Transforming Concrete from a Carbon Emitter to a Carbon Sink

Carbon-Negative Concrete Will Be a Game-Changer for the Building Industry

There are only a few countries that are carbon-negative, and they are all small. Only one has been officially certified, and that is the Kingdom of Bhutan. It offsets four times as much carbon as its economy emits.

Most materials have a positive carbon footprint, meaning that the harvesting, extraction, manufacture, and shipping related to them releases carbon, or in other words, that they contribute to the climate crisis. Steel, concrete, and aluminum are among the worst offenders.

The building sector has been a major contributor to carbon emissions. Cement, the binder component of concrete, accounts for 8 percent of global carbon emissions, or 25 percent of all industrial emissions. One ton of cement emits almost a ton (0.9) of carbon. If we could populate an imaginary country with all the cement manufactured every year, it would be the third largest carbon-emitting country, trailing only the U.S. and China.

Universities and private companies are researching ways to reduce concrete’s carbon impact. One company, Partanna Global, has developed a concrete that minimizes CO2 emissions during manufacture while offsetting these few emissions by absorbing carbon from the atmosphere during the curing process. According to the company, it is as versatile and affordable as traditional concrete, and in addition, it is stronger and more durable.

Of course, the company does not reveal its proprietary formulas, but does say it uses steel slag, a biproduct when iron ore is turned into steel. It also uses desalination waste, a chemical left behind when brine or saline water is made potable. This alkaline, calcium-laced water saturates the slag during formulation, creating reactive compounds that absorb CO2 into the concrete mix to become the binding agent. Moreover, these reactive compounds continue absorbing carbon from the air throughout the life of the concrete.

 Since cement, a key component of concrete, is ubiquitous in buildings, Partanna, by developing a carbon-negative concrete, has been able to easily take the next step and create carbon-negative homes. They have built their first negative homes in the Bahamas and have secured an agreement with the government to build 1,000 more. Each of these modest 1,250-square-foot homes will capture 182 tons of CO2 from the air, the equivalent to the annual carbon absorbed by more than 5,000 mature trees.

Another factor that helped convince the Bahamas to commit to these new homes is that the concrete gets stronger when exposed to seawater, whereas traditional concrete is weakened by this exposure. This makes it ideal for low-lying communities faced with the threat of sea rise and storm surges.

Carbon-negative concrete would shift the building industry from being one of the biggest contributors to climate change to helping heal the planet, while recycling waste products into the concrete. 

The Big Picture on Electric Vehicles

Fewer Vehicles and Driving Fewer Miles Needs to Be Our Future

The world is rapidly moving toward electric mobility — bikes, scooters, cars, buses, and trucks. New rules proposed by the Federal Environmental Protection Agency (EPA) for more rigorous tailpipe pollution reduction means that within 10 years, two-thirds of all new cars, half of new commercial vehicles, and up to a third of new 18-wheelers could be electric. California has set new standards that require manufacturers to sell an increasing number of zero-emission freight trucks and buses.

These moves are momentous in tackling the 28 percent of total U.S. climate pollution that comes from transportation. The truck and bus component represents about one-tenth of all U.S. vehicle traffic but accounts for more than half the sector’s air pollution.

A word of caution, however. The fossil-fuel industry, in spite of its public statements supporting clean energy and its massive spending on messaging, sends more lobbyists than any country to every national or international meeting on climate for the purpose of slowing or disrupting progress toward a cleaner energy future. Moreover, it collects $5.2 trillion in subsidies annually (6.5 percent of global GDP) and continues to develop every opportunity to extract more fossil fuel.

Clearly, this pattern of extraction and exploitation must change if the planet is to be saved. Furthermore, cutting back on the amount of energy produced, including renewable energy, will make the transition to 100 percent renewables easier and faster to accomplish. The exception is in the lowest-income countries that need to increase energy use to meet basic human needs. The IPCC (Intergovernmental Panel on Climate Change) indicates that if we want to limit warming to around 1.5 degrees Celsius above pre-industrial levels, then we need to scale down global energy use, mostly in high-income countries. Why in rich countries? Because on average, we consume 28 tons of material stuff per person per year. Focusing on materials has a range of powerful benefits, including taking pressure off ecosystems. It means less deforestation, less habitat destruction, and less biodiversity collapse.

The framework for thinking about electric cars and trucks should include reducing the total number of cars, making them smaller, and reducing miles driven. The best way to achieve this scaling back is to invest in affordable (or even free) public transportation, which is more efficient in terms of materials and energy. Making it as attractive, clean, and convenient as possible is essential.

