Brimstone Energy ($55M to use non-limestone to produce carbon-negative cement)

Brimstone Energy, a cleantech company founded in 2019, produces carbon-negative Portland cement and supplementary cementitious materials by using non-limestone from carbon-free calcium silicate rock instead of carbon-heavy limestone.

Challenges: cement production

Cement production begins with the heating of crushed minerals in a kiln to produce clinker. Cement is produced by grinding clinker into a powder, combining it with a few additives, and then combining it with other minerals.

The current method of cement production involves the use of fossil fuels to heat cement kilns. As dry-process kilns have replaced wet-process kilns and as grinding equipment has become more efficient, the thermal energy and electricity intensities of cement production have gradually decreased over the past few decades.

However, cement production contributes significantly to greenhouse gas emissions, especially carbon dioxide (CO₂) emissions. The cement industry is among the leading industrial sources of CO₂ emissions, accounting for 8% of global greenhouse gas emissions.

Therefore, reducing CO₂ emissions from cement production has been a topic of interest for university and industry researchers. However, it is difficult to reduce CO₂ emissions while producing enough cement to meet demand. During 2015-2021, the direct CO₂ intensity of cement production increased by approximately 1.5% per year. To get on track with the Net Zero Emissions by 2050 Scenario, annual emissions reductions of 3% are required until 2030.

To reduce carbon emissions in cement production, key strategies include improving energy efficiency, switching to lower-carbon fuels, promoting material efficiency, and advancing innovative near-zero emission production routes.

Improving energy efficiency involves using less energy to produce cement, which can be achieved through the use of more efficient equipment and processes. Switching to lower-carbon fuels involves using alternative fuels such as biomass, waste, and natural gas instead of coal. Promoting material efficiency involves reducing the clinker-to-cement ratio and total demand, which can be achieved through the use of alternative materials such as fly ash, slag, and pozzolana. Advancing innovative near-zero emission production routes involves developing new technologies such as carbon capture and storage (CCS) and alternative raw materials.

new blueprint for zero-emission cement and concrete by 2050 has been proposed by researchers. The blueprint examines two scenarios, production-centric and whole-systems approaches, for decarbonizing cement and concrete throughout their life cycle. The production-centric strategy investigates ways to achieve net-zero emissions solely by reducing the carbon intensity of cement and concrete production.

Brimstone Energy Technology

Brimstone Energy has developed a method for producing concrete from Portland cement and supplementary cementitious materials (SCM), such as pozzolan, derived from the same non-limestone rocks or minerals. This significantly simplifies the concrete production process and could potentially reduce production cost. In addition, Brimstone Energy’s concrete production process extracts magnesium compounds that can be used to capture CO₂, thereby reducing CO₂ emission and achieving carbon neutral or even carbon negative.

Brimstone Energy process

The diagram below depicts the Brimstone process of concrete production.

Brimstone Energy process for producing concrete (ref. US20230036470A1).
Brimstone Energy process for producing concrete (ref. US20230036470A1).

The production system mainly comprises apparatus of leacher, precipitator, dehydrator, dechlorinator, and clinkerer.

  • Leacher

As the starting material, non-limestone rocks or minerals are milled to a desired particle size range before being fed into the leacher.

In the leacher, the leaching agent, HCl (10-37%) leaches non-limestone particles. The leaching process yields a calcium-rich liquid (also referred to as a leach solution or pregnant leach solution) and a calcium-depleted solid (also referred to as a leachate residue). Through filtration, the separator separates the leachate residue from the leach solution. The leach solution is routed to a precipitator, and the leachate residue is sent to a solid processing system.

The predominant component of leachate residue is amorphous silica (SiO₂), which functions as supplementary cementitious material (SCM) or pozzolan. Other amorphous Fe and Al compounds that also serve as pozzolans may be present in the leachate residue. The solid processing system processes the leachate residue so that it has desired properties and delivers the processed leachate residue to the dechlorinator to supply silica.

  • Precipitator

The precipitator receives calcium-rich liquid from the leacher and removes non-calcium salts , such as salts of Al, Fe, and Mg, from the calcium-rich liquid.

The precipitator may have multiple precipitation units. For example, the precipitator has a first  base precipitation unit that uses bases such as CaO, Ca(OH)₂, or CaSiO₃ to precipitate a first set of aluminum, iron, and magnesium compounds. The precipitator may also include a second and third pyrohydrolysis precipitation units to precipitate aluminum and iron compounds from the calcium-rich liquid.

