Frequently Asked Questions


What is Anaerobic Digestion?

Anaerobic digestion is an interconnected series of biological processes in which microorganisms break down biodegradable material in the absence of oxygen. One by-product of this process is biogas, which can be used as a fuel to generate electricity and heat.

    What are the environmental advantages of a biodigester?
    • Biogas is a source of renewable energy and can replace fossil fuels.
    • Using biogas as a fuel reduces emissions of methane, a greenhouse gas that is over 25 times more potent than carbon dioxide
    • Reduction of greenhouse gas emissions
    • Reduced environmental pollution
    • Reduced waste disposal costs
    • Sustainable management of organic waste
    • On-site energy generation


    Why use a biodigester?
    • Waste stabilization and reduction
    • Odour and greenhouse gases reduced
    • Energy Production
    • Pathogen reduction
    • Weed seed inactivation
    • Nutrient conservation and mineralization
    • Fertilizer by-product (digestate)
    • Renewable energy certificates (RECs)
    • Carbon credits
    Factors effecting the functionality of an Anaerobic Digester
    • Contamination of feedstock with the following
      • Plastic, glass, metals, chemicals & antibiotics
    • Temperature
    • Solids retention time
    • Oxygen
    • pH
    • High volatile fatty acids (VFA)
    • Sulphides
    • Ammonia
    How do cows pollute the environment?

    Cows contain one of the most well-known fermentation vats, the rumen, which is part of the stomach (in other animals as well). Fermentation takes place during digestion. A cow on average releases between 70 and 120 kg of Methane per year. Methane is a greenhouse gas like carbon dioxide (CO2).

    Cows release methane as part of their digestion process. A significant portion of these emissions come from methane, which, in terms of its contribution to global warming, is 23 times more powerful than carbon dioxide.

    The world’s 1.5 billion cows and billions of other grazing animals emit dozens of polluting gases, including lots of methane.

    Do biodigesters smell?

    The gases methane and carbon dioxide produced by a biodigester do not smell. Unless the biodigester is opened for maintenance, cleaning, inspection, there should be minimal odour. The digestate leaving the biodigester has been largely consumed by the anaerobic microorganisms and therefore little is left to generate odours outside the system.

    Who designed the Gaia EnviroTech biodigester?

    The Gaia EnviroTech biodigester is designed by Sandy Gray (co-founder and Technical Director) and the team at Gekko Systems/Gaia EnviroTech.

    Can I have more than one biodigester?

    Yes, you can install the Gaia EnviroTech biodigester as a modular setup. Cells, or stacks of cells, can be added (or moved to a new location) as required.

    What materials can the biodigester process?

    Almost any organic material can be used to feed a biodigester, but some work better than others. Gaia biodigesters utilise a wet digestion method, and organic matter can form a 10-15% solids slurry (liquid) are generally optimal.  In general, wastes such as fruit and vegetable matter work well, animal manures offer stability but lower methane output. Contact us to discuss your waste option.

    How long does it take to process the material?

    Optimal digestion times are generally in the order of 10-25 days. However, depending on the drivers for the project this can be altered.

    How is the biogas used?

    The renewable biogas will be used as an energy source for your business. The biogas is considered climate change neutral, as the amount of greenhouse gases entering the atmosphere remains the same.

    How big is a Gaia EnviroTech biodigester?

    Gaia Biodigesters are relatively small units compared to the large, multi-megaliter versions installed at sewage treatment plants. This was done to fill a niche in the market for a lower cost, highly configurable and expandable system, with greater mobility. Generally, our systems treat 1,000 – 190,000 L organic waste per day, however smaller or larger systems can be installed.

    How much does a Gaia EnviroTech biodigester cost?

    As a Gaia Biodigester can be specifically sized to meet requirements and incorporate a number of pre- and post-treatment modules, this is a difficult question to answer. Please contact us to discuss any anaerobic digester options.

    Which feedstock is suitable for the Gaia Biodigester?

    Feedstock tested to date includes cheese whey, permeate, abattoir wastewater, waste bakery products, food manufacturing by-products, and agricultural wastes.

    Contact us today and find out if your waste is suitable for a Gaia EnviroTech Biodigester. 

    Download case study

    This case study is a review of the successful installation and operation of the Gaia EnviroTech Anaerobic Digester during a one-year full scale trial on dairy effluent at a fully robotic central Victorian dairy farm. 

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    This is an one-page technical overview of the Gaia EnviroTech Anaerobic Biodigester. 

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    This is a two-page technical overview of the Gaia EnviroTech Rapid Composter. 

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    Gaia EnviroTech's Capability profile includes:

    - Business Overview

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    - Technology installation examples

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