docs/fy16osti/64654.pdf). This study concluded that without carbon capture and storage (CCS) the increased use of natural gas does not provide a cost-effective path to zero CO2 emissions.

Considering that there will only be 30 years to achieve zero CO2 emissions, this assessment only considers technologies that are currently sufficiently mature that they can be readily deployed. This restraint is consistent with the timelines seen for the deployment of wind turbines, solar panels and nuclear power.

This excludes the use of CCS. There are multiple hurdles to CCS deployment including the absence of a clear business case for CCS investment and the absence of robust economic incentives to support the additional high capital and operating costs of the whole CCS process (https://www.sciencedirect.com/science/article/pii/S1364032114005450). There are no large-scale CCS power plants (defined as more than 500 megawatts of power) currently in operation, and most of our understanding of the technology comes from pilot-scale plants in the 1990s and subsequent scientific models of the capture process (https://www.iflscience.com/environment/latest-bad-news-carbon-capture-coal-power-plants-higher-costs/). In addition one study concluded that CCS required more intensive land use than solar generation (https://www.nature.com/articles/s41598-018-31505-3).

This effectively limits us to a strategy whereby fossil fuels are replaced directly and indirectly by electricity and end use efficiency increases. This limits us to wind, solar and nuclear as sources of carbon free electrical generation to replace existing use of fossil fuels. This assessment also assumes there are no major changes in lifestyle. The means to achieve zero CO2 emissions in each of these sectors is discussed next.

10.2.1 Commercial

Energy consumption of the commercial sector is comprised of electricity, natural gas, petroleum and a small amount of renewable. The EIA projects no substantive change in the fuel mix and a slight increase in the use of CO2 emitting fuels by 2050. In 2050 CO2 emitting fuels provide about 4.4 quads of energy per year and are used for space heating (55%), water heating (16%), cooking (7%) and other (22%). A means to achieve zero CO2 emissions by 2050 is to shift to electricity. For the purpose of this assessment 4 quads of energy supplied by CO2 emitting fuel in 2050 will be replaced by electricity to achieve zero CO2 emissions in the commercial sector.

10.2.2 Residential

Energy consumption of the residential sector is comprised of electricity, natural gas, propane, petroleum and a small amount of renewable. The EIA projects a significant growth in electricity and a reduction in the use of CO2 emitting fuels by 2050. In 2050 CO2 emitting fuels provide about 5.2 quads of energy per year and are used for space heating (72%), water heating (18%) and other (10%). A means to achieve zero CO2 emissions by 2050 is to accelerate this shift to electricity.

For the purpose of this assessment 5 quads of energy supplied by CO2 emitting fuel in 2050 will be replaced by electricity to achieve zero CO2 emissions in the residential sector.

10.2.3 Industrial

Energy consumption of the industrial sector is comprised of electricity, natural gas, petroleum and other liquids, coal and renewables. The industrial sector is bifurcated into refining and industrial excluding refining. Relative to developing a mitigation strategy, the refining sector (4.5 quads) can be excluded since reducing emissions to zero eliminates this sector. CO2 emitting fuels provide about 17 quads of energy in 2018 and are forecast (EIA) to increase to 23 quads in 2050, a 33% increase.

Determining the potential for reducing CO2 emissions in the industry sector is difficult because of the wide range of emitters in this sector. Using information from https://www.energy.gov/sites/prod/files/2013/11/f4/energy_use_and_loss_and_emissions.pdf the following table was developed

The following table lists emission sources from three industry subsectors (https://publications.iadb.org/publications/english/document/Chemical-Plants-GHG-Emissions-Reconciling-the-Financing-of-Chemical-Plants-with-Climate-Change-Objectives.pdf)

With an estimation of the potential for emission reduction for specific products in the chemical industry.