Magnesium precipitate, such as Mg(OH)₂, can be used to react with CO₂ (CO₂ in a flue gas, atmospheric CO₂, and CO₂ source) to produce magnesium-carbon dioxide products such as MgCO₃, and thus sequester CO₂. The amount of CO₂ thus sequestered can reduce the total amount of CO₂ produced by the total process, sufficiently to make the total process carbon neutral or even carbon negative.

The aluminum and iron precipitation products are delivered to the clinkerer for use as flux in the clinkerer.

  • Dehydrator

The dehydrator receives calcium-rich liquid from the precipitator after non-calcium compounds have been removed. The dehydrator removes water from the calcium-rich liquid to produce solid calcium chloride (CaCl₂) by heating the calcium-rich liquid until a desired level of dryness is achieved. The steam produced in the dehydrator is delivered to the dechlorinator.

  • Dechlorinator

The dechlorinator receives the calcium chloride (CaCl₂) from the dehydrator and dechlorinates CaCl₂ to produce calcium compounds, such as calcium oxide (CaO). In the dechlorinator, CaCl₂ is heated to a sufficient temperature in the presence of steam to drive chlorine gas (Cl₂) off. The chlorine gas reacts with protons (H⁺) from the steam to regenerate HCl, which can be reused as the leaching agent in the leacher. At the same time, CaCl₂ is converted to dechlorinated calcium compounds, CaO, via the following chemical reaction:
CaCl₂ + H₂O → CaO + 2HCl

More generally, reactions can be represented as:
CaCl₂ + SiO₂ + H₂O → Ca silicates and other species + 2HCl

  • Clinkerer

The clinkerer receives dechlorinated solid calcium compounds from the dechlorinator and further treats the solid in the presence of flux to produce clinker. Flux consists of aluminum and iron compounds delivered by precipitator units. Clinker from a clinkerer is sent to a clinker processor to produce Portland cement and other types of cement.

How Brimstone Energy reduces CO₂

Brimstone Energy processes produce less CO₂ than conventional cement production methods which typically require calcining of limestone and sintering.

Brimstone Energy processes do not utilize limestone starting materials that comprise large amounts of calcium carbonate (CaCO₃). Fuel used to provide energy for various steps (heating, etc.) emits 30-50% less CO₂ than a conventional method for producing the same amount of cement from limestone.

Magnesium compounds produced during the precipitation steps can be used to sequester CO₂, including atmospheric CO₂ and CO₂ that is a component of flue gas produced in combustion steps to produce energy for the process.

Brimstone Energy process is carbon neutral or even carbon negative, up to 500 kg CO₂ sequestered/1000 kg cement produced. It will be appreciated that the decreased amount of CO₂ compared to conventional processes, or even negative carbon dioxide, can be converted into carbon credits. Such credits can be based on CO₂ avoided (e.g., compared to a conventional process for producing the same amount of equivalent cement) and CO₂ sequestered (e.g., by magnesium species produced in the process).

Brimstone Energy Patent

  • US20230036470A1 Cementitious material production from non-limestone material
  • US17/894,621 Process to make calcium oxide or ordinary portland cement from calcium bearing rocks and minerals

Brimstone Energy Technology Applications

  • Low-carbon cement production

Brimstone Energy uses carbon-free calcium silicate rock instead of limestone, eliminating process emissions responsible for up to 60% of cement’s overall emissions. The cement produced using the Brimstone Process™ is chemically and physically identical to conventional portland cement, maintaining the same quality and performance.

Brimstone Energy Products

Brimstone Energy’s main project is the development and implementation of the Brimstone Process™, as described above. The Brimstone Process™ is a breakthrough in cement production, making carbon negative portland cement with carbon-free calcium silicate rock instead of limestone. Cement made with The Brimstone Process™ is chemically and physically identical to conventional portland cement, with the same quality and performance builders have trusted for over 150 years.

Brimstone Energy Funding

Brimstone Energy has raised a total of $55M in funding over 2 rounds:

Their latest funding was raised on Mar 24, 2022 from a Series A round.

The funding types of Brimstone Energy.
The funding types of Brimstone Energy.

Brimstone Energy Investors

Brimstone Energy is funded by 12 investors:

DCVC and OUP (Osage University Partners) are the most recent investors.

The funding rounds by investors of Brimstone Energy.
The funding rounds by investors of Brimstone Energy.

Brimstone Energy Founder

Cody Finke and Hugo Leandri are Co-Founder.

Brimstone Energy CEO

Cody Finke is CEO.

Brimstone Energy Board Member and Advisor

Rachel Slaybaugh and Stefan Zlatev are Board Member.

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