Landfill Biodegradation

2009

Danny Clark – ENSO Bottles

6/15/2009

Landfill Biodegradation

© All rights reserved LANDFILL BIODEGRADATION

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Landfill Biodegradation

An in-depth look at biodegradation in landfill environments

Prepared by:

Danny Clark ENSO Bottles, LLC

4710 E. Falcon Dr., Suite 220 Mesa, AZ 85215 866-936-3676


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What is the first thing that comes to your mind when I mention “landfills”? Perhaps you

immediately conjure images of garbage, pollution or smelly waste? How about a source for

clean inexpensive energy? Many of us, especially those who lived through the 1980’s and

1990’s were brought up on the belief that landfills were filling at an enormous rate and the

world would soon be one large garbage dump. We were taught that landfills created

mummified tombs that would never go away. What we now know is that landfills can be a

source of one of the most inexpensive clean energies available. We also know that despite our

efforts to prevent it, biodegradation does in fact continue within landfills.

Let’s begin by learning about the characteristics of landfills. There are two types of landfills; dry

tomb and bioreactors. Dry tomb landfills are simply a big hole in the ground where garbage is

compacted as tightly as possible to save space and the tomb is sealed off reduce the amount of

oxygen and moisture getting in. The approach to dry tomb landfills is to “try” and prevent

garbage from biodegrading. This approach, which has been used for hundreds of years, creates

a dry tomb in the hope that it will be ‘out of sight out of mind’.

Bioreactor landfills, on the other hand, are advancements in landfill design to promote

anaerobic biodegradation. This type of landfill continues to compact the garbage as tightly as

possible to keep the oxygen out and to reduce space. However, to encourage anaerobic

biodegradation bioreactor landfills do something that dry tomb landfills do not, they circulate

moisture through the garbage. By adding moisture, biodegradation happens very quickly and in

the case of bioreactor landfills the same area being used for the landfill can be extended by 20

– 50 years longer. The most wonderful aspect of bioreactor landfills is that the byproduct of

anaerobic biodegradation is the off gassing of methane which is used as a source for clean

inexpensive energy.

What is the definition of biodegradation?

Now that we have the basics of landfills, let’s look at biodegradation. What does

biodegradation mean and why is there so much confusion about something that sounds so

simple to define?

The first thing to keep in mind when answering this question is that everything on the planet

and in the universe is made from atomic particles. Even things that are considered "man made"

utilize atomic particles that were and always will be in existence. The other aspect to keep in

mind is that everything on the planet will decompose and biodegrade over time. Microbes are

found all over the planet in every aspect of our lives and are constantly breaking things back

into their atomic parts. 1

ASTM International, an international standards organization defines biodegradation as

“degradation resulting from the action of naturally-occurring micro-organisms such as bacteria,

fungi, and algae”. Wikipedia defines biodegradation as: “the chemical breakdown of materials

1 http://en.wikipedia.org/wiki/Biodegradation


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by a physiological environment. Organic material can be degraded aerobically, with oxygen, or

anaerobically, without oxygen.”

Now that we have a better understanding that biodegradation occurs through the natural

breakdown by micro-organisms in either an environment with oxygen (aerobic) or without

oxygen (anaerobic), lets delve deeper into this process. Let’s look at what micro-organisms are

to better understand how biodegradation occurs.

What is a micro-organism?

What is a micro-organism or the shorter name microbe? Microbes are the smallest organisms

on the planet and require the use of a microscope to be seen. There is a huge variety of

organisms in this section. They can work alone or in colonies. They can help you or hurt you.

Most importantly, they make up the largest number of living organisms on the planet. There

are trillions of trillions of trillions of microbes around the Earth.

Microbes include bacteria, fungi, some algae, and protozoa. A microbe 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. They can be solitary or colonial. A protozoan like an amoeba might spend its

whole life alone, cruising through the water. Others, like fungi, work together in colonies to

help each other survive. Most microorganisms are unicellular (single-celled), but this is not

universal, since some multi-cellular organisms are microscopic

Microbes live in all parts of the biosphere where there is liquid water, including soil, hot springs,

on the ocean floor, high in the atmosphere and deep inside rocks within the Earth's crust.

