Full Steam Ahead for Biomass Energy

THE GLOBAL drive for clean power demands relentless industrial innovation.

While raw wood stock has served as a highly reliable fuel source for centuries, it has some limitations as an energy source at industrial scale.

Low energy density and high moisture content have each proven to be drawbacks in using wood and white wood pellets as a viable fuel at scale in existing coal-fired energy infrastructure.

However, the steam explosion process, emerging at the forefront of the bioenergy industry, addresses these critical problems. 

And, in the process, it is helping to transform modern forestry and biofuel industries.

Its intense chemical reaction to high-pressure steam followed by rapid depressurization of a reactor chamber physically alters wood’s cellular structure, and enables the production of steam-treated black pellets.

Power Wood Energy is preparing to construct the Canada’s first two steam explosion process pellet plants in northern Alberta.

These advanced facilities will pioneer modern steam-treated black pellets in the country and reshape renewable energy in Canada.

Once part of northern Alberta's landscape, their steam explosion technology will produce steam-treated black pellets for global export markets, and support Canada's energy transition to low carbon systems.

This article looks a little closer at the steam explosion process for manufacturing steam-treated black pellets.

Steam explosion is an advanced hydrothermal treatment for turning raw wood chips into energy-dense black pellets. 

The process begins by feeding raw wood chips into a pressurized reactor chamber. High-pressure steam is then injected into the reactor to rapidly heat the organic material to approximately 240°C.

This pressurized state is maintained for a specific duration, dependent on the type of feedstock used, it softens the wood and raises its resident moisture past boiling point.

The chamber's pressure is then instantly released and this violent depressurization causes that moisture within the biomass to flash free as steam - rupturing the wood feedstock’s fibers as it leaves the chamber.

This sudden moisture loss causes the wood to shatter and into a dry granular powder that is coated with lignin - aloowing those granules to be compressed easily into black pellets.

Black pellets made from a steam explosion process are the most advanced solid biofuel in the renewable energy sector. Their qualities enable them to be used as a drop-in replacement for coal burned in the world's existing coal-fired power stations, without minimal modification to them. Their capacity to extend the lifespan of existing infrastructure, and their low carbon footprint, is part of their appeal to energy companies worldwide.

The decomposition of hemicellulose in a steam exposion process is a critical chemical change which results in steam-treated black pellets with a homogenous high energy value.

Hemicellulose draws and holds moisture inside the cellular walls of trees. It is one of a group of complex carbohydrates that, alongside cellulose and lignin, forms a supportive network within plant cell walls.

The intense high heat of the steam treatment process breaks down this hemicellulose into monomers. And this decomposition reduces the wood's natural ability to absorb water.

Coupled with the reallocation of lignin, the resulting steam-treated black pellets become highly water-resistant - enabling them to be transported and stored in open-air conditions.

Their high mechanical strength results in minimal degradation during storage outdoors - reducing the need for costly indoor, climate-controlled storage silos used to protect other types of biofuel pellets.      

Lignin is the complex polymer that gives trees and other plant life their rigid structural strength. 

During steam explosion, it undergoes chemical and physical changes that disrupt cell walls and make remaining cellular sugars easy to access.

A softening of the lignin at high temperature allows it to move within the feedstock during the steam explosion process. During the depressurization phase, lignin is redistributed to coat each granule emerging from the reactor chamber. 

Once on the outside of organic matter, it is available to act as a natural binder during pelletization. Once it has set rigid again it afford the black pellet a protective coating and high mechanical strength.

This reallocation of lignin is central to producing durable black pellets. 

The resulting steam-treated black pellets experience much reduced fragmentation and dust formation as a result of it - in turn reducing combustion risks in storage and furnace environments at energy infrastructure. 

Steam-treated black pellets provide significantly more usable energy than conventional wood pellets. 

Their dense structure resembles fossil coal much more closely than raw timber and traditional wood pellets.

As a result, steam-treated black pellets burn at substantially higher temperatures and produce less residual ash than other solid biofuels, while their high gigajoule energy density also makes transporting them more economic.

Most importantly, they serve as a direct, drop-in replacement for traditional thermal coal burned in the world’s existing coal-fired power generating stations, which need minimal material modifications to burn them.

Plant operators can blend these durable pellets directly with existing fossil fuels, for furnace burns. 

This flexibility of use allows power utilities and other heavy industries to significantly decrease their heavy carbon footprints, while retaining their existing energy infrastructure and meeting strict emissions targets.

Steam-treated black pellets' application in existing coal-fired power stations presents a cost-effective method for supporting the future of countries’ industrial heating sectors.

Power Wood Energy's two large black pellet plants in northern Alberta will quickly establish Canada as a lead producer of steam-treated black pellets.

Our extensive facilities will harness cutting-edge steam explosion technology to convert wildfire-damaged treestock, forest floor slash and residual forestry industry waste into a high-value premium biofuel for export.

This feedstock procurement has the potential to reduce greenhouse gas releases from decaying wood, by stemming methane emissions from stranded dead timber left by regional wildfires and beetle infestations.

Furthermore, it is anticiapted that our projects will create hundreds of well-paying ‘green jobs’ for rural Albertan communities, at a momenty when Canada’s forestry sector is faced with an uncertain future.

Each plant will demonstrate that industrial economic growth and environmental stewardship can combine to successfully strengthen Canada's economy, and supplement the blueprint for renewable energy in Canada. 

Global power grids require reliable, highly deliverable baseload energy sources. 

These foundational energy supplies are key to supporting less consistent sources of renewable energy, such as wind and solar power.

Steam-treated black pellets provide the consistent, on-demand baseload energy source needed for maintaining steady industrial electricity production.

When burned, they release carbon already cycling within the active modern biosphere. Unlike coal, oil and gas, they do not add ancient, deeply sequestered fossil carbons into our climate. 

As a result, international carbon accounting frameworks consider this fuel source to be carbon-neutral.

Furthermore, Power Wood Energy’s forest-based steam explosion plants will be fuelled by the same waste wood they use as feedstock, further reducing the environmental impact of producing black pellets.

They provide a pathway for nations to phase out dirty and unhealthy thermal coal from existing power plants, which have extended lifespans through the introduction of steam-treated black pellets.

The steam explosion process delivers a sustainable source of energy which enables grid stability as well as industrial decarbonization. 

ResearchGate Engineering Reports / Celignis Biomass Analysis. (2023, September 20). Steam explosion for biomass pre-treatment: Hemicellulose degradation and hydrophobic pelletization mechanics. ResearchGate Bioenergy Publications. https://www.researchgate.net/publication/374031507_Steam_explosion_for_biomass_pre-treatment 

Valmet Insights. (2017, October 24). A replacement for fossil coal in power plants: Black pellets and continuous BioTrac™ technology. Valmet Biofuels & Biomaterials Industry Reports. https://www.valmet.com/insights/articles/biofuels-and-biomaterials/black-pellets---a-replacement-for-fossil-coal-in-power-plants/

Valmet Bioenergy Division. (2022, November 18). From woody biomass or agricultural residues to black pellets: Technical and financial benefits. Valmet Bio-Coal Technology Reports. https://www.valmet.com/industries/bio/bio-coal/ 

Serrano, M. D. A., & Tranås, O. (2024, February 24). The CO2 reduction potential of using black pellets for energy production. Chemical Engineering Transactions. https://www.cetjournal.it/cet/24/109/036.pdf