What are the solutions?

Impact:

Our analysis includes emissions reductions that can be achieved through the management and destruction of refrigerants already in circulation. Over thirty years, containing 87 percent of refrigerants likely to be released could avoid emissions equivalent to 89.7 gigatons of carbon dioxide. Phasing out HFCs per the Kigali accord could avoid additional emissions equivalent to 25 to 78 gigatons of carbon dioxide (not included in the total shown here). The operational costs of refrigerant leak avoidance and destruction are high, resulting in a projected net cost of $903 billion by 2050.

Impact:

Because fly ash is a by-product of burning coal, each ton created is accompanied by 15 tons of carbon dioxide emissions. Using fly ash in cement can offset only 5 percent of those emissions. Even so, if 9 percent of cement produced between 2020 and 2050 is a blended mix of conventional Portland cement and 45 percent fly ash, 6.7 gigatons of carbon dioxide emissions could be avoided by 2050. The production savings of $274 billion are largely a result of longer cement life span.

Impact:

Ninety-five percent adoption of low-flow taps and showerheads by 2050 could reduce carbon dioxide emissions by 4.6 gigatons, by reducing energy consumption for heating wasted water. Scaling other water-saving technologies would drive additional reductions. We model hot water only in order to calculate energy savings.

Impact:

We estimate the total production of plastics to grow from 311 million tons in 2014 to at least 792 million tons by 2050. This is conservative, with other sources estimating over 1 billion tons if trends continue. We model the aggressive growth of bioplastics to capture 49 percent of the market by 2050, avoiding 4.3 gigatons of emissions. While technical potential is even higher, this solution is constrained by limited biomass feedstock available without additional land conversion. The cost to produce bioplastics in this scenario is $19 billion over thirty years. While the financial costs are currently higher for producers, they are dropping quickly.

Impact:

The household and industrial recycling solutions were modeled together and include metals, plastic, glass, and other materials, such as rubber, textiles, and e-waste. Paper products and organic wastes are treated in separate waste management solutions. Emissions reductions stem from avoiding emissions associated with landfilling and from substituting recycled materials for virgin feedstock. With about 50 percent of recycled materials coming from households, if the average worldwide recycling rate increases to 65 percent of total recyclable waste, household recycling could avoid 2.8 gigatons of carbon dioxide emissions by 2050.

Impact:

As mentioned above, household and industrial recycling were modeled together. The total additional implementation cost of both is estimated at $734 billion, with a net operational savings of $142 billion over thirty years. On average, 50 percent of recyclable materials come from industrial and commercial sectors. At a 65 percent recycling rate, the commercial and industrial sectors can avoid 2.8 gigatons of carbon dioxide by 2050.

Impact:

Over thirty years, recycled paper can deliver .9 gigatons of carbon dioxide emissions reductions. Two key assumptions inform that conclusion: (1) recycled paper produces about 25 percent fewer total emissions than conventional paper, and (2) the percentage of recycled paper being used to produce paper would rise from 55 percent to 75 percent by 2050. Although increasing recycled paper content uses more electricity, the emissions related to harvesting and processing — and the total emissions from pulping and manufacturing — are higher for paper using virgin wood feedstock. The emissions reductions for this solution do not include carbon sequestration from standing trees that would not be harvested if the use of recycled paper grows.

Description:

In 2006, the Cascadia Green Building Council issued the Living Building Challenge (LBC). LBC is a holistic approach based on a simple question: How do you design and make a building so that every action and outcome improves the world? LBC has seven performance categories—Place, Water, Energy, Health and Happiness, Materials, Equity, and Beauty—that define what a living building is and does to benefit both people and planet.

Living buildings should grow food, use rainwater, and protect habitat, for example. They need to incorporate biophilic design, satisfying humankind’s innate affinity for natural materials, sunlight, views of nature, and more. Living buildings avoid all “red-listed” materials, such as PVC and formaldehyde. They are required to intentionally educate and inspire others—building as teacher rather than container.

