Research and Development

Biofuel Tests at Milwaukee Zoo Train a Success, CSR and NRRI Look Ahead to Standard Gauge Trials

Milwaukee County Zoo train on a trial - the first locomotive is burning 100% torrefied biomass, and the trailing locomotive is burning a 50/50 blend of torrefied biomass and coal.

Milwaukee County Zoo train on a trial - the first locomotive is burning 100% torrefied biomass, and the trailing locomotive is burning a 50/50 blend of torrefied biomass and coal.

Two steam locomotives at the Milwaukee County Zoo were fueled with a renewable wood-based solid fuel last week to reduce fossil coal emissions, and the tests were a success.

The Coalition for Sustainable Rail (CSR) and the Natural Resources Research Institute (NRRI) completed a final series of three biofuel trials following more than a year and a half of development of the fuel at NRRI’s Renewable Energy Lab in Coleraine, Minn. Thanks to the generosity of the Milwaukee County Zoo, its small 15-inch gauge railroad has served as a demonstration platform for CSR and NRRI to see how a wood-based torrefied biomass fuel product burns in locomotive-style boilers. Tests in June and October 2016 revealed that the biofuel could make sufficient steam, but improper pelletizing methods resulted in spark emissions from the locomotive.

“Following the first trials, our researchers set about devising a better method to densify the material, including acquiring an industrial scale densification machine that we installed at our lab in Coleraine,” explained NRRI Associate Director, and CSR Board Member, Don Fosnacht, Ph.D. “Combined with a food-grade binding agent, we were able to make dense, pill-shaped pellets for use with these Zoo test trials that burned exactly like coal.”

No. 1924 hauls the test train up the steepest grade on the Zoo railroad burning 100% torrefied biomass.

No. 1924 hauls the test train up the steepest grade on the Zoo railroad burning 100% torrefied biomass.

NRRI is currently researching the opportunities in “torrefied biomass,” a wood-based biofuel that is made in a kiln not unlike a coffee roaster. After being “roasted,” the wood is transformed into a fuel that burns and reacts much like coal,  with virtually no heavy metal pollutants and reduced carbon emissions. NRRI provided three blends of torrefied biomass to the Zoo for testing: 1) a blend of 99 percent torrefied biomass and 1 percent binder agent; 2) a blend of 49.5 percent torrefied biomass, 49.5 percent Powder River Basin coal, and 1 percent binder; and 3) a 100 percent torrefied biomass pellet with no binder. Each of the fuels was tested in the Zoo train locomotives, and two were found to be ideal stand-in fuels for fossil coal.

Pre-blended torrefied biomass / Powder River Basin fuel pellets ready to load in the tender of No. 1924.

Pre-blended torrefied biomass / Powder River Basin fuel pellets ready to load in the tender of No. 1924.

“The torrefied biomass with binder, and the 50/50 blend of coal and biofuel, worked quite well in both locomotives,” said CSR President Davidson Ward. “Both fuels burned nearly identical to coal, including building a decent coal bed on the grates and maintaining pressure under a wide variety of operational circumstances, while being nearly smoke and odor free.”

Initial temperature data also indicate that the biofuel heating value is equal to coal. The maximum firebox temperatures recorded during the biofuel trials were in excess of 2,100 degrees Fahrenheit (1149 Degrees Celcius).

“I am quite impressed with what I saw from this round of biofuel testing, and I look forward to burning it in our steam locomotive,” said Zach Hall, Steam Operations manager at the Everett Railroad, who was on site to participate in the tests. “From my observations, both the biomass with binder and 50/50 blend of fuel will do just fine to make steam and minimize smoke, both of which are good things in my book.”

CSR and NRRI are ramping up for the next round of tests: manufacturing 10 tons of fuel for use by Everett Railroad steam locomotive No. 11 early next year. In support of these tests, CSR is undergoing a matching grant fundraising process, whereby donations to the non-profit made between now and December 15 will be matched dollar-for-dollar (up to $10,000).  

Zoo Tests: a sneak peek


The Coalition for Sustainable Rail, in conjunction with staff from the Natural Resources Research Institute, completed a third round of torrefied biomass fuel tests with the steam locomotives at the Milwaukee County Zoo this past Monday.  CSR will be providing more details about the findings of that research next week but, in short, it was a success!

