A Focus on Pyrolysis Coproducts

CHAR Technologies builds its business case around flexibility in feedstock and outputs.
By Sue Retka Schill | April 15, 2022

With three projects in development, Toronto-headquartered CHAR Technologies is poised for commercialization of its high-temperature pyrolysis (HTP) process, producing biocarbon and renewable gases. “We’re in the right time with the right technology, and the opportunities are pretty substantial,” CEO Andrew White says.

CHAR Technologies commissioned its demonstration/small commercial-scale plant in London, Ontario, in 2018, using anaerobic digestate as the feedstock and producing five tons per day of biocarbon for testing. Now, a California project, also using digestate, will double the throughput of the London plant and test hydrogen production from syngas. That project is expected to be online this fall. Two Canadian projects have been announced that will use woody biomass and quadruple the demo’s throughput.

The company’s approach has been to develop multiple products geared to existing markets, White says. “The financial viability of a project isn’t limited to a single output like biocarbon, but it’s biocarbon and syngas. The syngas can be used for direct energy, as renewable natural gas (RNG) or for green hydrogen.” On the feedstock side, the technology fits places where the biomass is challenging to handle or there are disposal issues. “Put all those pieces together, and you get a viable opportunity,” he says.  

De-risking is another theme for the company, White says, using a modular concept where the kiln—the core of the HTP process—can be factory built. And while the technology around the kiln, biocarbon products and syngas is proprietary, the systems used to upgrade the syngas to RNG or hydrogen are off the shelf.

CHAR Technologies’ process introduces raw biomass into a kiln—basically, a large tube heated externally with burners. When heated for 30 to 60 minutes at temperatures between 500 and 600 degrees Celsius (932 to 1,112 degrees Fahrenheit) and in the absence of oxygen, the biomass does not burn. Instead, syngas is driven off, leaving concentrated carbon. A portion of the syngas produced is cleaned up and used in the external burners to make the process self-sustaining. Excess pyrolysis gas can be upgraded to green hydrogen, as it will be in the California project, or RNG, which is the plan for the Canadian projects.

By adjusting temperature and holding time, CHAR Technologies produces either an activated charcoal, trademarked SulfaCHAR, or a biocoal, trademarked CleanFyre, that has a slightly higher energy density than the best coal it can displace. “In the Canadian context, biocoal to help heavy industry decarbonize is in huge demand,” White says.

Concept to Commercialization
White began working on pyrolysis as a graduate student at the University of Toronto. Following a tour of biogas plants aimed at improving methane gas cleanup, he brought back samples of the digestate to investigate means of upgrading the low-value waste stream. He formed CHAR Technologies in 2011 to commercialize the technology to make SulfaCHAR.

The initial concept was to use the activated charcoal to reduce hydrogen sulfide in biogas plants. SulfaCHAR can be used in the digester itself, or be used to help in cleaning the digester’s gas stream. The added benefit, White says, “is because of the chemistry of the SulfaCHAR, it converts hydrogen sulfide into elemental sulfur, so it has a second use as a sulfur-rich biochar for soil amendment.” By applying it to the soil, the material would be eligible for voluntary carbon credits.

The market as a soil amendment is likely to take some time to develop, however. The better opportunity is in producing CleanFyre as a biocoal, offsetting fossil coal. Canada is mandating carbon reductions and enacting carbon taxes if provincial targets aren’t met, White explains. “That carbon tax is supposed to rise to $170 per ton by 2030. If one ton of coal gives you three tons of greenhouse gas emissions, that’s over $500 for the carbon, plus the cost of commodity coal is something like $100 to $150 per ton.” CleanFyre’s carbon intensity ranges in the single digits above and below net neutral, mostly dependent upon the feedstock source, its transportation and handling, he says. “That emphasizes why there is a big demand and opportunity to help heavy industry decarbonize.” 

But while biocoal presents an important opportunity, White adds that the RNG side of the equation has been equally important in the company’s approach to developing its two Canadian projects. “You can’t get long-term contracts for biocoal, but we can get long-term, fixed contracts for RNG,” he explains. “So that’s what you can build your project financing on. We’ve got ambitions to get 2 million gigajoules (GJ), or 1.9 million Btu of RNG into the grid in the next five years, based on woody biomass.”  