Microbes act as decomposers and are critical to nutrient recycling in ecosystems. Some

microbes can fix nitrogen and are a vital part of the nitrogen cycle. Recent studies indicate that

airborne microbes may play a role in precipitation and weather.

Microbes are also exploited by people in biotechnology, both in traditional food and beverage

preparation, and in modern technologies based on genetic engineering. However, pathogenic

microbes are harmful, since they invade and grow within other organisms, causing diseases that

kill millions of people, other animals, and plants.

Microorganisms are vital to humans and the environment, as they participate in the Earth's

element cycles such as the carbon cycle and nitrogen cycle, as well as fulfilling other vital roles

in virtually all ecosystems, such as recycling other organisms' dead remains and waste products

through decomposition. Microbes also have an important place in most higher-order multi-

cellular organisms. Many blame the failure of Biosphere 2 on an improper balance of microbes.

Use in food - Microorganisms are used in brewing, winemaking, baking, pickling and

other food-making processes. They are also used to control the fermentation process in

the production of cultured dairy products such as yogurt and cheese. The cultures also

provide flavor and aroma, and inhibit undesirable organisms.


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Use in water treatment - Specially-cultured microbes are used in the biological

treatment of sewage and industrial waste effluent, a process known as bio-

augmentation.

Use in energy - Microbes are used in fermentation to produce ethanol, and in biogas

reactors to produce methane. Scientists are researching the use of algae to produce

liquid fuels, and bacteria to convert various forms of agricultural and urban waste into

usable fuels.

Use in science - Microbes are also essential tools in biotechnology, biochemistry,

genetics, and molecular biology.2

As we can see microorganisms are a big part of our environment and everything that happens

on the planet.3 For those interested in the biochemical processes of the microbial organisms

this document will provide a high level explanation of the aerobic and anaerobic

biodegradation processes.

The Biodegradation Process

Let’s look at microbes in action also known as biodegradation. Biodegradation is the process by

which organic substances are broken down into smaller compounds using the enzymes

produced by living microbial organisms. The microbial organisms transform the substance

through metabolic or enzymatic processes. Although biodegradation processes vary greatly, the

final product of the degradation is most often carbon dioxide and/or methane.

Biodegradable matter is generally organic material such as plant and animal matter and other

substances originating from living organisms, or artificial materials that are similar enough to

plant and animal matter to be put to use by microbes. Some microorganisms have the

astonishing, naturally occurring, microbial catabolic diversity to degrade, transform or

accumulate a huge range of compounds including hydrocarbons (e.g. oil), polychlorinated

biphenyls (PCBs), polyaromatic hydrocarbons (PAHs), pharmaceutical substances, radionuclides

and metals. Organic material can be degraded aerobically, with oxygen, or anaerobically,

without oxygen.

Aerobic Biodegradation

Aerobic biodegradation is the breakdown of organic contaminants by microorganisms when

oxygen is present. More specifically, it refers to occurring or living only in the presence of

oxygen; therefore, the chemistry of the system, environment, or organism is characterized by

oxidative conditions. Many organic contaminants are rapidly degraded under aerobic

conditions by aerobic bacteria called aerobes.

2 http://en.wikipedia.org/wiki/Microorganism 3 http://www.microbeworld.org/microbes/types.aspx


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Aerobic bacteria (aerobe) have an oxygen based metabolism. Aerobes, in a process known as

cellular respiration, use oxygen to oxidize substrates (for example sugars and fats) in order to

obtain energy.

Before cellular respiration begins, glucose molecules are broken down into two smaller

molecules. This happens in the cytoplasm of the aerobes. The smaller molecules then enter a

mitochondrion, where aerobic respiration takes place. Oxygen is used in the chemical reactions

that break down the small molecules into water and carbon dioxide. The reactions release

energy for use within the microbe.

Anaerobic Biodegradation

Biodegradable waste in landfill degrades in the absence of oxygen through the process of

anaerobic digestion. Paper and other materials that normally degrade in a few years degrade

more slowly over longer periods of time. Biogas contains methane which has approximately 21

times the global warming potential of carbon dioxide if released directly into the atmosphere.

