‘Fuel cubes’ hold promise as cleaner coal alternative


A Minnesota start-up company says it’s invented and successfully tested a new biomass briquette that could become to coal what ethanol has been to gasoline.

Renewafuel, a two-year-old subsidiary of Endres Processing in Rosemount, calls them “fuel cubes.” They’re made from a mix of plant materials that include wood, corn stalks and switch grass. Unlike raw biomass, the cubes can be blended with or substituted for coal in existing burners with little or no modifications, the company says.

Like ethanol, burning the fuel cubes creates far less pollution than fossil fuels and producing them has potential to boost rural economies. As with ethanol, too, though, there are concerns about whether harvesting material for the cubes will generate side effects that outweigh their value as an alternative.

“It’s an exciting development, as long as the dense fuel cubes are produced sustainably,” says Todd Reubold, communications director for the Initiative for Renewable Energy and the Environment at the University of Minnesota. “Burning these biomass pellets is beneficial to the environment, but you have to look at the whole system.”

Cleveland-Cliffs, an Ohio mining company that owns Hibbing Taconite, Northshore Mining and United Taconite in Minnesota, announced last week it has purchased a 70 percent controlling stake in Renewafuel. It is already using the fuel cubes to heat a pelletizing furnace at one of its Michigan mining facilities and it wants to use them at its Minnesota sites, too, the company said.

James Mennell, a Minneapolis environmental lawyer, and Leon Endres, owner of Endres Processing, started working on the fuel cubes a couple of years ago. Mennell learned the industry from representing many of the region’s ethanol projects, and Endres Processing was already in the business of combining varieties of food waste into livestock feed.

What they came up with was a way to aggregate several types of biomass, from grass to wood and grains to seed hulls, and process it all into dense, coal-like briquettes. The recipe can be adjusted depending on what biomass materials are available in the region where they’re being manufactured or to meet specific requests of customers.

“It’s a little bit of art and a little bit of science to getting different mixes to work,” says Mennell.

The cubes come out similar in size and moisture content, and they produce a consistent amount of heat that’s comparable to what’s created by coal. They generate nearly twice as much energy as other biomass, the company says, putting it on par with coal from the western United States. The cost is competitive with coal in some markets, says Mennell.

When burned, the cubes emit 90 percent less sulfur dioxides, 35 percent less particulate matter and 30 percent less acid gases compared to coal. That’s based on testing the company ran at the University of Iowa with supervision by the U.S. Environmental Protection Agency.

The company says burning the fuel cubes doesn’t contribute to global warming because the carbon emitted was only recently stored in the plant material. Coal and gas burning, on the other hand, release carbon into the atmosphere that had been stored underground for centuries and was no longer part of the natural balance.

That’s not necessarily true, says Matt Norton, forestry advocate for the Minnesota Center for Environmental Advocacy. He’s skeptical about the sources Renewafuel will use to harvest material for its cubes. If it relies too much on wood, it could rachet up pressure to clear forests, causing the release of carbon that had been stored there for decades.

“My fear is that wood is there and it’s ready, and it’s what they’re going to turn to,” says Norton. “And if they start consuming wood, then the claims they make with regard to carbon neutrality are not borne out. If they start consuming prairie grasses, hats off to them. This could be something we would support in a big way.”

Norton is part of a subgroup of Clean Energy Minnesota that’s trying to come up with a system for scoring biomass fuels based on things like how much net energy they produce, how much carbon they divert from the atmosphere, and how else they affect the economy and environment. It’s not yet clear whether Renewafuel’s project would rank high or low, he says.

Reubold says he expects questions will arise about whether energy is the best use for materials like wood fibers. The use of corn for ethanol fuel instead of food has generated debate and claims it is causing rising food prices. Increasing the use of wood for biomass energy could create competition and higher material prices for other industries.

But Renewafuel’s fuel cube appears to be an important breakthrough, Reubold says, because it allows companies to use biomass without building new facilities.

“The challenge is breaking into a market that’s dominated by coal,” says Reubold. “What this does is it gets a foot in the door for using new forms of biomass to produce bioenergy.”

3 thoughts on “‘Fuel cubes’ hold promise as cleaner coal alternative

  1. I like the concept of substituting biomass for coal. In Europe, this is all the rage – part of a movement to replace expensive, imported fossil fuels with clean, locally produced biomass. The closer the biomass is harvested to the point of use, the lower the transportation cost, the lower the fuel consumed to ship it, and the higher the efficiency to produce it. Since raw biomass is bulky, how cost effective is shipping it more than 25 to 50 miles? Therefore, the efficient production of biomass pellets or brickettes, means either making them in the field, with portable machines, or collecting biomass from a short radius. Then, once the biomass is compressed and its density is doubled or tripled, how far is it feasible to ship pellets and brickettes to the point of use? Localization is the master key to efficient use of biomass. With a short biomass collection radius and a short consumption radius, “Fuel Cubes” have my blessing. Pellet stoves are selling like hotcakes, because burning biomass pellets is half the price of burning heating oil. If you’re going to make biomass brickettes to co-fire with coal, you might as well make woodstove pellets to serve the local market. Best case scenario for coal burning power plants would be to grow onsite biomass algae off the coal plant fumes, press the algae into pellets, and co-fire the onsite algae biomass with the coal – no cost to ship the raw biomass to a pellet plant, and no cost to ship the compressed biomass pellets to the point of use. Second best case scenario would be to install the pellet / brickette factory adjacent to the coal burning power plant, and collect biomass from a 20 mile radius all around the plant. Then, from that location, also distribute woodstove pellets to the local community.

  2. Hi Ty, you’re right in what you say about the logistics and trade chains. The shorter the more efficient. However, biomass pellets are being increasingly traded internationally.

    The International Energy Agency’s Bioenergy Task 40, which analyses international trade in bioenergy, has just released a large report on this market. We discuss it here:

    December 25, 2007
    IEA Bioenergy releases comprehensive study on global wood pellets market

    Solid biofuel trade holds promise for developing countries, who can benefit from exporting part of their vast excess biomass resources.

    But you’re right about processing bulky biomass: keep transport chains short, and develop mobile pelletising plants – this is being done.

    However, once you have a good local chain, you can definitely look at exports. Transport in oceangoing bulk carriers is highly efficient and doesn’t take too much off the energy balance of the fuel.

    We track this market on our small website:

  3. The nice thing is that this process is providing a true alternative that makes sense to package, ship (short distances), and utilize. I work with various biofuels in the research and development of CHP or cogeration systems and think that fuel cubes have a lot of promise for localized power and production and heat reclamation.

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