While sunshine and wind are obviously clean, the infrastructure we need to capture them and the products that use this clean energy are not. Transitioning to them is going to require dramatic increases in extraction of metals and rare-earth minerals with real ecological and social costs. We have deluded ourselves (or been deluded) many times by new technologies or material efficiencies that promise sustainable gains yet lead to more production, consumption, and greenhouse gases. Only by universally applying a net green analysis, which looks at the entire picture and focuses squarely on environmental impact reduction, will we help ourselves and our planet.

Is Rapid and Complete Degradation of Plastics Possible?

Bringing Nature’s Secrets Into Plastic Production May Finally Solve Disposal Dilemma

Plastics are ubiquitous and do not decompose. Every piece of plastic produced since 1907 still exists. A combination of physical, biological, and sunlight exposures can degrade plastic debris, but at most to a micro or nano scale. In essence, plastics pollute land, water, and air, posing environmental and health issues for all living creatures.

Scientists are beginning to realize that this longevity dilemma might be solvable, since many species build strong, long-lasting materials that still break down into simpler compounds that can be reused by other organisms in a healthy, regenerative cycle. Plastics are made of repeating units called monomers, which can be bonded together in long, sturdy chains called polymers. 

Natural organisms also produce complex polymer chains, but they can be broken down when enzymes fit into the bonds between monomers. These enzymes, found in the natural world, catalyze chemical reactions that unlock the bonds and break the chains into their component parts. With plastics, microbes and enzymes are only able to attack the surface, leaving the bonds mostly intact and out of reach of enzymes.

Thinking to help facilitate the degradation of plastics, scientists tried embodying enzymes directly in the production process. The high heat and great pressure of manufacturing, however, damaged the sensitive enzymes before they could work their magic. 

At one company, called Intropic Materials, researchers surmounted this barrier by basically taking another process from the natural world and combining it with plastics. Specifically, they utilized specialized types of molecules that exist inside many organisms called “chaperone proteins” that assist enzymes to “switch on” or move to where they need to be to work effectively. 

Before embedding these proteins in the production process, they found that first they needed to wrap them in a biodegradable cover to protect them when plastic is melted and extruded. Thus undamaged, the enzymes can do their job when the plastic’s useful life has ended. When exposed to composting conditions, i.e., moderate heat and moisture, the enzymes eat the plastic from the inside out within hours or days — not simply breaking it down into microplastics, but disintegrating it back into simpler, reusable molecules as soil or even new plastics.

Efforts to recycle plastics have only been marginally successful. Our attempts to wean ourselves off plastics have been even less successful. But now, by bringing together natural and synthetic materials and processes, Intropic Materials is opening the door to a more innovative and sustainable future.

Homes of the Future?

A First: A Fully 3D-Printed House Made from Bio-Based, Low-Carbon Materials

One of my recent articles focused on the big potential of 3D-printed houses. However, the printing process used up until now has only created walls. Carpenters are still needed to install doors and windows, and build the roof. On the plus side, just printing wall panels produces walls of greater tensile and flexural strength and in half the time of traditional practices.

Modular building, panelized construction, and building with structural insulated panels (SIPs) have received attention as new technologies with potential to speed up production and reduce waste. Widely used in some countries, these innovations have been slow to be incorporated in the U.S. While 3D printing could just be another one of these new approaches, it could actually help solve the construction industry’s labor and supply-chain issues.

One building company, Mighty Buildings, has produced the first 3D-printed net-zero home using printed components. The one sustainable drawback of its process, as well as that of all other 3D efforts, is that they use concrete for their walls. The production of cement, the binder in concrete, accounts for around 8 percent of all greenhouse-gas emissions worldwide. In addition to high embodied carbon, concrete has poor insulative properties. Fortunately, new concrete mixes are being fed into the 3D-printing nozzles that are showing promise of reducing emissions by half or more. 

The latest campaign in green building is to utilize materials that have low embodied carbon while avoiding materials such as spray and rigid foam, steel, and concrete — all currently being used in 3D-printed houses. However, 3D printing may be on the cusp of conquering this challenge: The University of Maine has produced a prototype printed house made entirely of bio-based, low-carbon materials. The materials exuded by its printer are composites of wood fibers and bio-resins. About 60 percent of the material is wood flour by weight and the rest is resin. According to the team, this building is fully recyclable.

Another breakthrough with the BioHome3D is that all components — floors, walls, and roof — are printed and with high R-values (insulation values). Culminating decades of research by the university team, the printed material resists decay and rot because of the resin that prevents water intrusion. When it is time to recycle, the building can be ground up and sent through a printer to produce another house. Wall and roof sections are printed with an inner and outer layer connected by a truss-like reinforcement. The cavity between the two layers is filled with cellulose insulation. This design allows for increasing the wall thickness and improving the insulative performance as needed.

Construction is a traditional industry, slow to change. It is, however, moving toward net-zero performance buildings. Maybe it will also start making houses that are carbon storage units.