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Complete
Mix Digester We provide Anaerobic
Digester, Anaerobic Lagoon, Biogas
Recovery, BioMethane, Biomass
Gasification, and Landfill Gas To
Energy, project development services. Unlike most companies, we
are equipment supplier/vendor neutral. This means we help our
clients select the best equipment for their specific application. This
approach provides our customers with superior performance, decreased
operating expenses and increased return on investment.
We are Renewable Energy Technologies specialists and develop clean power and energy projects that will generate a "Renewable Energy Credit," Carbon Dioxide Credits and Emission Reduction Credits. Some of our products and services solutions and technologies include; Absorption Chillers, Adsorption Chillers, Automated Demand Response, Biodiesel Refineries, Biofuel Refineries, Biomass Gasification, BioMethane, Canola Biodiesel, Coconut Biodiesel, Cogeneration, Concentrating Solar Power, Demand Response Programs, Demand Side Management, Energy Conservation Measures, Energy Master Planning, Engine Driven Chillers, Solar CHP, Solar Cogeneration, Rapeseed Biodiesel, Solar Electric Heat Pumps, Solar Electric Power Systems, Solar Heating and Cooling, Solar Trigeneration, Soy Biodiesel, and Trigeneration. Unlike
most companies, we are equipment supplier/vendor neutral. This means we
help our clients select the best equipment for their specific application.
This approach provides our customers with superior performance, decreased
operating expenses and increased return on investment. What is an Anaerobic Digester?
An Anaerobic Digester is a device for optimizing the anaerobic digestion of biomass and/or animal manure, and possibly to recover biogas
also referred to as BioMethane for energy production. Digester types include batch, complete mix, continuous flow (horizontal or plug-flow, multiple-tank, and vertical tank), and covered lagoon. Anaerobic digestion is a biological process that produces a gas principally composed of methane (CH4) and carbon dioxide (CO2) otherwise known as biogas. These gases are produced from organic wastes such as livestock manure, food processing waste, etc.
The
The
U.S. EPA AgSTAR is an outreach program designed to reduce methane emissions
from livestock waste management operations by promoting the use of biogas
recovery systems. A biogas recovery system is an anaerobic digester with
biogas capture and combustion to produce electricity, heat or hot water.
Biogas recovery systems are effective at confined livestock facilities that
handle manure as liquids and slurries, typically swine and dairy farms.
Anaerobic digester technologies provide enhanced environmental and financial
performance when compared to traditional waste management systems such as
manure storages and lagoons. Anaerobic digesters are particularly effective
in reducing methane emissions but also provide other air and water pollution
control opportunities. AgSTAR provides an array of information and tools
designed to assist producers in the evaluation and implementation these
systems, including:
Methane Emissions from Animal Waste
Management
Methane
emissions occur whenever animal waste is managed in anaerobic conditions.
Liquid manure management systems, such as ponds, anaerobic lagoons, and
holding tanks create oxygen free environments that promote methane
production. Manure deposited on fields and pastures, or otherwise handled in
a dry form, produces insignificant amounts of methane. Currently, livestock
waste contributes about 8 percent of human-related methane emissions in the Methane (Biogas) from Anaerobic DigestersMethane is a gas that contains molecules of methane with one atom of carbon and four atoms of hydrogen (CH4 ). It is the major component of the "natural" gas used in many homes for cooking and heating. It is odorless, colorless, and yields about 1,000 British Thermal Units (Btu) [252 kilocalories (kcal)] of heat energy per cubic foot (0.028 cubic meters) when burned. Natural gas is a fossil fuel that was created eons ago by the anaerobic decomposition of organic materials. It is often found in association with oil and coal. The same types of anaerobic bacteria that produced natural gas also produce methane 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 "biogas" 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, biogas production is a highly useful but secondary benefit. Biogas 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 biogas depends on the feed material and management of the process. When burned, a cubic foot (0.028 cubic meters) of biogas yields about 10 Btu (2.52 kcal) of heat energy per percentage of methane composition. For example, biogas composed of 65% methane yields 650 Btu per cubic foot (5,857 kcal/cubic meter). Digester DesignsAnaerobic digesters are made out of concrete, steel, brick, or plastic. They are shaped like silos, troughs, basins or ponds, and may be placed underground or on the surface. All designs incorporate the same basic components: a pre-mixing area or tank, a digester vessel(s), a system for using the biogas, and a system for distributing or spreading the effluent (the remaining digested material). There are two basic types of digesters: batch and continuous. 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. They may be better suited for large-scale operations. 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. 