Recycling can be done with many different raw materials. Recycling helps create more sustainable economies by lowering costs and reducing harm to the environment from raw materials. Not all materials are easy to recycle, and sorting recyclable materials into the right waste groups takes a lot of energy. Some products are hard to separate unless they are specially processed, so they need special recycling methods.

Asphalt

Asphalt concrete removed during road maintenance, fixing roads, and repair work can be recycled and used again in new road mixtures, as a base layer for roads, or in other construction projects. According to a study by the Federal Highway Administration and the National Asphalt Pavement Association, which has been done every year since 2009, less than 1 percent of asphalt concrete is sent to landfills. When asphalt pavement material is reused, it can replace new materials used to make roads and the liquid asphalt used in road construction. In the same way, asphalt roof shingles can be recycled and used again in new road surfaces.

Concrete

Concrete recycling is the process of reusing broken concrete from buildings that are being torn down. Recycling is less expensive and better for the environment than sending broken concrete to a landfill. Crushed concrete can be used as material for roads, walls that prevent erosion, walls that hold soil in place, garden paths, or as a base for making new concrete. Larger pieces of broken concrete can be used as bricks, slabs, or mixed into new concrete for buildings, a material known as urbanite.

Glass

Glass recycling is the process of gathering, preparing, and making waste glass into new items. Glass is good for recycling because it does not break down or wear out from normal use. Broken glass pieces, called cullet, are used in making new glass products. This helps save energy and reduces the need for new materials. There are two types of cullet:

External cullet needs more careful cleaning and checking for quality because it may have dirt or other materials from how people use and collect it.

Before recycling, glass waste must be cleaned to remove dirt and other materials. Then, depending on what the glass will be used for and the tools available, it may also need to be sorted by size and color. Many recycling centers separate glass by color, such as clear (flint), brown (amber), and green, because glass keeps its color after recycling. Some recycling centers use machines that can sort glass by color, so separate bins for each color may not be needed.

Heat-resistant glass, such as borosilicate glass (like Pyrex), should not be recycled with regular glass. Even a small piece of this type of glass can change the way the glass melts in the furnace during the recycling process.

Metals

Aluminum is one of the most efficient and widely recycled materials. It is cut into small pieces or pressed into large bundles. These pieces or bundles are melted in a factory called an aluminum smelter to create liquid aluminum. At this point, recycled aluminum looks the same as newly made aluminum, and the rest of the process is the same for both. This process does not change the metal, so aluminum can be recycled forever.

Recycling aluminum saves 96% of the energy needed to make new aluminum. It also helps keep a lot of waste out of landfills. This is because melting recycled aluminum requires a temperature of 600 °C, while extracting aluminum from its raw material needs 900 °C. Reaching the higher temperature uses much more energy, which makes recycling aluminum very good for the environment. In the United States, people throw away enough aluminum each year to build all the planes used by airlines. Also, the energy saved by recycling one aluminum can is enough to power a television for three hours.

According to the International Resource Panel’s Metal Stocks in Society report, the average amount of copper used per person worldwide is 35–55 kg. Most of this is in more-developed countries (140–300 kg per person) rather than less-developed countries (30–40 kg per person). In 2001, a typical car had 20–30 kg of copper. By 2014, the amount of copper in cars with traditional engines dropped to 16.8 kg, but by 2023, it rose again to 24.5 kg. At the same time, electric cars already use about 91 kg of copper and copper alloys.

Like aluminum, copper can be recycled without losing quality, whether it is in its raw form or in finished products. About 80% of all copper ever mined is still being used today. In terms of volume, copper is the third most recycled metal after iron and aluminum. As of 2023, recycled copper meets about one-third of the world’s need for copper.

The process of recycling copper is similar to how copper is first extracted, but it has fewer steps. High-quality scrap copper is melted in a furnace and then purified and shaped into blocks or bars. Lower-quality scrap is melted to form black copper (70–90% pure, with impurities like iron, zinc, tin, and nickel). Impurities are then removed in a special machine to create blister copper (96–98% pure), which is purified again as before.

Iron and steel are the world’s most recycled materials and are among the easiest to reuse. They can be separated using magnets from waste. Recycling happens in steel factories: scrap is either melted in a furnace (using 90–100% scrap) or mixed with other materials in a different furnace (using about 25% scrap). Any type of steel can be recycled into high-quality new metal without losing quality, even after being recycled many times. About 42% of all raw steel made is recycled material.

For information about recycling other, less common metals, refer to:

• Bismuth recycling
• Lead recycling

Plastic

Plastic recycling is the process of turning plastic waste into new products. Recycling helps reduce the need for landfills, saves natural resources, and protects the environment from plastic pollution and harmful gases. Recycling rates are lower compared to other materials like aluminum, glass, and paper. Between the start of plastic production and 2015, the world created about 6.3 billion tons of plastic waste. Only 9% of this was recycled, and less than 1% was recycled more than once. Of the rest, 12% was burned, and 79% was either sent to landfills or became pollution in the environment.

Most plastic is not biodegradable, and without recycling, it spreads across the environment, causing plastic pollution. For example, as of 2015, about 8 million tons of plastic waste entered the oceans each year, harming ocean ecosystems and creating large garbage patches.

Most plastic recycling is currently mechanical, which involves melting and reshaping plastic into new items. This process can break down the plastic molecules over time. It also requires sorting waste by color and type before processing, which is often difficult and costly. Mistakes during sorting can lead to uneven materials that are not useful for industries. While filtration in mechanical recycling helps reduce tiny plastic particles, even the best systems cannot stop all microplastics from entering wastewater.

In feedstock recycling, waste plastic is broken down into its original chemicals, which can then be used to make new plastic. This method requires more energy and money. Alternatively, plastic can be burned to produce energy instead of using fossil fuels, or it can be chemically changed into other useful materials. In some countries, burning is the main way to handle plastic waste, especially where policies aim to reduce landfill use.

Plastic recycling is ranked lower in the waste hierarchy, meaning reducing and reusing plastic are better long-term solutions for sustainability. Recycling has been promoted since the 1970s, but due to economic and technical challenges, it did not significantly affect plastic waste management until the late 1980s.

Timber

Recycling timber is popular because people believe it helps protect the environment. They think buying recycled wood reduces the need for new wood, which helps protect forests. Greenpeace also says recycled wood is the best choice for the environment, as shown on their website. Using recycled wood in building projects has helped people and businesses learn about deforestation. It has also encouraged wood processing plants to use more eco-friendly methods.