UBC researchers are looking beyond forest material to crop straws and chaff to build renewable power products
That field of wheat straw could someday be pressed into pellets.
Producing biomass pellets from crop residue is the focus of a new project by researchers at the University of British Columbia.
Biomass and Bioenergy Research Group (BBRG), at the Chemical and Biological Engineering Department of the University of British Columbia is leading a four-year study, which received $2.4 million from Agriculture and Agri-Food Canada’s AgriScience Program.
The UBC biomass and bioenergy research group have also been studying woody biomass and working with forest residues, such as sawdust.
Dr. Mahmood Ebadian, who leads the development of cost-efficient biomass pellets supply chains in this study, said their goal is to produce pellets with consistent quality from under-utilized and low-quality agricultural biomass resources in Canada.
“We have been looking into the quality and the costs of agriculture, like wheat straw, for example, to use it for heat or power generation. We look at how we can improve the quality, how we can reduce the cost of transportation, harvesting and so on,” he said.
In fact, wheat straw is a good residue for making biomass pellets because its lignin content is similar to hardwoods. It also has one of the highest cellulose contents of all the agricultural fibres.
The amount of cereal and legume crop residue produced in the world annually is in the billions of tons.
A 2007 study by the United States Department of Energy estimated one billion tons of woody and agriculture biomass, as well as municipality solid waste, is produced annually in the United States. Attempts are underway to use the biomass for heat and power generation or as a biofuel.
While there have been no formal studies done in Canada, Ebadian said about 120 million tons of biomass is produced annually including forest, agriculture and municipal solid waste.
Most farmers use lignocellulosic residues, such as wheat straw as a fertilizer source or for animal bedding and feed. However in a few places it is burned as a means to control insects and weeds, reducing the heavy residue load and returning nutrients to the soil.
He said burning crop residue may be easy, but has no economic value.
However, because farmland is so widespread, developing a distribution system for the biomass presents a logistics challenge.
“How can we develop a supply chain network that we can collect all of this biomass from, let’s say a 200-kilometre radius from 100 farms and bring them into a central location and then improve the quality of that biomass so we can sell it for domestic markets, even for international markets?” he said.
Canada exports about three million tons of wood pellets to Europe and Japan, which is a marketing model researchers are using with agricultural biomass. Produced pellets will be integrated into the existing wood pellet and grain supply chains to minimize logistics costs.
“Our goal is to use the same approach for woody biomass and agriculture biomass, but improving the quality and reducing the cost of logistics, so we can make those underutilized biomass in Alberta, Saskatchewan and Manitoba, so farmers can have a new source of income,” Ebadian said.
Farmers can sell the crop residue to an end user, or they might invest in the necessary machinery and make pellets themselves, he said.
A custom service might also involve bailing the residue and producing pellets, which are then sold to an end user.
Capital investments could include collecting biomass independently using private equipment or hiring a custom harvest company. Another option is to buy a pellet machine.
Ebadian said capital investment in biomass pellet supply chains can be reduced by using the existing infrastructure in the established grain supply chains in Canada
“Pellets have similar physical properties as grain, so you can use the same grain cars, trucks and bins for storage. Farmers do not need to invest in new infrastructure. We are trying to piggyback on the existing grain supply chain.
“So there are different business models depending on the cost, amount of biomass available in the region, location and cost of energy. We are trying to figure out what are those sweet spots for producing pellets from wheat straw, for example, and then find a market for it.”
Woody biomass is considered higher quality with a lower natural ash content compared to agriculture biomass, which uses fertilizer to grow grain.
“Some of that nitrogen potassium or sulphur ends up in the residue and that’s why the quality is lower,” he said.
However, it’s not that significant where heating of woody biomass is about 18-19 gigajoules per dry ton compared to about 17 gigajoules per ton for wheat straw dry pellets.
“It’s definitely not a big difference, but ash content could be a challenge. So your boiler technology should be customized to be used for agriculture biomass because you have to remove the ash more frequently than (for) woody biomass,” he said.
Considering environmental and economic problems, Ebadian said making biomass pellets from crop residue is a good clean energy source, and it adds value to farmers’ crops and uses byproducts that would otherwise be wasted.
“These types of regulations like carbon tax and clean fuel standard — if you use wheat straw that has a low greenhouse gas emission profile — there might be a better business opportunity for using agriculture biomass for energy application,” he said.
“And that’s part of our research to show that if you have a carbon tax at, let’s say $30 per ton of CO2, does it make sense to use wheat straw as a source of heat and power for farmers? So that would be the type of question we are trying to answer.”