Improving safety with improved fibre pile management
June 28, 2021
By Gordon Murray, WPAC
An interview with Shahab Sokhansanj, Ph.D., research leader, Biomass and Bioenergy Research Group, University of British Columbia
Canada’s pellet industry gained a champion when Shahab Sokhansanj, Ph.D., created the Biomass and Bioenergy Research Group (BBRG) at the University of British Columbia (UBC) in 2003. The world-class research group has partnered with the Wood Pellet Association of Canada (WPAC) since 2006, and is currently collaborating with WPAC and BioFuelNet Canada (BFN) in a four-year research project (2019-2023) funded by Agriculture and Agri Food Canada’s AgriScience Program under the Canadian Agricultural Partnership.
Shahab received the 2016 International Bioenergy Conference and Exhibition’s Founders Award for his contribution to the development of engineering science around post-harvest handling of biomaterials, and a gold medal in drying science at the International Drying Symposium held in Valencia, Spain, in 2018.
How did you get involved in pellet industry?
I’m an agricultural engineer by training and spent more than 20 years in Saskatchewan working mostly on grain processing as well as hay, alfalfa and grasses. I taught agricultural engineering at the University of Saskatchewan where I hold the title of Emeritus Professor.
I had just retired in 2003 when I met Staffan Melin, who was WPAC’s director of research at the time. He was investigating a fatal accident involving a ship transporting wood pellets, and we decided to work together to look at how carbon monoxide is generated by wood pellets in combination with oxygen depletion.
I had a background working with Transport Canada so it was a great fit. We approached UBC and were encouraged to create the Biomass and Bioenergy Research Group within its Department of Chemical and Biological Engineering. It represented a wonderful niche opportunity for me. Today the research group has almost 20 professors, research associates, graduate students and under-graduate students.
While I was at UBC, I also worked as a research scientist for the U.S. Department of Energy’s Oak Ridge National Laboratory for 17 years on projects that promoted pelletization — a key technology for biomass mobility and use. I retired from Oak Ridge in 2017.
What kind of work is being done through the Biomass and Bioenergy Research Group?
Our engineers and scientists focus on the gap between the raw biomass source and biomass conversion. They evaluate physical and chemical properties in relation to biomass size reduction, drying, pelletization, and best practices for safe handling and storage of biomaterials.
No other place in the world is as focused on pelletization as our group, so we get the material, grind it, dry it, compact it, put it in storage. We do a lot of mathematical modelling on logistics of feedstock supply and post production handling of pellets.
One of the most important aspects of our work is collaboration. We talk to plant operators and work with industry and government in Canada and around the world to conduct advanced research and develop innovative solutions for emerging bio-based businesses.
We are currently collaborating with WPAC and BioFuelNet Canada on a four-year research project that began in 2019. It’s funded by the Canadian government with four research tasks related to the use of low-quality agricultural biomass, cost-efficient supply chains, best practices on safe handling and storage of pellets, and the development of quality certification for pellets.
One of the goals of our research group is to train and educate young engineers for the emerging bio-economy. Fahimeh Yazdan Panah, Ph.D., who is now WPAC’s director of research and technical development and is leading the research project on safe handling and storage of pellets, is one of our graduates.
What are some of the challenges in your work?
This is a complex subject and I’m a university person, not a plant operator — and English is my second language. So, I have to work hard to provide information that resonates with people working in the plants; information they can use and share with their colleagues.
When you work with nature, nothing is standardized. And pelletization creates a completely different product, one that behaves differently than raw biomass. We have to understand these characteristics so we can make pellets that are durable and safer when they are stored and transported.
It is getting more complex because there are more source materials from forests or farms. Pellets made with forest products once came only from sawmill waste such as sawdust and shavings. Now a broader range of materials are used, including bark, branches or low-quality trees. When you collect material from the forest floor, it has dirt and stones in it. So, the first critical stage is to inspect the material and remove contaminants like stones, dirt or bolts that cannot be handled by the grinding equipment. Advanced techniques like computer vision is a great tool for these applications.
Why is it important to manage fibre piles properly?
Biomass is biologically active. You cut it, it becomes more active – so, the greatest activities occur in smaller particles. Sawdust with high moisture content is more reactive because it has more surface to volume than wood chips, but they are all susceptible to mold and microbial attacks.
When fibre is stored in piles, self-heating and combustion can occur over time, sometimes for months. This can create gaps in the fibre, and it can collapse under any weight.
The risk of spontaneous ignition increases if the raw material or biofuel becomes moist, the stored volume is large, and the ambient temperature is high.
What are some of the key things you have learned?
First, keep fibre piles small – no more than seven metres high. If the pile is wide, the heat stays in and this can cause problems. If it is narrow, the heat can escape. And store the product for as short a time as possible – first in, first out.
Second, keep the material in the piles as dry as possible. If I had my way, piles would always be covered. But I know this is more expensive so part of our work is to find the sweet spot in terms of cost versus benefit.
Third, keep monitoring the temperature and carbon monoxide concentration to detect activity in the fuel bed, or self-heating. Use thermal imaging cameras to identify hot spots early.
Fourth, keep the raw material as clean as possible. Fibre piles should be located on dry, level ground, preferably on an asphalt or concrete surface.
Safety issues related to wood and grain dust is not new. Why has it taken until now for the pellet industry to embrace these concepts?
It is a complex area to study, and the pellet industry is young and changing all the time. It is a young industry and we are constantly learning. We talk a lot about technology, and a lot about safety. The wood pellet industry in Canada has embarked on extensive dust safety programs. We are following wood pellet example and applying valuable lessons learned to handling agricultural biomass.
Will you ever have all the answers?
No. This is a young industry, and we are constantly learning. In addition, the industry keeps being challenged with an ever increasing diverse feedstock and new technology. What we are working on is really a progress report, not a final report. Many of the challenges like cost competitiveness, product quality, and sustainability we are studying will be with us for many years to come.
Please note: Canada’s wood pellet industry has built a global reputation as a leading supplier of responsible, renewable clean energy. To achieve this, it depends on the kind of research Shahab and his colleagues are doing to improve safety and quality. WPAC welcomes the opportunity to collaborate with the Biomass and Bioenergy Research Group and the BC Forest Safety Council to make our industry safer and maintain our leadership in innovation. Please take the time to read our latest safety factsheet on Fibre Pile Management by clicking here.
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