In the United States (US), renewable natural gas (RNG) and renewable fuels company Aemetis Inc. has announced that it has completed the installation and commissioning at its Keyes ethanol plant in California (CA) of the first Mitsubishi ZEBREX system in North America, reducing overall energy use and lowering the carbon intensity of ethanol.
The Mitsubishi Chemical Corporation (MCC) ZEBREX ethanol dehydration system was commissioned after several years of engineering design, fabrication, installation, and testing at the Aemetis 65 million (US) gallons (≈ 246 million litres) per year, low carbon ethanol plant.
The patented ZEBREX technology replaces the energy-intensive molecular sieve ethanol dehydration process used by most fuel ethanol plants in the world. The Aemetis plant upgrade is the largest implementation of the ZEBREX system worldwide.
The cost of equipment, engineering, and installation of the Mitsubishi ZEBREX system was approximately US$10 million. Aemetis expects to receive more than US$1 million of grant funding from the PG&E and CPUC Energy Efficiency Program in support of the project.
Implementation of the Mitsubishi ZEBREX technology at the Aemetis Keyes plant completes another significant project as we transition our ethanol production process from petroleum-based energy sources to renewable electricity, said Andy Foster, President of Aemetis Advanced Fuels Keyes.
Reduce costs and carbon intensity
The upgrade from the traditional Pressure Swing Adsorption (PSA) ethanol dehydration process to the ZEBREX system has reduced petroleum natural gas consumption at the Keyes facility by more than 20 percent, which is estimated to provide energy savings of approximately US$3.4 million per year.
Additionally, by reducing the amount of fossil fuel energy used in the production process, Aemetis expects to receive a lower carbon intensity (CI) score for the fuel ethanol produced at the Keyes plant, which will increase revenue for each gallon of fuel ethanol sold.
Our engineering team worked closely with Mitsubishi in Japan to customize the design of the system for large-scale fuel ethanol production. The ZEBREX technology is delivering as promised and Mitsubishi has been an outstanding partner throughout this multi-year process, Andy Foster added.
The Aemetis carbon intensity reduction projects at the Keyes ethanol plant include a 1.9 MWe solar microgrid with battery backup that will produce zero carbon electricity to reduce natural gas usage, and a Mechanical Vapor Recompression (MVR) system using electric motors furthers the transition to renewable electricity.
Combined, the Aemetis carbon reduction projects are expected to reduce the use of petroleum natural gas at the Keyes biofuel facility by 85 percent, which will save the company more than US$1 million per month in natural gas costs and provide a significant increase in the value of the ethanol produced at the plant.