Until then, check out the following video of Zoo train 4-6-2 No. 1924 hauling our test train. The locomotive is burning torrefied biomass fuel.

The deep "humming" noise is the locomotive "drumming." Similar to pulse jet engines, the fuel is generating so much combustable matter that the firebox is consuming more air than it can bring in at one time. As air comes through the firebed, it flash ignites, causing a small "boom." Multiply this by hundreds of bursts of air coming through the firebed at once, you get drumming. This is alleviated through better ash pan design, installing overfire tubes (like most late-model steam engines), or cracking the door a bit. Notice that the noise stops when the engineer opens the door to shovel each scoop of fuel into the firebox.

Research Team Completes First Milestone of $1.9 Million Grant to Develop Locally Sourced Electricity and Solid Biofuel


D U L U T H,  M I N N. | April 19, 2017 –The Natural Resources Research Institute at the University of Minnesota is Principal Investigator and leader on a $1.9 million Renewable Development Fund grant funded through Xcel Energy to develop a Biofuel Conversion Center at the NRRI Coleraine Lab. The Coalition for Sustainable Rail is one of two industry partners aiding NRRI on the grant; its responsibility includes designing and building a 100 kW steam-electric boiler generator. The other industry partner, SynGas Technology, LLC, is championing development of a proprietary moving bed torrefaction reactor to supply fuel to the boiler generator. This month, the NRRI Development Team completed the first milestone of the Grant: Preliminary Engineering.

“I am excited by the engineering progress seen in the grant work to-date,” explained Don Fosnacht, Ph.D., NRRI Associate Director, CSR Board Member, and the project’s Principal Investigator. “The steam-electric generator the CSR engineering team is designing will be a one-of-a-kind addition to our Biofuel Conversion Center, and it will serve as an important research tool in the development of remote, distributed generation systems.”


  • CSR has been awarded a $405,000 portion of a $1.9 million grant from Xcel Energy’s Renewable Development Fund

  • CSR is designing and building a modern 100 kW steam-electric boiler generator that runs on torrefied biomass

  • This release comes as the NRRI Team completed the first grant milestone

  • The boiler generator will build upon the principles of advanced locomotive-style boiler and compound engine

  • Zoo train trials also served to provide key biofuel combustion metrics for the boiler generator

The steam-electric generator being developed by CSR will employ an advanced locomotive-style boiler and compound expansion piston steam engine to generate sufficient power to make 100 kW of electricity. The boiler is designed to burn torrefied biomass fuel in a Gas Producer Combustion System and will be able to operate automatically, thanks to an additional $25,000 National Instruments Green Engineering Grant awarded to CSR in support of the RDF project.

“The Xcel grant provides a significant opportunity to push the state-of-the-art in firetube boiler, compound reciprocating steam engine, solid fuel combustion, and distributed generation system design,” said Wolfgang Fengler, MSME, CSR Senior Mechanical Engineer. “Developing an efficient boiler-generator package that can fit into a 20 foot shipping container is no small task, but our experienced team brings a diverse skillset that has translated into an innovative concept which we are eager to fashion into a working prototype.”

The NRRI RDF Grant is broken into multiple milestones, including preliminary engineering, detailed engineering, fabrication, testing, and steady state operation phases. CSR is currently focusing on the detailed engineering and fabrication milestones. Fabrication of boiler, engine, and electrical components is set to begin this summer.

“What the RDF grant has enabled CSR to do is really push boiler and steam piston engine design as can only be achieved through new-build construction,” explained CSR Technical Advisor Hugh Odom, P.E. “I am honored to serve as the Professional Engineer on this project, working with the CSR engineering team in a capacity to verify compliance of the design with ASME and other applicable codes.”

When completed, the boiler generator unit will be installed at NRRI’s Biofuel Conversion in Coleraine, Minnesota, where it will undergo commissioning and steady state operations. That facility is a former Oliver Iron Mining Railroad maintenance complex which has been converted into a one-of-a-kind minerals and biofuel research center by NRRI.

