______________________________________________________________________ Complete
Mix
Digester
Complete Mix Digesters are one of three basic types of anaerobic digesters. Complete Mix Digesters have an enclosed, heated tank with either a mechanical, hydraulic, or gas mixing system. Complete mix digesters work best when there is dilution of the manure with water, i.e. milking center wastewater. A cross-section diagram of a complete mix digester is found below. _________________________________________
More information on Complete Mix Digesters found at: or _________________________________________
Complete
Mix
Digester ______________________________________________________________________
How
Anaerobic Digesters Work, and
Biomethane
and Anaerobic Bacteria Natural gas,
or methane, is a fossil fuel - was created hundreds of thousands of years ago by the anaerobic
decomposition of organic materials (primarily algae). It is often found in association with oil
and coal. The
same types of anaerobic bacteria that produce natural gas also produce biomethane
today. Anaerobic bacteria are some of the oldest forms of life on
earth. They evolved before the photosynthesis of green plants released large
quantities of oxygen into the atmosphere. Anaerobic bacteria break down or
"digest" organic material in the absence of oxygen and produce "Biomethane"
as a waste product. (Aerobic decomposition, or composting, requires large
amounts of oxygen and produces heat.) Anaerobic
decomposition occurs naturally in swamps, water-logged soils and rice fields,
deep bodies of water, and in the digestive systems of termites and large
animals. Anaerobic processes can be managed in a "digester" (an
airtight tank) or a covered lagoon (a pond used to store manure) for waste
treatment. The primary benefits of anaerobic digestion are nutrient recycling,
waste treatment, and odor control. Except in very large systems, biomethane
production is a highly useful but secondary benefit. Biomethane
produced in anaerobic digesters consists of methane (50%–80%), carbon dioxide
(20%–50%), and trace levels of other gases such as hydrogen, carbon monoxide,
nitrogen, oxygen, and hydrogen sulfide. The relative percentage of these gases
in biomethane
depends on the feed material and management of the process. When
burned, a cubic foot (0.028 cubic meters) of biomethane
yields about 10 Btu
(2.52 kcal) of heat energy per percentage of methane composition. For example, biomethane
composed of 65% methane yields 650 Btu per cubic foot (5,857
kcal/cubic meter). Anaerobic
Digestion Anaerobic
decomposition is a complex process. It occurs in three basic stages as the
result of the activity of a variety of microorganisms. Initially, a group of
microorganisms converts organic material to a form that a second group of
organisms utilizes to form organic acids. Methane-producing (methanogenic)
anaerobic bacteria utilize these acids and complete the decomposition process. A
variety of factors affect the rate of digestion and Biomethane
production. The
most important is temperature. Anaerobic bacteria communities can endure
temperatures ranging from below freezing to above 135° Fahrenheit (F) (57.2°
Centigrade [C]), but they thrive best at temperatures of about 98°F (36.7°C) (mesophilic)
and 130°F (54.4°C) (thermophilic). Bacteria activity, and thus biomethane
production, falls off significantly between about 103° and 125°F (39.4° and
51.7°C) and gradually from 95° to 32°F (35° to 0°C). In
the thermophilic range, decomposition and biomethane
production occur more
rapidly than in the mesophilic range. However, the process is highly sensitive
to disturbances, such as changes in feed materials or temperature. While all anaerobic digesters
reduce the viability of weed seeds and disease-producing
(pathogenic) organisms, the higher temperatures of thermophilic digestion result
in more complete destruction. Although anaerobic digesters
operated in the mesophilic
range must be larger (to accommodate a longer period of decomposition within the
tank (hydraulic retention time), the process is less sensitive to upset or change in
operating regimen. To
optimize the digestion process, anaerobic digesters
must be kept at a
consistent temperature, as rapid changes will upset bacterial activity. In most
areas of the United States, digestion vessels require some level of insulation
and/or heating. Some installations circulate the coolant from their biomethane-powered
engines in or around the digester to keep it warm, while others burn part of the
biomethane
to heat the digester. In a properly designed system, heating
generally results in an increase in biomethane
production during colder periods.
