Sorghum Straw Pellets for Stabilizing Clean Transition To Renewable Energy

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The world is racing to replace fossil fuels with renewable energy to combat climate change. Countries like Australia, blessed with abundant sunshine and wind, face a critical challenge: solar and wind power are intermittent.

They don’t produce energy when the sun isn’t shining or the wind isn’t blowing. To keep the lights on 24/7, Australia needs reliable, on-demand energy sources, known as dispatchable renewables energy that can be stored and used whenever required.

A groundbreaking study from the University of Queensland, published in Energy Conversion and Management: X, highlights an unexpected hero in this transition: sorghum straw pellets.

This agricultural waste product, often burned or left to rot, could become a cornerstone of Australia’s renewable energy strategy.

Why Australia Needs Reliable Renewable Energy Sources

Australia has made impressive strides in renewable energy. As of 2025, renewables supply 32.4% of the National Electricity Market (NEM), with solar leading at 23.3%.

However, solar and wind energy alone can’t guarantee a stable grid. During cloudy days or calm nights, energy production drops, forcing reliance on fossil fuels like coal or gas as backups.

This gap highlights the urgent need for dispatchable renewables. Bioenergy—energy derived from organic materials like plants or agricultural waste is uniquely positioned to fill this role.

Unlike solar or wind, biomass like sorghum straw can be converted into pellets, stored indefinitely, and burned when needed.

Sorghum’s Role in Sustainable Energy Production

Sorghum, a hardy cereal crop, is Australia’s third-largest grain crop, grown across 671,000 hectares annually.

Primarily cultivated for livestock feed, it leaves behind 3.6 million tonnes of straw after harvest.

Straw refers to the dry stalks and leaves left in the field after the grain is harvested. Traditionally, this straw is either burned—releasing carbon dioxide—or plowed back into the soil.

However, the study proposes a transformative alternative: compressing this straw into dense, energy-rich pellets. This approach not only reduces waste but also taps into an underutilized resource.

Transforming Agricultural Waste into Energy-Dense Pellets

The process of pelleting sorghum straw is both practical and efficient. Raw straw has a low energy density (a measure of energy stored per unit volume) of 3.7 gigajoules per cubic meter (GJ/m³) and is bulky to transport.

By grinding the straw, adjusting its moisture content, and pressing it under high heat, researchers achieved pellets with 10.2 GJ/m³—nearly triple the energy density. These pellets burn cleaner than raw biomass and can be easily stored or transported.

For example, pelleted straw takes up 60% less space than loose straw, slashing transportation costs.

Quantifying Sorghum’s Contribution to Bioenergy Goals

The study estimates that converting all available sorghum straw into pellets could generate 165.8 petajoules (PJ) of energy annually—enough to meet 15.4% of Australia’s agricultural bioenergy needs.

A petajoule (PJ) is a unit of energy equivalent to one quadrillion joules, often used to measure large-scale energy production.To put this into perspective, Australia’s total agricultural bioenergy potential is estimated at 1,077.5 PJ per year.

Sorghum pellets alone could contribute 43.5% of the nation’s bioelectricity potential (380.9 PJ/year), outperforming established sources like sugarcane bagasse (26.3%) and wood (23.4%).

Sorghum Pellets Outperform Traditional Biofuel Sources

Bagasse refers to the fibrous residue left after sugarcane is crushed for juice, commonly burned for energy in sugar mills.

This is not just a theoretical exercise. In regions like Queensland and New South Wales, where sorghum is widely grown, farmers could supply pellet plants with straw, creating a decentralized energy network.

For instance, using 50% of available straw for pellets could generate 2.6 gigawatts (GW) of electricity annually, enough to power 700,000 homes.

With advanced processing techniques like torrefaction (a heat treatment at 200–300°C in low-oxygen conditions to remove moisture and volatile compounds), this could rise to 4.4 GW/year.

Addressing Challenges in Sorghum Pellet Production

However, challenges remain. Sorghum pellets have a higher ash content (3.4–7.9%) compared to wood pellets (0.7–2.0%). Ash refers to the inorganic residue left after combustion, which can clog boilers and reduce efficiency.

