Aemetis commissions Mitsubishi Zebrex system at Keyes plant

By Aemetis Inc. | August 31, 2022

Aemetis Inc., a renewable natural gas (RNG) and renewable fuels company focused on negative carbon intensity products, completed the installation and commissioning at the Keyes ethanol plant in California of the first Mitsubishi Zebrex system in North America, reducing overall energy use and lowering the carbon intensity of ethanol. The system is now fully operational, reducing energy costs and increasing biofuel value by more than $5 million per year.

The cost of equipment, engineering and installation of the Mitsubishi Zebrex system was approximately $10 million. Aemetis expects to receive more than $1 million of grant funding from the PG&E and CPUC Energy Efficiency Program in support of the project.

The Mitsubishi Chemical Corp. Zebrex ethanol dehydration system was commissioned after several years of engineering design, fabrication, installation and testing at the Aemetis 65 million gallon 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 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 $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.

“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 Inc. “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,” added Foster.

The Aemetis carbon intensity reduction projects at the Keyes ethanol plant include a 1.9-megawatt 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 $1 million per month in natural gas costs and provide a significant increase in the value of the ethanol produced at the plant.

Aemetis is focused on producing below zero carbon intensity renewable fuels, including negative carbon intensity renewable natural gas (RNG), sustainable aviation fuel (SAF), renewable diesel (RD), and bioethanol. Aemetis projects maximize the use of agricultural waste or by-products as low carbon feedstocks to produce renewable fuels, while leveraging the value of federal and state carbon reduction programs. Aemetis is developing two carbon capture and sequestration (CCS) wells near its biofuel facilities in Central California that are expected to store about 2 million metric tons per year of CO2.