Environmental engineering is a sub-discipline of civil engineering, chemical engineering and mechanical engineering. Environmental engineers are involved in challenges as diverse as water management and building design as well as the assessment of the environmental impact of proposed construction projects. And in the past few years, they’ve made five significant advancements in environmental engineering.

1. Alternatives to Concrete

Researchers in Australia have created cement from the hundreds of thousands of tons of glass that is no longer being processed in a failing recycling system. To create waste glass-based concrete, researchers break the glass waste down into increasingly smaller sizes until it becomes a fine powder that is combined with other, more traditional industrial waste-products (e.g., fly ash, blast-furnace slag, etc.) and is tested for stability. The resulting cement has a 10-30% waste-glass composition, is cheaper, stronger and lighter than traditional cement and delivers functional insulation, fire-resistance and a lower emissions threshold.

Other researchers are exploring alginate—a biopolymer obtained from brown seaweed—to create unfired clay bricks as an alternative to conventional fired bricks and concrete blocks. Swiss researchers are also moving cement-bonded wood products into the realm of weight-bearing wood-based concrete.

Another breakthrough is an invention from New Zealand’s ByFusion, which is turning all forms of plastic waste into concrete brick-shaped building blocks. The machinery shreds plastic waste, fuses the shredded plastic into blocks using superheated water and compression (no adhesives needed) and creates modular plastic bricks that can be used for non-load-bearing construction. In addition to being nontoxic and having a lower carbon footprint than concrete blocks, the bricks don’t crumble under pressure, provide high-level sound and temperature insulation, and can be made into customized shapes and densities. While not useful for all forms of construction, this solution could eliminate the need for concrete in a wide range of infrastructural uses and would aid in the fight against the scourge of plastic that threatens our planet.

2. Corrosion-Improved Durability of Structural Alloys

When it comes to the integrity of structural alloys, it turns out that a little corrosion may be a good thing. Cornell researchers have used advanced atomic modeling to explore the ways in which the environment can influence the growth of cracks in alloys such as aluminum and steel—knowledge that could help engineers better predict—and possibly postpone—structural failures.

The proclivity of a crack to grow depends on how sharp it is. A big, round notch is unlikely to propagate like a crack. But if you have some sharp feature, like a slit cut with a knife, it is more likely to grow. By removing atoms from the tip of a crack—akin to what occurs during natural corrosion—you can actually improve the material’s mechanical performance.

The research is of particular interest to the Office of Naval Research, which funded the study, and its efforts to keep expensive aircraft in safe working condition amid the extreme ocean environment.

3. Electric Planes and Vertical Take-Offs

The electrification of air travel is currently underway, with one solar-powered around-the-world-flight already completed in 2016. Although replacing fossil-fuel airliners may not be a reality until 2050, researchers are starting the journey toward an electrified air fleet with short-range planes built for a small number of passengers. Perhaps the most exciting breakthrough in the pack is the Lilium Jet—a 100% electric plane with a 300 km range that can travel 300 km/h for one hour, takes off vertically, and can be ordered on-demand like a carshare vehicle.

The key to the Lilium Jet’s vertical takeoff and lightning-fast speed is its tilting-flap technology: 36 electric ducted fans (EDF) sit in four flaps that start in a vertical position for takeoff and tilt to a fully horizontal position when the plane is ready to cruise. Shaped like a manta ray, the lift-to-drag ratio of the jet is 21:1—the highest ratio among all sustainable aviation.

As a result of a lower drag coefficient, the use of lightweight carbon fiber and the distributed propulsion coming from the EDFs, the Lilium Jet’s energy consumption is comparable to an electric car, yet it is much faster. The jet has the potential to reduce time and fossil fuels spent in long-distance commutes and decrease the need for cars.

4. Discarded Tree Forks Become Load-Bearing Joints

Concern about climate change has focused significant attention on the extraction and processing of construction materials. The concrete and steel industries together are responsible for as much as 15% of global C02 emissions. By contrast, wood provides a natural form of carbon sequestration, so there’s a move to use timber instead.

As the timber industry seeks to produce wooden replacements for traditional concrete and steel elements, the focus is on harvesting the straight sections of trees. Irregular sections such as knots and forks are turned into pellets and burned, or ground up to make garden mulch. Both approaches release into the atmosphere the carbon that is trapped in the wood. But there are new opportunities for sustainability gains.

For the past four years, Caitlin Mueller, Ph.D., an associate professor of architecture and civil and environmental engineering at MIT, and her Digital Structures research group have been developing a strategy for “upcycling” tree forks (spots where a tree trunk or branch divides in two, forming a Y-shaped piece) by using them in construction—not for aesthetic purposes, but as structural components. Tree forks are naturally-engineered structural connections with extra internal fiber structure that makes them work as cantilevers in trees. As a result, they have the potential to very efficiently transfer force in load-bearing applications.

5. Solar Glass

Imagine if windows and doors could change the way we provide electric power to homes and buildings. It might happen sooner than you think. Researchers at the University of Michigan have innovated solar glass for windows, doors, skylights and other building-related glass applications. According to the research team, 5 to 7 billion square meters of usable window space exists—enough to power a full 40% of U.S. energy needs using solar glass.

Do you have any experience working with renewable energy? Feel free to share your thoughts below.