In a cradle to cradle approach, this biogas is collected and converted into eco-friendly

inexpensive power generation and carbon dioxide.

Anaerobic digestion is a series of processes in which microbes break down

biodegradable material in the absence of oxygen. It is widely used to treat wastewater sludge

and biodegradable waste because it provides volume and mass reduction of the input material.

As part of an integrated waste management system, anaerobic digestion reduces the emission

of landfill gas into the atmosphere. Anaerobic digestion is a renewable energy source because

the process produces Methane and Carbon dioxide rich biogas suitable for energy production

and helps replace fossil fuels. Also, the nutrient-rich solids left after digestion can be used as

fertilizer.

An anaerobic Digester contains a synergistic community of microorganisms to carry out the

process of fermenting organic matter into methane.4

The Anaerobic Biodegradation Process

Let’s take a detailed look at the process of anaerobic biodegradation. There are a number of

bacteria that are involved in the process of anaerobic digestion including acetic acid-forming

bacteria and methane-forming bacteria. These bacteria feed upon the initial feedstock, which

undergoes a number of different processes converting it to intermediate molecules including

sugars, hydrogen & acetic acid before finally being converted to biogas.

The process begins with bacterial hydrolysis of the input materials in order to break down

insoluble organic polymers such as carbohydrates and make them available for other bacteria.

Acidogenic bacteria then convert the sugars and amino acids into carbon dioxide, hydrogen ,

4 http://en.wikipedia.org/wiki/Anaerobic_digestion


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ammonia , and organic acid. Acetogenic bacteria then convert these resulting organic acids into

acetic acid, along with additional ammonia, hydrogen, and carbon dioxide. Methanogen finally

are able to convert these products to methane and carbon dioxide.

Anaerobic Biodegradation Stages

There are four key biological and chemical stages of anaerobic digestion:

1) Hydrolysis: In most cases biomass is made up of large organic polymers. In order for the

bacteria in anaerobic digesters to access the energy potential of the material, these

chains must first be broken down into their smaller constituent parts. These constituent

parts or monomers such as sugars are readily available by other bacteria (fats,

carbohydrates, protein and cellulose). The process of breaking these chains and

dissolving the smaller molecules into solution is called hydrolysis. Therefore hydrolysis

of these high molecular weight polymeric components is the necessary first step in

anaerobic digestion. Through hydrolysis the complex organic molecules are broken

down into simple sugars, amino acids, and fatty acids. Acetate and hydrogen produced

in the first stages can be used directly by methanogens. Other remaining molecules such

as volatile fatty acids (VFA’s) with a chain length that is greater than acetate must first

be catabolised into compounds before they can be directly utilized by methanogens.

2) Acidogenesis: The biological process of acidogenesis is where there is further

breakdown of the remaining components by acidogenic (fermentative) bacteria. Here

the microbial process metabolizes hydrolyzed organic material into organic acids and H2,

CO2 and other by-products. The process of acidogenesis is similar to the way that milk

sours.

3) Acetogenesis: The third stage of anaerobic digestion is acetogenesis . Here simple

molecules created through the acidogenesis phase are further digested by acetogens to

produce acetic acid, carbon dioxide and hydrogen.

4) Methanogenesis: The final stage of anaerobic digestion is the biological process of

methanogenesis. This is where methanogens utilize the intermediate products of the

preceding stages and convert them into CH4 (methane), CO2 (carbon dioxide) and H2O

(water). It is after this stage that biogas can be collected for energy production .

Landfill Decomposition Cycle

Aerobic Phase (first few days in landfill) - Period when aerobic microbes are becoming

established and moisture is building up in the refuse. While standard plastic absorption

capability is relatively small, Bio-Batch 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.

Anaerobic, Non-methanogenic Phase (roughly 2 weeks to 6 months) - After O2

concentrations have declined sufficiently, the anaerobic processes begin. During the

initial stage (hydrolysis), the microbe colonies eat the particulates, and through an

enzymatic process, solubilize large polymers down into simpler monomers. As time


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progresses, acidogenesis occurs where the simple monomers are converted into fatty

acids. CO2 production occurs rapidly at this stage.

