Renewed Interest in Bovine Biomass

Researchers are taking another look at animal-processed fiber (APF), a coproduct of the anaerobic digestion process. APF contains an abundance of protein and fiber fractions such as cellulose, hemicellulose and lignin and can be used for a variety of biobased products.
By Bryan Sims
For years, horticulturists and agricultural researchers have exploited the valuable properties of ruminant animal waste for energy production. Today, those same researchers are reviving the science known as "chemurgy," the development of nonfood, industrial products made from agricultural materials.

Much of the energy captured from cattle manure is derived from anaerobic digestion. On dairy farms, the system is used to sequester methane and carbon dioxide to generate energy, control pathogens and reduce odors. The anaerobic digestion process also produces a coproduct called animal-processed fiber (APF) that has become a target of scientific interest. Many in the biomass industry have come to perceive APF as one of the most undervalued and underutilized forms of cellulosic material. Research in APF involves uncovering the various values and properties the material holds for a number of biobased industrial products.

APFs are the undigested residual material that neither the animal nor the anaerobic digester can breakdown any further. APF can be used in animal bedding and potting soil, but agricultural scientists would like to learn more about its potential applications. Although the material does contain trace amounts of nonvaluable components, APF also contains an abundance of protein and fiber fractions such as cellulose, hemicellulose, lignin and other valuable components. These fractions, along with minerals and other nutrients, represent a biologically processed feedstock suitable for a variety of purposes-as a supplement in the paper, pulp and wood industries, in wood-derived composite products such as fiberboard, floor tiling, siding and other wood-derived biocomposite products, and as a binding agent in adhesives, industrial tape and masonry patching materials.

According to Steve Dvorak, president of Chilton, Wis.-based GHD Inc., a firm that designs and installs anaerobic digesters, extensive research on APF uses should take off in the next five to 10 years. "There's a lot of potential in this and there are many people looking at it," Dvorak says. "I think we're going to see a lot of changes in the next year or two of where this material goes."

The key to transforming APF and manure, often perceived as low-grade waste, into value-added biorenewable products involves the development of refining operations that convert these components into commercially viable commodities.

Making Strides
Since 1989, Deland Meyers, considered by many in the biomass industry to be a pioneer in APF and ruminant manure-related biobased products research, has been successfully converting APF into potentially marketable biobased composite products such as fiberboard, particleboard and various types of fiber-based plastics. Shortly after Meyers joined Iowa State University's Food Science and Human Nutrition Department, he began to explore the idea of creating nonfood products from plant proteins for the Center for Crops Utilization Research. The same functional properties of protein are applied to both food and nonfood products, he says. "[The research] was trying to find a new use for a biobased material that has been produced in the state [of Iowa]," says Meyers, now director of a newly created department at North Dakota State University in Fargo that will be called the School of Food Systems and is currently the Department of Cereal and Food Sciences. "We were able to take that fiber and add a little processing and essentially came up with fiberboards that look very similar to wood or other types of agriculture-[based] fiber products."

Farmers traditionally use manure to fertilize their fields. As farms have grown and animals are densely concentrated in single locations, farmers have more manure than land to spread it on, especially in the livestock-heavy states of Wisconsin and Texas. Finding new uses for APF and the raw manure could provide a solution to disposing of the more than 2 trillion pounds of manure produced annually in the United States. It would also help to allay environmentalists concerns about contamination of streams and underground water sources from manure runoff. "In some regions of the country there's a shortage of [the nutrients found in manure] and in many regions there's an excess because of large livestock concentrations," says Tom Richard, associate professor of agriculture and bioenergy at Pennsylvania State University. Richard has research ties with Meyers on manure-based applications. "In the regions where there's an excess of manure this looks like a potential win-win solution," he says.

There are concerns about odors and pathogens when APF products are produced in tandem in the pulp, paper and wood mill industries. However, noxious odors and microbes that manifest disease are killed off by the manufacturing process, according to Richard. Once the final product is dry enough it doesn't serve as a substrate for microbial growth, unless it gets wet, which is something researchers are looking at very closely, he says. So far, fiberboard made with APF seems to match or beat the quality of wood-based products. "The downside is that the fiber is weakening throughout that process," Richard says. "I expect that for structural applications where strength is important it may be necessary to blend in some additional wood fiber in order to strengthen that material."

Another possible APF-related application that is currently being researched is potting soil. Tim Zauche, associate professor of chemistry at the University of Wisconsin-Platteville, is in the process of developing a soilless potting mix for orchids from APF. Creating a marketable soil for the floral industry could be commercially viable because orchid sales in the United States have increased and the cost of peat moss, which is mostly imported from Canada, has risen. "Greenhouses would like this material because it's so consistent," Zauche says. "APFs are consistent over three to four months, whereas composted material depends on whether the pile was warm here or there or not, greenhouse growers don't always like it." Zauche has also worked with the USDA Forest Products Laboratory to develop APF-derived fibrous material that can act as a substitute for sawdust in the making of fiberboard.

Tackling the Obstacles
One of the biggest challenges in APF research is successfully marketing the biobased products and convincing industrial product retailers like Menards, The Home Depot or Lowe's stores to sell the products. In an attempt to promote his products, Meyers and his team created biobased composite novelties such as "cow pie Frisbees" and demonstrated the products' unique qualities at Iowa fairgrounds, expos and other public events. But still the products "never really took off commercially," he says, which is impeding widespread market acceptance.

According to Monlin Kuo, an associate professor of natural resources and ecology management at ISU and a former colleague of Meyers during their joint research efforts on biobased composite products, other major hindrances for advancing APF-derived products include the cost of research and competition from the existing wood mill production. This is especially true in the United States, which has sufficient supplies of wood from forestry sources for wood milling. In countries without a sufficient fiber source, however, APF could potentially be a valuable commodity. "I think [APF] would be more applicable in more fiber-hungry countries like China," Kuo says. Although the technology is available, it's a matter of getting the most out of the research and time allocated for that research to find new uses for APF-derived biobased composite products and gain consumer acceptance Kuo says.

Dvorak has observed that more livestock farmers are changing their perceptions of APF and/or manure. Once viewed as a low-value, recycled material that's expensive to dispose of, APF could be transformed into a valued commodity with the potential for significant profit if a solid market can be established. As a result, GHD sales have risen. "If we can bring the value up on [APF] then it becomes a little more feasible to build more anaerobic digesters, which is good for the entire livestock industry," Dvorak says.

According to Richard, it may only be a matter time before we see more manure-based materials integrated into conventional wood-derived products. The end result could be so transparent that consumers don't even realize it's happening. "I think over time, excitement about biobased energy is going to need to be coupled with excitement about biobased materials," Richard says. "There are many livestock operators who would love to find something different to do with their manure and this looks like one of the choices to evaluate."

Bryan Sims is a Biomass Magazine staff writer. Reach him at or (701) 746-8385.