Minn. startup uses plants to trap CO2 emissions

A Minneapolis startup company wants to become a leader in the emerging carbon capture and storage market.

Carba, co-founded by a University of Minnesota chemical engineering professor and a former student, has developed a portable reactor that converts plant waste into a charcoal-like substance called biochar. That material can then be buried to seal carbon in place for generations.

The company's backers believe it could prove to be an inexpensive and energy-efficient method to remove carbon dioxide from the atmosphere — something the latest Intergovernmental Panel on Climate Change report, released Monday, says will be necessary for preventing the most devastating effects of climate change.

"There's a huge negative emissions problem and nobody has the technology to scale without using a ton of energy or capital," said Andrew Jones, Carba's founder and CEO. "We believe we have cracked that nut."

Trees and plants are the world's biggest carbon sink. Through photosynthesis, they store carbon dioxide throughout their lives, but after they die, they decay and release that carbon back into the atmosphere.

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Carba's technology offers a way to lock that into a solid form instead. The company promises to consume a fraction of the energy of other technologies, such as direct air capture methods. In addition, those technologies demand either centralized plants or investments of hundreds of millions of dollars per site.

Carba's answer: let trees and plants do the work of pulling carbon from the atmosphere, and then lock that biomass into a stable form before it can decay. Jones believes biochar should be buried to remove any chance of carbon release.

"If we harvest all the biomass waste out there and convert it to something more stable, like a char, then bury it underground, we’re reversing the coal mining process," Jones said. "We can take 1 trillion tons of CO2 that we’ve dug up and put into the air, suck it into the trees and the plants, take their waste product, bury it underground, and store it indefinitely."

The company was recently named a finalist for an incubator program by Minnesota clean energy accelerator Grid Catalyst, and it is partnering with trash and recycling giant Waste Management to deploy its first reactor at a Twin Cities waste facility.

Waste Management said in a prepared statement that it seeks to reduce its carbon emissions by 42% by 2032 and sees biochar as a potential solution. Wood waste at its suburban facility currently either becomes compost or is burned for energy.

The company is "excited to partner with Carba on this sustainability research project that has the potential to demonstrate tangible scientific progress towards climate solutions."

Jones said biochar offers co-benefits for Waste Management. It helps contain environmentally destructive elements such as the fluoridated forever chemicals (widely known as PFAS), mercury, methane and odors. "That's a benefit to the whole community," he said.

Grid Catalyst founder and president Nina Axelson said Carba merges energy innovation and clean energy ecosystems. "I feel like Carba sits exactly between those two because it's carbon capture technology, but there's a very big energy efficiency component to their technology," she said.

Jones met co-founder Paul Dauenhauer in 2005 while he was a chemistry undergraduate at the University of Minnesota. Dauenhauer holds an endowed chair, runs his own research lab, and has won many awards, including a MacArthur Foundation "genius grant" in 2020. The serial entrepreneur has spun off his research into three startup businesses involving biomass.

The two previously co-founded Activated Research Company, which provides chemical analysis for greenhouse gases, biofuels, sustainable aviation fuels, jet fuels and pyrolysis products.

An inexpensive, scalable technology like Carba is the key to combating carbon emissions, Dauenhauer said. The energy consumption is a fraction of what direct air capture would consume. "I think a lot of people may be good at chemistry or physics and they understand how to sequester carbon but don't know how to do it cheaply," he said. "You have to cut every cent out of the processing and logistical sequence of getting that carbon underground. And that's where we excel."

The North American market alone creates a billion tons of biomass annually, which means the company shouldn't be limited by supply chain shortages. Carba's technology is also feedstock agnostic, so it can use whatever waste materials are cheaply available.

The mobile reactors can move to different dropoff sites to reduce miles traveled by truckers hauling biomass. The size of a wood chipper, the reactors heat plant waste in an oxygen-less environment to a temperature around that of a commercial pizza oven in a process known as torrefaction.

Initially, Carba considered building a biomass plant before deciding that would take too long, cost too much, and require years of studies and permitting, Jones said. However, that remains the problem of carbon capture facilities at coal or other fossil fuel plants — the cost can top $1 billion and the infrastructure takes years to build.

Several other companies are pursuing similar approaches to carbon capture. CDR.fyi, a community-driven initiative to monitor the carbon removal market, wrote in a Medium post that biochar delivered 87% of the carbon removed from the market last year. Of the 10 most active companies, nine targeted biochar for carbon removal.

Jones and Dauenhauer wrote a peer-reviewed article for ACS Engineering that reported that torrified carbon requires just a small energy input compared to direct carbon capture.

Carba believes the bioreactor will cost less than $200 to break down a ton of biomass. Through selling credits on the evolving carbon removal market Carba should more than pay for the bioreactor's production costs and generate profits, Jones said.

Carba plans to build and own the reactors, with revenue coming from the sale of carbon removal credits in voluntary markets. The markets reward producers with more money for permanence, defined as carbon storage for at least 100 years.

The global carbon removal market is expected to grow from nearly $2 billion in 2020 to $7 billion by 2028, Fortune Business Insights predicts. CDR.fyi reports 593,000 tons of carbon were purchased last year, a 533% increase over 2021.

Last year Stripe, Alphabet, Shopify, Meta, McKinsey Sustainability and a handful of other companies announced they would invest $925 million in carbon removal companies. More than 3,000 companies have committed to being net zero in the future, a goal that will likely lead to buying carbon dioxide removal credits from Puro.Earth, Carbonfuture or other marketplaces.

Jones identified travel, bank and technology sectors as leaders in the carbon dioxide removal market, with even oil and gas companies expressing interest.

Brendan Jordan, vice president of the Great Plains Institute, said carbon removal technology and markets would become increasingly crucial to reducing global greenhouse gases. The International Energy Agency and the Intergovernmental Panel on Climate Change predict the world will "overshoot carbon budgets, and that's why there is so much interest in carbon removal strategies," he said.

Frank is an independent journalist and consultant based in St. Paul and a longtime contributor to Midwest Energy News. His articles have appeared in more than 50 publications, including Minnesota Monthly, Wired, the Los Angeles Times, the Minneapolis Star Tribune, Minnesota Technology, Finance & Commerce and others. Frank has also been a Humphrey policy fellow at the University of Minnesota, a Fulbright journalism teacher in Pakistan and Albania, and a program director of the World Press Institute at Macalester College. Frank covers the state of Minnesota.