Packing Heat and Power
Combusting compact biomass briquettes, cubes or logs for heat and power isn’t as common in the U.S. as it is in Europe, but it’s starting to make some headway in the country’s solid biomass fuel sector. Private and municipal power utilities, universities and others are interested in using the fuel as a means to reduce emissions, efficiently utilize waste streams that they would otherwise have to pay to dispose of or to meet renewable energy mandates such as state renewable portfolio standards.
Wood or agriculture-based briquettes vary in weight and shape but are typically 10 to 12 times less the bulk density of the original biomass source and have an energy value of about 7,500 Btu per pound.
The most important factors in producing briquettes are the type of biomass used and its particle size and moisture content, according to Steven Smith, managing partner of Renew Energy Systems, an Iowa-based equipment distributor for C.F. Neilson, which is a Denmark-based biomass briquette system manufacturer that has been selling machines globally since the 1980s.
Weighing in on Briquettes
Briquetting is largely an automated process, Smith says. “Generally speaking, we can briquette things in the range of 10 to 20 percent moisture, but it really depends on the type of feedstock,” he says. “For wood, we want that number to be somewhere between 8 and 15 percent moisture.”
Once proper moisture content is determined, or the material is dried, the briquetting process begins with feeding the biomass into the system. From there, the process is relatively simple—the material is compressed, pressured and heated to between 225 to 250 degrees Fahrenheit. In Renew’s system, the material is fed out of the machine in a continuous line and cut into 4½- to 5-pound briquettes and packaged into 20-pound bags for residential use, or broken into pucks or pieces for industrial use.
The largest machine, which comes with a $325,000 to $400,000 price tag, is capable of processing about 1 ton of briquettes every half hour, up to 2 tons per hour. “If you’re briquetting straw, miscanthus, switchgrass, hay or anything very spongy that doesn’t have a lot of density, you won’t get 2 tons an hour,” Smith explains. “With hickory or oak, we can pack more punch into a foot, and the brick is a lot heavier.”
Dave Schmucker, president of California-based Biomass Briquette Systems LLC, points out that some agricultural feedstocks such as miscanthus and switchgrass, depending on how the machine is built, may need some type of binder. “A wood feedstock binds well because it has lignin in it,” he says. “Others don’t, so you’ll have to add a binder or mix in some other feedstock that has a natural binder.”
Choosing a System
Biomass Briquette Systems currently markets two commercial-sized briquetters, a hydraulic system and a mechanical system. “Hydraulics are typically, but not always, less expensive overall, and they are slower with lower production, so they’re good for small- to medium-size operations,” Schmucker explains. “Mechanical systems are usually used in high-volume operations and are more expensive.”
Similar to Renew Energy, Biomass Briquette System’s machines are manufactured overseas, but engineered and designed in the states to ensure that they meet U.S. standards. The company has a parts warehouse in southern California, and manufactures support equipment including silos, grinders and augers to feed the biomass into the briquetters. Biomass Briquette Systems is also the exclusive U.S. distributor for Denmark-based LIN-KA’s biomass boiler systems.
Biomass Briquette Systems aids in the design and layout of a briquette plant and performs the installation. The company’s Web page contains a feature allowing buyers and sellers of densified fuel to post ads at no charge.
While Renew Energy and Biomass Briquette primarily provide briquetting systems to customers, Cliffs Natural Resources subsidiary Renewafuel LLC has entered the briquetting business from a different angle—building, owning and operating plants that serve as alternative fuel suppliers. Renewafuel’s product, which is smaller and in the shape of a cube, differs slightly from typical briquettes.
The company recently completed construction of its first full-scale biomass cube production plant in Marquette, Mich., and is focusing on marketing the cubes as a cofiring option for large-scale coal-fired utilities.
Chairman and CEO Bill Brake says the 1¼x1¼x2 inch cubes, which are composed of locally sourced wood and agricultural feedstocks, have about the same energy content as coal. “We know customers need something that looks, handles and performs as much like coal as possible,” he says.
To make their product more economical, Renewafuel’s transportation rule of thumb is 75 miles to source the feedstock and 150 miles to deliver the finished product. “Our model is very much regional—from the collection to the processing and delivery of biomass,” Brake says.
Beyond coal replacements, a biomass briquette or cube may serve as an attractive alternative to pellets, depending on the desired end use.
Briquettes Versus Pellets
Briquette producers believe their process is more efficient than pelleting because the biomass materials they use don’t necessarily have to be preprocessed or uniformly ground up, according to Smith. If they do have to be preprocessed, the preparation required is less forgiving than it is when making pellets. “Because of the mass of a briquette compared with the small pellet, we’re able to briquette things that can’t be pelletized,” he says. “For example, we can briquette manure, and we’ve briquetted things such as pepperoni sausage casings from food processing plants.”
Briquetting waste byproducts and using them on-site for energy rather than transporting them to another location or to a landfill can save on disposal costs. Renew has a mobile briquette system that can be set up inside or outside a factory to briquette waste materials. “Obviously geographic factors are limiting, but the connection time is a lot quicker than if we set up a whole feed system in a factory,” Smith says.
Further comparing briquettes to pellets, Smith says they generally use less horsepower to produce—Renew’s largest machines, including the feed system, use about 105 horsepower (HP). Schmucker says Biomass Briquette’s largest machines use 100 HP motors, but the cost of running them largely depends on the regional power rates. Based on those rates, the company will help customers determine the cost of running their machines.
Schmucker says that from a capital purchase standpoint, the machines used to make briquettes are less expensive and require less maintenance than pellet machines. There are advantages to using pellets, however, he points out. “Pellets have been considered more of a residential fuel even though they are used in some larger, commercial applications, Schmucker says. “Arguably, if you’re doing a lot of transporting, after you densify a pellet and put it into a container you get more pounds per foot than you would a briquette, especially if the briquettes are larger, just because of the air between them when they are stacked.” Overall, it’s a matter of the application and purpose, he adds.
Business and Interest
Business in the past few years has fluctuated, Smith says. “We went through a period where interest was huge, but the economy drove some of that away and we saw a decline in equipment sales.”
Lately, the value of the euro and the U.S. dollar has been more balanced and that’s been a bright spot for Renew. “The equipment that we sell is made in Denmark, so it’s imported and sold in euros,” he says. “When it was 1:5 or 1:6 a year-and-a-half ago, it was much more difficult to afford than now—it’s at about 1:2 right now. So as far as getting equipment imported from Europe, it’s a whole lot cheaper and that interest is coming back.”
New interest is also being driven by state and federal legislation prompting utilities and other companies to look at energy and biomass systems, he says. Mindset and adaptability of customers plays a big role as well, according to Brake. “We’re doing test burns with utilities, and there’s interest from some who want to permit new facilities or expand the capacity of existing facilities and need a fuel to help them become compliant with regulations,” he says.
An operator who burns bulk fuel month after month must have the proper heat output and furnace stability to switch fuels, Brake says. “Understanding the type of furnace they have, the type of coal they are currently using and the type of delivery system that they have determines the variety of biomass blends and configurations that we think would work best. What works best in a suspension type pulverized coal boiler is not necessarily at all the same fuel that would work well in a traditional stoker bed.”
Overall, Brake adds, biomass fuel runs the gamut of users and motivations. “In general, we’re finding that the enlightened user understands the value [of biomass] and the need to adapt.”
Author: Anna Austin
Associate Editor, Biomass Power & Thermal