Almost 45 percent of industry’s CO2 emissions result from the manufacturing of cement, steel, ammonia, and ethylene. These four sectors are the focus of a McKinsey & Company report (https://www.mckinsey.com/business-functions/sustainability/our-insights/how-industry-can-move-toward-a-low-carbon-future). In these four production processes, about 45 percent of CO2 emissions come from feedstocks, which are the raw materials that companies process into industrial products (for example, limestone in cement production and natural gas in ammonia production). Another 35 percent of CO2 emissions come from burning fuel to generate high-temperature heat. The remaining 20 percent of CO2 emissions are the result of other energy requirements: either the onsite burning of fossil fuels to produce medium- or low-temperature heat, and other uses on the industrial site (about 13 percent) or machine drive (about 7 percent).

The McKinsey report concludes a combination of decarbonization technologies could bring industry emissions close to zero: demand-side measures, energy efficiency improvements, electrification of heat, using hydrogen (made with zero-carbon electricity) as feedstock or fuel, using biomass as feedstock or fuel, carbon capture and storage (CCS), and other innovations. It shows that decarbonization of industry is technically possible through a combination of technical solutions, the optimum mix of which will vary widely between sectors and regions.

The selected mix of decarbonization options creates additional demand for between 15% and 35% of projected electricity generation per year by 2050. Assuming a 35% increase, 14.4 quads of additional electrical generation will be required. Decarbonization of the four focus sectors could cost between 0.4 and 0.8 percent of GDP per year.

Combining the information from these sources to estimate the amount of energy that can be shifted to non-CO2 emitting sources (electricity), 75% or 17 Quads can be shifted to electricity in 2050.

10.2.4 Transportation

Energy consumption of the transportation sector is comprised petroleum and other liquids (97%), and 3% natural gas and contributing 24.8 quads of CO2 emitting energy in 2050. By 2050 EIA projects a mix of petroleum and other liquids (92.2%), natural gas and hydrogen (5.3%) with hydrogen making a 0.2% contribution and electricity (2.5%). Petroleum and other liquids are divided between motor gasoline (60%), fuel oil (28%) and jet fuel (12%). The dominant transportation mode is highway since light duty vehicles and trucks and freight trucks use ~80% of petroleum. Use from other modes include air with 9%, shipping with 4% and rail with 2%.

Because of its operating characteristics, price structure, dependence on virtually one energy source (oil), and the enormous installed infrastructure, the transportation sector will likely represent a particularly difficult challenge for CO2 emissions mitigation. Until the cost of alternative vehicle/energy systems falls enough to be attractive, taxes and subsidies are needed. Greene et al. (https://www.sciencedirect.com/science/article/abs/pii/S0016328713001456) argue that transitioning to electric vehicles requires policy initiatives of many types, such as standards, mandates and subsidies for vehicles and fuels. A carbon tax in line with the generally accepted Social Cost of Carbon (SCC) would not be enough to tip the balance (https://www.tandfonline.com/doi/abs/10.1080/15568318.2012.749962). Instead, taxes and subsidies would need to be political decisions based on environmental, rather than on economic efficiency grounds(https://reader.elsevier.com/reader/sd/pii/S0967070X17304262?token=BC87A4103E6DB378CDB851D95543B9991E657840D40258A3D30220E20CE1B370B608237E1B2E2C7D36C51DA97788B691).

This assessment assumes that petroleum powered light vehicles and trucks will transition to rechargeable battery technology and will shift ~12 quads of petroleum energy to electricity in 2050. Since electric cars are about three times more efficient than petroleum ~4 quads of electrical energy will be required. Fuel oil is assumed to be replaced by hydrogen with hydrogen being produced without CO2 emissions using either catalytic pyrolysis of petroleum or CO2 capture.

Since there no available CO2 free substitute for jet fuel it is assumed the use of jet fuel will continue to be a source of CO2.

10.2.5 Electricity

At this point in time the only option available to achieve zero CO2 emissions in the electricity sector is to replace CO2 emitting power palnts. Electricity generation is supplied from these fuels

and used by these sectors

Overall electricity consumption is expected to grow by 4.2 Quads by 2050 and electricity supplied from CO2 emitting sources is expected to grow by 1.6 quads while carbon free sources are expected to grow by 2.8 quads.

