Steam Explosion Black Pellets in the Circular Economy

EACH year, millions of tons of low-quality agricultural residues and forestry waste are left to rot in situ or are incinerated openly – releasing uncaptured carbon directly into earth’s atmosphere.

Crop stalks, wildfire-damaged deadwood, forest thinning, decaying foliage and sawdust emit billions of metric tons of carbon gases between them every year.

Scientists at the Australian National University determined five years ago that the annual contribution made by forest deadwood alone to the global carbon cycle was 10.9 gigatons. [1]

Then, 14 months later, a study at Scotland’s University of Stirling found decaying plant litter (including agricultural residues) releases 60 gigatons of carbon into the atmosphere every year – six times more than all human emissions. [2]

Combined, these sources of spent organic matter contribute more than 10 percent of the total amount of carbon in earth’s atmosphere at any given time.

But still the world struggles to find scalable ways to repurpose this biological waste through innovative adoptions of modern circular economies.

Transforming nature’s underutilized forestry and agricultural waste streams into high-grade energy products eliminates climate-damaging decomposition emissions and provides clean, reliable fuel sources to power heavy industry.

It is an innovation of steam explosion technology – a transformative thermochemical process for upgrading raw organic materials into sustainable products – that is allowing industry to now do this at scale.

In this article we more closely at how steam explosion technology facilitates circular economy, and creates steam-treated black pellets to support decarbonization targets for reducing the effects of climate change.  

Steam-treated black pellets represent a pivotal step forward in sustainable fuel technology.

The steam explosion process converts low-value raw biomass materials, such as agricultural residue and forestry waste that would otherwise decompose or be incinerated, into high-value, energy-dense, top-tier biofuel products.

The resulting black pellets, unlike conventional white pellets, have undergone a hydrothermal treatment using superheated steam and rapid depressurization to re-structure the biomass at cellular level.

This sustainable approach to manufacturing pure biofuel pellets generates a circular economy by repurposing waste streams into reliable fossil fuel alternatives that are ready to use in modern low-carbon energy systems. [3]

Whether consumed in coal-fired infrastructure or specialized biomass energy plants, black pellets reduce both facility carbon footprints and upstream decomposition emissions to tackle climate change. 

Northern Alberta is littered with forest waste that can be used to manufacture steam exploded black pellet biocoal, after wildfires left vast woodlands strewn with dead wood stock. This natural resource can be used alongside agricultural waste, including empty fruit bunches shown in the cover image of this article, to contribute to the wider circular economy and further reduce carbon emissions. 

The more conventional method of manufacturing biofuel pellets draws on significant quantities of energy for both drying raw biomass feedstock and white pellet end-product.

While processes to make both white pellets and torrefied pellets typically yield products with lower energy density and poorer moisture resistance than steam-treated black pellets.

Inherently, by subjecting forestry and agricultural waste to high heat steam there is no need to dry vast quantities of timber before it is processed. This process inside a reactor chamber causes cellulosic materials to hydrolize.

Sudden depressurization in the steam explosion process then breaks down the cellular structure of biomass, degrading a proportion of its lower-calorie hemicellulose while softening and freeing higher-energy natural lignin to disperse throughout granular fibres. [4]

This flashing process also removes alkali metals which are retained in white wood biomass pellets and often concentrated in dry torrefaction pellets.

After pelletization, the resulting product is a highly water-resistant, steam-treated black pellet with enhanced bulk density and calorific value for economic transportation and storage.  

As global demand for sustainable fuels expands, pioneering industrial engineering and biofuel companies have focusedd on waste-to-energy solutions for meeting power generation and industrial heating needs.

Power Wood Energy will utlilize Valmet's Biotrac continuous feed technology as one of very few renewable energy companies in Canada to adopt steam explosion as a process for manufacturing black pellets. 

Both of our modern black pellet production plants to be built in Mackenzie County, northern Alberta, will produce steam-treated black pellets from Valmet's cutting edge hydrothermal process.

Additionally, Power Wood Energy carries out extensive research and development through steam explosion at its partner Wilhelmina commercial test plant in Kuantan, Pahang, Malaysia. There it researches agricultural residues including empty fruit bunches and oil palm fronds as well as fire-damaged aspen deadwood as feedstocks for producing its best-in-class black pellets.

Along its entire value chain it also works with forward-thinking engineering companies, including WB Melback and KTC Industrial Engineering as well as Valmet, to develop a near-net-zero steam explosion process for converting regional forestry slash and crop residues into economically upgraded, standardized black pellet products for export.      

Steam explosion black pellets are a pure biofuel with reduced alkali metal and ash contents as well as higher heating values, greater water resistance and more bulk density than  solid biofuels produced by more conventional biofuel pellet manufacturing processes. 

Heavy industry and manufacturing plants can reduce their carbon footprints to meet sustainability targets by adopting black pellets as their primary source of heat and energy.

Transitioning away from fossil coal to using steam-exploded black pellets made from forestry residues and agricultural waste offers them an immediate, scalable solution for decarbonizing their operations.

Steam-treated black pellets made from waste biomass share similar handling, milling and combustion characteristics with coal. 

Facilities can co-fire or completely replace coal without requiring costly infrastructure overhauls, or incurring the similarly expensive downtime to implement them. [5]

By integrating high-grade black pellets into their power mix, factories and power plants can significantly diminish greenhouse gas emissions, support zero-waste circular supply chains and foster long-term environmental sustainability. [6]

This is why biomass energy products like steam-treated black pellets are increasingly being seen as an obvious step change to be undertaken by energy companies seekign to commit to the global energy transition and remain competitive in energy markets. 

[1] SciTechDaily (2021, September 20) Deadwood Releasing 10.9 Gigatons of Carbon Every Year – More Than All Fossil Fuel Emissions Combined. Australian National University. https://scitechdaily.com/deadwood-releasing-10-9-gigatons-of-carbon-every-year-more-than-all-fossil-fuel-emissions-combined/

[2] Nature, Ecology & Evolution (2023, January 9) Climate key to determining dead plant decomposition and predicting carbon emissions. University of Stirling.  https://www.nature.com/articles/s41559-022-01948-z  

[3] Circle Economy Hub. (2025, May 9). From coal to wood pellets: Utilizing residual waste and steam explosion technology for industrial bioenergy. Circle Economy Knowledge Hub Reports. https://www.circle-economy.com/knowledge-hub/article/8453

[4] 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/

[5] ScienceDirect. (2009, April) Julia Hansson, Göran Berndes, Filip Johnsson, Jan Kjärstad. Co-firing biomass with coal for electricity generation—An assessment of the potential in EU27. Chalmers University.  https://www.sciencedirect.com/science/article/abs/pii/S0301421508007301

[6] 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