Landfill and Biodegradation Questions

What is biodegradation?

Biodegradation is a process by which complex molecules are changed into simple molecules through the actions of microorganisms.

What is a Microbe?

Microbes, or microorganisms, are the smallest organisms on the planet and require the use of a microscope to see them. There are a huge variety of organisms that can be classified as “microbes.” They can live alone or in colonies. They can help you or they can hurt you. These creatures make up the largest number of living organisms on the planet. There are trillions and trillions of microbes on the Earth. Microbes include bacteria, fungi, some algae, and protozoa. A microorganism can be heterotrophic or autotrophic. These two terms mean they either eat other things (hetero) or make food for themselves (auto). Think about it this way: plants are autotrophic and animals are heterotrophic. A protozoan like an amoeba might spend its whole life alone, cruising through the water. Others, like fungi, work together in colonies to survive.

What are the differences between biodegradation and degradation?

Biodegradation: The process by which an organic material degrades through the action of microorganisms over a period of time. Biodegradation can occur in either aerobic (with oxygen) or anaerobic (without oxygen) environments. Degradation: The process by which a material is broken down into smaller pieces but never completely disappears. Plastic degradation can be initiated by the presence of oxygen, UV light, and heat. In many cases these products begin to degrade the moment they are manufactured, resulting in an abbreviated shelf-life.

What is the difference between Aerobic and Anaerobic Biodegradation?

Aerobic biodegradation is the breakdown of organic matter by microorganism in the presence of oxygen. Anaerobic biodegradation is the breakdown of organic matter by microorganism when oxygen is not present.

Is the EcoPure® biodegradation process strictly anaerobic/aerobic or a combination of both?

It is a combination of both aerobic (with oxygen) and anaerobic (without oxygen). Microbes found in both environments will be attracted to the plastic with EcoPure® and will colonize on the plastic which will result in accelerated biodegradation*.

Isn’t composting the only form of biodegradation?

No, there is much confusion surrounding the term “biodegradation.” Different organizations that support different types of biodegradable plastics do represent composting as the only form of biodegradation. ASTM defines biodegradable plastic as “a degradable plastic in which the degradation results from the action of naturally-occurring micro-organisms such as bacteria, fungi, and algae.” These types of organisms exist in composting environments, but also exist in different environments, as well. “Composting” is not the definitive process of biodegradation.

What is a landfill?

A landfill is a site for the disposal of waste materials by burial and is a traditional form of waste treatment. Landfilling is common around the globe. There are two basic landfill operations for handling waste disposal: dry tomb and bioreactor. A “dry tomb” sanitary landfill involves burying waste and attempting to maintain dry conditions in order to minimize biodegradation, as well as leachate and biogas production. This landfill design is commonly used in developed nations. In a bioreactor landfill, controlled quantities of liquid are added and circulated throughout waste in order to accelerate the natural biodegradation of buried waste. Bioreactor landfills are present at several test locations and may replace current landfill designs. Read more - http://www.epa.gov/landfill/

What is a bioreactor?

A bioreactor landfill operates to rapidly degrade organic waste. The increase in waste degradation and stabilization is accomplished through the addition of liquid and air to enhance microbial processes. A bioreactor landfill has the capability to produce significant amounts of methane gas, which can be used for clean energy production. The Advantages of Bioreactor Landfills: • Decomposition and stabilization of wastes in years instead of decades • Lower waste toxicity due to both aerobic and anaerobic conditions • Reduced leachate disposal costs • Possible 15 to 30 percent increase in landfill space due to an increase in the density of waste mass • Significant increased LFG generation that can be used for energy generation • Reduced post-closure care Read more: http://www.bioreactor.org/

Besides methane production, why would do we want plastic to biodegrade in landfills?

Currently, approximately 85% of all plastics produced in the U.S. end up in landfills. This plastic waste builds up in landfills, taking hundreds of years to biodegrade. It makes environmental sense to put an additive into existing plastic resins which will not impact the physical properties of that plastic, if recycled will have no negative impact on the recycling stream, and if landfilled will naturally biodegrade creating methane which can then be used as a source for clean, inexpensive energy.

What is considered an active microbial environment?

Landfills and compost piles are considered to be active microbial environments.

What environmental conditions need to be present for EcoPure® to activate?

There are three types of microbial environments: suspended, dormant, and active. Plastics treated with EcoPure® require an active microbial environment in order to biodegrade. In environments such as warehouses, offices, and retail locations the microbial environment is suspended or dormant and does not provide the circumstances needed for biodegradation to occur. An active microbial environment is one that contains active fungal and bacterial colonies and would be extremely dirty in either aerobic or anaerobic conditions. This allows the microbes to colonize on the plastic and begin to digest the polymer.

What are the stages of biodegradation in a landfill environment?

1. Aerobic Phase (first few days) – This is the phase when aerobic microbes are becoming established and moisture is building up in the refuse. While standard plastic absorption capability is relatively small, the additive causes further swelling, weakening the polymer bonds and creating molecular spaces where moisture and microbial growth can rapidly begin the aerobic degradation process. Oxygen is replaced with CO2.