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 where fatty acids are

converted into acetic acid, carbon dioxide and hydrogen. As this process continues, CO2

rates decline and H2 production eventually ceases.

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, while 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.5

Environmental Benefit

Utilizing the anaerobic biodegradation process within landfills has many benefits. The United

Nations Development Program has recognized anaerobic digestion facilities as one of the most

useful decentralized sources of energy supply. Utilizing anaerobic digestion technologies can

help to reduce the emission of greenhouse gases and improve environmental conditions in a

number of key ways:

• Energy Production – by replacing fossil fuels

• Combat Global Warming – by reducing methane emission from landfills

• Nutrient Recovery – by displacing industrially-produced chemical fertilizers

• Reducing electrical grid transportation losses

• Conserve Land

• Pathogen Reduction

• Waste Reduction

Methane and power produced in anaerobic digestion facilities can be utilized to replace energy

derived from fossil fuels, and hence reduce emissions of greenhouse gases. This is due to the

fact that the carbon in biodegradable material is part of a carbon cycle. The carbon released

into the atmosphere from the combustion of biogas has been removed by plants in order for

them to grow in the recent past. This can have occurred within the last decade, but more

typically within the last growing season. If the plants are re-grown, taking the carbon out of the

atmosphere once more, the system will be carbon neutral. This contrasts to carbon in fossil

fuels that has been sequestered in the earth for many millions of years, the combustion of

which increases the overall levels of carbon dioxide in the atmosphere.

Dr. Chong from York University:

5 http://www.biogreenplastic.com/landfill.php


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“Microbes could provide a clean, renewable energy source and use up carbon dioxide in the

process, suggested Dr. James Chong at a Science Media Centre press briefing.

“Methanogens are microbes called archaea that are similar to bacteria. They are responsible for

the vast majority of methane produced on earth by living things”. “They use carbon dioxide to

make methane, the major flammable component of natural gas. So methanogens could be used

to make a renewable, carbon neutral gas substitute.”

Methanogens produce about one billion tonnes of methane every year. They thrive in oxygen-

free environments like the guts of cows and sheep, humans and even termites. They are widely

distributed in nature living in swamps, bogs, natural waters sewage processing plants and

landfills.”6

What is better for the environment professional composting or bioreactors?

There have been a number of studies conducted to compare the environmental impact of

professional composting vs. landfill bioreactors. In these studies, the potential environmental

impacts associated with aerobic composting and bioreactor landfills were assessed using the

life cycle inventory (LCI) tool. The results are fairly the same across the studies performed.

These studies concluded that the emissions to air and water that contribute to human toxicity

are greater for the composting option than for the landfill option and the landfill option yields

greater energy savings due to the conversion of the landfill gas (LFG) to electrical energy.

One such study was conducted at the Michigan State University under the Fulbright Research

Grant by Maria Theresa I. Cabaraban, Milind V. Khire and Evangelyn C. Alocilja and was later

published in November 2007. Their study looked at the potential environmental impacts

associated with aerobic in-vessel composting verse bioreactor landfilling. The results using the

LCI model showed that the estimated energy recovery from bioreactor landfilling was

approximately 9.6 MJ per kg of waste. The air emissions from in-vessel composting contributed

to a GWP of 0.86 kg of CO2, compared to 1.54 kg of CO2 from the bioreactor landfill. Emissions

to air and water that contribute to human toxicity were greater for the composting option that

for the landfill. In addition, costs associated with in-vessel composting were about 6 times

greater than that for the landfilling alternative.

In conclusion, bioreactor landfill was a favorable option over in-vessel composting in regards to

cost, overall energy use, and airborne and waterborne emissions.

Are Plastics Biodegradable?

