Discover
Compost
Published November 30, 2021
This jaded plain, speckled green by vernal green, flinches not from the sun’s rays or ravenous pests. Thin leaves now sprout from their tiny stems, splayed systematically in columns so long, almost perpetual. Corn? Soybeans? Wheat, perhaps? A rolling behemoth revs onto the field; its rear nozzles begin their annual hiss.
The most abundant atom in the atmosphere, the most dependent atom for plants: nitrogen. It is everywhere around us, although for plants there’s not a single one to take from the air. It would be too easy to grow crops if they could simply grab a leaf-full of nitrogen themselves, but it never is.
Waves upon waves of synthetic fertilizer pour liquid nitrate and ammonia into the soil. Here, the plants are given more than they have ever needed—far, far more than necessary. In fact, plants only use a little less than half the amount of nitrogen that synthetic fertilizer supplies them with.
In a process known as denitrification, microorganisms reduce nitrogen into a handful of different compounds. Below is a diagram of a chain of compounds that nitrogen follows:
When synthetic fertilizers provide the soil with so many ammonium and nitrate ions—as per usual—microorganisms are overwhelmed. Inefficiency takes its toll, and right before the denitrification process is complete, nitrous oxide (N2O) escapes from their grasp and releases into the atmosphere.
An N2O molecule stays in the atmosphere for up to 114 years, until either ultraviolet radiation shatters its chemical bonds or bacteria alter its structure. According to the Environmental Protection Agency (EPA), its global warming potential is 2981, rendering it far more hazardous than CO2.
75% of N2O emissions in the US come from agricultural soil management, such as the application of synthetic and organic fertilizers, the management of manure, or the burning of agricultural residues. This percentage is enough to suggest that the agriculture industry needs some sort of change—a change to be implemented fast.
If any change is to occur, it has to involve the type of fertilizer we use. Doing away with fertilizer completely is not an option. If it weren’t for synthetic fertilizer, the world’s population today would be a little over half of what it is now.
Organic fertilizers, however, offer promising potential. Similarly with synthetic fertilizer, they release nitrogen into the soil to encourage plant growth, but at a slower and more manageable pace for microorganisms. This particularly makes them more suitable than synthetic fertilizers because they can better match plants’ nutrient needs, and more of the nitrogen from organic fertilizers is absorbed immediately as it becomes available. This leads to less excess nitrogen for microorganisms to feast on, and less leaching of that excess nitrogen into groundwater.
The most common organic fertilizer used today is compost: a balanced mixture of organic material used to enrich soil and prevent plant diseases. Its moisture allows for a suitable environment to produce beneficial bacteria and fungi. These microorganisms in turn break down organic matter to form humus, a favorable component of soil to encourage plant growth.
Conditions
There are five main areas that need to be considered to produce compost as an effective fertilizer.
Material Size
One of the most crucial factors in determining the speed of chemical reactions is surface area. This logic applies to compost as well: the greater the surface area of the organic material, the faster it takes to compost. Large pieces of brown and green matter are generally chopped or shredded before piling it all together for composting. Smaller materials make it easier to create a homogenous mixture and improve heat insulation.
Moisture
Microorganisms are essential to the composting process. To encourage their reproduction and nutrient intake, you must have a controlled supply of water. Enough water should be added so every piece of brown and green matter has some degree of moisture. Submerging the organic material in water should be avoided because the concentration of microorganisms would fall for every piece of brown or green matter, dramatically slowing the composting process.
Oxygen Availability
Aerobic microorganisms—such as those breaking down the organic material—thrive in oxygenated environments. Oxygen levels must be kept the same at every part of the pile so these aerobic microorganisms break down the organic material effectively. Since it’s very difficult for contents at the bottom to have the same access to oxygen as those resting at the top, turning the pile 2-3 times a week will assure all contents are breaking down aerobically. Including bulking agents such as shredded newspaper and wood chips can separate clumps of organic matter for oxygen to flow throughout the pile. Too much oxygen, however, can dry out the pile and worsen the environment for the microorganisms.
