The world sees invasive seaweed. This gardener sees housing bricks.

WindowDressers mobilizes community volunteers to build low-cost insulating window inserts for older homes. Their efforts have saved nearly 4 million gallons of heating fuel, preventing 44,000 tons of CO2 emissions, and strengthening neighborhood ties while making heating more affordable—especially for low-income households who now represent nearly 40% of recipients.

Two Texas-based companies are 3D printing homes in an effort to combat the housing crisis and produce fewer emissions than a typical home construction. The companies lay the foundation and rebar for support. Then, a machine with a robotic arm builds up the walls by printing layers of a cement-like material.

The Kensington Corridor Trust acquires properties along three blocks in its Philadelphia neighborhood to give the community agency and control over how that real estate is used, with an emphasis on keeping housing affordable. The trust has acquired 16 properties so far and has signed its first commercial tenant, providing space for a local business owner.

Developers in Cleveland are salvaging building parts that can be reused in other construction projects. The sustainable initiative known as deconstructing helps reduce carbon footprints and helps avoid the “high social and environmental costs of dumping demolition material in landfills.”

After the 2008 economic recession hit, Carla Walker-Miller shifted her energy services business model to not only supply electrical equipment but also implement energy efficiency programs for communities of color in Detroit. She has been able to service 75 households, which has resulted in energy bill savings up to $600 a year for families. The company also has a robust recruitment and training program for young people and those experiencing economic hardship.

The app Too Good to Go helps restaurants and other shops prevent food waste by selling their extra food to people for a cheaper price. So far, more than 700,000 people in the United States have downloaded the app and the company estimates that, on average, each meal sold halts 2.2 pounds of food from ending up in the garbage, which ends up reducing carbon emissions. There are challenges to widespread implementation, but the app has launched in New York City, Boston, San Francisco, and Seattle.

Inspired by the Dutch concept of “Energiesprong,” or “energy jump,” a developer in France retrofitted a group of townhouses for social housing to be more environmentally friendly. They installed polyurethane facades to avoid heat loss and solar panels on the roof. Upgrading the units to be more green cost more than a conventional retrofit, but over time, energy bills were cut in half. These green retrofits are being implemented in towns around the world and could be a model for developers that want to reduce their carbon footprints.

A Spanish chef piloted a project to start a “marine garden” — cultivating eelgrass and obtaining grains it produces to be used in different recipes. The grain has healthy benefits, including 50 percent more protein than rice, and growing the seagrass can transform salt marshes into biodiverse ecosystems that can also capture carbon emissions. They are working to scale the project to understand the ideal conditions to grow the plants.

A housing project in Brooklyn is taking nine apartment buildings and retrofitting them to be more sustainable and cut carbon emissions. Casa Pasiva is a $20 million project that aims to reduce heating and cooling costs because of updated machinery and thick exteriors that will improve air quality. Funding for these types of initiatives is not always certain, but a collaboration between a developer and a nonprofit, with some city financing, made this first-of-a-kind green building renovation in New York possible.

In Florida, a land-based salmon farming operation has optimized the ideal conditions for fish to be raised sustainably on land. “There is no winter here, there are no diseases, there are no sea lice. We optimize everything the fish needs," explains the company's chief sales and marketing officer. Although the practice is still "in its infancy" and struggles to return a profit, it has caught on elsewhere and land-based salmon are now sold in a variety of grocery stores.