From composting bins in the kitchen to dead leaves rotting on the forest floor, decomposition plays an important role in many natural cycles. Decomposition can turn waste (like organic food matter) into something more useful and can even be used to produce electrical energy in the process.
But how can decomposition be used to produce electricity? And how many types of decomposition energy are there? Let’s take a look at how long it takes for certain types of matter to decompose and how we can put decomposition energy to use.
What Is Decomposition?
Decomposition is, in simple terms, the “breakdown of matter into its basic components,” according to the Center for Aquatic and Invasive Plants at the University of Florida. This could take the form of plant material decaying at the bottom of a lake or a dead animal carcass disintegrating on the forest floor.
This type of decomposition is known as organic or biotic decomposition, and it requires living organisms, such as fungi, worms, or bacteria, to drive the process. Over time, it produces fresh, nutrient-rich soil or sediment that nourishes new plants and animals.
There’s a second type of decomposition, known as chemical decomposition, in which molecules themselves break down into smaller components. This usually requires more extreme circumstances, such as the application of radiation or acidity.
Chemical decomposition is used in scientific research, such as when measuring the mass of small particles (mass spectrometry), but this process is also found in everyday objects, including airbags when they inflate. Scientific American explains how “decomposition of the sodium azide and the generation of nitrogen gas … fills the air bag,” demonstrating how useful decomposition energy can be.
What Causes Decomposition?
As Utah State University points out, decomposition is a “complex process,” and it isn’t as simple as just putting food waste out in your garden for it to decay. The speed or rate of decomposition “depends on the temperature, moisture and chemical composition of the organic matter. If the temperature is too low, or too high, fungi and bacteria cannot grow and the rate of decomposition is slow.”
That’s why it takes much longer for food waste to degrade in a landfill than it does in a compost bin, or for plant matter to decay in cold climates as compared to warm ones.
In addition to a suitable temperature, organic decomposition requires the presence of living organisms such as worms and fungi – helpfully known as “decomposers” – that essentially eat and digest dead plant material and animal tissue.
Gardeners may be able to speed up the process by adding certain types of bacteria or enzymes to their compost pile, but this isn’t usually necessary to get started.
Does Decomposition Need Energy?
Biotic decomposition is a natural process that doesn’t require human input. It’s a little bit different in the laboratory, where chemical reactions may require some form of energy to get started. One great example of chemical decomposition is the electrolysis of water, in which an electric current is used to break water down into hydrogen and oxygen. The hydrogen can then be used as fuel for electric cars or for industrial purposes.
Chemical decomposition reactions require energy because the bonds that link chemical compounds together are strong. By applying energy to a chemical compound, we can break down the bonds that hold it together and reduce it into smaller components.
This process can also release energy that is stored in the chemical bonds, such as in the form of an explosion. In scientific terms, “decomposition energy” refers to the total amount of energy that’s released during a chemical decomposition reaction.
What Energy Can Be Used for a Decomposition Reaction to Take Place?
While organic decomposition occurs naturally, chemical decomposition requires one of three main energy sources to initiate the reaction:
- Thermal decomposition uses heat.
- Electrolytic decomposition uses electricity.
- Photolytic decomposition uses light.
This can be as simple as running an electric current through a liquid, leaving a powder exposed to the light, or exposing a chemical to a spark or heat source.
What Are Some Examples of Common Decomposition Reactions?
Decomposition reactions are more common than you might think. Here are five examples of decomposition reactions you might encounter in your everyday life:
- Hydrogen peroxide into water and oxygen: Hydrogen peroxide breaks down in the presence of light; that’s why it always needs to be stored in a dark bottle and can’t be left out in direct sunlight.
- Carbonic acid into water and carbon dioxide: The sound that you hear when you open a can of soda is a decomposition reaction. Carbonic acid decomposes when it’s mixed with water, but the reaction can only occur once you release the pressure inside the can.
- Sodium azide into nitrogen and sodium: This is the decomposition reaction that inflates your airbag. Sodium azide breaks down when it’s exposed to heat, so an igniter initiates the reaction, releasing up to 67 liters of nitrogen gas per 130 grams of sodium azide.
- Water into hydrogen and oxygen: The process of chemical electrolysis is used to separate water into its two chemical components. The hydrogen can then be used as a fuel cell to power electric cars.