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 Digestion ProcessAnaerobic 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 biogas 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 biogas 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 biogas 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 digesters operated in the mesophilic range must be larger (to accommodate a longer period of decomposition within the tank [residence time]), the process is less sensitive to upset or change in operating regimen. To optimize the digestion process, the digester 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 biogas-powered engines in or around the digester to keep it warm, while others burn part of the biogas to heat the digester. In a properly designed system, heating generally results in an increase in biogas 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 biogas production can occur in digesters maintained at temperatures as low as 72°F (22.2°C). Other factors affect the rate and amount of biogas 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. Producing and Using BiogasAs long as proper conditions are present, anaerobic bacteria will continuously produce biogas. Minor fluctuations may occur that reflect the loading routine. Biogas can be used for heating, cooking, and to operate an internal combustion engine for mechanical and electric power. For engine applications, it may be advisable to scrub out hydrogen sulfide (a highly corrosive and toxic gas). Very large-scale systems/producers may be able to sell the gas to natural gas companies, but this may require scrubbing out the carbon dioxide. Using the EffluentThe material drawn from the digester is called 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 digester feedstock material may become concentrated in the effluent. Therefore, it is important to test the effluent before using it on a large scale. EconomicsAnaerobic digester system costs vary widely. Systems can be put together using off-the-shelf materials. There are also a few companies that build system components. Sophisticated systems have been designed by professionals whose major focus is research, not low cost. Factors to consider when building a digester are cost, size, the local climate, and the availability and type of organic feedstock material. 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 of controlled anaerobic digestion are receiving increasing interest, especially for large-scale livestock operations such as dairies, feedlots, and slaughterhouses. Where costs are high for sewage, agricultural, or animal waste disposal, and the effluent has economic value, anaerobic digestion and biogas production can reduce overall operating costs. Biogas production for generating cost effective electricity requires manure from more than 150 large animals. Below-ground, concrete anaerobic digesters have proven to be especially useful to agricultural communities in parts of the world such as China, where fossil fuels and electricity are expensive or unavailable. The primary purpose of these anaerobic digesters is waste (sewage) treatment and fertilizer production. Biogas production is secondary.
Accomplishments
The AgSTAR Program has been very successful in encouraging the development
and adoption of anaerobic digestion technology. Since the establishment of
the program in 1994, the number of operational digester systems has doubled.
This has produced significant environmental and energy benefits, including
methane emission reductions of approximately 124,000 metric tons of carbon
equivalent and annual energy generation of about 30 million kWh. The graph
below shows the historical use of biogas recovery technology for animal
waste management.
The
development of anaerobic digesters for livestock manure treatment and energy
production has accelerated at a very fast pace over the past few years.
Factors influencing this market demand include: increased technical
reliability of anaerobic digesters through the deployment of successful
operating systems over the past five years; growing concern of farm owners
about environmental quality; an increasing number of state and federal
programs designed to cost share in the development of these systems; and the
emergence of new state energy policies (such as net metering legislation)
designed to expand growth in reliable renewable energy and green power
markets.
In
the past 2 years alone, the number of operational digester systems has
increased by 30%. For more detailed information on anaerobic digester use in
the
The process of anaerobic digestion consists of three steps.
This section
describes the anaerobic digestion (AD) process, outlines guidelines for
assessing the feasibility of AD and biogas usage at a swine facility and
provides summary information on AD system performance and reliability. Anaerobic
Digestion Technology Description AD promotes the
bacterial decomposition of the volatile solids (VS) in animal wastes to
biogas, thereby reducing lagoon loading rates and odor. The primary
component of an AD system is the anaerobic digester, a waste vessel
containing bacteria that digest the organic matter in waste streams under
controlled conditions to produce biogas. As an effluent, AD yields nearly
all of the liquid that is fed to the digester. This remaining fluid
consists of mostly water and is allowed to evaporate from a secondary
lagoon, land-applied for irrigation and fertilizer value or recycled to
flush manure from the swine building to the digester. The benefits of AD
include:
AD takes place in
three steps: hydrolysis, acid formation, and methane generation. During
the first step, hydrolysis, bacterial enzymes break down proteins, fats
and sugars in the waste to simple sugars. During acid formation, bacteria
convert the sugars to acetic acid, carbon dioxide and hydrogen. Then the
bacteria convert the acetic acid to methane and carbon dioxide, and
combine carbon dioxide and hydrogen to form methane and water. Digester
technologies that can be used to collect biogas from swine facilities
include:
Although a
sequencing batch reactor has been used for AD at one swine facility in the
Appendix B provides
contact information that can help producers find AD system
designers/installers, odor control technologies, generators, heating and
cooling equipment, and other information to help manage air and water
quality at hog facilities. Covered lagoon
digesters are the simplest AD system. These systems typically consist of
an anaerobic combined storage and treatment lagoon, an anaerobic lagoon
cover, an evaporative pond for the digester effluent, and a gas treatment
and/or energy conversion system. Figure 1 shows a typical schematic for a
floating covered anaerobic lagoon.