The trade-offs in maintaining optimum digester temperatures to maximize gas
production while minimizing expenses are somewhat complex. Studies on digesters
in the north-central areas of the country indicate that maximum net biomethane
production can occur in anaerobic digesters
maintained at temperatures as low as 72°F
(22.2°C). Other
factors affect the rate and amount of biomethane
output. These include pH,
water/solids ratio, carbon/nitrogen ratio, mixing of the digesting material, the
particle size of the material being digested, and retention time. Pre-sizing and
mixing of the feed material for a uniform consistency allows the bacteria to
work more quickly. The pH is self-regulating in most cases. Bicarbonate of soda
can be added to maintain a consistent pH; for example, when too much
"green" or material high in nitrogen content is added. It may be
necessary to add water to the feed material if it is too dry or if the nitrogen
content is very high. A carbon/nitrogen ratio of 20/1 to 30/1 is best.
Occasional mixing or agitation of the digesting material can aid the digestion
process. Antibiotics in livestock feed have been known to kill the anaerobic
bacteria in digesters. Complete digestion, and retention times, depend on all of
the above factors. Sewage
Sludge or Effluent The
material drawn from the anaerobic digester is called sewage
sludge, or effluent.
It is rich in nutrients (ammonia, phosphorus, potassium, and more than a dozen
trace elements) and is an excellent soil conditioner. It can also be used as a
livestock feed additive when dried. Any toxic compounds (pesticides, etc.) that
are in the anaerobic digesters'
feedstock material may become concentrated in the effluent.
Therefore, it is important to test the effluent before using it on a large
scale. Anaerobic
Digester Types and Designs Factors
to consider when designing an anaerobic digester system include cost, size,
local climate, and the availability and type of organic feedstock material. Anaerobic digesters
can be manufactured from different materials depending on the location, climate
and waste to be processed. These materials include; concrete, steel, brick, or plastic.
Anaerobic digesters
are also manufactured in a variety of shapes, including; silos, troughs, basins or
may also be a pond or lagoon, and may be placed underground or on the
surface. All anaerobic digesters
system designs incorporate the same basic
components:
Batch-type
digesters are the simplest to build. Their operation consists of loading the
digester with organic materials and allowing it to digest. The retention time
depends on temperature and other factors. Once the digestion is complete, the
effluent is removed and the process is repeated.
In
a continuous digester, organic material is constantly or regularly fed into the
digester. The material moves through the digester either mechanically or by the
force of the new feed pushing out digested material. Unlike batch-type
digesters, continuous digesters produce biogas without the interruption of
loading material and unloading effluent. There are three types of continuous
digesters: vertical tank systems, horizontal tank or plug-flow systems, and
multiple tank systems. Proper
design, operation, and maintenance of continuous digesters produce a steady and
predictable supply of usable biogas. They may be better suited for large-scale
operations. Many
livestock operations store the manure they produce in waste lagoons, or ponds. A
growing number of these operations are placing floating covers on their lagoons
to capture the biogas. They use it to run an engine/generator to produce
electricity. The
cost of designing an constructing an anaerobic
digester
and the associated "balance of
plant" can vary widely. Systems can be put together using
off-the-shelf materials. There are also a few companies that build system
components. Some sophisticated systems have been designed by professionals whose
major focus is research, not low cost. The
Economics and Benefits of Anaerobic Digesters
Before you install one or more anaerobic digesters on your farm or ranch, food processing plant, or facility, you should explore its economic value and potential benefits. You will also want to consider an anaerobic digester "feasibility study" that specifically reviews your operation and requirements. An
anaerobic
digester usually requires manure from more than 150 large animals to
cost effectively generate electricity. The anaerobic
digester and associated biogas production
can also reduce overall operating costs where costs are high for sewage,
agricultural, or animal waste disposal, and the effluent has economic value. In the United States, the availability of inexpensive fossil fuels has limited the use of digesters solely for biogas production. However, the waste treatment and odor reduction benefits that anaerobic digesters provide are receiving increasing interest, especially for large-scale livestock operations such as dairies, feedlots, and slaughterhouses. Multiple Environmental and Economic Benefits for Installing Anaerobic Digesters: Anaerobic digesters generate numerous economic and environmental dividends:
______________________________________________________________________ What is Biomethane? Biomethane is "renewable natural gas" made from organic sources - which starts out as "biogas" but then is cleaned up in a process called "Biogas to Biomethane" which removes the impurities in biogas such as carbon dioxide, siloxanes and hydrogen sulfides (H2S). Biomethane is soon to be re-classified from the category of "Low Carbon Fuels" to "Super Low Carbon Fuel" due to it being the greenest of all biofuels! "Cleaned-up"
and ready for use in an onsite cogeneration or
trigeneration power plant, the Biomethane could also be sold to a pipeline company and completely replace the
"natural gas" that is typically transported to markets via the vast
underground pipeline system. Biomethane has an unlimited supply, whereas the methane sold by gas companies has a limited supply. Biomethane is renewable, whereas the methane sold by your gas utility company is not renewable. Biomethane recovery, use and production generates "Greentags" or a "Renewable Energy Credit" for the owners and is GOOD for our environment. As previously mentioned, Biomethane is "naturally" produced from organic materials as they decay. Sources of Biomethane include; landfills, POTW's/Wastewaster Treatment Systems, and every tree or agricultural product that is no longer living. Biomethane is also generated from animal operations where manure can be collected and the Biomethane is generated from anaerobic digesters where the manure decomposes. Biomethane, after installation of the Biomethane equipment is essentially free, as opposed to buying natural gas, presently costing around $10.00/mmbtu. Methanogenesis is the production of CH4 and CO2 by biological processes that are carried out by methanogens. Unlike the price of natural gas, which has been very unstable, and wildly fluctuating from $5.50 to as much as $17.00/mmbtu this past year, Biomethane prices will tend to be more stable over the years. As more and more Biomethane is produced, and produced in reliable and sustainable methods that can fuel our energy needs now and for. ______________________________________________________________________ When
It Comes to Energy Independence,
Biomethane,
NOT Coal, is America's True "Ace in the Hole" when it comes to our
energy future, economics, the environment, sustainability and America's
“Energy Independence.” And biomethane is also receiving recognition as one
of the greenest of all biofuels. For
years now, the coal industry has been touting "coal is America's 'Ace in
the Hole'" when they discuss the abundance of our coal reserves here in the
U.S. and the role they hope coal will play in America's energy future. But
coal is far from being the “Ace in the Hole” the coal lobby would have
everyone believe. That’s due to
the proverbial “black eye” not to mention the “black lungs” and other
problems that are inherent with “dirty coal.” While
there may be a place for coal in America's energy future, coal must become
"clean" for America to value it as a possible energy resource. Plans
or building 18 new Coal fired power plants were cancelled in Texas last year due
to the fact that coal isn't clean, and utilities aren't interested in investing
the extra costs for building power plants that use "Clean Coal
Technology" or "Integrated Gasification Combined Cycle" power
plants that also now need to include "Carbon Capture and
Sequestration" technologies to remove the carbon dioxide emissions from the
stacks. Plans for many other coal fired power plants are being cancelled. And
even now, owners of coal fired power plants (pulverized coal) are switching from
coal, to biomass, and biomass gasification technologies, as the writing is on
the wall. Unless
our society relishes the thoughts of moving back to the caves, and using
candles, and foregoing our modern-day comforts, we need to move forward with
renewable energy technologies such as biomethane, as the alternative is power
shortages and blackouts. We
believe biomethane represents the best and greenest of all biofuels. There are
no supply problems with biomethane, and we have a virtually unlimited supply for
using biomethane wherever natural gas is presently used as a fuel. It
should be pointed out that biomethane is chemically no different than natural
gas from the "fossil fuel" form of natural gas or CH4. However,
one important distinction between biomethane and the fossil-fuel variety of
natural gas, is that the production and use of biomethane is “carbon
neutral” in that the greenhouse gas emissions from biomethane use do not add
any new net greenhouse gas emissions. Biomethane
starts out as “biogas” but must be cleaned and purified before it can be
used as a renewable fuel. The
process of cleaning and purifying the biogas is called “biogas to biomethane.”