Surveying and geotechnical siting began in the fall at Kirkland Lake, Ontario, for an HTP project CHAR will build, own and operate next to a sawmill and down the road from a biomass power plant. The plant is projected to be online in 2025. In January, CHAR announced a second project in Quebec where it will deploy, own and operate an HTP system located next to a biomass power plant operated by a public-private consortium between the municipality of Saint Felicien and Greenleaf Power. Being colocated with a biomass power plant, much of the feedstock processing and handling systems are in place, lowering capital requirements and speeding up the project which is expected to come online in 2024.

Similarly sized, the two woody biomass HTP projects will initially have one kiln train, processing about 3.5 tons per hour of biomass. White explains that the London, Ontario, unit processes between 500 and 550 kilograms of biomass per hour, with an annual output of 2,000 metric tons of biocarbon when running 24/5. The two Canadian projects will use kilns that are about 2.5 times larger than the demo, achieving a throughput about four times greater. The Kirkland Lake project’s October announcement projected RNG production of 500,000 gigajoules per year and 10,000 metric tons of CleanFyre.

The scale up for the California project, billed as a test project, falls between the London demo and the two Canadian projects. Scheduled to come online this fall, the HTP-to-green hydrogen project is being developed in a partnerships with Hitachi Zosen Inova at Hitachi’s existing San Luis Obispo anaerobic digestion facility in California, processing 18,000 tons of solid anaerobic digestate into 1,320 tons of green hydrogen and 2,800 tons of biocarbon annually.

Feedstock, Output Flexibility
The projects and their varying feedstocks illustrate the flexibility of the CHAR Technologies process. White explains the kiln design can handle variable moisture. “Because we have burners, if we have higher moisture content coming in, it means we have to recover and recycle more of the syngas we generate to run the burners,” he says. “But we can manage moisture variability that starts at 10% and goes to 30% throughout the day. It just means we get a little less gas net output, because we use more internally to drop the moisture.”

Digestate at 65% moisture is a wet feedstock, White admits, but not that much wetter than green wood chips that can push 50% moisture. “For both, we want to pre-dry the biomass using waste heat and bring it down to between 15% and 30% moisture, depending on a particular recipe for that feedstock and the output.” 

The feedstock does impact outputs. “The kiln can run on either anaerobic digestate or woody biomass, or a blend,” White says. “But we want the project to be fed fairly consistently by feedstock type, so we know the output.” Whether the feedstock is digestate or woody biomass changes the percentage of hydrogen and carbon monoxide in the syngas, determining the design of the backend gas process.

On the biocarbon side, they won’t use digestate for CleanFyre because the ash would be too high, White explains. The better use would be for SulfaCHAR and soil application. “When you do pyrolysis, solid yields are about 25% on a dry basis. Any elements in the feedstock end up getting concentrated. I called it ash, but there are nutrients like potassium phosphorus. Digestate has a lot of those elements because it’s made from food waste.” 

When CHAR Technologies began operating its London, Ontario, plant four years ago, there was no budget for the gas piece, White continues. Instead, as the HTP kiln produced biocarbon for test runs, the syngas was analyzed by an online mass spectrometer before being destroyed in a thermal oxidizer. “We have a lot of data now on gas quality,” White says, “so we can go the next steps of converting that to green hydrogen in California or RNG in these Ontario and Quebec projects.”

RNG production uses a standard catalytic methanation process. “Our goal is to provide consistent, clean syngas to the catalytic process that has been built on the back end of the plant,” White says. “After that, you take it through standard biogas separation because it’s just like a biogas plant or landfill point at that point.”

The hydrogen upgrade has two options, depending on budget and hydrogen prices. “Directly off the kiln, we’re 40% hydrogen, sometimes 50% by volume. At that level of hydrogen, we can take it through a pressure swing adsorption unit to separate the hydrogen from the rest of the gas to get a nice, clean hydrogen. The other option is a catalytic process where we can boost the hydrogen to the order of 60 to 65% and take it through separation.”

 CHAR Technologies’ focus on gas coproducts is key, White says. “Simplest way to explain the difficulty in relying on just the biocarbon is to look at yield on dry basis—25% plus or minus, based on feedstock. Now, your feedstock has to be so cheap to be able to support a biochar price. But if we’re able to leverage that biomass and create RNG along with the biocarbon stream, suddenly, the economics of a plant are different. You can get a biocarbon produced for a price that the market needs for its adoption.”

Contact: Anna Simet