Figure 1 .
Covered anaerobic lagoon digester Covered lagoon
digesters typically have a hydraulic retention time (HRT) of 40 to 60
days. The HRT is the amount of time a given volume of waste remains in the
treatment lagoon. A collection pipe leading from the digester carries the
biogas to either a gas treatment system such as a combustion flare, or to
an engine/generator or boiler that uses the biogas to produce electricity
and heat. Following treatment, the digester effluent is often transferred
to an evaporative pond or to a storage lagoon prior to land application. Climate affects the
feasibility of using covered lagoon digesters to generate electricity.
Engine/generator systems typically do not produce sufficient waste heat to
maintain temperatures high enough in covered lagoon digesters in the
winter to sustain consistently high biogas production rates. Using propane
or natural gas to provide additional heat for the lagoon contents is
typically not an economically viable option. Without that additional heat,
most covered lagoon digesters produce less biogas in colder temperatures,
and little or no gas below 39 FACE= "Symbol">° F. As a
result, covered lagoon digesters are most appropriate for use in warm
climates if the biogas is to be used for energy or heating purposes. Complete mix
digester systems consist of a mix tank, a complete mix digester and a
secondary storage or evaporative pond. The mix tank is either an
aboveground tank or concrete in-ground tank that is fed regularly from
underfloor waste storage below the animal feedlot. Waste is stirred in the
mix tank to prevent solids from settling in the waste prior to being fed
to the digester. The complete mix digester is essentially a
constant-volume aboveground tank or in-ground covered lagoon that is fed
daily from the mix tank. Complete mix digesters with in-ground lagoons
often employ covers similar to those used in covered lagoon digesters. In
the digester, a mix pump circulates waste material slowly around the
heater to maintain a uniform temperature. Hot water from an
engine/generator cogeneration water jacket or boiler is used to heat the
digester. A cylindrical aboveground tank, such as that shown in Figure 2,
optimizes biogas production, but is more capital intensive than in-ground
tanks. The only operating AD system in Source:
EPA. (February 1997). AgStar Technical Series: Complete Mix Digesters –
A Methane Recovery Figure 2 . Complete
mix digester schematic Complete mix
digesters have an HRT of 15 to 20 days, which means that complete mix
digesters can reduce the overall lagoon volume required for waste storage
and treatment. This makes complete mix digesters comparable to covered
lagoon digesters in cost, despite the increased complexity of stirring,
mixing and plumbing components. In addition, biogas production rates, and
therefore heat and electricity production, are greater and more consistent
than for covered lagoons. This can help reduce system payback periods
compared to covered lagoon systems. Like covered lagoon systems, digester
effluent from complete mix digesters is frequently stored in evaporative
ponds or storage lagoons. System
Requirements This section
provides guidelines for conducting a preliminary assessment of the
feasibility of using AD at a swine facility. Although AD system
requirements will vary depending on the application and system design,
there are some rule-of-thumb measures that should be noted when assessing
the feasibility of AD at a given location. For AD to potentially be
technically feasible and cost-effective, a swine facility should:
If the above
characteristics are present, the facility is a possible candidate for AD.
Many pre-existing waste storage and treatment lagoons are too large to
practically or cost-effectively employ covers over their entire area.