To achieve near zero CO2 emissions by 2050, carbon free generation will have to replace the planned increase in carbon emitting electricity (1.6 quad) and an additional 30 quads of carbon free generation are needed to displace carbon emitting sources in the end user sectors.

Considering that the US grid currently produces about 13.5 quads per year, to add an additional 31.6 quads is a monumental task. If you assume a base-load power plant has a 90% capacity factor, adding this much generation requires building 1200 1000 MWe plants in the next 30 years (about one every nine days starting in 2020) to achieve the emission curve for the US shown at the beginning of this section. (A similar conclusion is reached in an article in Forbes (https://www.forbes.com/sites/rogerpielke/2019/09/30/net-zero-carbon-dioxide-emissions-by-2050-requires-a-new-nuclear-power-plant-every-day/#e2dc1e235f7e). However, additional generation is required to meet peak load plus reserve margin requirements. The 2050 peak load is projected to be about 25% higher than the average load (https://www.nrel.gov/docs/fy12osti/52409-3.pdf ) and a 15% reserve margin (https://www.eia.gov/todayinenergy/detail.php?id=39892) is maintained by the NERC regions. This translates to an additional 400 1000 MWe plants in the next 30 years for a 1600 1000 MWe plants.

Detailed electrical system modeling is required to determine the extra amount of renewable generating capacity or variable renewable energy (VRE) resources necessary to handle the diurnal and monthly variation in wind and solar energy. The insolation (solar radiation power per square meter at the earth's surface) is daily modulated between zero and a maximum that depends on the latitude on earth and the season. (https://aip.scitation.org/doi/10.1063/1.4874845)

Top: daily insolation at noon during the months of the year on the indicated northern latitudes. Bottom: estimated average cubed windspeed v3 in the US for on shore (blue) and off shore (purple) locations and a simple sinusoidal approximation (green).

Wind resources within a continent sized electricity grid depend on the instantaneous wind speeds averaged over the grid surface area. It is well known that the wind power is about two times stronger in winter than in summer on northern latitudes. Next to this seasonal timescale there is however also a diurnal periodicity of relevance.

Daily averaged v3 for a large 800 × 1000 km2 area in the US and the average surface temperature for three consecutive days.

The MIT developed electricity resource model (https://energy.mit.edu/wp-content/uploads/2017/10/Enhanced-Decision-Support-for-a-Changing-Electricity-Landscape.pdf) was used in multiple scenarios to evaluate alternatives for implementing low carbon electricity resources to achieve near zero carbon power generation (https://www.cell.com/joule/fulltext/S2542-4351(18)30386-6?_returnURL=https%3A%2F%2Flinkinghub.elsevier.com%2Fretrieve%2Fpii%2FS2542435118303866%3Fshowall%3Dtrue). These scenarios found that to meet demand reliably during periods of low wind and solar availability, large amounts of VRE capacity must be deployed, along with energy storage to shift available supply from high to low VRE output periods. For zero emissions cases without firm resources (These are technologies that can be counted on to meet demand when needed in all seasons and over long durations (e.g., weeks or longer) and include nuclear power plants capable of flexible operations, hydro plants with high-capacity reservoirs, coal and natural gas plants with CCS and capable of flexible operations, geothermal power, and biomass- and biogas-fueled power plants.), the total required installed generation and storage power capacity in each system would be five to eight times the peak system demand, compared with 1.3–2.6 times peak demand when firm resources are available.

10.2.6 Land Use

Assuming two times the peak demand would require ~3,000,000 MWe of wind or solar power. Installation of that amount of wind power would take ~331,000 square miles (Equals Texas and Oklahoma) and solar would take ~203,000 square miles (Equals Kansas, Nebraska and South Dakota) using land area estimates from https://www.strata.org/pdf/2017/footprints-full.pdf. One nuclear station requires only 1,100 acres (1.7 square miles) to produce 1,800 megawatts operating at a 90 percent capacity factor. A study estimates that for modern wind and solar plants operating at the same capacity, they would require 108,000 acres (169 square miles) and 13,320 acres (21 square miles) of land respectively to produce the same amount of power.

