Sierra Energy-Trash, Hydrogen, And Locomotive

Company and History of Renewable Fuel Use

The Sierra Railroad Company, established in 1897, is one of California’s oldest operating railroads. With approximately 230 employees across multiple counties, the company owns and maintains about 180 miles of track. Its fleet includes 42 locomotives, supporting the movement of 15,000 to 20,000 carloads of freight annually, in addition to serving around 130,000 passengers each year. Among its many subdivisions, Sierra Railroad Company (SRC) includes Sierra Northern Railway (SERA), Sierra Energy as well as recently acquired RailPower. SRC owns its infrastructure—including tracks, land, and locomotives—and operates both freight and passenger services. The company partners with major Class I railroads, including BNSF and Union Pacific, exchanging freight in a collaborative, integrated logistics network

SRC began exploring alternative fuel sources for its fleet of locomotives in response to the California energy crisis in the early 2000s. Although initial discussions started around 1999, the pivotal moment came during the blackouts of 2001. California experienced an energy crisis marked by widespread rolling blackouts, soaring electricity costs, and severe financial strain on the state’s utility providers. The leadership realized that locomotives could be used not only for transportation but also as generators capable of producing electricity. Each locomotive was able to generate 2.1 megawatts of electricity, transforming them into mobile, dispatchable power sources—a concept the company referred to as a “powertrain.” This initiative was developed over several years in partnership with the State of California. To power these locomotives sustainably, the company turned to biodiesel. This led to the largest biodiesel purchase in American history and positioned the company as the first railroad in the United States to operate entirely on 100% biodiesel. Beyond diesel, SRC has taken significant steps toward self-sufficiency by producing its own hydrogen to fuel its fuel cell locomotive fleet through Sierra Energy. Sierra Energy sources waste materials and other bioderived feedstocks to supply its gasifier technology. Together, these initiatives present a strong self-reliant business case for a localized, vertically integrated hydrogen hub—from source to application. This article is the third installment in the the Reformed Carbon series.

Gasification Technology

Soon after starting to operate entirely on 100% biodiesel, questions arose regarding the sustainability of using food-based sources for production of biodiesel. In response, the company sought more efficient and environmentally responsible alternatives. They identified waste—specifically, trash—as a promising feedstock. Leveraging technology originally developed at the Kaiser Steel mill in Fontana, CA, the company acquired the license and adapted a high-temperature gasification process capable of operating at 4,000 degrees Fahrenheit. FastOx gasification uses steam and oxygen to reformat waste at the molecular level. Organic compounds turn into energy-dense synthesis gas (syngas) composed primarily of carbon dioxide, carbon monoxide and hydrogen (CO₂, CO and H₂)

Around two decades ago, the company began scaling up the gasification technology, collaborating with the U.S. Army to develop progressively larger systems. One of the principal facilities, located at Fort Hunter Liggett in Monterey County, California, stands as a testament to the project’s success. The gasification process leaves no residual waste: metals melt and can be recovered, inorganics turn into slag usable in cement applications, and the remaining material becomes syngas. This syngas has a wide range of potential applications, including the production of hydrogen fuel.

Sierra Energy’s gasification project on Fort Hunter Liggett is helping the US Army to meet its zero net waste and zero net energy goals, both of which protect our troops and save taxpayers money. Sierra’s newest project to convert forest waste to hydrogen for hydrogen powered trains is helping to reduce diesel pollution and decarbonize rail transport. These are really exciting projects that we need to replicate around the state.

A key advantage of injecting steam alongside oxygen is the elevated hydrogen yield. The process produces a syngas rich in hydrogen and carbon monoxide. When this syngas is subjected to a water-gas shift reaction, the end result is a hydrogen output of approximately 100 kilograms per metric ton of waste processed—equating to a 10% hydrogen yield by mass.

The system is designed with flexibility in mind. It can process up to 100 tons of garbage per day and can operate efficiently even when reducing down to 20% of its full capacity. This operational flexibility allows the gasifier to ramp down production. Biomass and trash are seen as ideal inputs. While biomass was incentivized through environmental programs, trash presented an even more compelling business opportunity, as it not only avoided landfill use but also prevented landfill gas emissions. Moreover, the company could be compensated for diverting waste from landfills.

The plant utilizes a conveyor belt that feeds waste material into the top of the gasifier through a sealed feed mechanism, commonly referred to as a Paul Wurth feeder. This design includes a chamber that isolates the feedstock, evacuates ambient air, and then introduces the material into the gasifier. This approach minimizes the presence of air in the system, which is essential because the gasifier operates under oxygen-blown—not air-blown—conditions. Maintaining a low-oxygen, near-atmospheric pressure environment is critical, as the process relies on an oxygen-starved atmosphere to optimize gasification performance and prevent unwanted combustion.

The reactor requires an initial heat input to reach operating temperature, which is typically supplied using natural gas or propane. Once operational, the system relies on oxygen injection to sustain the gasification process. The injected oxygen reacts with carbon in the biowaste feedstock, generating the heat needed for the endothermic reactions within the gasifier. This internal reaction becomes the primary source of thermal energy, reducing the need for external heating once steady-state conditions are reached.

The gasifier achieves over 80% cold gas efficiency—meaning more than 80% of the energy contained in the biowaste is successfully converted into syngas. This high efficiency supports long-term operational viability and energy recovery. Depending on feedstock and system configuration, carbon dioxide emissions per ton of hydrogen produced can vary, but overall performance is optimized to minimize CO₂ output while maximizing hydrogen yield.

The system produces a medium-BTU, tar-free syngas. Beyond the reactor, the design of the overall plant relies on standard equipment from other industrial suppliers including syngas purification, water-gas-shift reactors and pressure swing absorption to a robust seven-stage hydrogen cleanup process. The purity of the resulting hydrogen is extremely high—reaching “five nines” (99.999%)—making it suitable for fuel cell applications. This level of purification also enables flexible downstream uses, depending on market demand or project requirements.

Business Case

At a certain point, not today, but at some point, garbage will be valuable. And you’ll be paying for it.

The company selected a 100-tons-per-day material processing capacity as a convenient benchmark producing 10% of hydrogen by weight, though the actual system size is highly flexible. Designs are inherently modular, allowing for scalable deployment. While some companies can support large, single-unit gasifiers of up to 1,000 tons per day, most systems will be offered in clusters designed around the 100-ton size. This modularity enables configurations of 200, 300, or even 400 tons per day by combining two, three, or four units, tailored to project needs.

Among the 11,000 current global requests for the company’s gasification systems, hydrogen has emerged as the most sought-after end product. Other high-demand outputs include methanol (and its derivatives), ammonia, and sustainable aviation fuel (SAF). From the company’s perspective, these fuels are essentially interchangeable in that they all originate from syngas; the subsequent conversion steps, while industrially significant, are not proprietary or unique to the company’s platform.

Of the approximately 11,000 potential business partners expressing interest, the company has identified a select group—just a few dozen—that are appropriate, technologically experienced, candidates for first-of-a-kind deployments of novel technology. The vast majority of these 11,000 sites consist of municipalities, small communities, and local landfills focused on economic development opportunities. These are generally not suitable for early-stage technology integration. Instead, the company prioritizes working with large mature industrial partners where its gasifier is not on the project’s critical path. The company intentionally avoids scenarios where its technology would serve as the primary risk or bottleneck in a partner’s only lead project.

Through these innovations, the Sierra Energy has demonstrated a comprehensive, closed-loop solution for converting waste into clean energy and reusable materials—paving the way for a more sustainable future in both transportation and energy production.