When it comes to greenhouse gas emissions, living buildings make their greatest impact by producing more energy than they consume and offsetting all embodied carbon as well. LBC proves that, with the right investment and expertise, buildings can do more than simply be less bad. They can function like a forest, generating a net surplus of positives in function and form and exhaling value into the world.

Description:

Environmentalists have long struggled to save the world’s oceans from the perils of overfishing, climate change, and pollution. What if we have it backward? What if the question is not how we can preserve the wildness of our oceans, but how the oceans can be developed to protect them and the planet?

Ocean farming is not a modern innovation. Once a sustainable practice, aquaculture has devolved into monolithic factory farms known for their low-quality fish treated with antibiotics and fungicides that pollute local waterways.

A small group of ocean farmers and scientists are charting a different course—developing small-scale farms where complementary species are cultivated to provide food and biofuel, clean up the environment, and reverse climate change. Instead of finfish, the anchor crops of green ocean farms are seaweed and shellfish, two organisms that may well be Mother Nature’s Rx for global warming.

How so? Among other benefits, oysters filter nitrogen out of the water column. Seaweed pulls carbon from the atmosphere and the water, with some varieties capable of absorbing five times more carbon dioxide than land-based plants. Seaweed farms also have the capacity to grow massive amounts of nutrient-rich food and provide a clean replacement for biofuels.

Description:

For decades, scientists have attempted to replicate natural photosynthesis in an artificial plant leaf and create fuels directly from the atmosphere, powered by sunlight. The inspiration is obvious: Almost all energy comes from the sun, and most of that comes from photosynthesis.

Imagine if you could make fuel from water and carbon dioxide, wherever you and the water reside. That is the goal of the artificial leaf project, founded by Daniel Nocera, a Harvard professor of energy science. Throughout his career, Nocera has been determined to invent an energy source and technology accessible and affordable to all.

In June 2016, Nocera and his colleague Pamela Silver announced that they had successfully created energy-dense fuel by combining solar energy, water, and carbon dioxide. First, a solar-electric current runs through a cobalt-phosphorus catalyst to break water into hydrogen and oxygen. Then, an engineered bacteria (Ralstonia eutropha) consumes the hydrogen, along with carbon dioxide, and synthesizes fuel. When fed pure carbon dioxide, the process is ten times more efficient than photosynthesis.

This breakthrough is a giant step toward the goal of inexpensive energy made with sunshine, water, air…and bacteria. Nocera wants to develop the technology in India, where distributed renewables could have an outsized impact.

Description:

The convergence of motion sensors, GPS, electric vehicles, big data, radar, laser scanning, computer vision, and artificial intelligence is hastening the arrival of autonomous vehicles (AVs)—cars that drive themselves. Experts predict they will make up 75 percent of road vehicles by 2040. Whether AVs will have a benign, neutral, or negative impact on society and the planet is unclear.

How cars are owned and utilized today could not be less efficient: They are driven 4 percent of the time. If mobility comes to be viewed as an on-demand service—rather than private ownership of expensive, two-ton assemblages of steel, glass, plastic, and rubber—the material savings would be immense. The U.S. auto fleet could decline by 50 to 60 percent. But it would require a massive cultural shift.

There are other potential advantages. For starters, AV concept models are smaller and more aerodynamic. In dedicated lanes, they can form platoons and draft, as cyclists do in a peloton. Autonomy is likely to accelerate the adoption of electric vehicles because most trips are local and in battery range. Still, big questions remain: Will AVs be used for ridesharing or single occupancy? Will their convenience drive miles traveled up, rather than down?

Description:

For hundreds of millions of years, plants have been harnessing the power of photosynthesis to capture carbon dioxide from air and transform it into biomass. Recently, humans have attempted to engineer a similar feat through direct air capture (DAC) systems. The long-term hope: To use DAC to help achieve and maintain drawdown.

DAC machines act like a two-in-one chemical sieve and sponge. Ambient air passes over a solid or liquid substance; its carbon dioxide binds with chemicals in the substance that are selectively “sticky,” while other gases in the air are free to go. Once those capture chemicals become fully saturated with carbon dioxide, energy is used to release the molecules in a purified form.

