Approximately one-third of all food produced worldwide is wasted, with much of it ending up in landfills, where it becomes a source of methane, a greenhouse gas 25 times more potent than carbon dioxide. The ultimate solution is to eliminate waste, but some will always remain. Composting is a simple solution that almost anyone can implement.
Composting converts rotting garbage into a valuable soil enhancer that promotes plant growth. Farmers refer to it as "black gold." And, whether you compost in your backyard or at a community facility, experts say it will reduce your trash while also helping to combat climate change.
What happens in a compost pile?
Food decomposes due to the efforts of small microorganisms such as bacteria, fungi, and protozoa. "Having a compost pile turns you into a microbe farmer." "You're dealing with microbes," says Rhonda Sherman, a composting specialist at North Carolina State University. "And what do microbes require?" They require the same things that we do. That is, air, water, food, and shelter."
On a small scale, a compost pile in your backyard or neighbourhood should include three components: food scraps, water, and dry, woody material such as yard trimmings or raked leaves.
Yard trimmings are high in carbon and are commonly referred to as "browns." Food scraps, also known as "greens," are high in nitrogen. A compost pile should contain twice as many browns as greens.
Aside from preventing a pile from becoming a sloshy mess, browns are bulkier and allow oxygen to circulate throughout the pile. This oxygen aids tiny microbes in the decomposition of food waste, a process known as aerobic digestion.
Deep piles of trash in landfills prevent oxygen from reaching decomposing food, which is instead broken down by microbes that can survive without air. Methane is produced by the microbes' anaerobic digestion.
In contrast, as aerobic microbes break down waste—"first, easier sugary compounds, then proteins and fats, and finally fibre," says Rynk—they emit carbon dioxide, a greenhouse gas that is less potent than methane.
The microbes also emit heat, which can reach over 130 degrees Fahrenheit in a large, well-managed pile, killing pathogens. Fresh compost left after several months decomposes more slowly; it's high in microorganisms and nutrients like nitrogen, phosphorus, and potassium.
How to make a successful pile
At home, you should stir or mix the pile on a regular basis and keep it damp. Both of these steps will hasten the decomposition process. The stirring allows oxygen to reach all the nooks and crannies, while the dampness ensures the survival of microorganisms, which require moisture to survive.
In fact, the most common reason backyard compost piles fail is that they are too dry. However, don't drown the pile—adding more greens that contain moisture may suffice. If not, a gentle spray of water over the pile should suffice.
"That's what your compost pile should look and feel like," Sherman says. Wring out a wet sponge and examine its only slightly damp texture. "You can see that it's moist, but it's not dripping all over the place."
Not all food scraps should be composted in the backyard. Fruits and vegetables are usually safe to toss in the compost pile, but uneaten meat or dairy is more likely to smell and attract pests. They also have higher fat levels, which take longer to break down. While rodents are not uncommon in compost bins, turning the pile on a regular basis prevents them from building nests, and compost can be effectively made in enclosed bins.
The Environmental Protection Agency has a more detailed list of what should not be composted. It includes things like yard trimmings that have been treated with pesticides that may kill microorganisms. Some communities are now providing food scrap bins in addition to trash and recycling bins. Food scraps collected at the city level are usually taken to a large industrial composter, where they are shredded or chopped upon arrival and processed at high temperatures.
At this level, composting may be done in large piles or in silos. Municipalities accept a wider variety of scraps than what you can throw in your backyard because they send food waste to industrial compost facilities, and regulations vary by city. Many urban gardens and farmers' markets accept compost if you don't have a backyard, don't have access to a city-run food scrap service, or simply don't want to mess with a compost pile.
If you're worried about odours from keeping compost on your countertop or in your kitchen before transferring it to a larger compost pile, Sherman says freezing food scraps is a "game-changer." By freezing your scraps, you pause the decomposition process and prevent odours from forming.
(Source: National Geographic)
