A Sweet New Way to Capture Carbon

CC&E's Brian Snyder investigates the potential of sugarcane and other feedstocks to help capture carbon emissions.

BATON ROUGE - Carbon capture projects have been big news in Louisiana lately, as industrial facilities in the state look to reduce their overall carbon emissions in hopes of meeting the state’s goal of net-zero emissions of carbon dioxide by 2050.

The majority of these projects use energy intensive industrial technologies to capture emissions from smokestacks and there are also plans to achieve negative emissions, ie activities that remove carbon directly from the atmosphere. But Department of Environmental Sciences Associate Professor Brian Snyder, along with Harun Rashid and Olufemi Olorode of the Department of Petroleum Engineering, and Carlie Dutile of the Department of Biological and Agricultural Engineering, is working on another method, one using something familiar to denizens of south Louisiana: sugar cane, in a process called Biomass Slurry Fracture Injection.

Snyder sat down with us to discuss his research. The following conversation has been edited for clarity.

So carbon capture is normally associated with industrial processes. Can you explain how carbon capture would work using biomass?

So when we do direct air carbon capture, that is taking the carbon dioxide out of the air with industrial systems, it’s very energy intensive. But plants naturally do the same thing, gather carbon dioxide out of the atmosphere, and this process takes advantage of that.

Use sugar cane as an example. A field of sugar cane naturally pulls carbon dioxide out of the atmosphere as it grows. When that sugar cane is harvested, only a portion of it is used, leaving behind the rest of the plant, which is known as sugar cane bagasse. Normally, this bagasse would release carbon dioxide back into the atmosphere as it decomposed. In fact, if you drive around south Louisiana after a harvest, you’ll see these giant mounds of sugarcane bagasse, that are just left to decompose. But with biomass slurry injection, instead of allowing that biomass to decompose above ground, you would grind the plant matter into a slurry and inject it deep into the ground, using a waste disposal process the oil and gas industry has been using for years called slurry fracture injection. The only difference between what the oil and gas industry has been doing and what we are proposing is we want to use a biomass slurry.

You’re talking about sugar cane. Are there other types of crops good candidates for this process? 

We’ve conducted analysis using sugarcane bagasse, rice straw and energy cane. We’ve found that all have significant economic potential and can store carbon underground while simultaneously reducing the flux of other greenhouse gases, like methane. There is also a waste from bourbon production called stillage which I think has potential.

How does BSFI compare to industrial carbon-capture projects?

“ We are going to need something like 5 billion tonnes of negative emissions every year in order to meet the goals of the Paris Agreement on Climate Change...We are going to need industrial direct air capture, new technologies like BSFI, and all the other systems that other CC&E faculty are working on like carbon storage in wetlands and oceans. ”

In industrial carbon-capture projects, you’re probably injecting something like a million or 2 million tonnes of CO2 a year. But with BSFI, you’d be injecting more like 30,000 tonnes per year, which means you don’t have to transport as much biomass over long distances, but you would need more wells than in industrial direct air capture systems.

So the scale is different. 

And the cost. The Department of Energy has a goal for carbon removal from the atmosphere for costing less than $100 a tonne. Our models suggest that the BSFI process comes out to less than about $95 a tonne using the feedstocks we are studying which is less than half the cost of industrial direct air capture. But in total, we are going to need something like 5 billion tonnes of negative emissions every year in order to meet the goals of the Paris Agreement on Climate Change.  No single process can do that, so we are going to need industrial direct air capture, new technologies like BSFI, and all the other systems that other CC&E faculty are working on like carbon storage in wetlands and oceans.