Adams, Clark - 2009 - Landfill Bio Degradation

8/9/2019 Adams, Clark - 2009 - Landfill Bio Degradation

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2009

Sam Adams Bio-tec Environmental and

Danny Clark ENSO Bottles

6/15/2009

Landfill Biodegradation


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All rights reserved LANDFILL BIODEGRADATION Page 2 of17

Landfill Biodegradation

An in-depth look at biodegradation in landfill environments

By

Samuel Adams

Bio-tec Environmental, LLC

7009 Prospect Ave NE #202

Albuquerque,NM 87110

505-999-1160

Danny ClarkENSO Bottles, LLC

PO Box 15886

Phoenix, AZ 85060

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 1980s and 1990s were brought up on the

belief that landfills were filling at an enormous rate and the world would soon be one large garbagedump. 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.

Lets 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, lets 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 by a physiologicalenvironment. 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. Lets look at what micro-organisms are to better understand how

biodegradation occurs.

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


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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 thissection. 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.

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.


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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 theplanet.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

Lets 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

Aerobicbiodegradation 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.

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.

2http://en.wikipedia.org/wiki/Microorganism

3http://www.microbeworld.org/microbes/types.aspx


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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

Lets 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 , 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 complexorganic 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 (VFAs) with a chain length that is greater than acetate

must first be catabolised into compounds before they can be directly utilized by methanogens

(see Appendix C).

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

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


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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 (see Appendix C).

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 aceticacid, carbon dioxide and hydrogen (see Appendix C).

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 (see Appendix C).

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. 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.

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 remainingelement 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

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


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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:

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 tomake 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 associatedwith 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.

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


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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 preservedfrom 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 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 is manufactured by Bio-tec Environmental. This additive, EcoPure, uses

organic compounds to open the polymer chain, and 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 andprocess 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 trustedsource 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.


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ASTM Plastics Degradation Standards

Specifications

D6400 Standard Specification for Compostable Plastics

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 ofPlastic 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 Americas future Bruce Logan at Penn State states;

7http://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.

8http://features.csmonitor.com/innovation/2009/04/03/how-microbes-can-power-americas-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 onEarth.

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.

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).


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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 fromelectron 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 bodyturning over its own weight in ATP each day.

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.


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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 Marketshttp://www.methanetomarkets.org/

Bioreactor.orghttp://www.bioreactor.org/

Solid Waste Association of North America Waste to Energy Divisionhttp://swana.org/Education/TechnicalDivisions/WastetoEnergy/tabid/108/Default.aspx

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

Waste-to-Energy Research and Technology Councilhttp://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 Engineershttp://www.universetoday.com/2008/02/01/microbes-make-the-best-climate-engineers/

Methane from Microbes: A Fuel For The Futurehttp://www.lockergnome.com/news/2007/12/10/methane-from-microbes-a-fuel-for-the-future/

Microbes - By Howard Gesthttp://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 Americas futurehttp://features.csmonitor.com/innovation/2009/04/03/how-microbes-can-power-america%E2%80%99s-

future/

Landfill Methane Recoveryhttp://www.methanetomarkets.org/resources/factsheets/landfill_eng.pdf

Wikipedia Anaerobic Digestionhttp://en.wikipedia.org/wiki/Anaerobic_digestion


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Appendix C: Tables and Figures

Hydrolysis: A chemical reaction where particulates are solubilized and

large polymers are converted into simpler monomers.

H2O

Plastic material treatedwith

Sugars

Amino Acids

Fatty Acids

Figure 1: Hydrolysis phase of anaerobic biodegradation

Acidogenesis: A biological reaction where simplemonomers are converted into volatile acids.

Carbonic Acids

Hydrogen

Carbon Dioxide

Ammonia

Figure 2: Acidogenesis phase of anaerobic biodegradation


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Acetogenesis: An anaerobic microbial processwhere volatile acids are converted into acetic acid,

carbon dioxide, and hydrogen.

C

O

OHH3C

CO OH

H

Acetic Acid + H2 +CO2

Carbonic AcidHydrogen

Carbon DioxideAmmonia

Figure 3: Acetogenesis phase of anaerobic biodegradation

Methanogenesis: This is the final stage in microbialmetabolism when acetate molecules are converted intomethane and carbon dioxide.

C

O

OHH3C

H2

+ CO O

Acetic Acid Methane Carbon Dioxide

Figure 4: Methanogenesis phase of anaerobic biodegradation

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