The Biofuel Conversion Center of the Natural Resources Research Institute is housed in the former railroad shops of the Oliver Iron Mining Company in Coleraine, Minnesota. Shown here is the main hall, which serves to house the large torrefaction reactor (center) that can create 14 tons of torrefied material per day. The boiler generator and additional torrefaction reactor will also be housed in this one-of-a-kind reserach facility.

CSR Undertakes First Test of Biocoal with a Steam Locomotive

Milwaukee County Zoo locomotive number 1924 served as the "guinea pig" on these first torrefied biomass tests. Operating on 15 inch gauge track, the locomotive is the perfect scale to begin combustion analyses of torrefied fuel under the highly variable drafting of steam locomotive boilers.

Milwaukee County Zoo locomotive number 1924 served as the "guinea pig" on these first torrefied biomass tests. Operating on 15 inch gauge track, the locomotive is the perfect scale to begin combustion analyses of torrefied fuel under the highly variable drafting of steam locomotive boilers.

From June 10-12, CSR teamed up with the Milwaukee County Zoo, the Natural Resources Research Institute, and New Biomass Energy to undertake the first test of torrefied biomass on a steam locomotive. The tests are a key step in ensuring that the fuel can be used in steam locomotives of all sizes in the face of shuttering coal mines. 

Torrefied biomass pellets used in the testing.

The Milwaukee County Zoo operates two steam locomotives on its 15 inch gauge railroad. With just over a mile of mainline track and upwards of 30 trains per day, the Zoo operation provided CSR the opportunity to compare runs burning coal with identical runs burning "torrefied biomass," also known as "biocoal," in a controlled, test-scale environment.

"We instrumented the locomotive with four, Inconel-sheathed thermocouples to gauge firebed, combustion space, and exhaust gas temperatures when burning coal vs biocoal," explained CSR Senior Mechanical Engineer Wolf Fengler. "Tests were run on Saturday and Sunday, with trains Saturday burning coal and the first runs of Sunday burning biocoal."

Modified grates [bottom] and two of the three thermocouples poking through staybolt telltale holes [left]. Click to Enlarge

CSR worked hand-in-hand with Zoo staff to instrument 4-6-2 steam locomotive number 1924 and undertake the tests [see diagram below]. Torrefied biomass fuel was graciously donated by New Biomass Energy for use during research. The small fuel pellets were burned on a modified stainless steel grate installed by CSR on-site.

"We used National Instruments hardware in concert with its LabView software to record second-by-second temperature data from the sensors," said CSR President Davidson Ward. "Perhaps most exciting was the fact that three of the sensors were directly in the firebox, one submerged in the firebed and two at varying heights above, each of which provided better insights into the combustion behaviors of each fuel."

[Click to Enlarge]

While data processing is still underway, initial results indicate that the torrefied biomass fuel burns with a very similar temperature profile as the coal used by the Zoo, but the biomass had a much longer flame profile, which bodes well for producing more uniform stresses in the firebox.

The video below shows a comparison of coal with biocoal under identical, hostling circumstances. Note the length of flame and brightness of the fire generated by the torrefied biomass.

More information, including additional videos of the tests and a detailed White Paper, will be made available later this summer. CSR plans to undertake a second set of tests with the Milwaukee County Zoo with larger torrefied biomass pellets created by NRRI at its Coleraine Minerals Research Laboratory later this year. The organization has also been in discussions with standard-gauge operators about undertaking full scale tests in the future.

The Milwaukee Zoo train tests were made possible by the outstanding assistance of the Milwaukee County Zoo, the Natural Resources Research Institute, New Biomass Energy, the American Boiler Manufacturers Association, and the support of CSR's donors, including generous contributions by Bon French and Fred Gullette.

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Dedicated to: Randy Rawson

For the duration of biofuel testing, CSR renamed locomotive 1924 "Randy Rawson" in honor of the former President of the American Boiler Manufacturers Association, W. Randall Rawson, who died in November 2013. He was a superb friend and advocate of CSR, having expressed unwavering interest and support of our biofuel and steam locomotive research. He had always wanted to be present for the first tests of torrefied biomass in a steam locomotive, and we wanted to do our part to honor him. To this day, Rawson's legacy, sense of humor, and enthusiasm continue to serve as an inspiration to the leaders of CSR.