- Starch into glucose and other molecules: In this catabolic reaction, digestive enzymes convert complex starch molecules into smaller components. This type of reaction plays a key role in the decomposition of plant matter.
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What Happens During Decomposition?
The decomposition process can vary widely depending on the type of material involved and the environmental conditions. Let’s start by looking in-depth at one type of decomposition – the breakdown of leaf litter – before considering the decomposition of a few other materials.
The first step in leaf decomposition is called fragmentation. This is a physical process in which earthworms and other organisms contribute to the breakdown of the material into smaller sizes. Although the chemical composition of the material hasn’t changed, it’s now easier for bacteria and microorganisms to interact with it.
Another step in the decomposition process is leaching, in which rainwater dissolves some of the leaf material and carries water-soluble nutrients into the soil.
Other steps include catabolism, in which the remaining plant material is broken down by bacteria in a metabolic process, and mineralization, in which organic compounds are made available to living plants to use in their own growth cycle.
Most leaves decompose within a year, while dense plant material can take up to three years to break down. Not all types of decomposition will involve each of these stages; for example, an enclosed compost bin won’t be exposed to rainwater leaching, and a landfill won’t have sufficient oxygen for bacteria to do their job efficiently.
Here’s how long it takes for other common materials to decompose:
How Long Does It Take for Plastic to Decompose?
Plastic takes longer to break down than organic matter because plastic is broken down by UV light rather than bacteria. The World Wildlife Fund estimates that a plastic bag can take up to 20 years to decompose, while a plastic straw takes 200 years and a plastic water bottle takes up to 450 years.
How Long Does It Take for Styrofoam to Decompose?
Styrofoam is also broken down by photodegradation, so it takes longer to break down in dark, airless environments. The Society of Environmental Journalists reports that “some estimates put the lifespan of Styrofoam in a landfill at around 500 years.”
How Long Does It Take for Paper to Decompose?
Since paper is made up of organic fibers, it decomposes at a much faster rate than plastic, in as little as two to six weeks in a landfill. However, the amount of time it takes depends on the type of paper and how much heat and oxygen is in the environment. Toilet paper can take as long as three years to decompose outdoors, which is why you shouldn’t leave it behind when you go camping.
How Long Does It Take for Glass to Decompose?
Glass is one of the most durable materials that humans produce, with some estimates putting its decomposition rate at 1 million years. This makes sense when you consider that glass artifacts have been found from ancient Egypt and other early civilizations.
Does Decomposition Release Energy?
Yes, decomposing matter can release a significant amount of energy. As one science experiment showed, the temperature in a compost pile can get higher than 150°F — generating enough warmth to heat water.
It works like this: As mesophilic bacteria (those that thrive in moderate temperatures) start to break down the composting scraps, the temperature of the compost pile goes up. Thermophilic bacteria (those that thrive in high temperatures) get to work until they run out of composting material to digest, and then the temperature drops again.
A well-maintained compost pile should be maintained at or below 150°F to avoid killing bacteria that can’t tolerate higher temperatures. It should also have a ratio of 30 parts carbon to 1 part nitrogen to ensure a healthy environment for bacteria.
Can Decomposition Energy Be Used to Produce Electricity?
Since decomposition produces energy, could you use it to heat your home or generate electricity the way you can with geothermal energy? That depends. Although it doesn’t produce anywhere near as much energy as geothermal power, decomposition energy could play a role as a renewable energy source.
During a science experiment at Emory University, students created a compost bin that could “maintain an average of five volts of electricity” — enough to charge a smartphone or another small electronic device.
What Are Microbial Fuel Cells?
Another technology called microbial fuel cells can capture the energy produced during the decomposition process and store it in battery form.
This is most commonly used in wastewater treatment, including at a PepsiCo plant in California and at Foster’s brewery in Australia. As bacteria processes the sugar and other waste products in the water, it produces small amounts of electricity.
Although the quantity of energy isn’t enough to run an entire power grid, microbial fuel cells are certainly worth exploring as part of a renewable energy future.
Explore Your Options With Just Energy
As energy prices rise and rolling blackouts become a widespread issue, understanding your home energy options is more important than ever. You may not be able to power your home with DIY composting, but there are plenty of other ways to lower your energy costs and reduce your carbon footprint.
At Just Energy, we make it easy for you to power your home with renewable energy with one of our green energy plans. You can also check out these energy saving tips to learn more about home energy efficiency and the best heating and cooling strategies.
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