A startup plans to build a new type of fuel-producing plant in California’s fertile Central Valley that would, if it works as hoped, continually capture and bury carbon dioxide.
The facility, developed by Mote of Los Angeles, would rely on the mounds of agricultural waste produced on the state’s sprawling almond orchards and other types of farms. It would heat leftovers like tree trimmings and fruit pits to temperatures above 1,500 ˚F, hot enough to convert the biomass into hydrogen and carbon dioxide.
Mote plans to separate out the carbon dioxide and pump it deep underground into saline aquifers or retired oil wells near the plant. The hydrogen would be sold to serve the state’s growing fleets of emissions-free buses and trucks.
The process should permanently store away the carbon captured by the plants as they grow. And the hydrogen would defray the high costs of the process.
Mote says its facility would be the first to convert biomass to hydrogen while capturing the carbon emissions. But it’s among a growing number of efforts to commercialize a concept first proposed two decades ago as a means of combating climate change, known as bioenergy with carbon capture and sequestration, or BECCS.
Such operations could remove greenhouse gas from the atmosphere over time, even as they provide low- or no-emissions replacements for fossil fuel. But there are serious challenges to doing it affordably and in ways that reliably suck down significant levels of carbon dioxide.
Dan Sanchez, who runs the Carbon Removal Lab at the University of California, Berkeley, says the process that Mote intends to use, known as biomass gasification, is technically difficult and expensive. It requires careful pre-treatment of the waste and cleaning of the resulting gases. And gathering up the fuels from scattered farms or forests will be complicated and costly.
In addition, the company’s longer-term prospects could be constrained by the lack of infrastructure for moving around and storing the resulting gases, as well as limited demand for the high-cost variety of hydrogen it plans to produce.
But Mote’s plant might be a particularly effective approach to BECCS because the resulting fuel is carbon free, while other types of plants produce fuels that release some amount back in the end.
And Mac Kennedy, the company’s chief executive, says the facility could become profitable within a few years by taking advantage of state subsidies for low-carbon fuels and federal tax credits for carbon storage. He hopes to eventually build more plants across California and beyond, potentially tapping into other fuel sources like trees removed from forests, whether in the aftermath of wildfires or in the hopes of preventing them.
BECCS is a loosely defined technology that can include facilities running on wood chips, switchgrass, or municipal waste, and producing electricity, ethanol, or so-called synthetic fuels that can power today’s cars, trucks, and planes.
The concept has seized a growing share of attention in research and policy discussions as climate models increasingly find that the only way to avoid very dangerous levels of warming this century is to suck vast amounts of greenhouse gases from the atmosphere.
Plants and trees do a great job at that, but when they die, rot, or burn, much of the carbon is returned to the air. Various BECCS schemes promise to “make sure it’s permanently out of the atmosphere,” says Roger Aines, who leads the Carbon Initiative at Lawrence Livermore National Laboratory.
The hope is that these operations can be at least carbon neutral, adding no more greenhouse gases than they remove. But some promise to draw down much more than is generated, achieving what’s known as negative emissions.
In 2018, the UN’s climate panel concluded that limiting warming to 1.5 ˚C over preindustrial levels could require the removal of as much as 8 billion tons of carbon dioxide per year through BECCS by 2050. Estimates for the technology’s carbon removal capacity vary widely, ranging from 1 billion to 15 billion tons per year globally by midcentury, according to a review of the scientific literature by the Energy Futures Initiative, published in January.
Cost estimates vary widely depending on the technologies, fuel sources, and outputs. But a 2020 study, led by researchers at Oak Ridge National Laboratory, found that costs for using biomass to capture and permanently store nearly 200 million tons of carbon dioxide would run between $62 and $137 per ton in the US. That includes the revenue from resulting products, which the study assumed would mean selling electricity generated from such plants.
That range is well below the current cost of another popular idea for removing carbon from the air, direct air capture, which can exceed $600 per ton. But even with costs nearly as low as $60 per ton, BECCS wouldn’t be profitable on its own.
That means, for now, such operations will often depend on government subsidies to be viable. “Certainly the added costs of BECCS, or any negative-emissions decarbonization strategy, would need to be somehow compensated for the industry to grow,” Matthew Langholtz, a natural-resources economist at the Oak Ridge Lab and one of the authors of the study, said in an email.
If BECCS does reach large scales, some experts fear, it could come at the expense of food production as plants expand beyond agricultural waste for fuel sources. Eventually, it could even create incentives to raze forests and grasslands and grow crops for bioenergy in their place.
