Last updated on November 19th, 2019
A number of people don’t realize the benefits and downsides of anaerobic digesters. Here is an overview of the anaerobic digestion process, which includes key facts about anaerobic digesters.
Facts About Anaerobic Digesters: What Are the Pros & Cons?
With the world so eager to move from non-renewable energy sources to clean and green energy sources, anaerobic digestion has become one of the main areas that many countries are focusing.
Before we explore the various pros and cons of anaerobic digestors, let’s first define what it means and highlight a few facts about anaerobic digesters.
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What is anaerobic digestion?
Anaerobic Digestion is the process of treating organic waste and involves a series of biological processes in which organic waste is broken down using microorganisms in the absence of oxygen. The end product of the process is Biogas, which is a methane-rich gas.
Once the biogas is cleaned, it is taken to a Combined Heat and Power (CHP) unit, where it is used to generate renewable energy.
The byproduct of the process is often used as fertilizer. The whole process of anaerobic bio-digestion takes place in a tank called the Anaerobic Biodigester.
A biodigester breaks down organic matter using bacteria and in the absence of oxygen to capture methane gas released by the bacteria in the process. Methane, which is the main chemical in natural gas, is trapped and can then be burned for heating and electricity.
One of the commonly known types of the digester is called a “wet biodigester”. They are used on farms around the world to digest liquefied manure. The anaerobic digestor process is similar to compostable organic matter. The output is just gas that can be used for power.
Facts About Anaerobic Digestors
Many people use wet digesters to produce methane from manure which is then used to light their stoves and other appliances. Here are some few facts about anaerobic digesters
- The digester disinfects the feedstock/ waste which goes through it, as long as the temperature is maintained above a required level for a pre-defined period.
- One of the most impressive facts about anaerobic digestor is that it produces gas, liquid and fibrous fertilizers which are very beneficial.
- It reduces the odor levels if run efficiently.
Here are advantages and disadvantages of anaerobic digesters:
Pros of anaerobic digesters
Here are some of the advantages to anaerobic digesters.
Consistent supply of power
One of the major pros of anaerobic digesters is that it can offer a constant power supply to the universe. Since there is a continuous production of the waste materials used for the digestion process, anaerobic digestion can ensure a steady source of electricity generation.
For instance, every cow is estimated to produce 2kwh – 3kwh of electricity daily, which in turn can be sent to the electricity grid. Anaerobic digestion also generates renewable energy that is in the form of biogas. These biogases will likely qualify for Renewable Identification Numbers (RINs).
Another advantage of anaerobic digestion is that it is a renewable source of energy since waste products from animals and humans are produced continually, and unlike non-renewable energy, it does not exploit natural resources.
The resources used provide a steady stream of inputs into the digesters.
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Anaerobic digestion offers beneficial by-products. The by-products released in the process, which includes compost and fertilizer, can further be used in farms. The by-products can thus be used to create an additional stream of revenue. The liquid digestate that is produced in the process is a form of a fertilizer which is better in many ways than the standard chemical fertilizers.
Due to its high fiber content and the separated solids (ADS), it can also be sold as a horticultural potting mix or used as livestock bedding. The process produces both liquid and fibrous fertilizers which can be used in the farms or sold to create more income.
The effect of the compost is longer lasting than for untreated organic waste.
Long-term exposure to pollution in the air can result in health complications and even death. The use of the waste products from the farms in the anaerobic digesters reduces the amount of odor that would otherwise be present if the wastes were left exposed to the environment. The anaerobic digestion process reduces smell to levels below unprocessed waste odor levels.
Improved water quality
Another advantage is that the process of anaerobic digestion helps to remove phosphorous and other metals from the waste products, which would otherwise contaminate water supplies if left unattended.
Passing the wastes through the digesters thus ensures an improved quality of water supplies.
Greenhouse gases reduction
A primary reason the world is moving from the use of the non-renewable sources of energy is to reduce the emission of greenhouse gases that destroy the ozone layer and expose the world to global warming. Anaerobic biodigester minimizes the amount of GHG gasses released by the farms into the environment by around 66%. The reduction of the gases earns the farm carbon credits which can be sold to generate extra revenue for the farm.
Businesses that are required to pay a carbon levy for their carbon dioxide emissions can also run their biogas plant to help them offset their levy costs against the carbon savings.
Passing the waste materials through a digester reduces pollution to the environment since the waste materials are used as feedstock for digesters. It is less likely to cause air pollution to the environment unlike spreading untreated organic waste in landfills.
Decarbonization is a huge component of the AD movement.
Reducing disease-causing pathogens in the manure
One of the most remarkable facts about anaerobic digesters is that the operating temperature of the anaerobic digester systems decreases the number of pathogens in the slurry which may cause diseases to the plants. It is also an advantage of anaerobic digesters.
See Related: Biofuel Pros and Cons Analysis
Cons of anaerobic digesters
Here are some of the disadvantages to anaerobic digesters.
Installation costs of the anaerobic digesters can be prohibitive since it requires some massive financing to set it up. The operating expenses and the maintenance cost are also costly which makes it difficult for farmers to acquire.
When anaerobic digestion is complete on a large commercial scale, it can require a high level of investment in large manure tanks and other process containers.
Limited to large farms only
The Anaerobic digesters are only economically feasible for larger farms. The EPA recommends that a farm should have at least 300 cows to be able to install and run the system. This limitation makes it difficult for smaller farmers with less number of animals to have these systems.
Another con of anaerobic digesters is that the system operation and maintenance requirements are pretty much needed every day. It is estimated that it takes 30 to 60 minutes daily to ensure the efficient running of the system.
High land use
The more significant the amount of biogas you want to produce, the larger the farm you need for a large number of cows and large manure tanks. The residue from the process after manure has completed the digestion cycle, will also require a large chunk of land for storage.
Must have a reliable source and the process must run efficiently
The anaerobic digestion process must have a constant source of the raw materials (animal or human wastes) for the anaerobic digestion plant to be successful. It may require a farm to have many different reliable sources of feedstock materials, for example, a few cows.
These sources can be challenging to acquire. If the anaerobic digesters run inefficiently, it can cause odor levels which can be a nuisance.
Conclusion on Facts About Anaerobic Digestion
Stimulating facts about anaerobic digestion is that it is a viable source of renewable energy and can serve the world needs for clean and green energy. Different sectors should join hands to create more room for it and to improve this cheap source of renewable energy.
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