The fundamental challenge is showing that DAC can be done efficiently and cost effectively. In the near term, the purified carbon dioxide released from DAC units could be used in a wide range of manufacturing applications from synthetic transportation fuels to the creation of plastics, cement, and carbon fiber. Others are looking to use atmospheric carbon dioxide in greenhouses to improve indoor agricultural yields. Eventually, DAC could help clean up carbon dioxide from the atmosphere as a sequestration technology.

Description:

Atoms can generate energy in two ways: divide or unite; fission or fusion. In 1924, physicist Arthur Eddington theorized that nuclear fusion must be at the heart of the sun’s radiant energy. Unwittingly, he set off a scientific quest to create the power of a star with a fusion reactor. Since then, millions of experiments have been tried, well over $100 billion invested, and no one came close to succeeding. Until recently, that is.

In June 2015, Tri Alpha Energy (TAE) announced it had achieved one-half of the nuclear fusion equation, nicknamed “long enough.” Long enough refers to the ability of a fusion reactor to contain and control plasma, an ionized gas that is virtually impossible to sustain—but vital.

TAE chose hydrogen-boron as their fuel because of safety, practicality, and availability. Hydrogen-boron fusion produces three to four times more energy per mass of fuel than nuclear fission, with no risk and virtually no waste.

What’s next for the maverick company? The other half of successful fusion: hot enough, a temperature of 5.4 billion degrees Fahrenheit. Achieving that could herald clean, safe, affordable energy generation to take the world beyond fossil fuels.

Description:

Imagine pods—7.5 feet in diameter with ergonomic chairs and shoulder belts—thrusting you up to 760 miles per hour through steel conduits from San Francisco to Los Angeles in 35 minutes, for the cost of a bus ticket. That is the vision of the Hyperloop, 700 miles of low-pressure tubes running up and down California.

The promise of a Hyperloop is speed; the virtue is how little energy it uses to move people and cargo. Estimates per passenger mile are 90 to 95 percent less than planes, trains, or cars.

Hyperloops are levitated by magnets powered by solar and wind power, with the only real friction being the residual amount of air in tubes. Linear-induction motors, the same kind used in airport shuttle systems, would be used to start and accelerate the passenger pod. A center rail with magnets on both sides would act as a stabilizer at high speed and an emergency braking system if needed.

There are now several companies in the world striving to create complete Hyperloop systems. Successful test runs have achieved 330 miles per hour in open air, but Hyperloop will have to overcome challenges from safety to infrastructure costs to permitting.

Description:

Sometime after the last ice age, human beings began to cultivate annuals for food—the first being an early ancestor of wheat called emmer in the Fertile Crescent. 10,000 years ago rice was grown in Asia, and 9,000 years ago corn was domesticated in Mesoamerica. These three annuals became the staple crops of the world and remain so to this day.

Perennial grains and cereals would be a game-changer for soil, carbon, and cost. Perennial crops are the most effective way to sequester carbon in any agricultural system because they leave the soil intact. The difference between annuals and perennials is that annuals die back every year, roots and all, and regenerate solely through seeds. Perennials die back too, but not the roots, which produce new growth.

Researchers are pursuing grain, cereal, and oilseed plants that are perennial food providers. Two successful efforts to breed perennial staple crops have emerged. The Yunnan Academy of Agricultural Sciences in China focuses on rice. The Land Institute in Kansas has been attempting to breed perennial wheat for more than forty years, and may have it in a variety called Kernza. They may ultimately make it possible to farm without disturbing the soil.

Description:

To keep the planet cool, you want grasses in subpolar regions, not trees, and you get grasses when you reintroduce herbivores. That is the driving logic for Sergey and Nikita Zimov, Russian father-and-son scientists working to protect the world’s permafrost.

Permafrost is a thick layer of perennially frozen, carbon-rich soil that covers 24 percent of the Northern Hemisphere. Perma indicates permanence, except it is thawing as the world warms, releasing greenhouse gases from defrosted ground. A vast grassland ecosystem called the mammoth steppe once spanned the regions where permafrost is found. Today, herbivores no longer roam and steppe has been replaced by taiga forest and mossy tundra.