Plastics are known as hydro-carbons, meaning they are made mostly from hydrogen and carbon

atoms. Plastics have been designed to keep out oxygen so that the food product inside is

preserved from naturally biodegrading/rotting. Oxygen is an extremely permeable atom and

can make its way into just about any type of barrier (including plastics). Plastics have been also

6 http://www.lockergnome.com/news/2007/12/10/methane-from-microbes-a-fuel-for-the-future/


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been engineered for high strength which is why traditional plastics take thousands of years for

microbes to break it down into biogases and biomass.

Biodegradable plastics on the other hand, are plastics engineered to decompose in the natural

environment. Biodegradation of plastics can be achieved by enabling microbes in the

environment to metabolize the molecular structure of plastic films and produce an inert humus

material and biogases. Biodegradable plastics, or bio-plastics as they are known, are plastics

whose components are derived from either renewable raw materials, or petroleum based

plastics with a biodegradable additive.

One such technology uses organic compounds which are attractants to stimulate microbial

colonization on the plastic. Once the polymer chain is open the microbes can use the carbon

chain as a source of food and energy. This biodegradation is happening at the atomic level and

during which anaerobic microbes produce CO2, CH4 and inert humus. Many of these products

will degrade in a landfill to provide CO2 and CH4 that can be captured and burned to create

clean inexpensive energy.

It is very important when discussing biodegradable plastics to understand the definition and

process of biodegradation. This term has been grossly misused and misunderstood. By

definition, plastics that fragment, or degrade through chemical and/or mechanical processes

are not biodegradable. They are simply degradable and very often leave metals, toxins and

polymer residue in the environment.

Note: Plastics which biodegrade by microbes do not leave behind any polymer residue or toxic materials.

Plastics Degradation Standards

ASTM International, originally known as the American Society for Testing and Materials (ASTM),

is one of the largest voluntary standards development organizations in the world - a trusted

source providing technical standards for materials, products, systems, and services. Known for

their high technical quality and market relevancy, ASTM International standards have an

important role in the information infrastructure that guides design, manufacturing and trade in

the global economy.

ASTM International has developed a set of specifications, test methods and guidelines for biodegradable

plastics. Visit the ASTM website at http://www.astm.org.

ASTM Plastics Degradation Standards

Specifications

• D6400 Standard Specification for Compostable Plastics


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• D7081 Standard Specification for Non-floating Biodegradable Plastics in Marine

Environments

Test Methods

• D5247 Standard Test Method for Determining the Aerobic Biodegradability of

Degradable Plastics by Specific Microorganisms

• D5338 Standard Test Method for Determining Aerobic Biodegradation of Plastic

Materials Under Controlled Composting Conditions

• D5511 Standard Test Method for Determining Anaerobic Biodegradation of

Plastic Materials Under High-Solids Anaerobic-Digestion Conditions

• D5526 Standard Test Method for Determining Anaerobic Biodegradation of

Plastic Materials Under Accelerated Landfill Conditions

Summary

Previously, the technical expertise required to maintain anaerobic digesters coupled with high

capital costs and low process efficiencies had limited the level of industrial application as a

waste treatment technology. Anaerobic digestion facilities have, however, been recognized by

the United Nations Development Program as one of the most useful decentralized sources of

energy supply.

A bioreactor landfill operates to rapidly transform and degrade organic waste. The increase in

waste degradation and stabilization is accomplished through the addition of liquid to enhance

microbial processes. By efficiently designing and operating a landfill, the life of a landfill can be

significantly extended, leachate is effectively detoxified and greenhouse gases are reduced.

Landfill gases such as methane are fuel sources which are then used for clean energy

production.7 Bioreactor landfills offer many benefits such as:

• Decomposition and biological stabilization in years vs. decades in “dry tombs”

• Lower waste toxicity and mobility due to both aerobic and anaerobic conditions

• Reduced leachate disposal costs and leachate detoxification

• A 15 to 30 percent gain in landfill space due to an increase in density of waste mass

• Increased landfill settlement due to rapid decomposition of waste

• Significant increased LFG generation that, when captured, is used for onsite energy use

or sold

• Reduced post-closure activities and care

From an article titled “How microbes can power America’s future” Bruce Logan at Penn State

states;

7 http://www.bioreactor.org


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“They found certain microbes that use electricity to convert CO2 and water into

methane. These hydrolysis cells convert electrical energy into energy stored in methane

with 80 percent efficiency.