The impurities that are found in biogas include hydrogen sulfides,
siloxanes, and carbon dioxide. When the impurities are removed from biogas, it
is then referred to as biomethane and available for use as a clean fuel, just as
the fossil-fuel form of natural gas is used.
Biomethane reserves and supplies, unlike fossil-fuel natural gas, are virtually unlimited. Biomethane is produced from many sources including anaerobic digesters, wastewater treatment systems, landfills and most agricultural and forestry operations. Last year, the first Biomethane NGV refueling station was opened in Eugendorf, Austria. Like a gas station provides gasoline for cars, the the NGV Biomethane station in Eugendorf provides biomethane for NGVs (Natural Gas Vehicles). Presently, the station provides a blend of biomethane and natural gas. Eventually, they hope to provide 100% biomethane for natural gas vehicles. Companies and researchers in Germany and Austria have determined that “Cellulosic Biomethane” is the greenest of all biofuels, and the least expensive biofuel to produce. Germany and Austria are now planting vast amounts of a form of Kentucky Bluegrass which will be harvested for use in producing “Cellulosic Biomethane,” through anaerobic digesters and fermentation. Researchers
from around the world, starting in Austria, are finding that grasses such as
Kentucky Bluegrass are easily converted into biomethane as well as organic
fertilizer. Cellulosic Biomethane production doesn’t require the fermentation
of sugars or starches - as the first generation of liquid biofuels – requiring
grains and oilseeds from food crops. As the Austrian Cellulosic Biomethane
project shows, biomethane can be produced from a cellulosic biomass feedstock
like grass. Yield estimates from the Austrian Cellulosic Biomethane research
indicate that one natural gas vehicle can travel 10,000 to 15,000 miles on just
one acre of Kentucky Bluegrass that was processed into biomethane. At
a Jan. 8, 2009 public workshop held by the California Natural Gas Vehicle
Coalition, they documented the superior benefits and potential of biomethane as
a clean, renewable energy resource. The
California Natural Gas Vehicle Coalition stated that Biomethane should be
classified as a "Super Ultra Low Carbon fuel."
Super Ultra Low Carbon fuel is defined as providing at least an 82
percent reduction in greenhouse gas emissions - based on the California Air
Resource Board’s analysis of biomethane from landfill gas. Biomethane
has a carbon dioxide emissions intensity of only 11 as compared with:
67.9 for natural gas Biomethane
can displace and substitute the equivalent of 29% percent of all petroleum
diesel transportation fuel used - almost immediately. According
to the California Energy Commission and the Biomass Collaborative, landfills,
wastewater treatment, and dairy waste sources - which are "developable
today" and can start producing Biomethane almost immediately, with low
investment/high returns, could yield 121 billion cubic feet of Biomethane. At
$8.00/mmbtu, that's a $1 billion market opportunity in California alone.
The 121 billion cubic feet of Biomethane equals about 860 million gallons
of petroleum diesel. California alone uses about 3 billion gallons of diesel
annually for transportation. Emerging biomass gasification and Biomethanation
technologies could more than double Biomethane supplies. Biomethane
- like natural gas from "fossil fuels" - can be compressed or
liquefied. And using "Compressed Biomethane" is a significantly better
choice as a transportation fuel than traditional "natural gas." Biomethane
is the "natural, natural gas" and is far better for the environment
and the economy than natural gas. Biomethane, when "vented" to the
environment, is 21 times more hazardous to the climate than carbon dioxide
emissions which are the only emissions (and water vaport) from compressed
natural gas vehicles' engines when used as a fuel. Again,
we are reminded that Biomethane is the same chemical compound as natural gas:
CH4, and completely replaces and substitutes for natural gas. Engines, turbines,
boilers and every other natural gas appliance can use Biomethane without any
adjustments or modifications - just like natural gas. Biomethane
supplies, as opposed to natural gas supplies from the fossil fuel industry, are
available in an unlimited supply. Moving
forward with a “Biomethane Infrastructure” is the direction our country
needs to be moving as one of our fuel choices as we become energy-independent.