The Zimovs created the Pleistocene Park in Siberia to demonstrate that by restoring grazers and grasslands, permafrost melting can be prevented. How so? When horses, reindeer, musk oxen, and other denizens of the frozen north push away snow and expose the turf underneath, the soil is no longer insulated and is 3 to 4 degrees Fahrenheit colder—perhaps just cold enough.

1.4 trillion tons of carbon are buried in permafrost—two times more than what is held in all the forests worldwide. Restoring the mammoth steppe might create the margin of safety needed to keep that carbon where it is.

Description:

Oceans remain the largest untapped source of renewable energy on earth, surging with roughly 80,000 terawatt hours of power. A single terawatt is the equivalent of 1 trillion watts and sufficient to provide electricity to 33 million U.S. homes.

Because water is nearly one thousand times denser than air, aqua turbines are technically more efficient than wind turbines. The problem with wave energy technologies is economic inefficiency. They require moving parts that can withstand the stress and corrosion of the sea. The raw energy found in the ocean can easily become wave power’s downfall.

A company in Seattle, Oscilla Power, has created a wave-energy technology that converts the kinetic energy of the ocean without external moving parts. Compression and decompression within Oscilla’s wave energy converter create electricity.

Solid-state wave energy eliminates some of the key issues that have plagued other start-ups in the field of marine energy. It may be the breakthrough, if it can capture ocean energy affordably.

Description:

With the Industrial Revolution, steel and concrete became the dominant construction materials. Wood use declined, relegated to single-family homes and low-rise structures. But that is beginning to change thanks to high-strength wood technologies, namely glued laminated timber (glulam) and cross-laminated timber (CLT), and the need to reduce emissions from construction.

Building with wood has two key climate benefits:

1. As they grow, trees absorb and sequester carbon, which remains stored in timber construction materials. A unit of dry wood is 50 percent carbon, and that carbon is locked in while the wood is in use.
2. The process of producing those materials generates fewer greenhouse gas emissions than wood’s alternatives, like cement or steel.

According to a 2014 study, building with wood could reduce annual global emissions of carbon dioxide by 14 to 31 percent.

Conventional wisdom suggests that wood and high-rise buildings are incompatible, and that flammability is an issue. A renaissance in the processing and manufacturing of wood is challenging those limitations. New high-performance products are more fire resistant, as well as more cost-effective and stronger than ever. What’s more, they can be prefabricated and then put together like a giant piece of furniture, reducing construction costs.

Description:

During Earth’s 3.7 billion-year journey, rocks have sequestered many trillions of tons of carbon dioxide. Natural rock weathering removes approximately 1 billion tons of atmospheric carbon dioxide annually. Various types of silicate rock on the surface of the earth are weathered by carbon dioxide and dissolved in rainwater, which transforms the carbon dioxide into inorganic carbonates. These carbonates find their way into streams, rivers, and oceans, eventually becoming calcium carbonate.

Enhanced weathering of minerals refers to technologies that hasten this process sustainably. One type of silicate that would work well is olivine, a greenish mineral, rich in magnesium and iron. Enhanced weathering would involve mining and milling olivine and then applying the resulting rock powder to land and water, so that the soil, oceans, and biota can act as “reactors” for accelerated weathering.

The rock powder could be strategically distributed over various landscapes, using existing infrastructure for the management of farm and forest soils. Agricultural land in the tropics, where soils are warmer and wetter and have fewer minerals that would inhibit dissolution, are ideal. If applied to one-third of tropical land, olivine could lower atmospheric carbon dioxide by 30 to 300 parts per million by 2100.

Description:

Hemp’s long, strong fibers have been spun into clothing for millennia. Today, hemp is a commodity crop around the globe, used to produce paper, textiles, cordage, caulking, carpets, and canvas. Hemp is a global warming solution less because of what it can do than what it can replace: cotton.

Cotton is the dirtiest crop in the world with respect to chemical use and is largely dependent on fossil fuel inputs. Total emissions for a white cotton shirt from field to customer are 80 pounds of carbon dioxide. Hemp cannot compete with cotton on fiber softness, but if cost competitive it could certainly replace half of the cotton in the world for everyday garments, such as jeans, jackets, canvas shoes, caps, and more.