2. Anaerobic, Non-Methanogenic Phase (roughly 2 weeks to 6 months) - After oxygen concentrations have declined sufficiently the anaerobic processes begin. During the initial stage (hydrolysis), the microbe colonies eat the particulates, and through an enzymatic process, reduce large polymers into simpler monomers. The secreted monomers mix with the organic additive, causing additional swelling and opening of the polymer chain and increased quorum sensing. This further excites the microbes to increase their colonization and consumption of the polymer chain. As time progresses, acidogenesis occurs where the simple monomers are converted into fatty acids. CO2 production occurs rapidly at this stage.

3. Anaerobic, Methanogenic Unsteady Phase (6 to 18 months) - The microbe colonies continue to grow eating away at the polymer chain and creating increasingly larger molecular spaces. During this phase acetogenesis occurs, converting fatty acids into acetic acid, carbon dioxide and hydrogen. As this process continues, CO2 rates decline and hydrogen production eventually ceases. 4. Anaerobic, Methanogenic Steady Phase (1 year to 5 years)

- The final stage of decomposition involves methanogensis. As colonies of microbes continue to eat away at the remaining surface of the polymer, acetates are converted into methane and carbon dioxide, and hydrogen is consumed. The process continues until the only remaining element is humus. This highly nutritional soil creates and improved environment for the microbes and enhances the final stage of decomposition.

When a plastic made with EcoPure® breaks down into biomass, what makes up that biomass?

Biomass is essentially organic matter similar to soil or dirt. It is made up of nutrients and the remains of bacterial colonies.

What are the typical bacterial strains that feed off of EcoPure®?

The specific microbes for consuming plastics have taken years for Bio-Tec Environmental to identify and are considered confidential information within Bio-Tec.

Won’t microbes consume and digest traditional plastic?

Yes, microbes are very similar to other organisms in that they move to areas where food and other necessities are available or plentiful. Microbes that find their way onto traditional plastic might begin to consume it, but would more likely disdain it in favor of easier food. We believe that un-treated plastic might take hundred of years to be completely digested by microbes.

What is microbial quorum sensing?

Microbes use quorum sensing to coordinate certain behaviors based on the local density of the bacterial population. Microbes that use quorum sensing constantly produce and secrete certain signaling molecules (called autoinducers or pheromones). These microbes have a receptor that can specifically detect the signaling molecule (inducer). When the inducer binds the receptor, it activates transcription of certain genes, including those for inducer synthesis. As the microbial population grows the concentration of the inducer passes a threshold, causing more inducer to be synthesized. This forms a positive feedback loop, and the receptor becomes fully activated. Activation of the receptor induces the up regulation of other specific genes, causing all of the cells to begin transcription at approximately the same time. This coordinated behavior of microbial cells can be useful in a variety of situations such as multiplying. Read more – http://en.wikipedia.org/wiki/Quorum_sensing

Does microbial digestion consume the entire polymer chain or just the EcoPure® additive?

Tests have been completed to show that biodegradation is occurring on the entire polymer chain versus just consuming the EcoPure® additive present in the treated plastic. ASTM testing has consistently shown biodegradation* of treated materials far in excess of the amount of EcoPure® additive being used in the sample.

What byproducts are produced during the process of biodegradation?

Products treated with EcoPure® biodegrade* as a result of microbial digestion. The process of microbial digestion can take place in either aerobic (with oxygen) or anaerobic (without oxygen) conditions. These conditions determine what by-products are produced. In aerobic microbial environments the by-products will be carbon dioxide, water, and humus. Humus is the degraded organic material in soil, which causes some soil layers to be dark brown or black. In soil science, humus refers to any organic matter that has reached a point of stability, where it will break down no further. For anaerobic microbial environments the by-products will be carbon dioxide, methane, and humus.

Are the by-products of biodegradation harmful to our environment?

Biodegradation is a natural process that is essential in maintaining our planet’s ecosystem and nutrient cycles. We at Bio-Tec Environmental believe that we as humans should strive to keep our world clean and not leave today’s waste for future generations to deal with. The waste gasses produced through the process of plastic biodegradation are manageable and even economically useful.

Do polymers still remain in the soil after biodegradation?

No, the microbes utilize the carbon backbone of the polymer chain. Microbes use the carbon for energy and leave nothing of the polymer behind when the process of digestion is complete.

* Biodegradation rates of EcoPure®-treated plastic materials measured according to the ASTM D5511 test method.  Tests are generally conducted using 20% to 30% solids content; solids content in naturally wetter landfills range from 55% to 65%, while the driest landfills may reach 93%.  Actual biodegradation rates will vary in biologically-active landfills according to the type of plastic used, the product configuration, and the solid content, temperature and moisture levels of the landfill. Find out more about biodegradability testing in our resource library.