Every MCF of Biomethane that we use displaces about 8 gallons of gasoline
and creates jobs that will never be outsourced or downsized. (Some
of the above information from the California Natural Gas Vehicle Coalition.) ______________________________________________________________________ Please
Support H.R. 1158, The Biogas Production Incentive Act of 2009 SUMMARY:
The Biogas Production Incentive Act of 2009 if enacted, will amend the
Internal Revenue Code to allow a business-related tax credit for the production,
sale, or use of biogas. Defines biogas as a gas that is derived by processing
qualified energy feedstock (i.e., manure of agricultural livestock and other
organic agricultural or food industry byproduct waste material) in an anaerobic
digester and that contains at least 52% methane and carbon dioxide and trace
gases. Provides an increased credit for biogas produced from qualified
cellulosic energy feedstock. I
am writing to you in support of HR 1158, the Biogas Production Incentive Act of
2009 and recommend that Congress develops and passes this much needed
legislation that provides a $4.27 per MMBTU tax credit for the production of
Biogas – also known as "Renewable Natural Gas," "Renewable
Biogas" or "Biomethane."
H.R. 1158, the Biogas Production Incentive Act would establish this tax
credit that will help jumpstart this vital industry.
Renewable biogas and biomethane have been heralded by many as being the
greenest of all biofuels. Biomethane
has a carbon dioxide emissions intensity of only 11 as compared with 67.9 for
natural gas, 95.8 for diesel and 96.7 for gasoline.
Biomethane can displace and substitute the equivalent of 29% percent of
all petroleum diesel transportation fuel used - almost immediately.
The California Natural Gas Vehicle Coalition stated that Biomethane
should be classified as a "Super Ultra Low Carbon fuel."
Super Ultra Low Carbon fuel is defined as providing at least an 82
percent reduction in greenhouse gas emissions - based on the California Air
Resource Board’s analysis of biomethane from landfill gas. The
U.S. Congress has wisely supported the expanded use of domestic renewable
resources through a variety of tax incentives and other programs.
Up to this point, Congress has focused primarily on measures that support
the production of renewable liquid transportation fuels or electricity.
In the U.S., however, natural gas represents 23 percent of the energy
consumed. Natural
gas is the fuel of choice to provide residential and commercial heat for space
and hot water in most applications and is used to produce steam in a variety of
commercial and industrial applications. Natural gas is also the fuel that
provides the energy to manufacture many industrial products including aluminum,
steel, glass, chemicals, fertilizer, and ethanol.
Incentivizing
the production of renewable natural gas or "Biomethane" from sources
that include animal manure, landfills, renewable biomass and agricultural wastes
will support expanding the role of renewables into this existing energy sector,
where little opportunity exists today.
It will also create another business investment prospect for renewable
project developers and the potential to expand rural economies while supporting
existing industrial jobs and dramatically reducing carbon emissions.
Please
consider the following: •
Renewable Biomethane is a versatile form of bio-energy. It can be used
directly at the site of production, or placed in the pipeline to support a
variety of residential commercial or industrial applications. •
Renewable Biomethane produced from renewable sources including animal
manure, landfills, renewable biomass and agricultural wastes can be produced at
high efficiencies ranging from 60–70 percent.
Additionally, all of the technology components to produce renewable gas
from this variety of sources exist today. •
Renewable Biomethane can be delivered to customers via the existing U.S.
pipeline infrastructure. •
Renewable Biomethane can provide a renewable option for many heavy
industries, which could save existing industrial jobs in a carbon constrained
economy - while creating new rural green jobs to produce Renewable Biomethane. •
Renewable Biomethane production in digesters provides the agricultural
sector additional environmental benefits by improving waste management and
nutrient control.