These and other issues make it tricky to properly account for how much carbon is removed and how much is released throughout the process. Farming produces lots of highly potent greenhouse gases. Up until now, most BECCS plants have produced carbon-containing fuels like ethanol that release some CO2 when they’re burned. And operations that sell the resulting carbon dioxide for one of its most common uses, enhanced oil recovery, will be helping to extract additional fossil fuel from wells. (Mote says it wouldn’t use carbon dioxide for this purpose).
Technically, all these applications can still remove more carbon than is released across the entire process. But making sure that’s actually happening as the sector scales up will require creating common, reliable accounting standards, and that has proved very difficult in similar areas, like forest carbon offsets.
“Walk the talk”
The idea for Mote sprang from a research effort that took shape several years ago when scientists at Lawrence Livermore Lab tried to solve a conundrum facing California.
Toward the end of his administration in 2018, Governor Jerry Brown issued an executive order that, while nonbinding, set a goal of achieving “carbon neutrality” across every sector of the state’s economy by 2045. The riddle: How could the world’s fifth-largest economy achieve that goal when researchers and businesses have yet to develop affordable and clean ways of growing crops, raising livestock, powering planes, and operating other industries?
It’s a local version of the same basic problem that forced climate modelers to factor high levels of BECCS into their projections as they calculated ways to prevent the planet from blowing past 1.5 ˚C of warming, given rising emissions, rising temperatures, and slow progress toward clean energy. If companies, states, or nations can remove enough greenhouse gas from the atmosphere, they can theoretically balance out the levels they’re continuing to emit, or even achieve a net decrease.
In a report published in January 2020, the Lawrence Livermore team concluded that the only way to make the math work for California was to remove more than 125 million metric tons of carbon dioxide per year by 2045. And they highlighted one approach that promised to do so in an especially scalable and affordable way, using an old and well-known process: cooking but not combusting waste biomass, under high temperatures and pressures and with limited amounts of oxygen, to convert it into gases. By adding systems that captured and stored the resulting carbon dioxide, this technique promised to offset the state’s ongoing emissions.
It was the best option for removing the greenhouse gas “from an environmental and economic perspective,” says Joshuah Stolaroff, an author of the resulting paper. A few months later, in March of 2020, Stolaroff and Kennedy cofounded Mote to build a full-size facility to do it.
“This is my attempt to walk the talk,” Stolaroff says.
The first plant
Mote’s first plant, which could go online as early as 2024, would remove 150,000 tons of carbon dioxide a year and produce 7,000 tons of hydrogen.
Mote is in partnership talks with CarbonCure Technologies, which adds captured CO2 to concrete. But the crucial agreement that’s not yet sealed—one that will determine the ultimate location of the plant—is with the owner of a site where the plant could inject the greenhouse gas underground.
Kern County, California, could be an ideal test bed for such a project, given its proximity both to farms and to oil and gas wells. Moreover, the state has numerous climate and pollution policies that could support the effort, including significant subsidies for low-carbon fuels, funding for hydrogen infrastructure, and tightening rules on burning agriculture waste.
California’s low-carbon fuel standard program, which sets declining limits on the carbon intensity of fuels sold in the state over time, provides credits to companies that sell cleaner fuels. And it effectively creates a market for them. Fuel producers and importers must meet the state’s targets by producing low-carbon fuels, buying them or purchasing credits from other businesses that have generated such fuels or exceeded the goals. Those credits, which each represent a ton of carbon dioxide, have recently traded for around $175.
Mote should also be able to take advantage of a federal tax credit that by 2026 will provide as much as $50 for every ton of carbon dioxide injected into geological formations.
The company expects the heavy trucking industry, which will need to switch to low-carbon fuels under California rules, to serve as an early market for the hydrogen. But hydrogen can also be used to generate electricity, or as a feedstock in steel production and other industrial processes.
Mote’s founders argue that the startup’s particular approach deliberately sidesteps or minimizes some of the known issues with BECCS.
By taking advantage of agricultural and forest by-products, it should avoid competing with food production or creating pressure to convert forests or grasslands to farms. By gasifying biomass, rather than combusting it as some forms of BECCS do, they expect to minimize the resulting air pollution, particularly compared with the amount that would result if farmers burned their waste.
Finally, they argue, the process should result in significant net carbon removal. Not only will they mainly inject the captured CO2 underground, but they plan to use emissions-free vehicles to collect the biomass, while the hydrogen they produce will be a zero-carbon fuel.
Asked whether it will be too costly and complex to continually gather up agricultural waste and trees, Kennedy responded in email that that’s a “very common perspective outside of the Central Valley.” But he stressed there are already highly efficient, large-scale trucking and logistics operations in place, moving vast amounts of goods around the region each day.
