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Module #52: The Three R’s and Composting

Module #52 Review Questions: B, C, A, E, B	Review Essential Knowledge: 8.2, 8.9, 8.10

Learning Objectives After this module you should be able to: Describe the three Rs. Understand the process and benefits of composting.

Additional Resources to Review
Bozeman: Solid Waste Plastic Bottles into Fabric How Worms Reduce Our Waste Nat Geo: How to Compost

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Essential Knowledge

8.2 Human Impacts on Ecosystems (Modules 25, 41-44, 51-54, 57, 60)

Organisms have a range of tolerance for various pollutants. Organisms have an optimum range for each factor where they can maintain homeostasis. Outside of this range, organisms may experience physiological stress, limited growth, reduced reproduction, and in extreme cases, death.
Coral reefs have been suffering damage due to a variety of factors, including increasing ocean temperature, sediment runoff, and destructive fishing practices.
Oil spills in marine waters cause organisms to die from the hydrocarbons in oil. Oil that floats on the surface of water can coat the feathers of birds and fur of marine mammals. Some components of oil sink to the ocean floor, killing some bottom-dwelling organisms.
Oil that washes up on the beach can have economic consequences on the fishing and tourism industries.

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Essential Knowledge

8.2 Human Impacts on Ecosystems (Continued)

Oceanic dead zones are areas of low oxygen in the world’s oceans caused by increased nutrient pollution.
An oxygen sag curve is a plot of dissolved oxygen levels versus the distance from a source of pollution, usually excess nutrients and biological refuse.
Heavy metals used for industry, especially mining and burning of fossil fuels, can reach the groundwater, impacting the drinking water supply.
Litter that reaches aquatic ecosystems, besides being unsightly, can create intestinal blockage and choking hazards for wildlife and introduce toxic substances to the food chain.
Increased sediment in waterways can reduce light infiltration, which can affect primary producers and visual predators. Sediment can also settle, disrupting habitats.
When elemental sources of mercury enter aquatic environments, bacteria in the water convert it to highly toxic methylmercury.

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Essential Knowledge

8.9 Solid Waste Disposal (Modules 51, 53)

Solid waste is any discarded material that is not a liquid or gas. It is generated in domestic, industrial, business, and agricultural sectors.
Solid waste is most often disposed of in landfills. Landfills can contaminate groundwater and release harmful gases.
Electronic waste, or e-waste, is composed of discarded electronic devices including televisions, cell phones, and computers.

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Essential Knowledge

8.9 Solid Waste Disposal Continued (Modules 51, 53)

A sanitary municipal landfill consists of a bottom liner (plastic or clay), a storm water collection system, a leachate collection system, a cap, and a methane collection system.
Factors in landfill decomposition include the composition of the trash and conditions needed for microbial decomposition of the waste.
Solid waste can also be disposed of through incineration, where waste is burned at high temperatures. This method significantly reduces the volume of solid waste but releases air pollutants.
Some items are not accepted in sanitary landfills and may be disposed of illegally, leading to environmental problems. One example is used rubber tires, which when left in piles can become breeding grounds for mosquitoes that can spread disease.
Some countries dispose of their waste by dumping it in the ocean. This practice, along with other sources of plastic, has led to large floating islands of trash in the oceans. Additionally, wildlife can become entangled in the waste, as well as ingest it.

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Essential Knowledge

8.10 Waste Reduction Methods (Modules 52-55)

Recycling is a process by which certain solid waste materials are processed and converted into new products.
Recycling is one way to reduce the current global demand on minerals, but this process is energy-intensive and can be costly.
Composting is the process of organic matter such as food scraps, paper, and yard waste decomposing. The product of this decomposition can be used as fertilizer. Drawbacks to composting include odor and rodents.
E-waste can be reduced by recycling and reuse. E-wastes may contain hazardous chemicals, including heavy metals such as lead and mercury, which can leach from landfills into groundwater if they are not disposed of properly.
Landfill mitigation strategies range from burning waste for energy to restoring habitat on former landfills for use as parks.
The combustion of gases produced from decomposition of organic material in landfills can be used to turn turbines and generate electricity. This process reduces landfill volume.

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The 3 Rs

The three Rs divert materials from the waste stream.
Reduce, reuse, recycle: A popular phrase promoting the idea of diverting materials from the waste stream. Also known as the three Rs.
In terms of effectiveness: reduce > reuse > recycle
“Recycling is an aspirin, alleviating a rather large collective hangover...overconsumption. The best way to reduce any environmental impact is not to recycle more, but to produce and dispose of less.” - Robert Lilienfield and William Rathje’s 1998 Use Less Stuff: Environmental Solutions for Who We Really Are.

Recycling can be an effective means of reducing waste generation, but only for certain products like paper, cardboard and metal. Recycling simply is not effective for plastics; it is always cheaper to produce new plastic than recycle old plastics, which also generates pollution. We lack critical infrastructure to recycle plastics in a meaningful way and disposal in a landfill may actually be the best option for plastic products we cannot avoid using.