Partial covers may be an option to recover methane from these older
systems, as an alternative to installing a completely new storage and
treatment lagoon system. If energy recovery
is to be employed, methane production and gas quality should be considered
and compared to energy requirements at the facility. Daily biogas
production at installed farm-based anaerobic digesters in the Facilities that are
located south of the line of climate limitation in Figure 3 are usually
warm enough for cost-effective energy recovery from covered lagoon
digesters. In most cases, facilities north of the climate line in Figure 3
are too cold for cost-effective energy recovery from covered lagoon
digesters. Complete mix digesters can be used in cold or warm climates. If
odor control is the only objective, either covered lagoon or complete mix
digesters may be used, but odor control will be less effective in the
winter for covered lagoon digesters south of the line of climate
limitation in Figure 3. In general, complete mix digesters are the most
appropriate choice for use in
Figure 3 . Line of
climate limitation for biogas energy recovery Table 2 shows which
digesters are appropriate for the waste collection strategies at covered
swine facilities. Complete mix digesters can operate with a waste total
solids (TS) percentage between 3 and 10 percent, while covered lagoon
digesters can use waste with a TS percentage less than 2 percent. Table
2 . Matching a digester to existing waste collection practices
Source – Adapted
from: EPA. (July 1997). AgStar Handbook: A Manual for Developing Biogas
Systems at Commercial Appendix C describes
each of the various waste collection technologies listed in Table 2. This section
discusses some of the biogas utilization options that are available for
use with AD. Electricity generation with waste heat recovery
(cogeneration) and direct combustion and use in equipment that normally
uses propane or natural gas are the two primary options for biogas
utilization. Electricity generated using biogas can be generated for
on-farm use or for sale to the electric power grid if an economically
attractive power purchase agreement can be negotiated through the local
utility or rural electric cooperative. Direct combustion allows the gas to
be used in existing equipment that normally uses propane or natural gas
such as boilers or forced air furnaces with minor equipment modifications.
Combustion is usually a seasonal use for biogas, as most boiler and
furnace applications are only required during the winter. The EPA FarmWare
manual describes some characteristics of engine/generator and direct
combustion systems that can be used with biogas. The following subsections
draw from the FarmWare manual to provide some basic information about the
use of these systems at covered swine facilities and other farm
applications. Electricity Generation Commercial
electricity generation systems that use biogas typically consist of an
internal combustion (IC) engine, a generator, a control system and an
optional heat recovery system. IC engines designed
to burn propane or natural gas are easily converted to burn biogas by
adjusting carburation and ignition systems. Such engines are available in
nearly any capacity, but the most successful varieties are industrial
engines that are designed to work with wellhead natural gas. A
biogas-fueled engine will normally convert 18 to 25 percent of the biogas
Btu value to electricity. Two types of
generators are used on farms: induction generators and synchronous
generators. Induction generators operate in parallel with the utility and
cannot operate as a stand-alone power source. Induction generators derive
their phase, frequency and voltage from the utility. Synchronous
generators operate as an isolated system or in parallel to the utility,
and require more sophisticated intertie systems to match output to utility
phase, frequency and voltage. Control systems are
required to protect the engine and the utility. Control packages are
available that can shut the engine off due to mechanical problems, utility
power outage or utility voltage and frequency fluctuations, or in the
event that excess power is generated that the utility will not accept.
Generators that operate in parallel with the utility system, such as
induction generators, require an intertie system with safety relays to
shut off the engine and disconnect from the utility in the event of a
problem. Intertie negotiations with a utility for induction generators are
typically much easier than for a synchronous generator, due to the level
of control the utility has over the characteristics of power entering the
grid from an induction generator. The primary advantage of a synchronous
generator is its ability to act as a stand-alone power source. However, if
operated as an isolated system, a synchronous generator must be oversized
to meet the highest electrical demand, while operating less efficiently at
average or partial loads. Due to the system size and more complicated
control requirements, a synchronous generator operating as an isolated
system is typically more expensive than an induction generator. Biogas engines
reject approximately 75 to 82 percent of the energy input as waste heat.
This waste heat can be used to heat the digester and/or provide water or
space heat to the facility. Commercial heat exchangers can recover waste
heat from the engine water cooling system and the engine exhaust,
recovering up to 7,000 Btu/hour for each kW of generator load. Waste heat
recovery increases the energy efficiency of the system to 40 to 50
percent.
