Aemetis Inc., a renewable natural gas (RNG) and renewable fuels company, and the American Power Group (APG) recently demonstrated the patented Turbocharged Natural Gas Dual Fuel System for California regulatory agencies and policy makers in Sacramento.
The technology allows a turbo-diesel engine to operate on up to 65% natural gas and 35% diesel, including renewable diesel. The system is already operating in more than 3,000 stationary engines and 1,000 trucks worldwide.
A truck operated using Aemetis RNG and renewable diesel or biodiesel would be carbon-negative, low-emission and lower in cost than diesel, the companies say. The system maintains the power of a 100% diesel engine while using less than half as much diesel fuel, leading to significantly fewer emissions.
Annual fuel savings from using RNG to replace up to 65% of diesel fuel have been shown to exceed $30,000 per truck per year, depending upon the respective cost of the fuel sources. Dairy RNG is usually $2.00 to $3.00 per diesel gallon equivalent (DGE), which is less expensive than petroleum diesel. Retrofit costs are about $10,000, plus the cost of an on-board natural gas tank. The fully automated dual-fuel system adds natural gas tanks to a Class 8 diesel tractor and uses software to manage the two fuels.
APG created a design that safely introduces natural gas into the air induction system before the turbocharger spins up – in essence, turbocharging air already going to the engine. The spinning air reaches the compression chamber to create higher energy at the point of combustion.
“These dual fuel systems represent an important transition step in California’s evolution to cleaner air and ultimately net-zero carbon emissions,” says Eric McAfee, chairman and CEO of Aemetis. “Currently, the heavy-duty vehicle fleet in California is still more than 98 percent diesel-powered. The low-cost conversion of existing diesel trucks will drive the adoption of reduced-cost, lower-emission fuels such as dairy-generated RNG.”