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Reduce

Reduce is the first choice among the three Rs because reducing inputs is the optimal way to achieve a reduction in solid waste generation.
Source reduction: An approach to waste management that seeks to cut waste by reducing the use of potential waste materials in the early stages of design and manufacture.
Source reduction can also increase energy efficiency; manufacturing produces less waste and can minimize disposal processes.
Source reduction may also involve substituting less toxic materials or products.

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Reuse�

Reuse: Using a product or material that was intended to be discarded.
Optimally, no additional energy or resources are needed for the object to be reused.
Energy may be required to prepare or transport an object for reuse by someone other than the original user. So reuse does have environmental costs that typically exceed reducing the use of something, but this is still preferable to using new materials.
Reuse is still a common strategy in many countries and was a common practice in the United States before the ‘Throw-Away’ society mentality became commonplace.

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Recycle�

Recycling: The process by which materials destined to become municipal solid waste (MSW) are collected and converted into raw material that is then used to produce new objects.
Closed-loop recycling: Recycling a product into the same product.
Open-loop recycling: Recycling one product into a different product.
Both the total weight of MSW that is recycled and the percentage of MSW that is recycled have increased over time, but…. See this article and quote →

“The plastics industry has worked for decades to convince people and policymakers that recycling would keep waste out of landfills and the environment. Consumers sort their trash so plastic packaging can be repurposed, and local governments use taxpayer money to gather and process the material. Yet from the early days of recycling, plastic makers, including oil and gas companies, knew that it wasn't a viable solution to deal with increasing amounts of waste, according to documents uncovered by the Center for Climate Integrity.”

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Single Stream Recycling

Single-stream recycling refers to a system in which all paper fibers, plastics, metals, and other containers are mixed in a collection truck, instead of being sorted by the depositor into separate commodities and handled separately throughout the collection process.
This saves time for residents and helps generate greater economic returns at the recycling plant.

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Closed vs. Open-Loop Recycling

(a) In closed-loop recycling, a discarded carpet can be recycled into a new carpet, although some additional energy and raw material are needed.
(b) In open-loop recycling, a material such as a beverage container is used once and then recycled into something else, such as a fleece jacket.

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Three Rs Summary

	Reduce	Reuse	Recycle
Effect on solid waste management	If inputs are decreased, then output will also decrease.	Materials cycle within system for a longer time with no additional energy or resources needed.	Fewer raw materials must be extracted, which reduces pollution, environmental degradation and energy use.
Potential economic benefits	Companies can save money when they use less packaging; people can manage on a smaller budget if they use less.	Money can be saved by reusing an item rather than purchasing a new one; used item can be acquired at reduced prices.	Recycling cuts the cost of extracting or harvesting raw materials, which can save money in the production process.
Potential disadvantages	Sometimes using less can be considered a lower standard of living.	Energy may be required to clean and transport an item for reuse; water may be required to clean an item for reuse and wastewater may be generated.	Recycling materials requires time for processing, cleaning, transporting and possible modification before material is usable.

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Composting

Organic materials such as food and yard waste that end up in landfills are unstable; the absence of oxygen in landfills causes organic material to decompose anaerobically, which produces methane a potent greenhouse gas.
Composting: Creation of organic matter (humus) by decomposition under controlled conditions to produce an organic-rich material that enhances soil structure, cation exchange capacity, and fertility.

A typical facility collects almost 100,000 metric tons of food scraps and paper per year and turns it into usable compost. Most facilities have some kind of mechanized system to allow mixing and aeration of the organic material, which speeds conversion to compost.

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Composting Basics and Benefits

Materials suitable for compositing include vegetables and vegetable by-products, animal manure, yard wastes, and paper fiber not destined for recycling.
Composting requires a 30:1 ratio of carbon to nitrogen* (C:N) to support proper microbial growth.

*Remember, N is a limiting factor.

Frequent turning or agitation is usually necessary to maintain appropriate moisture levels to avoid anaerobic conditions that would result in the production of methane gas (CH₄).

Good compost has a pleasant smell and improves soil quality by adding nutrients and improving moisture and nutrient retention. With frequent turning, compost can be ready to use in a few months.

National Geographic: How to Compost-And Why It's Good For The Environment

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Anaerobic Conditions

As organic materials decompose (such as in composting or landfills) they generate different greenhouse gases (GHGs) depending on the type of conditions they are under.
Under anaerobic conditions (ie. no oxygen), decomposition results in the formation of methane (CH₄). Methane is a potent greenhouse gas with 25x the warming potential of carbon dioxide, although its retention time in the atmosphere is far shorter.

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Module Review:

In this module, we have seen that reduce, reuse, recycle, and compost are appropriate actions to take before sending a solid waste material into the waste stream.
It is important to observe the “three Rs” in the order stated here, because each action uses less energy than the next action.
Composting is another pathway for diverting material from the waste stream.
The diversion of compostable materials from the landfill reduces methane production and produces a desirable end product, decomposed organic matter.