Changing Transportation and Housing Patterns

Addressing Climate Change by Changing Mobility and Housing Biking, small businesses, and social housing are preserving the charm of Paris.

With increasingly bleak reports of atmospheric concentrations of carbon dioxide, are there any places making rapid progress on climate change that can offer hope? Maybe.

Transportation, the second largest source of greenhouse-gas emissions, is becoming electrified. Even better, however, is reducing the use of cars through policies designed to increase walking, biking, and public transportation. In 2021, Paris rolled out a plan to become 100 percent cycle-friendly in five years. This journey was already well underway — car trips in Paris fell by more than 60 percent in the previous two decades, public transit rides increased by 40 percent, and bicycle trips increased by 20 percent. Bicycling in the French capital more than doubled between 2020 and 2024 from 5 percent to 11 percent. Cycling infrastructure, bicycle parking spots, and traffic light changes prioritizing cyclists are mushrooming. Car parking on Paris streets is systematically being eliminated and has shrunk by more than 50 percent.

Another innovation that complements these mobility changes is in housing. Since the start of this century, municipal policies have aggressively been creating social housing to keep middle- and lower-income residents in the heart of the city. One of the goals of this effort is to preserve the ineffable character of Paris — beloved by the French and tourists alike. One-quarter of all Parisians live in public housing, an increase from 13 percent in 2000. The philosophy is that those who produce the riches of the city deserve to live in it. Teachers, sanitation workers, janitors, nurses, university students, bakers, and butchers are all benefiting from this program.

Like cities around the world, Paris is confronting growing homelessness. The initiatives that City Hall has taken to keep low-income citizens from being squeezed out go far beyond what most other cities are doing. Whether Paris will achieve an equitable, diverse city remains to be seen. The challenges are formidable, but the goal is to have 30 percent public housing for low-income residents and 10 percent for middle-income inhabitants by 2035. Paris is already a dense city, but it can use its legal authority to preempt the private sale of a building and convert it into public housing. The city has also sharply restricted short-term rentals, while transforming old train rights-of-way and condemned buildings into social housing. Over the past 25 years, the city has built or renovated 82,000 apartments for families and added 14,000 student units. Rents can be as little as $650 per month for apartments.

Housing is only part of the equation for achieving a balanced city; the other part is creating a healthy mix of small businesses: boulangeries, cheese shops, bicycle repair places, corner delis, flower stalls, and artisan workshops. The city can favor these types of small businesses because it is the landlord of 19 percent of city shops. It limits the number of chain businesses in preference for small operations, thus creating continuity and an enhanced sense of timelessness.

Moving Biking from Minority to Majority Status

Slowing Cars on Most Urban Streets to Lower than 18 mph Opens Cycling to All Ages

Santa Barbara has been investing heavily in growing and improving its bicycle infrastructure, as have many other cities in this country. These investments lead to a growth in cycling but seem to plateau at around 8 percent. In Europe, however, there are many cities where cycling reaches 80-90 percent of the population. What accounts for the huge disparity?

The difference seems to be safety. In the Netherlands, for instance, bike and pedestrian safety is addressed holistically and uncompromisingly. Dutch road engineers continuously seek to remove “conflict points and zones” for riders, which mostly occur at intersections, transition sections, or stretches of roads where bikes are competing for space with other modes of transportation. In California, bike-lane engineering standards provide high-level safety between conflict points but not at intersections where conflict danger is greatest. We still prioritize speed and comfort for car drivers over the people that live, work, walk, and bike on our streets.

What does safe infrastructure look like? The Dutch have a lot of bike lanes that are separated and protected from cars with highly engineered intersections that almost eliminate interaction (conflict) between drivers and cyclists. Wherever the two have the possibility of interacting, the speed limits are below 20 miles per hour (mph) with cameras for enforcement. The Dutch know that slow cars are safer; fast cars are never safe. Eighty percent of all urban streets in Holland are posted at 18 mph or less, a speed at which collisions can cause serious but survivable injuries.

Another critical safety factor is that most drivers are also cyclists with children (this is the case whenever cycling gets near 80 percent), so they are extremely careful and attentive of cyclists. In most northern European cities where bike riders are ubiquitous, urban streets are intentionally narrow, designed with frequent speed bumps, and have many stop signs. When collisions do occur, the default assumption is that the larger mode is at fault, which is not the case in the U.S. 

Uncompromisingly safe infrastructure for cyclists leads to the quantum leap from around 8 percent to 80 percent. Many benefits accompany this growth: improvements in air quality and public health, plus significant offsets to climate change. It also moves a community toward 15-minute neighborhoods.

People love to ride bikes: It is invigorating, relaxing, efficient, and convenient. It fulfills our need for daily exercise, keeps us limber, and it’s free. It is a truly equitable form of transportation, available to rich and poor alike. Seniors can bike years after they give up driving. Kids who bike tend to be among the happiest young people. Even people with disabilities can use adaptive bicycles.

Santa Barbara needs to learn from European cities that have mastered the leap to 80 percent bike riders. It seems a perfect fit for our benign climate.

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. 

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.