Methane Digesters and
Cogeneration - Producing Renewable Energy and
Protecting the Environment
How Our Methane Digesters
& Cogeneration Systems Work*
Methane digesters are
anaerobic treatment lagoons covered with a gas-tight
high-strength plastic (HDPE) fabric that produces
methane-rich biogas through the anaerobic (without
oxygen) digestion of manure or other agricultural
waste. Our digester designs will work with either
flush dairies, scrape dairies or other agricultural
facilities. In flush dairies, manure is
flushed to a collection point where the large
solids are removed and recycled. The dairy
manure wastewater is then sent in through the
bottom of the digester were it is typically
retained for a period of 40 to 60 days.
As the manure wastewater moves up in the digester,
bacteria digest the waste and produce a methane
rich gas known as biogas. The biogas is
typically about 60% to 80% methane or more.
Anaerobic Digesters
Work!
Background:
A
History of Biogas Production
Large Solids are Re-Usable
as Fertilizer or Bedding
The large solids separated out
can be dried or composted for use as fertilizer,
as a soil amendment or as bedding.
Digester Effluent
Re-Usable as Liquid Fertilizer
After the dairy wastewater
makes it way from the bottom of the digester
to the top it will be ready for use as part
of a comprehensive on-farm nutrient management
system. The digester effluent is a valuable
natural liquid fertilizer containing nitrogen,
phosphorous and potassium.
Methane Digester/Cogeneration System Flow Diagram
Biogas Treatment &
Monitoring for Engine/Microturbine Protection
Our exclusive biogas
treatment and monitoring systems are designed to protect your engine or
microturbine by improving the quality of the biogas (making it more
like natural gas) and by monitoring the biogas fuel to prevent serious
engine damage. Untreated biogas contains 60% to 80% methane
(CH4), carbon dioxide (CO2) and hydrogen sulphide (H2S). Under
certain circumstances, like frequent engine start and stops, relatively
high moisture levels, etc. acids may be produced in the engine.
Presence of these acids, if unnoticed, will accelerate wear and
possibly
even corrode critical engine parts that could result in a major
unplanned repair and downtime.
Our system
proactively treats the biogas to produce a fuel and engine/turbine
pairing that should run for thousands of hours without any unplanned
downtime. In addition, we place electronic gas monitoring sensors
throughout the gas treatment process leading up to the engine/turbine,
so we are able to remotely monitor the methane, carbon dioxide,
hydrogen sulphide, moisture level and biogas flow rates, etc. to
identify potential problems early and reduce the possibly of an engine
problem later.
Cogeneration
-
Electricity and Hot Water
Cogeneration refers to
the simultaneous production of electricity from the generator and the
production of heat from the engine or microturbine exhaust or cooling
system. Electricity is generally the primary output but the main
byproduct, heat, can also be captured and used for food processing,
water heating, steam production and many other uses.
Interconnection-
Sending
Electricity to the Grid or to the Farm
This portion of the
system controls the flow of
electricity either from "the Grid" to your farm or from your farm to
"the Grid." The electricity generator is
connected to "the Grid" through a series of redundant electronic and
manual interconnection relays, called switchgear, that is designed to
prevent damage to "the Grid", the generator and to protect the safety
of utility workers, farm workers and the general public. Much
effort goes into designing a safe and reliable switchgear and
interconnection system. We work with your utility provider to
determine the best equipment to use based on your reliability
needs, blackout/brownout independence requirements (do you want
your lights on even if "the Grid" goes out) and the unique
characteristics of your Grid/utility connection and service
capacity. You will maintain a backup connection to the utility to
provide electrical power to your farm for periods of system maintenance
and to provide additional power during your peak usage typically during
the summer.
We'll also help determine the right interconnection strategy (Rule 21,
E-Bio Net Metering, Import/Export) for your operation and whether if
you may be a candidate to sell your surplus power through our surplus
power aggregation and wholesale program. Through this program you
may be able generate modest incremental revenue through the wholesale
sale of your surplus power while you continue to generate per kilowatt
hour tax credits.
Extended
Warranty & Onsite Service, Repairs and Overhauls
We also offer optional extended "Repair
or Replace" warranties and service agreements for up to three years
where we'll perform all routine scheduled maintenance, perform major
overhauls and provide all the parts, supplies and labor needed (the
dairy/facility will be required to perform some very minor onsite
inspections). Systems that are located within the PG&E, SCE,
or SDG&E service areas and that are applying for the $1500 per
Kilowatt Self-Generation Rebate may choose to prepay some or all of the
optional three year extended warranty or service agreement costs since
these costs are eligible for reimbursement under the current
Self-Generation rebate
program.
Summary of Benefits of
Methane Digesters and Cogeneration
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