•
Jump-start new biomethane gas production •
Begin the creation of the biomethane infrastructure and biomethane
industry •
Increase biomethane “reserves” •
Creation of green jobs •
Expand the rural economy and increase revenues for farming and
agricultural operations •
Increase energy independence •
Reduce greenhouse gas emissions. Thank
you for your support and consideration of this legislation. Sincerely, _______________________
Thank
you! For more information on Biomethane, see www.Biomethane.com ______________________________________________________________________
Biomethane -
Equal to 2.0 cents per KWH (approximately $5.66 per MMBtu) for electricity produced on-site from
Biomethane.
Biomethane
- As Biomethane
is a near perfect fuel, and since Biomethane
represents the best of all biofuels in terms of Recycling Carbon, and has the
highest Net Energy Balance, and as
Biomethane technologies such as Anaerobic
Digesters and Biomass
Gasification development increases and becomes even more commonplace, one of
the fundamental questions is: what is the size of the potential biomass resource
supply in the U.S.? This study doesn't address the opportunities for Biomethane production from biomass feedstock or Biomass Gasification technologies. Some recent estimates indicate that Biomethane could replace up to 50% of present natural gas consumption in the U.S. and in some countries, such as Iceland, Biomethane already provides 100% of the natural gas requirements. There
are many assumptions in the Billion Ton Study report that impact these
estimates, but we believe the estimates reasonably reflect the potential
availability and impact of biomass resources. Biomass to Biofuels By "converting" biomass wastes – such as municipal solid waste, sewage sludge, crop residues, energy crops, and manure – into biofuels, this will resolve the energy, environmental and political problems in an economical and environmentally sound manner - that will produce over one million new jobs. According
to Jeff Seisler, Director of the European Natural Gas Vehicle Association,
"Biomethane
has
an outstanding potential as a multifaceted solution to multifaceted social
problems: urban and agricultural waste management, water purification, and clean
air. Urban and agricultural waste can be processed into usable methane, as can
the sewage during the water purification process. Cleaning and compressing the
gas for use in vehicles then provides cleaner air than petroleum-consuming
vehicles." According
to Peter Boisen Chairman, of ENGVA, "various well respected European
research institutes now estimate more than three times better fuel output per
hectare of land used than if going for ethanol or biodiesel. Sweden currently
has a 51% Biomethane
share,
and Switzerland 37%. France, Norway, Germany and Austria use smaller amounts for
vehicles. Iceland, completely without natural gas, uses 100% biomethane in its
NGVs," Boisen says. Continuing, Boisen adds, "China, India,
Korea, the Ukraine, Spain and Italy are other examples of countries now starting
up projects where Biomethane
will be used as a vehicle fuel." ______________________________________________________________________ Biomethane
- The Best of All Renewable Fuels! 1.
Biomethane
is One of the Most Common and Harmful of All Greenhouse
Gas Emissions. ______________________________________________________________________ California and Sweden Sign Agreement to Jointly Develop Thursday, 29
June 2006 ______________________________________________________________________ For more information, call or email:
______________________________________________________________________ We support the Renewable Energy Institute by donating a portion of our profits to the Renewable Energy Institute in their efforts to reduce fossil fuel use through renewable energy and their goals to end fossil fuel pollution by reducing/eliminating Carbon Emissions, Carbon Dioxide Emissions and Greenhouse Gas Emissions. The Renewable Energy Institute is "Changing The Way The World Does Energy by Providing Research & Development, Funding and Resources That Creates Sustainable Energy via 'Carbon Free Energy' and 'Pollution Free Power' Through Expanding the use of Renewable Energy Technologies."
Email:
info(@)Renewable Energy Institute (.)org
The information contained on this site is
copyright protected and
Complete
Mix
Digester
Renewable Energy Institute
Copyright © 2003
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||