Ongoing research and
development is focusing on the use of microturbines and fuel cells for
converting biogas to electricity. Microturbines are high-speed,
small-scale (typically less than 100 kW) gas-driven turbine systems that
produce electricity efficiently, have low emissions and require little
maintenance. Reflective Energies in The Department of
Energy’s WRBEP funded a project in fiscal year 2000 in Direct combustion of
biogas on-site in a boiler or forced air furnace can provide seasonal heat
to nurseries, farrowing rooms and other facilities at a swine facility. A
cast iron natural gas boiler can be used for most farm boiler
applications. The air-fuel mixture will require adjustment and burner jets
will need to be enlarged for use with low-Btu gas. Cast iron boilers are
available in many sizes, from 45,000 Btu/hour and up. Untreated biogas may
be used, but all metal surfaces of the boiler housing should be painted to
prevent corrosion. Flame tube boilers with heavy gauge flame tubes may be
used if the exhaust temperature is maintained above 300 FACE=
"Symbol">° F to prevent condensation. Forced air furnaces
can be used in place of direct fire room heaters, but biogas must be
treated to remove hydrogen sulfide because of potential corrosion problems
in metal ductwork. System
Performance and Benefits of AD There are several
measures of waste management system performance that are relevant for
producers considering the use of AD. These include:
AD is the only waste
management strategy available that provides the option to recover methane
for energy production. The APCD has
determined that the minimum standard for compliance with odor control
regulations for waste vessels and impoundments is an 80 percent reduction
in all odor-causing gases, including hydrogen sulfide, ammonia and
volatile organic compounds from waste vessels or impoundments. Table 3
compares the effectiveness of some of the odor control methods being
implemented at covered swine facilities in Table
3 . Odor control effectiveness of management strategies for
anaerobic lagoons
Source: Iversen,
Kirk and Jessica Davis. (February 1999). Innovations in odor management
technology. In addition to
regulating odors from waste lagoons, the new odor control regulations have
requirements for waste that is applied to agricultural land. The new
regulations for waste treatment at covered swine facilities require that
waste applied to agricultural land and not injected be treated to remove
at least 65 percent of the TS and over 90 percent of the total volatile
fatty acids or 60 percent of total VS. If not treated, waste applied to
agricultural land must be injected or knifed into the soil upon
application. Land application is not permitted between November 1 and
February 28. Of the waste management strategies in Table 3, four will help
reduce the TS and VS content prior to land application.
Wet feeding can
reduce the TS and VS by a value equal to the dilution rate of the feed
(i.e., 3:1 ratio of water to feed). However, introducing this type of
feeding system increases water requirements and may increase required
anaerobic lagoon volumes. Solids separation can reduce TS by 30 to 45
percent. Solids separation methods include screen separators, mechanical
presses, settling tanks, settling basins, vacuum filters and many other
means. An efficient AD installation will reduce the TS percentage by up to
76 percent and VS by up to 90 percent. Of the above technologies, AD with
covered anaerobic lagoons is the only one the APCD considers a proven
technology because of their odor control effectiveness. Therefore, unlike
the other options above, covered anaerobic digesters do not have to meet
the additional testing requirements for technologies that the APCD
considers experimental. Composting may or
may not meet the TS requirement because it often involves the addition of
a bulking agent to increase TS to optimize waste decomposition. However,
composting can be effective at controlling odors and reducing pathogens.
The APCD is presently reviewing the compliance status of one facility that
uses composting. Composting has applications besides manure treatment for
livestock facilities. The Colorado Governor’s Office of Energy
Management and Conservation is currently supporting the demonstration of
composting technology for hog mortality disposal at a hog farm in In an AD system,
most of the organic nitrogen (N) from the digester is converted to
ammonium, an easily manageable fertilizer with slow release properties
when compared to mineralized fertilizers. This is an advantage over
anaerobic lagoons alone. Organic N in the form of protein and urea is
mineralized in soil solution after land application. This mineralized N
can pose a groundwater problem when land-applied because mineralized N can
be converted to nitrates and leach into groundwater in the spring and fall
when plant uptake of N is low. A disadvantage of
reducing the nutrient content of lagoon effluent via AD is the loss of the
value of nutrients. Reducing the use of lagoon effluent as fertilizer
increases the need for industrial fertilizers, the manufacture and
transportation of which uses significant quantities of petroleum. However,
this loss is balanced by the benefits of increased control farmers have
over the nutrient content of effluent used for irrigation purposes. System reliability
is a key concern for swine producers that are considering AD with energy
recovery as an objective. AD systems first began to be used extensively
after World War II in A recent survey of
anaerobic digesters yielded mixed results for system reliability (Table
4). At farms across the Table
4 . Status of farm-based digesters at swine facilities in the
Source: Lusk, Phil
(September 1998). Methane Recovery from Animal Manures: the Current
Opportunities Casebook. NREL/SR-25145. NREL. Golden, CO. pp. 1-2. The most common
reasons that systems are not operating include poor design and
installation and poor equipment specification. The lessons learned that
should be kept in mind for future systems include the need to select
qualified contractors and the fact that amortizing the cost of appropriate
equipment is less costly than a system failure. The improved reliability
of newer systems and increased understanding of the biological systems
that operate in an anaerobic digester suggest that the reliability of
systems will continue to improve as long as the lessons of past system
failures are heeded.