When Hu Jintao, China’s president in 2009, visited his country’s hemp processors, he implored them to increase China’s cultivation to 2 million acres to avert the harmful impacts of cotton. In the United States, on the other hand, cultivation of hemp remains obstructed due to lack of approval from the federal Drug Enforcement Agency—though it has negligible amounts of the cannabinoids associated with recreational or medical marijuana.

Description:

Once a systems engineering consultant, Brian Von Herzen now devotes his life to reversing global warming by increasing the primary production of oceans, using kelp. Primary production is the creation of organic compounds from carbon dioxide through photosynthesis.

Oceans face a dire situation. They absorb half of the carbon dioxide recaptured from the atmosphere, which causes acidification, and over 90 percent of the heat from global warming. Ocean deserts are expanding. Von Herzen wants to restore marine life in subtropical waters with thousands of new kelp forests—what he calls marine permaculture.

The key technology involves marine permaculture arrays (MPAs), lightweight latticed structures roughly half a square mile in size, submerged 80 feet below sea level, to which kelp can attach. Attached buoys rise and fall with the waves, powering pumps that bring up colder, nutrient-rich waters from far below. Kelp soak up the nutrients and grow, establishing a trophic pyramid rich in plant and animal life.

Plants that are not consumed die off and drop into the deep sea, sequestering carbon for centuries in the form of dissolved carbon and carbonates. Floating kelp forests could sequester billions of tons of carbon dioxide, while providing food, feed, fertilizer, fiber, and biofuels to the world.

Description:

Australian farmer Colin Seis “discovered” pasture cropping when his 2,000-acre family farm burned to the ground—outbuildings, trees, 20 miles of fencing, 3,000 sheep, and all.

After three generations of work were reduced to ash, Seis found himself at a pub with a fellow farmer. They both grew grain (annuals) and grazed sheep on pastures—activities taking place on separate parts of their farms. The pastures tended to be overgrazed, and the grain acreage was plowed and disked every year, drying and decarbonizing the soil.

A vision emerged that night that would evolve into what is now called pasture cropping—a method of double-cropping (grains and animals) while increasing carbon sequestration. Planting annual crops in a living perennial pasture creates an ecosystem that gets healthier every year. A complex relationship between the forbs, fungi, grasses, herbs, and bacteria reknits the web of life, increasing the health, resilience, and vitality of the soil, crops, grasses, and animals. On pasture-cropped land, the soil is never broken, and fertilizers, herbicides, and pesticides are unnecessary.

Pasture cropping is now practiced on more than 2,000 farms in Australia and is spreading throughout the temperate world. Farmers benefit from reaping two crops from the same land: grain, and wool or meat.

Description:

Last century’s electric grid was not designed for this century’s shift to clean, renewable energy. Accommodating the fluctuations of wind and solar power necessitates a more nimble, adaptive grid. The emerging “smart grid” is a digital retooling of the traditional grid with the needs of a clean energy economy in mind.

A smart grid is smart in the sense that it engages in two-way communication between suppliers and consumers to predict, adjust, and sync power supply and demand. Today, the balancing act between producers and users takes place within utilities’ operations centers. Internet connectivity, intelligent software, and responsive technologies can assist and even automate the management of electricity flow.

To smooth out peaks in demand and absorb variable supply, smart grids need:

1. High-voltage power lines with sensors
2. Advanced meters that communicate wirelessly
3. Responsive appliances, plugs, and thermostats

The current grid has been called the largest and most interconnected machine on earth. Making it smarter is a massive undertaking that will occur in phases over the coming decades. Studies show the investment required will be well worth it, as smart grids improve grid stability and overall efficiency while facilitating the shift away from fossil fuels.

Description:

Ruminants, such as cows, sheep, and goats, have a special digestion process that produces large quantities of methane, which has a warming effect 34 times more powerful than carbon dioxide. Ruminant methane accounts for 4 to 5 percent of annual greenhouse gas emissions. Seaweed, which has been used as livestock feed for thousands of years, shows promise for reducing them.

