"To reach its ambitious goal of economy-wide carbon-neutrality by 2045, California will likely have to remove on the order of 125 million tons per year of CO2 from the atmosphere. California can achieve this level of negative emissions at modest cost, using resources and jobs within the State, and with technology that is already demonstrated or mature. This is our conclusion after a comprehensive, first-of-its-kind, quantitative analysis of natural carbon removal strategies, negative emissions technologies, and biomass and geologic resources in the State, using methods that are transparently detailed in this report. We also find that realizing this goal will require concerted efforts to implement underground carbon storage at scale, build new CO2 pipelines, expand collection and processing of waste biomass, and accelerate learning on important technologies, like direct air capture."

If 125 MTCO2/year removed for $8 billion, the average cost/ton is about $65. It is quite inexpensive because around 80% of the CO2 removed is by "agricultural processes" -not sure how applicable this is for other states. With US GHG emissions at about 6,500 MtCO2e, California is responsible for about 6.7% of US emissions. If other states have the same targets as California, the US would need to remove about 1,865 MtCO2 annually, equivalent to about 30% current annual emissions. If all states have the same average capture costs, the total US costs would be about $125 billion/year ($340/person/year).

Figure 1. The green wedge represents the global amount of negative emissions?removal of CO2 from the atmosphere?required to offset residual emissions and keep worldwide greenhouse gas emissions below that required to meet a 2⁰C future. Adapted from Fuss et al., 2018.

KEY FINDINGS

 By redoubling efforts to reduce and avoid existing emissions, and proactively pursuing negative emission pathways, California can achieve its ambitious carbon-neutral goal by 2045.

By increasing the uptake of carbon in its natural and working lands, converting waste biomass into fuels, and removing CO2 directly from the atmosphere with purpose-built machines, California can remove on the order of 125 million metric tons of CO2 per year from the atmosphere by 2045, and achieve economy-wide net-zero emissions.

California can achieve this amount of negative without buying offsets from outside the State. This approach addresses local emissions without the risk of leakage or offshoring, so the overwhelming majority of the money is spent on local jobs and local industry.

These negative emissions pathways come with important co-benefits to air and water quality, resilience to a changing climate, and protection of life and property.

California can achieve this goal at a cost of less than $10 billion per year, less than 0.4% of the State's current gross domestic product.

Some of the removed carbon will be bound in natural systems or soils, but the bulk will need to be permanently and safely stored deep underground.

Only moderately and highly mature technologies are required to achieve this negative emissions potential; however, accelerating demonstration and deployment for some of them is a key need.

To realize these benefits, concerted efforts are required to broaden uptake of new land management practices, establish infrastructure, including waste biomass processing plants, to produce carbon-negative fuels and pipelines to transport CO2 to underground permanent storage sites.

The importance of achieving this level of negative emissions stretches far beyond California ? the Golden State can demonstrate to the world that carbon neutrality is achievable.

Figure ES-5. Cost of the negative emissions system. (top) Average costs and cumulative quantities for the lowest-cost set of negative emissions pathways for California. All collection, transport, processing, and final storage costs for CO2 are included, assuming full use of projected waste biomass resources in 2045.

Using the Power of Nature to Remove CO2 from the Atmosphere

All of California can participate in collecting the biomass needed for negative emissions.

Natural solutions encompass activities such as changes to forest management to increase forest health and carbon uptake, restoration of woodlands, grasslands and wetlands, and other practices that increase the amount of carbon stored in trees and soils. These approaches are among the least expensive we examined, averaging $11 per ton of CO2 removed from the atmosphere. In addition, they have important co-benefits to air and water quality, ecosystem and soil health, resilience to a changing climate, and protection of life and property through fire risk reduction. Unfortunately they are limited by land and ecosystem availability. Details on land treatment measures, costs, and uncertainty can be found in Chapter 2.

Waste biomass is widely available across California, with about 56 million bone dry tons per year available from trash, agricultural waste, sewage and manure, logging, and fire prevention activities (Figure ES-3). Today, this biomass returns its carbon to the atmosphere when it decays or burns in prescribed fires or wildfires, or is used to produce energy at a power plant that vents its carbon emissions. Details on the waste biomass sources and quantities we used in our analysis, and associated constraints, collection costs, and current uses, can be found in Chapter 3. Converting this biomass into fuels with simultaneous capture of the process CO2 emissions holds the greatest potential for negative emissions in the State. A broad array of processing options is available, and includes collecting biogas from landfills, dairies, and wastewater treatment plants for upgrading to pipeline renewable natural gas; conversion of woody biomass to liquid fuels and biochar through pyrolysis; and conversion of woody biomass to gaseous fuels through gasification. Gasifying biomass to make hydrogen fuel and CO2 has the largest promise for CO2 removal at the lowest cost and aligns with the State's goals on renewable hydrogen. We link biomass processing technologies to each source of biomass and compare these processing technologies in terms of the amount and cost of CO2 that can be derived from a given biomass source in Chapter 4.

Direct Air Capture Machines to Remove CO2 from the Air and Permanently Store it Underground Direct air capture is more expensive than most negative emissions options for California, but has a nearly unlimited technical capacity, provided its energy needs (primarily heat) can be met from a low-carbon source. This option will inevitably have to be used to some extent, depending on the degree of adoption of other, less expensive options. Captured CO2 must be directed to permanent storage. We envision facilities located near the highly suitable permanent geologic storage sites in California's Central Valley, as well as a smaller set that utilize geothermal heat where it is available in the Salton Sea region. Because land use for renewables would be very large for the amount of power needed for this amount of direct air capture (roughly 250 MW per million tons per year), natural gas power (with gas sourced nearby in California fields) at the direct air capture plant is the second best option after geothermal heat. Almost all the CO2 from combustion would be captured and stored, resulting in a net reduction in atmospheric CO2. Direct air capture technology options and associated costs are described in Chapter 5; Direct air capture and other technologies that have not been deployed at scale will get less expensive as more units are deployed. We describe how these costs decrease with technology learning in Chapter 8

Figure 30. Negative emissions potential, avoided fossil emissions, and weighted average cost to capture CO2 for forest biomass, calculated for the year 2045. Note that the weighted average cost does not include the avoided fossil emissions?only the actual negative emissions were used in this calculation, per Equation 2 and Figure 16. Avoided fossil emissions are for 2045, when grid electricity is assumed to have zero carbon intensity. The error bars on the weighted average cost represent the range of costs arising from variation in feedstock collection costs.

Figure 34. Variation of cost to capture CO2 from thermal processes to the cost of biomass. Dashed vertical lines indicate weighted average biomass costs used to calculate the cost to capture CO2 above: Forest Biomass $40 per ton, Agricultural Residue $60 per ton, Municipal Solid Waste $0 per ton. Processes that have a lower inherent negative emissions potential (due to production of carbon-containing fuels) are more sensitive to this parameter.

 A summary of total system costs is shown below. The Gasification system cost of $8 Billion/yr amounts to 6% of current state government spending and about 0.1% of California's current gross domestic product in 2045. We find the costs of meeting negative emissions goals to be quite moderate, suggesting that the State can achieve carbon neutrality by 2045.