Here's what it could cost for California to hit zero-emissions goal, Ars Technica

Cleaning up our mess –

For something like $ 8 billion a year, it could soak up a lot of CO₂.

Scott K. Johnson – Feb 4, 01575879 : (UTC UTC)

(In September) , California Governor Jerry Brown set a greenhouse goal for the state: net-zero emissions by . It’s a very aggressive goal. The easiest part of the energy transition is the first bit: growing the meager share of renewables on the grid. But cleaning up the last percent or so of our energy use is a bigger challenge and one that has yet to be tackled. From industry to air travel to agriculture, some things look like a very heavy lift.

However, achieving

net – zero emissions is easier than “actual” zero because activities that actively remove CO 2 from the atmosphere (sometimes called “negative emissions”) could cancel out some of the stubborn emissions we can’t get rid of. To find out how that might work in California’s case, a Lawrence Livermore National Laboratory report analyzed options to estimate costs. It points to a hefty — though not impossible — price tag to meet that goal. Drawdown

The first question is just how much CO (2) California is going to need to suck out of the atmosphere to achieve its goal. The Golden State’s current plan is to see emissions cut from over million tons per year to about (million tons by) . To hit net-zero in that case, negative emissions would have to grow to million tons per year by

Enlarge / The green line shows how much greenhouse gas California would need to remove from the atmosphere each year to reach net-zero emissions by . (LLNL)

The report works out the cheapest and most plausible combination of negative emissions to reach 400 million tons. About million tons per year could come from land management. Another 125 million tons could be provided by a system producing fuels and capturing CO (2) from organic waste like crop stalks and brush cleared for fire hazard reduction. The final million tons would be handled by facilities that use industrial processes to capture CO (2) from ambient air — which currently exist only as pilot projects.

Land management includes a range of activities, some of which are really cheap. Restoring some agricultural land to grassland or wetland, for example, would allow it to soak up a bunch of carbon. And altering the way that logged forests are managed by allowing longer growth cycles between harvests, or selectively removing dead trees to make space for something to grow, would also remove some carbon from the atmosphere.

About four of the 86 million tons per year in this category relate to increasing the carbon accumulation in soils. That could include trading out some annual crops for perennials that grow bigger roots and reduce the need for tilling up the soil. Compost or even charcoal . produced from plant waste can also be added to the soil as an input, improving soil quality while contributing to negative emissions.

The future of carbon

After that, the story gets a little more unconventional. The biggest share of negative emissions in the report comes from “waste biomass conversion.” This can take several forms, but the report highlights hydrogen fuel production as the top option. Heating organic material to a high temperature in controlled conditions that prevent combustion produces carbon monoxide, CO (2) , and hydrogen gas. The hydrogen gas can be separated for use as a fuel, and the rest can be stored underground.

The report notes that the hydrogen does not even necessarily have to be sent off to specific hydrogen-burning applications (although it could). A fair amount of hydrogen can be injected right into existing natural gas pipelines without the need for any changes.

As for the biomass feeding this process, the report identifies about million tons of agricultural chaff each year, million tons of things like lumber and cardboard thrown out every year, and 30 million tons of brush cut to reduce wildfire hazards. This would provide a market to pay for material from brush-cutting — something sorely lacking at present. Finally, the report includes sewage and manure digesters producing biogas.

The other big strategy would be “direct air capture” plants, which filter air through a chemical process that captures and separates CO 2 gas. This is currently the most expensive option for obtaining carbon dioxide, but it has the advantage of scaling about as much as you’d like. Because this technology is in the early stages, there’s plenty of room for that price to come down. The report actually suggests that California could “buy down” the cost by providing the early investment the technology needs to mature. Specifically, it estimated that the cost per ton of CO 2 (would drop) (-) percent after the first few plants were built.

Enlarge

/ The mix of “negative emissions” options highlighted by the report. The cost of each option is shown on the vertical axis, with the amount of carbon that could be absorbed shown by the width of each bar.

LLNL (A to B to CO) 2

That leaves two logistical questions: how are all these solid materials and gases going to be transported, and where will the captured CO 2 be dumped?

For all that brush and agricultural waste, rail is the cheapest way to move it around. But rather than a random scattering of facilities that process this or handle that, the report envisions a centralized trunk line down the middle of the state along which everything would be located. This way, trucks wouldn’t have to travel very far to reach a railroad, which could carry it along that trunk line.

Along that central line, there would be a single CO 2 pipeline. Gasification plants would process biomass and push their captured CO 2 _{into the pipeline, which would carry it to the storage facilities that would pump it under ground. Just as California has some oil and gas resources, it has rocks suitable for holding and trapping CO (2) . Injected to sufficient depth (where the pressure is great), CO}

becomes denser, losing interest in buoyantly bubbling upward.

The report estimates that California has enough geologic capacity to accept at least (years of CO) (2) capture at the rate being discussed here. And the plan should be to eliminate the need for carbon storage in that time, anyway.

The estimated overall cost for the variety of actions outlined in the report, which would bring California to net-zero emissions by , is about $ 8 billion per year. While no one will be excited to squeeze $ 8 billion into a budget, the report notes that this is just 0.4 percent of the state’s current GDP. Or for another comparison, it’s equal to a little over 5 percent of the state’s current tax revenue.

Of course, if the state failed to follow through on emissions reductions, it could cost a whole lot more to counter that extra carbon.

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