In January 2020, Lawrence Livermore Laboratory released their detailed report Getting to Neutral: Options for Negative Carbon Emissions in California. It provides a detailed plan, with estimated costs, to reach California’s goal of net-zero by 2045, and net-negative thereafter, thus reducing carbon in the atmosphere and potentially returning it to pre-industrial levels.

The plan’s focus is carbon sequestration. For a plan on carbon emissions reductions, see California’s 2017 Climate Change Scoping Plan.

[Note: “ton” always refers to tons of CO2 equivalent (tCO2e).]

The plan relies on three main pillars:

1. Natural sequestration thru improved land management (sequesters 25 million tons/yr);
2. Biomass fuels made from forestry and agricultural waste, and garbage, with capture and storage of CO2 (sequesters 83 million tons/yr) (and also displaces the use of fossil fuels);
3. Direct air capture of carbon, sucking carbon out of the air with large machines (sequesters 17 million tons/yr).

• Natural sequestration

Chapter 2 focuses on natural solutions, which are among the cheapest options for sequestering carbon. However, they are also all limited by the number of acres upon which we can apply them. There are only so many acres of forests, wetlands, etc. By far, the largest (and cheapest) option in this category is changes in forest management.

Changes in forest management

The easiest way to increase carbon sequestration is to change to the way forests are managed. Specifically, those changes include increasing harvest rotation length, maintaining stocks at a high level, and increasing productivity by removing diseased or suppressed trees. Negative emissions are based on ongoing sequestration of carbon, which may include the transfer of harvested carbon to durable wood products. These practices would sequester 15.5 million tons/yr at a cost of $0.80/ton.

Other natural solutions

Other natural options, in order of the maximum amount of carbon they can sequester, are reforestation, tidal marsh restoration, freshwater wetland restoration, and grassland restoration. These are smaller players—more limited and more expensive. The habitat restoration options are especially limited in their potential contributions and very expensive per ton of CO2 sequestered (although restoration provides other benefits, of course). Together, these options can sequester another 10 million tons/yr at costs that range from $16.4/ton (for reforestation) to $440/ton (freshwater wetland restoration).

• Biomass fuels

Analogous to current ethanol production, Chapters 3 and 4 call for turning leaves, branches, almond hulls, and human garbage into biofuels, but then also capturing the CO2 and burying it in old oil fields. A small part of the plan includes sequestering, rather than releasing, the CO2 produced during ethanol production. In terms of sequestration, this is the largest plank of the plan. It envisions a massive shift from fossil fuels to plant-based fuels, complete with new pipelines to transport and bury the CO2. It relies heavily on the Central Valley’s agricultural sector and old oil fields. The plan assumes existing crops and does not consider planting crops purely to create biofuels; thus, it does not displace food production.

Because biofuels would displace fossil fuels, it would also result in massive reductions of carbon emissions. However, that is not the focus of the report; the focus of the report is to sequester carbon.

Here is where the biomass would come from:

Forest biomass

Slag from logging, sawdust from sawmills, cleared shrub and chaparral. This would sequester 24 million tons/yr.

Municipal solid waste (household garbage)

This would sequester 13 million tons/yr.

Ag residue

1. Almond hulls and shells (41% of total ag residue biomass)
2. orchard and vineyard clippings (30%)
3. other above-ground plant parts after harvesting from other crops (29%).

These would sequester 13 million tons/yr.

Other

Landfill and anaerobic digester gas. This would sequester 6 million tons/yr.

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All this biomass would be converted, thru various processes (gasification, combustion, fast pyrolysis, hydrothermal liquefaction, and biogas utilization) into various products: hydrogen, grid electricity, liquid fuels (e.g. “gasoline”), biochar, and renewable natural gas.

The cost depends on the biomass collection, transport, biofuel conversion process, and CO2 transport for sequestration. All of these will vary in order to provide a suite of biofuel energy needs (e.g. electricity, transport fuel, etc.). Overall, this biomass fuel network would sequester 83 million tons/yr at an average cost of about $60/ton (ranging from $29-96/ton).

• Direct Air Capture

Chapter 5 of the report goes into detail about direct air capture (DAC) technology, machines that would suck carbon out of the air and store it in underground (primarily around oil and gas fields in the Central Valley). The report highlights DAC’s unlimited potential in sequestering carbon, but also its high energy demands (and thus expensive cost). In the end, they focus on two main options:

1. Natural gas-based plants located near underground storage sites. These would still be net-negative.
2. Geothermal plants (primarily around the Salton Sea), which would require the captured CO2 to be transported a long distance to underground storage sites.

They reject solar and wind-powered DAC as requiring too much land for the energy needed. They do not explore nuclear-powered DAC, such as fourth generation thorium reactors.

All of Chapter 6 is dedicated to long-term geologic storage. They conclude that oil and gas fields in the Central Valley offer the greatest promise, and that “these areas will be safe and effective storage sites. At depths below 3,000 feet, CO2 converts to a liquid-like form that has about the same density and viscosity as oil.”

Their initial cost estimates for DAC exceed $200/ton, though they assume, with learning, an eventual cost of $190/ton.

The Whole System

Chapter 7 dives into the logistical details and infrastructure needed to connect the gathered biomass to the biomass fuel plants and the DAC plants to underground storage reservoirs. Among their main conclusions:

• Transportation is a relatively small portion of total system cost, between $10 and $20/ton of CO2 removed.
• Preexisting rail would the most efficient way to move collected biomass to biomass fuel plants, though some short spur lines would need to be constructed, depending on plant location.
• A CO2 pipeline would need to be constructed along existing pipeline corridors in the Central Valley and to the Salton Sea, but not elsewhere.

Chapter 8 explores technology learning curves and cost reductions over time, mostly with respect to DAC.

Chapter 9 explores total system cost under several scenarios. They note there is “considerable flexibility among the technology pathways and scenario options.” Table 40 offers the optimum combination of technologies, sequestering 125 million tons per year (and avoiding another 62 million tons in emissions avoided) for a total of $8.1 billion/year, which is an a total average cost of about $65/ton.

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The Role of State Government

There is a plan for California; will it be implemented?

The report does not go into specific policy initiatives or economic incentives necessary to jump start, implement, or transition to this plan. I will address that in another post. Their only mention of public policy is with regard to the CO2 pipeline, where the report notes: “industry experts have expressed concern about the costs and legal difficulties of obtaining rights-of-way for new pipelines in California. One power company shared that running CO2 pipelines on existing natural gas rights-of-way requires renegotiating with the landowners because CO2 pipelines are higher pressure and thus are not covered by existing agreements.”