What Is Anaerobic Digestion?

Anaerobic digestion (AD) is a biological process that breaks down organic materials in the absence of oxygen using microorganisms.

AD occurs naturally in environments such as wetlands, lakes, and ocean sediments. Generate Upcycle harnesses this natural process using built systems like lagoons or tanks that capture AD’s end products: biogas and digestate, a nutrient-rich fertilizer.

Biogas can be used directly for electricity, heating, and transportation, or upgraded to renewable natural gas (RNG), a sustainable substitute for fossil fuel-based natural gas.

RNG increases domestic energy independence by reducing reliance on imported fuels and can be a cost-effective alternative to traditional fossil fuels.

Stages of the Anaerobic Digestion Process

Our anaerobic digestion facilities support the unique needs of each community they serve, but all use the same foundational science to convert waste into energy.

Food and agricultural waste are separated from packaging and blended in preparation for processing.
This organic “soup” of waste is loaded into AD tanks. Microorganisms begin breaking down the organic material.
Biogas released during the AD process rises to the tank’s dome, where it is captured for use as renewable energy. Liquid and solid digestate are captured below for use as nutrient-rich soil amendments.

From Biogas to Renewable Energy

The biogas created during our waste-to-energy process powers the grid and provides heat to homes in the regions where we operate.

At our facilities that generate renewable electricity, our biogas provides a reliable source of baseload energy to the grid by powering generators that can run 24/7. Using combined heat and power, or CHP, on site also lets us maximize our operational efficiency: By using the biogas we produce to power the digesters, we’re creating another level of circularity in our process.

Our plants also leverage upgrading technology that converts the biogas produced during AD into grid-injectable RNG. Upgrading increases the methane concentration in biogas to make it chemically identical to fossil fuel-created natural gas — without the additional greenhouse gasses resulting from extraction. Because our RNG is created from aboveground sources, it has a much lower carbon footprint and in some cases is even carbon negative.

Real-World Results

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Food and Agricultural Waste Processed

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Renewable Natural Gas Produced

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Renewable Electricity Generation

Environmental Benefits of Anaerobic Digestion

Food waste is one of the largest contributors to methane emissions in landfills. Some landfills capture a portion of this potent greenhouse gas, but food waste decomposes quickly, and methane from food and agricultural waste often escapes into the atmosphere before it can be captured.

Anaerobic digestion and composting offer the most sustainable options for managing organic waste. But AD offers some key benefits over composting for food waste recycling.

Pros

Anaerobic digestion is much faster than composting, making it ideal for processing large volumes of waste that accumulate daily, such as municipal and agricultural waste. Our digesters process food and agricultural waste in 18-21 days. Commercial composting takes months to break down organic waste.
AD tanks capture nearly all methane produced from the breakdown of organic waste, which lets us recycle it into renewable energy products. Large commercial composting operations often release methane as food waste slowly decomposes.
AD facilities have a smaller footprint than composting operations.

Cons

Anaerobic digestion requires more complex equipment than composting.
The AD process can be more energy intensive, which is why we use circular methods, using the biogas produced by AD for combined heat and power to run our digesters.
Both AD and commercial composting produce odors, which we minimize through odor-capturing technologies including negative air pressure and biofilters.

See How Anaerobic Digestion Works at Generate Upcycle

Explore how Generate Upcycle’s anaerobic digestion technology turns food and agricultural waste into renewable energy, powering homes, businesses, and a sustainable future.

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