Building on anecdotal evidence from dairy farmers, a team of scientists in North Queensland, Australia, have tested a wide range of seaweeds mixed with feed in artificial cow stomachs. Asparagopsis taxiformis, a species of red algae, reduced methane production by 99 percent—and required a dose of just 2 percent of feed to do so. In live sheep, the same dose led to a 70 to 80 percent drop in methane. Tests have yet to be performed with live cows.

With more than 1.4 billion cows and nearly 1.9 billion sheep and goats inhabiting the planet, scale is a major challenge for this solution. Champions argue it is well worth cracking. If fed to ruminants worldwide, Asparagopsis taxiformis would reduce the amount of soy, corn, and grass required as feed. Most critically, it could dramatically reduce livestock methane emissions.

Description:

Silvopasture is the most commonly practiced form of agroforestry today, covering 1.1 billion acres worldwide. The theory is simple: Combine trees or woody shrubs and pasture grasses to foster greater livestock yields. What happens if you intensify the process? Add more animals, plant different types of trees, and rotate the herd more quickly? It seems counterintuitive that it could have a beneficial effect on land and climate, but it does.

Developed by ranchers, intensive silvopasture is practiced today on more than 500,000 acres in Australia, Colombia, and Mexico. Most systems use a quickly growing, edible, leguminous woody shrub: Leucaena leucocephala. Planted 4,000 per acre, it is intercropped with grasses and native trees. Trees keep the wind in check and improve water retention, which causes increases in biomass. Livestock move through rapid rotational grazing. Species biodiversity doubles, stocking rates nearly triple, and animals gain more weight.

Sound too good to be true? In a five-year study of intensive silvopasture in which trees were incorporated with grasses and Leucaena leucocephala, the rate of carbon sequestration exceeded 10 tons per acre. That makes it one of the most effective means known to sequester carbon.

Description:

In one gram of soil, a thimble’s worth, there can be up to 10 billion microbial denizens. The bacteria, viruses, nematodes, and fungi in the soil have sweeping potential to address agriculture’s impact on global warming. The possibilities are rooted in microbes’ ability to dramatically reduce the need for synthetic fertilizers, pesticides, and herbicides, while improving crop yields, plant health, and food security.

At present, converting nitrogen to ammonia for fertilizer requires 1.2 percent of the world’s energy use. Much of that nitrogen ends up in the sky as nitrous oxides—a greenhouse gas 298 times more powerful than carbon dioxide. Or it leaches into groundwater and waterways, causing the overgrowth of algae and marine dead zones.

The soil microbiome invites agriculture to do a much better job of getting what is wanted from the land—healthy, tasty, abundant food—by harmonizing farming with the needs of the soil. It comes down to a simple fact: Plants and soil feed upon each other. With a healthy microbiome, soil is rich in carbon and organic matter, requires few if any synthetic fertilizers, and creates healthier plants. Someday, a farmer may drive to the local fertilizer store not to buy fertilizer but to pick up nitrogen-fixing bacteria instead.

Description:

More than 160,000 miles of asphalt comprise the U.S. National Highway System. On 18 of them, located south of Atlanta, Georgia, an initiative called The Ray is working to reimagine what a highway could be.

The Ray aims to morph this stretch of road into a positive social and environmental force—the world’s first sustainable highway. Electric vehicles (EVs) are a focal point. Currently, more than 100,000 tons of carbon dioxide are emitted along the 18-mile corridor each year. To shift that, The Ray is creating infrastructure for EVs, including a solar photovoltaic (PV) charging station.

Clean energy is central. The Ray will feature a 1-megawatt PV farm along its right-of-way. Exposed 90 percent of the time, road surfaces themselves are prime for solar generation. The aptly named Wattway PV pavement, a French technology, will allow The Ray to produce clean electricity, while improving tire grip and surface durability.

Modern motorways have seen little advancement in design since their inception. Now, climate change and the arrival of electric and autonomous vehicles are placing new demands on them. Highways need a smarter way forward. The Ray may prove that this dirty infrastructure can become clean, safe, and even elegant.