Technical details of this research appeared in the journal Environmental Science and

Technology, and Professor Logan emphasized the potential environmental benefits in a

separate statement. No extra carbon has to be added to make methane, he writes.

When the gas is burned for fuel, it only lets off as much CO2 as originally went in, saving

utilities from pumping more greenhouse gases into the environment. Furthermore, if

the electricity used in the process comes from solar or wind power, the entire fuel cycle

would not add any extra CO2 to the environment.

“The process does not sequester carbon, but it does turn carbon dioxide into fuel,”

Logan explains. “If the methane is burned and carbon dioxide captured, then the

process can be carbon neutral.”8

Microbes have been an important part of our planet for millions of years. They were the first

life forms on the planet and have been instrumental in creating the life sustaining environment

we enjoy today. Without them our planet would not be able to sustain life. Microbes are

found in the deepest depths of our oceans and the highest peaks of our mountains, they are

literally everywhere on our planet, including landfills.

8 http://features.csmonitor.com/innovation/2009/04/03/how-microbes-can-power-america’s-future/


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Appendix A: Bio-Chemistry of a Micro-Organism for Biodegradation

Although food contains energy, it is not in a form that can be used by cells. Cellular respiration

changes food energy into a form all cells can use. This energy drives the life processes of

almost all organisms on Earth.

• Oxidation – describes the loss of an electron

• Reduction – describes the gain of an electron

• Respiration – uses electron acceptors to produce reduced compounds

Cellular respiration is the set of the metabolic reactions and processes that take place in

organisms' cells to convert biochemical energy from nutrients into adenosine tri phosphate

(ATP), and then release waste products. The reactions involved in respiration are catabolic

reactions that involve the oxidation of one molecule and the reduction of another.

Nutrients commonly used by animal and plant cells in respiration include glucose, amino acids

and fatty acids, and a common oxidizing agent (electron acceptor) is molecular oxygen (O2).

Bacteria organisms may respire using a broad range of inorganic molecules as electron donors

and acceptors, such as sulfur, metal ions, methane or hydrogen. Organisms that use oxygen as a

final electron acceptor in respiration are described as aerobic, while those that do not are

referred to as anaerobic.

When cells do not have enough oxygen for respiration, they use a process called fermentation

to release some of the energy stored in glucose molecules. Like respiration, fermentation

begins in the cytoplasm. Again, as the glucose molecules are broken down, energy is released.

But the simple molecules from the breakdown of glucose do not move into the mitochondria.

Instead, more chemical reactions occur in the cytoplasm. These reactions release some energy

and produce wastes, i.e. methane.

The energy released in respiration is used to synthesize ATP to store this energy. The energy

stored in ATP can then be used to drive processes requiring energy, including biosynthesis,

locomotion or transportation of molecules across cell membranes. Because of its ubiquity in

nature, ATP is also known as the "universal energy currency".

Electron Acceptor: Microorganisms such as bacteria obtain energy to grow by

transferring electrons from an electron donor to an electron acceptor. An

electron acceptor is a compound that receives or accepts an electron during

cellular respiration.

The microorganism through its cellular machinery collects the energy for its use.

The process starts with the transfer of an electron from an electron donor. During

this process (electron transport chain) the electron acceptor is reduced and the

electron donor is oxidized.


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Examples of acceptors include; oxygen, nitrate, iron (III), manganese (IV), sulfate,

carbon dioxide, or in some cases the chlorinated solvents such as

tetrachloroethene (PCE), trichloroethene (TCE), dichloroethene (DCE), and vinyl

chloride (VC).

These reactions are of interest not only because they allow organisms to obtain

energy, but also because they are involved in the natural biodegradation of

organic substances.

Electron Donor: Microorganisms, such as bacteria, obtain energy to grow by

transferring electrons from an electron donor to an electron acceptor. An

electron donor is a compound that gives up or donates an electron during cellular

respiration, resulting in the release of energy.

The microorganism through its cellular machinery collects the energy for its use.