Note
When organic matter does not have access to oxygen, anaerobic decomposition occurs. This process produces methane (CH4), a greenhouse gas that’s 25 times more potent in heat retention than CO2.
Temperature
Microorganisms function best at a temperature range of 131-160°F. As the temperature reaches this range, microorganisms will increase their respiration rate, breaking down the organic matter quicker. Generally, reaching this temperature range is effortless if the contents are covered with a heat-retentive material such as a tarp or other types of polyethylene sheets. This not only absorbs any heat from the sun, but also retains the heat produced from microorganisms as they break down the surrounding material.
Contents
There are three basic components of a compostable pile:
Brown Matter—dead leaves, branches, and twigs that supply carbon.
Green Matter—grass clippings, vegetable waste, fruit scraps, and coffee grounds that supply nitrogen.
Water—provided manually or via rainwater to help microorganisms break down the organic matter.
Note
Piles become compost most efficiently when there’s an equal amount of green and brown matter.
Here’s a complete list of compostable materials according to the EPA:
Fruits and vegetables
Dried eggshells (yokes should not be included in the pile)
Coffee grounds and filters
Tea bags
Nut shells
Shredded newspaper
Cardboard
Paper
Yard trimmings
Grass clippings
Houseplants
Hay and straw
Leaves
Sawdust
Wood chips
Cotton and Wool Rags
Hair and fur
Fireplace ashes
Similarly with what materials can be composted, there are some materials that must be avoided. The following list specifies what materials cannot be composted:
Black walnut tree leaves and twigs—release juglone, a chemical extremely toxic to plants and animals.
Coal and charcoal ash—might contain substances harmful to plants.
Dairy products (butter, milk, sour cream, yogurt) and eggs—create odor problems and attract pests such as rodents and flies.
Diseased or insect-ridden plants—diseases or insects might survive and be transferred back to other plants.
Fats, grease, lard, and oils—create odor problems and attract rodents and flies.
Meat, fish bones, and scraps—create odor problems and attract rodents and flies.
Pet wastes (e.g., dog or cat feces, soiled cat litter)—might contain parasites, bacteria, germs, pathogens, and viruses harmful to humans.
Yard trimmings treated with chemical pesticides—might kill beneficial composting organisms.
Over time your pile will accumulate a certain liquid called leachate, which can contaminate local groundwater. It’s best to safely collect leachate and keep away from consumable plants.
Wrapping Up
Compost can be produced within 3-6 months if the pile is maintained as instructed. You will know when the pile is finished composting when the contents are rich, dark brown, and soil-like. Any evidence of rotting suggests that the pile was not supplied with enough oxygen, either because the pile was sealed off from the outside air or wasn’t turned enough each week.
Note
Be sure to not use the compost for houseplants; the presence of weed and grass seeds may grow alongside them.
Not every part of the compost needs to look the same. Some pieces such as grass clippings can be placed back onto your lawn—a process known as grasscycling, where the clippings decompose in the lawn and return nutrients back into the soil. Other pieces of organic matter that may not compost entirely are dried leaves; they can be placed as mulch around trees and other herbs to retain moisture in the surrounding soil.
Compost made up of plant-based feedstocks alone consists of low nutrient levels. Therefore, over-applying compost won’t bring on excess nutrients and endanger plant growth. Fortunately these low nutrient levels prevent the abundance of ammonia—unlike synthetic fertilizers—from entering the surrounding soil of the targeted plants. As a result, fewer amounts of N2O are released into the atmosphere.
Producing compost means so much more than simply providing plants with a healthier environment, or for us a healthier supply of fruits and vegetables. It means reducing greenhouse gas emissions—the building blocks of an imminent global catastrophe—in the agriculture industry, accounting for up to 1.3 billion tons of greenhouse gases emitted annually.
Global warming creeps toward us like a silent, invisible hand that slowly picks up speed; when it nears too close, its speed will be exponentially fast, a crisis we cannot run from. Compost is not the answer to global warming, but it will help tremendously with approaching net zero emissions in the agriculture industry, a sector that provides all of that which is essential for animals and humans worldwide.