Blue Planet Carbon-Negative Synthetic Limestone Aggregate

Blue Planet Systems is a carbon capture and utilisation company based in Los Gatos, California, founded and led by Dr. Brent Constantz, with a Canadian subsidiary, Blue Planet Technologies Canada Ltd. It addresses concrete's share of global CO2 emissions by turning captured CO2 into the aggregate that makes up about 75% of concrete by mass.

Its patented geomimetic mineralisation process mimics how limestone forms in nature: CO2 from cement plants, steel plants, gas power stations, refineries, hydrogen plants or direct air capture, used directly from flue gas without purification and at concentrations as low as 5%, is combined with calcium and alkalinity from waste materials such as demolished or returned concrete, cement kiln dust, steel slag, fly ash, bauxite residue or silicate rock. The output is carbon-negative synthetic limestone aggregate, plus upcycled recycled concrete aggregate or an SCM by-product depending on the feedstock. Buyers include aggregate suppliers, ready-mix producers, cement and steel plants, and developers.

• Geomimetic mineralisation: converts CO2 into synthetic limestone that stores it permanently as a mineral.
• Any CO2 source: uses raw flue gas without purification, demonstrated at as little as 5% CO2.
• Waste calcium feedstocks: demolished concrete, cement kiln dust, steel slag, fly ash, bauxite residue or silicate rock.
• Upcycled RCA: processing waste concrete yields recycled aggregate usable at higher rates in structural concrete.
• SCM by-product: slag or kiln dust feedstocks also produce a supplementary cementitious material.
• Carbon credits: permanent mineralisation generates carbon removal credits offered for sale.

Cement and steel plants in Vietnam can partner to turn flue gas and slag into synthetic aggregate sold to ready-mix producers. Construction waste recyclers can upgrade demolished concrete into higher-value aggregate. Developers of green-certified projects can specify carbon-storing aggregate to reach near net zero embodied carbon concrete.

Each tonne of synthetic limestone aggregate permanently mineralises 440 kg of CO2, and the company states the aggregate matches quarried aggregate in strength, performance and cost. Because aggregate is about 75% of concrete by mass, swapping it can bring concrete to net zero embodied carbon, as in a 2025 slab placement. Using flue gas directly avoids costly CO2 purification and liquefaction, and waste concrete or slag replaces quarried rock.

Aggregate is the largest component of concrete, yet most decarbonisation efforts focus on cement, leaving a large untapped carbon storage opportunity. Vietnam faces tightening river sand and quarry supply alongside rising construction waste, slag and fly ash volumes, so manufactured aggregates that also store CO2 address both resource and emissions pressures.

Located at 100 Cooper Court, Los Gatos, California, with subsidiary Blue Planet Technologies Canada Ltd. Founder and CEO Dr. Brent Constantz previously founded Norian, Skeletal Kinetics, Calera and DeepWater Desal. Has a VP of business development and licensing; Holcim appears among its partners. In 2025 it placed what it calls the world's first net zero embodied carbon concrete slab.