What is BioMethane? The cost of producing
BioMethane, after installation of the
BioMass Gasification equipment used to produce BioMethane (the process of
making BioMethane is called "BioMethanation") is called is
essentially free. More About
Biomass
Gasification and BioMethanation Technology As previously stated,
Biomethanation is the process of conversion of organic matter in the waste (liquid or solid) to
BioMethane (sometimes referred to as "BioGas) and manure by microbial action in the absence of
air, known as "anaerobic digestion." Interest in BioMethanation as an
economic, environmental and energy-saving waste treatment continues to gain
greater interest world-wide and has led to the development of a range of anaerobic reactor designs. These high-rate,
high-efficiency anaerobic digesters are also referred to as "retained biomass reactors" since they are based on the concept of retaining viable biomass by sludge immobilization. More and more, cities, counties and municipalities are faced with greater environmental compliance issues relating to their municipally-owned landfills, Publicly Owned Treatment Works ("POTW's") or Wastewater Treatment Systems. A city's landfill and/or POTW provides an excellent opportunity for cities to reduce their emissions as well as provide an additional revenue stream. These facilities may have valuable gases that our company recovers and pipes to one of our clean, environmentally-friendly cogeneration or trigeneration energy systems. We solve a city's environmental liabilities (air emissions) and provide a new cash flow simultaneously. We offer turn-key solutions for cities that includes the preliminary feasibility analysis, engineering and design, project management, permitting and commissioning. We provide very attractive financing packages for cities that does not add to a city's liability, yet provides a valuable new revenue stream. And, we are also able to offer a turn-key solution for qualified municipalities that includes our company owning, operating and maintaining the onsite power and energy plant. At the heart of
the system is a (Bio) Methane Gas Recovery system similar those used in Flare Gas Recovery or Vapor Recovery
Units. Methane Gas Recovery, Flare Gas Recovery,
Vapor Recovery, Waste to Energy and Vapor Recovery Units all recover valuable
"waste" or vented fuels that can be used to provide fuel for an
onsite power generation plant. Our waste-to-energy and waste to fuel
systems significantly or entirely, reduces your facility's emissions (such
as Methane Gas
Recovery
and vapor recovery units can be located in hundreds of applications and
locations. At a landfill, Wastewaster Treatment System (or Publicly Owned
Treatment Works - "POTW") gases from the facility can be
captured from the anaerobic digesters, and manifolded/piped to one of our
onsite power generation plants, and make, essentially, "free"
electricity for your facility's use. These
associated "biogases"
that are generated from municipally owned landfills or wastewater
treatment plants have low btu content or heating values, ranging around
550-650 btu's. This makes them
Additionally, if heat (steam and/or hot water) is required, we will incorporate our cogeneration or trigeneration system into the project and provide some, or all, of your hot water/steam requirements. Similarly, at crude oil refineries, gas processing plants, exploration and production sites, and gasoline storage/tank farm site, we convert your facility's "waste fuel" and environmental liabilities into profitable, environmentally-friendly solutions. Our Methane Gas
Recovery systems are designed and engineered for
these specific applications. It is important to note that there are
many internal combustion engines or combustion turbines that are NOT
suited for these applications. Our systems are engineered precisely
for your facility's application, and our engineers know the engines and
turbines that will work as well as those that don't. More
importantly, we are vendor and supplier neutral! Our only
concerns are for the optimum system solution Our turn-key systems includes design, engineering, permitting, project management, commissioning, as well as financing for our qualified customers. Additionally, we may be interested in owning and operating the flare gas recovery or vapor recovery units. For these applications, there is no investment required from the customer. For more information, please provide us with the following information about the flare gas or vapor:
Anaerobic lagoons are perhaps the most trouble free, low maintenance systems available for treatment of animal waste. This is particularly true in the southern U.S. By Leland M. Seale,
Environmental Engineer, USDA-NRCS
Some
of the above information from the Department of Energy and U.S. Department
of Agriculture with permission, and our thanks. |
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Biofuel Industries |
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