The final result is the electron is donated to an electron acceptor. During this

process (Electron Transport Chain) the electron donor is oxidized and the

electron acceptor is reduced.

Petroleum hydrocarbons, less chlorinated solvents like vinyl chloride, soil organic

matter, and reduced inorganic compounds are all compounds that can act as

electron donors. These reactions are of interest not only because they allow

organisms to obtain energy, but also because they are involved in the natural

biodegradation of organic substances.

Note: Aerobic respiration produces 30 ATP compared to the 2 ATP yielded from

anaerobic respiration per glucose molecule.

Electron transfer chain

The electron transfer chain, also called the electron transport chain, is a sequence

of complexes found in the mitochondrial membrane that accept electrons from

electron donors, shuttle these electrons across the mitochondrial membrane

creating an electrical and chemical gradient, and, through the proton driven

chemistry of the ATP synthase, generate adenosine triphosphate.

Adenosine-5'-triphosphate (ATP) is a multifunctional nucleotide, and is most important in cell

biology as a coenzyme that is the "molecular unit of currency" of intracellular energy transfer.

In this role, ATP transports chemical energy within cells for metabolism. It is produced as an

energy source during the processes of photosynthesis and cellular respiration and consumed by

many enzymes and a multitude of cellular processes including biosynthetic reactions, motility

and cell division. ATP is made from adenosine diphosphate (ADP) or adenosine

monophosphate (AMP), and its use in metabolism converts it back into these precursors. ATP is

therefore continuously recycled in organisms, with the human body turning over its own weight

in ATP each day.


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In signal transduction pathways, ATP is used as a substrate by kinases that phosphorylate

proteins and lipids, as well as by adenylate cyclase, which uses ATP to produce the second

messenger molecule cyclic AMP. The ratio between ATP and AMP is used as a way for a cell to

sense how much energy is available and control the metabolic pathways that produce and

consume ATP. Apart from its roles in energy metabolism and signaling, ATP is also incorporated

into nucleic acids by polymerases in the processes of DNA replication and transcription.

Note: Aerobic respiration produces 30 ATP compared to the 2 ATP yielded from anaerobic respiration per

glucose molecule. The energy not converted to ATP during anaerobic respiration is unavailable to microbes and

is contained in CH4 (methane) which has stored energy.


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Appendix B: References

Methane to Energy

• Methane to Markets

http://www.methanetomarkets.org/

• Bioreactor.org

http://www.bioreactor.org/

• Solid Waste Association of North America – Waste to Energy Division

http://swana.org/Education/TechnicalDivisions/WastetoEnergy/tabid/108/Default.aspx

• Energy Recovery Council - Waste to Energy http://www.wte.org/

• Waste-to-Energy Research and Technology Council

http://www.seas.columbia.edu/earth/wtert/index.html

• Biogreen Plastic

http://www.biogreenplastic.com/landfill.php

Methane and Microbe Articles and Books

• Microbes Make the Best Climate Engineers

http://www.universetoday.com/2008/02/01/microbes-make-the-best-climate-engineers/

• Methane from Microbes: A Fuel For The Future

http://www.lockergnome.com/news/2007/12/10/methane-from-microbes-a-fuel-for-the-future/

• Microbes - By Howard Gest

http://books.google.com/books?id=nXfcOvmZ3qsC&pg=PA60&lpg=PA60&dq=landfills+and+microbes+an

d+methane&source=bl&ots=J6AWmc5n4Z&sig=eK8VzeXzWipGPniMA0KyfDS8kRo&hl=en&ei=0E80SqPUJ4

zasgPcuv3BDg&sa=X&oi=book_result&ct=result&resnum=2#PPA61,M1

• How microbes can power America’s future

http://features.csmonitor.com/innovation/2009/04/03/how-microbes-can-power-america%E2%80%99s-

future/

• Landfill Methane Recovery

http://www.methanetomarkets.org/resources/factsheets/landfill_eng.pdf

• Wikipedia Anaerobic Digestion

http://en.wikipedia.org/wiki/Anaerobic_digestion

Documents

Landfill Biodegradation