Standardizing Pellet Safety
Fires and explosions are an undesirable reality of the pellet industry, and can result in employee injury or death, economic loss, and facility damage. As global pellet production and consumption have soared over the past several years, the buzz surrounding safety and health issues in the manufacturing, handling and storage of wood pellets has become much louder. So loud, that the International Standards Organization has launched an effort, under the direction of Working Group 4 of ISO/TC238, to develop global standards for numerous components of commercial, industrial and small-scale applications. Topics to be addressed include not only prevention, detection, suppression and management of fires and explosions, but also safe handling and storage, analysis of spontaneous heat generation and analysis of off-gassing products.
While all issues up for discussion are essential, Chris Wiberg, manager at Biomass Energy Laboratory and participating member of the new working group, a spin-off of the ISO standards for solid biomass fuels initiative, says that in his opinion, self-heating and carbon monoxide (CO) are the most critical because of the dangers each presents. “For example, on vessels, whenever there is a large store of pellets, it has the natural ability to offgas carbon monoxide,” Wiberg explains. “So in confined spaces like the hull of a ship, pellets generate CO and it can build up in the ship, and there have been some deaths associated with it.”
When it comes down to documented instances, considering all of the circumstances, it’s debatable whether it was truly caused by pellet off-gassing, Wiberg admits. “However, the phenomena has been documented enough to show that it does occur, we just don’t understand exactly why. It has also been reported in small storage—residential home heating models with basement-type storage. Again, it’s confined, and if someone goes in there after off-gassing has occurred, it can create a very dangerous circumstance. Figuring out why this occurs and developing safe practices to eliminate these types of issues, is the key driver behind this initiative, and it’s one I personally take great interest in.”
For self-heating, which is the result of chemical reactions that produce heat at sufficient rates to raise the temperature of surrounding material in a stockpile, Wiberg says it’s the same scenario—why it occurs isn’t really known, but researchers are digging into to all potentials. “In the meantime, how do we keep the pellets from getting out of control thermally? When there’s a silo hot spot that grows out of control until it’s a smoldering fire, how do you put it out? You can’t pour water onto the pellets, as the first few inches will absorb the water so it cannot get it down deeper in the silo, so it’s a very difficult fire to fight and can persist for a very long time.”
Fires related to the pellet process potentially result in explosions, Wiberg adds, which serve as an interconnection to the issues of explosivity and safe handling of dust and materials. “All of the different topics are really important—it’s interesting that there is so much left to be understood and discovered.”
While the ISO standards will change safety and health protocol within the pellet industry in a very meaningful way, lots of work done by experts around the globe over the past several years has led up to this effort.
The Wood Pellet Association of Canada and the University of British Columbia have performed considerable work in the realm of pellet safety, drawing much attention to the topic, and, not directly related to the ISO group activities, a pellet safety workshop was held in Fügen, Austria, last year. It was expected that progress made since that meeting would be detailed at this year’s event in early May.
Christian Rakos, president of the European Pellet Council, says this year, self-heating is high on the agenda. The SafePellets project, which has been investigating mechanisms responsible for self-heating since early 2012, were to present research results for the first time. “Also, safety in the supply chain particularly in terminals, seems to be a topic that is going to draw attention because of large investments in terminals.”
Rakos says that while the EPC wanted to have this year’s workshop directly attached to the next meeting of the ISO group in early June to allow direct interaction, it wasn’t possible for organizational reasons. “But we will seek close interaction and flow of information,” he says.
Wiberg, who attended the Fügen work-shop last year, says he’d also like to see the groups cooperate to prevent redundancy, but it’s likely that individuals at Fügen will also be attending the ISO initiative, allowing a confluence of information between safety experts. Rakos says he believes last year’s meeting did just that. “Most of the benefits of these interactions are not directly visible, but I am sure they are there,” he says. “A lot of learning has been taking place, and will continue.”
The June ISO meeting follows the first meeting in October, which members from seven countries attended. Representing the U.S. was Scott Cedarquist of the American Society of Agricultural and Biological Engineers, the standards development organization assigned by ANSI to oversee the activities of ISO TC 238, and the administrator of the U.S. technical advisory group. At the upcoming meeting, feedback on a base document that is considered the first draft of the standards will be discussed, and work for the next year will be plotted, according to Cedarquist.
Global interest in development of the ISO Standards has been healthy, but still has room to grow, he says. When initiatives first began, efforts were very European dominated, but that dynamic is changing. “The number of countries [involved] has really expanded—Korea and Thailand are starting to participate, and they [the group] have reached out to Russia and others that are big powerbrokers when it comes to woody biofuels. We’d like to see an expansion of participants as we’re trying to get a world view on this, but at least right now, we have Asia, North America and Europe.”
While all countries interested in the ISO work may not have physical representation at the meetings, participating nations may still vote and have committees developing that each respective nation’s position, Cedarquist says. In the U.S., interest has been satisfactory. “We’ve got a fairly large group, and it seems like we add a couple people every month, many who just want to know what’s going on, because they may just be interested in a small subset of the committee.”
Observing members may weigh in only on topics of great interest, rather than all topics under the working group, which includes pellet testing standards. “For example, a company that makes sampling equipment or chemical testing equipment may not care about all the other topics,” Cedarquist explains. “If you’re a company that makes fire suppression equipment, you’d certainly want to see the stuff that comes through on safe handling and storage, but maybe not sampling and things of that nature. We continue to reach out, and we haven’t yet set a limit on the number of people in the committee.”
So why has it been imperative for the U.S. to become involved in standardization efforts? There’s more to it than one might think. “In the context of current EN [testing] standards already published and being utilized in contracts, for the simplest of comparisons, in the U.S., the definition of fines is particles that will pass through a one-eighth-inch mesh screen, and the definition in Europe is 3.15-millimeter round hole. If it’s determined a 3.15-millimeter round-hole screen is needed, there aren’t any U.S. manufacturers that make such a screen. So in order to get appropriate testing equipment, we have to make an order from Europe, pay extra dollars because of shipping, the Euro exchange, and it takes time to get equipment from overseas. This results in equipment issues, time delays, and inconsistency in data comparability.”
Relating back to safety, similar issues are present. “We understand what our scenario is for pellets, how they’re produced and what safety issues there are. But if the issues there aren’t the same—and it’s likely they aren’t, because here the species prominent are hardwoods and southern yellow pine and in Europe it’s predominately spruce—there will be differences, such as the volatiles that might off-gas, or the behavior of dust.”
If standards are developed based on the European model and the U.S. isn’t at the table, it will not be able to provide its interpretation, making it difficult or impossible for U.S. producers to meet contract specifications. “Power companies or anyone purchasing pellets will cite the standards in their contracts, and if we aren’t there during their development to tell them ‘wait a second, this doesn’t apply to us,’ it will be written into the standard and a contractual requirement. We have to be on our toes and watch this very closely as it develops.”
The key to successful development of the standards is through means of a two-stage approach—creating safe practices, but also understanding why events occur, Wiberg says. “That’s why it’s been so difficult, up until now, to develop these standards, because it hasn’t been well understood.”
The nature of the pellet industry is that fires are a reality, he adds. “But it’s good we’re starting to collaborate at this level to help identify cause and effect, and change practice that will hopefully improve our industry’s safety record.”
Author: Anna Simet
Managing Editor, Biomass Magazine