10.2.7 Cost to Build Additional Generation

This study is limited to the cost to increase the amount of electrical generation and storage and makes the assumption that storage capability will exist. It does not include the electricity delivery. The cost to build the necessary generation to supply 31.6 quads of energy per year using nuclear power, based on Lazard’s Levelized Cost of Generation, is $8.5 trillion. The cost to generate and store the same amount of energy using solar is $13.2 trillion.

These values are consistent with an estimate provided by Wood Mackenzie (https://www.woodmac.com/news/feature/deep-decarbonisation-the-multi-trillion-dollar-question/) to replace the existing US CO2 emitting generation. This report also estimates the cost of building the generation at $1.5 trillion and the cost of storage at $2.5 trillion. This study assumes approximately 900 GW of storage investments would be required to ensure clean energy from wind and solar resources are available and reliable exactly when consumers need it. Worldwide, there are only 5.5 GW of battery storage in operation or under construction. Upgrading the transmission and distribution system requires $0.7 trillion. Supply chain and raw material costs will also increase.

In summary – excluding supply chain impacts and other items, such as stranded costs – an investment of $4.7 trillion would be required to fully transition the current US power grid to wind and solar over the next 10 to 20 years. That implies an investment of roughly US$225 to US$450 billion a year – a scale comparable to the total US defense budget. Further underlying the scale of this endeavor, the IEA estimates global power sector spending averaged US$675 billion from 2007 to 2017.

10.3 Results of Zero CO2 2050 Evaluation

This study only evaluated the upgrade of the US electrical generation to support zero CO2 emissions by 2050. It was limited to currently available CO2 free generation source

1)There are three paths to achieving zero CO2 emissions by 2050.

a. Transitioning to a combination of solar, wind and nuclear generation at a cost of $8.5 trillion

b. Transitioning to solar and wind generation with battery storage at a cost of $13.2 trillion

c. Transitioning to a combination of solar, wind and natural gas generation as a stop gap measure and then replacing natural gas generation with battery storage at a cost of about $26 trillion

2)A monumental undertaking of a scale that has not been previously undertaken is required for the US to achieve near-zero emissions by 2050. The only viable means of achieving zero CO2 emissions by 2050 is transition all energy supply to the electrical grid. To meet the goal requires the addition of about 1000 MWe of generation every week starting in 2020.

3) Options using wind and/or solar with battery storage and nuclear were evaluated. Carbon capture and storage was not considered because the technology has never been demonstrated beyond the pilot demonstration stage of development.

4) The study assumes thousands of GWh of battery storage are available although there are currently only 5.5 GW of battery storage in operation or under construction, worldwide.

5) Land use is significant. Wind power would take ~331,000 square miles (Equals Texas and Oklahoma) and solar would take ~203,000 square miles (Equals Kansas, Nebraska and South Dakota). Using nuclear generation requires 3,200 square miles.

6) An investment of $13.2 trillion is required to fully transition the US power grid to wind and solar over the next 30 years if sufficient battery storage is available. That implies an investment of roughly US$225 to US$450 billion a year – a scale comparable to the total US defense budget. Further underlying the scale of this endeavor, the IEA estimates global power sector spending averaged US$675 billion from 2007 to 2017.

7) The investment required implement the strategy with nuclear power is estimated to cost of $8.5 trillion.

8) The time to build up an infrastructure necessary to support this level of construction is estimated to be 5 years.

9) The US achievement of zero CO2 emissions by 2050 reduces global warming by 0.5 degree C by 2100. If both the US and the EU achieve zero CO2 by 2050 global warming is reduced by 0.7 degree C.