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.

A 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.