For all the promise of BECCS, it's been slow to get off the ground. The Energy Futures Initiative report only lists 16 projects globally to date, nearly all in the pilot or demonstration phase. Most are existing operations, like ethanol facilities and biomass power plants, that have added on carbon capture systems.
The only large-scale one is Archer-Daniels-Midland’s ethanol facility in Decatur, Illinois. The plant captures up to 1 million tons of carbon per year and sequesters it within a layer of sandstone underground. But, the report notes, it still emits more CO2 than it removes. The company is continuing to refine the carbon capture technology.
The San Francisco startup Charm Industrial has taken a different approach. It’s converting agricultural waste into a carbon-rich liquid, and simply pumping it underground into salt caverns or other types of regulated geological sites. The company earns money by selling carbon credits to companies looking to offset their ongoing or historic emissions in a permanent way. Early customers include Microsoft, Stripe, and Shopify.
Notably, Charm started out by trying to gasify biomass to produce hydrogen as well. But the company soon found that the associated transportation costs were too expensive, as Grist reported earlier, and as the chief executive colorfully reiterated this week.
“Biomass is just too fluffy,” CEO Peter Reinhardt wrote on Twitter, explaining why the company switched directions. “So fluffy we were gonna die.”
Last March, Chevron, Schlumberger New Energy, Microsoft, and Clean Energy Systems announced a partnership to retrofit a power plant in Mendota, California, enabling it to generate electricity from agricultural waste while capturing the resulting emissions. Those would be injected into nearby underground geological formations.
In a press release, the companies said the facility will remove around 300,000 tons of carbon dioxide annually.
There are also efforts underway to create infrastructure to support future BECCS projects. Summit Carbon Solutions of Iowa has proposed a $4.5 billion project to install thousands of miles of pipelines to carry the carbon dioxide that could be captured at dozens of ethanol plants across five states to a storage site in near Bismarck, North Dakota. Building the pipeline will enable the plants to produce “net zero” fuel by 2030, allowing them to sell into markets that have adopted low-carbon fuel standards, the company says.
The proposal, however, has already sparked concerns among landowners and some environmental groups. Critics argue that industrial BECCS plants and supporting infrastructure will carry risks of leaks and pollution, and they fear that poor areas will shoulder the bulk of them, as they have in the past.
A Carbon 180 piece last year laid out a set of principles that should guide BECCS developments and inform federal policy, including safeguards for farm workers, reliable carbon accounting methods, and strong community protections.
Project developers should “start engaging the community early and take in their perspective and account for how it will impact them, their quality of life, their economic opportunities, or their environment,” says Meron Tesfaye, the author and a senior policy analyst at the Bipartisan Policy Center.
In effect, Mote is building an expensive hydrogen plant, which couldn’t compete on its own against the cheaper, dirty version made from natural gas. The economics may work in California, thanks to the state’s climate policies, but it and other BECCS projects will likely face trouble expanding elsewhere.
How widespread BECCS plants become, and how much they’ll actually help to remove carbon dioxide, will likely depend on what sorts of policies and regulations are put in place, and how careful companies are—or are forced to be—about the carbon accounting.
Other US projects could also take advantage of the federal tax credit, but in many cases that won’t be enough on its own to ensure that they can raise financing and earn profits, Tesfaye says. And only a handful of areas have enacted low-carbon fuel standards like California’s, including Oregon and British Columbia. Additional states have proposed or considered them, including Washington, New York, and Colorado.
Scaling up within California will entail other challenges as well. It will require building more plants, and deploying or developing trucks, pipelines, and storage sites for the fuels and carbon dioxide. In other words, it will necessitate a lot of permitting and development in a state where it’s notoriously difficult to approve and construct projects.
“If everything goes right, we will be producing molecules by 2024, but we are planning for unavoidable permitting delays,” Kennedy said. Still, Mote’s founders argue, there’s plenty of biowaste available to fuel their plants for the foreseeable future. And they’re confident the economics will work now and only improve over time as climate regulations tighten, assuming that they do.
Do these heat waves mean climate change is happening faster than expected?
General warming predictions are still on track, but recent heat waves are a stress test for the modeling of extreme events.
This CRISPR pioneer wants to capture more carbon with crops
New research at Jennifer Doudna's institute aims to create faster-growing, carbon-hungry plants using the gene-editing tool.
The future of urban housing is energy-efficient refrigerators
Adapting old, energy-inefficient buildings is less sexy but far greener than many high-tech solutions.
Running Tide is facing scientist departures and growing concerns over seaweed sinking for carbon removal
The venture-backed startup believes kelp could be a powerful tool to combat climate change. But some scientists fear the ecological risks on large scales.
Get the latest updates from
MIT Technology Review
Discover special offers, top stories, upcoming events, and more.