Cement and concrete rank after coal and oil as the largest industrial climate killers: the construction sector accounts for roughly eight percent of global CO2 emissions. Researchers at Worcester Polytechnic Institute (WPI) in Massachusetts have now developed a building material that reverses this cycle. It absorbs CO2 from the air during hardening instead of emitting it, while withstanding structural loads.
How ESM Works: An Enzyme as Builder
The material is called Enzymatic Structural Material, or ESM. WPI researcher Nima Rahbar and his team announced in December 2025 in the journal Matter that they use an enzyme that converts carbon dioxide directly from ambient air into solid calcium carbonate minerals. These minerals form the material's basic structure during hardening.
Calcium carbonate is not new. Shells and corals build it the same way: through enzymatic mineralization. The WPI team replicated this biological process in the laboratory and translated it into an industrially producible building material. The result: one cubic meter of ESM binds more than 6 kilograms of CO2 during manufacture and hardening, according to the Matter study. Conventional concrete emits 330 kilograms per cubic meter during production. That's a 55-fold difference.
The measured compressive strength is 25.8 megapascals, exceeding the minimum standard for construction concrete. The material is also repairable and fully recyclable, which according to WPI could reduce construction costs and landfill waste long-term.
Why the Construction Sector Burdens the Climate Particularly
Concrete is the world's most-used building material: roughly four billion tons of cement are produced annually. The problem lies in manufacturing. Producing cement clinker, the binder in concrete, requires burning limestone above 1,400 degrees Celsius. Two sources of CO2 escape: fuel combustion and the thermal decomposition of limestone itself. Together these emissions account for roughly eight percent of global CO2 emissions, more than all global air traffic combined.
Previous approaches have focused on cement production itself: additions like fly ash or slag, alternative cement types, or CO2 capture at cement plants. ESM follows different logic: the material needs no kiln and uses CO2 as a building block instead of waste product. Researchers cite roof plates, wall panels, and modular building elements as potential first applications.
In Perspective: Hempcrete, Cross-Laminated Timber, and What Makes ESM Different
ESM is not the first building material developed as an alternative to CO2-heavy concrete. Hemp concrete (hempcrete), a mix of hemp stalks and lime, is considered CO2-negative over its lifecycle because the hemp plant binds far more carbon during growth than is released through processing and transport. Hempcrete, however, cannot serve structural roles: its compressive strength is too low for floors or foundations. It's used mainly for insulation.
Cross-laminated timber (CLT) stores carbon bound during tree growth long-term in the wood itself. Germany's Federal Environmental Agency estimates wooden buildings save substantial CO2 compared to concrete if sustainably managed forest regrows. CLT is now used in Germany, Austria, and Switzerland for multi-story buildings. Limits: fire safety codes and limited availability of construction wood restrict scalability.
ESM is thus the first described material that is both CO2-negative and pressure-resistant enough for structural applications. The decisive difference from wood and hemp: ESM requires no agricultural land. It binds CO2 directly from the air, independent of location or season.
What Still Prevents Global Deployment
ESM is a laboratory success, not yet a building product. Several hurdles stand between publication in Matter and use on construction sites.
First is scalability: the enzyme must be producible in industrial quantities without costs destroying competitiveness against concrete. Cement clinker currently costs roughly 80 euros per ton. Every alternative material must stay in this range to be relevant in the mass market.
Second is long-term behavior: the study describes compressive strength and CO2 binding in the lab, but makes no claims about behavior under moisture, frost, or salt over decades. Concrete has been in use for centuries; ESM for mere months in the lab.
According to the university, WPI has begun talks with industry partners to move the material from lab to pilot projects. Whether and when ESM reaches regular construction work will depend on scalability of the enzyme production process. The construction industry is one of the least innovation-prone globally: new materials typically take ten to twenty years from lab study to market approval.