11.8.2: Recycling and Composting
In 2018, the United States generated 292.4 million tons of MSW, and recycled or composted 94 million tons of it - amounting to about 32.1% of the total. While some other methods were also used to recover energy or create animal feed, over ½ of all waste still ended up in a landfill. While this may not seem like progress, the amount of MSW discarded in landfills has remained relatively constant since 1990 - in spite of population growth - while other methods like recycling and composting have grown (EPA, 2023a). While metals (like steel and aluminum), glass and paper products (including cardboard), are relatively easy to recycle, plastics are much less commonly recycled. Approximately 9% of the world’s plastic containers, bottles, bags and other materials are recycled; 50% end up in landfills, another 20% are mismanaged (burned or dumped, potentially ending up in lakes and rivers), and 0.5% end up in the ocean (Ritchie et al., 2023). See Fig. \(\PageIndex{1}\) below.
Plastic pollution is particularly hazardous because of the characteristics of plastic that make it so desirable. Plastic is durable, and doesn’t break down easily. It may take a plastic water bottle floating in the ocean nearly 450 years to decompose (Harris, 2023), broken down by UV rays into smaller and smaller pieces called microplastics. The Great Pacific Garbage Patch is really a misnomer because it’s not an island or “patch” of trash floating in the Pacific Ocean: much of the plastic pollution is microplastics, swirling around the ocean currents like a plastic soup (Evers, 2024). These microplastics can get into our food and water sources, be ingested by birds and fish, and make their way up the food chain into human tissues. Microplastics have been found in the human gastrointestinal tract and in placental tissue (Ragusa et al., 2021). We may even be breathing in microplastics in the air, which can get into lungs and eventually the bloodstream. Exposure to microplastics and the chemicals that make them could have profound effects on human health, particularly in the immune system response to plastic toxins, chronic inflammation, and a myriad of other subsequent health problems (Prata et al., 2020). The best way to manage plastic waste is not to rely on recycling, but to produce less of it in the first place.
Composting is another way to manage biodegradable waste such as food waste. In the U.S., it is estimated that 30-40% of the food supply ends up as waste - much of that at the retail or consumer level (USDA, n.d.). Food waste may include inedible food scraps such as eggshells or fruit rinds, but it also includes food that could have been consumed but perhaps was spoiled or uneaten. Not only does the food wasted cost energy to grow and transport, it also produces methane gas while decomposing in a landfill - contributing to GHG production and climate change. Food waste can be reduced at the retail and consumer levels by only producing and purchasing what is needed, donating leftover food and preventing spoilage. Composting is also a much better use of food waste, as it produces usable fertilizer for agricultural and landscaping purposes (EPA, 2015). While backyard composting can support a home garden, industrial or large-scale composting has much greater potential for managing food waste, yard waste, sludge and other agricultural or industrial wastes. Bacteria and fungi feed off of the waste products, creating heat which destroys undesirable microbes and weed seeds, and turns the solids into excellent fertilizer for plants. When those raw materials are chipped up into smaller pieces, combined in appropriate ratios, and well-aerated, the composting process can be completed more quickly and produce high-quality soil amendment (Sherman, 2020). As of 2022, California requires that organics be disposed of separately to recyclables and MSW in order to be composted or used to generate biofuel (CalRecycle, 2024).