Minerals like potassium and sodium in sorghum straw melt at lower temperatures, forming sticky slag (a glass-like byproduct) that damages equipment. To address this, researchers recommend mixing pellets with additives like calcium or silicon, which raise ash melting points.

Pre-treatment methods, such as washing straw to remove surface minerals, could also help. Additionally, breeding sorghum varieties with deeper roots and higher silicon content may improve both soil health and pellet quality.

Another critical concern is soil sustainability. Removing too much straw from fields risks depleting organic matter—the carbon-rich material in soil that supports microbial life and nutrient retention—leading to erosion and reduced fertility.

Boosting Rural Economies Through Sorghum Pellet Initiatives

The study emphasizes leaving at least 30% of straw (1.8 million tonnes annually) on fields to protect soil. Crop rotation with nitrogen-fixing plants like legumes (plants that convert atmospheric nitrogen into soil nutrients) could further restore soil health.

These measures ensure that bioenergy production doesn’t come at the expense of agricultural productivity.Economically, sorghum pellets offer significant opportunities.

• Farmers could earn $50–$100 per tonne by selling straw to pellet plants, injecting $180–$360 million annually into rural economies.

Pellet production facilities in regions like Queensland’s Liverpool Plains or Western Australia’s Ord Valley could create over 2,000 jobs in processing, logistics, and engineering. Moreover, global demand for non-wood pellets is rising.

Europe, which imported 46 million tonnes of pellets in 2022, is shifting away from wood-based biofuels due to deforestation concerns. Australia, which exported 1.7 million tonnes of wood pellets in 2022, could leverage sorghum to tap into this growing market.

Protecting Ecosystems with Sorghum-Based Energy Solutions

The environmental benefits extend beyond clean energy. Sorghum cultivation could play a vital role in protecting Australia’s ecosystems.

For example, sugarcane farming in Great Barrier Reef catchments contributes to nitrogen runoff—excess nitrogen from fertilizers washing into waterways which harms coral reefs.

Planting sorghum during fallow periods (the time between crop cycles when fields are left unplanted) between sugarcane crops can absorb excess nitrogen, reducing runoff by 30–50%. Sorghum’s deep roots also stabilize soil, preventing erosion.

• Furthermore, sorghum shows promise in rehabilitating polluted sites.
• Australia has over 80,000 abandoned mines contaminated with heavy metals like cadmium and zinc.

Special hyperaccumulator varieties of sorghum (plants that absorb unusually high levels of toxins) can absorb these metals from the soil. After harvest, the metal-laden biomass can be safely burned in controlled facilities, preventing toxins from leaching into waterways.

Government Policies to Accelerate Sorghum Pellet Adoption

Despite these advantages, scaling sorghum pellet production requires coordinated effort. The study recommends three key steps: government incentives, better data collection, and industry collaboration.

For instance, subsidies under the Renewable Energy Target (RET)—a policy mechanism to accelerate renewable energy adoption—could accelerate pellet plant construction.

Satellite imagery and AI could map regional straw yields, optimizing supply chains. Partnerships with coal plants, like Queensland’s Ensham Coal Mine—which already co-fires (mixes biomass with coal) biomass with coal—could provide immediate markets for pellets.

Scaling Sorghum Pellet Technology for National Impact

Looking ahead, education and innovation will be critical. Farmers need training in sustainable straw management to balance bioenergy production with soil health.

Researchers must continue developing low-ash sorghum hybrids and efficient pelleting technologies. Policymakers should prioritize long-term sustainability over short-term gains, ensuring bioenergy growth aligns with environmental goals.

Conclusion

In conclusion, sorghum straw pellets represent a transformative opportunity for Australia. By converting agricultural waste into a reliable energy source, the nation can reduce fossil fuel dependence, cut greenhouse gas emissions, and revitalize rural communities. While challenges like ash management and supply chain logistics persist, the study outlines a clear, actionable path forward.

As climate change intensifies, solutions like sorghum pellets remind us that innovation often lies in unexpected places—like the straw left behind in a farmer’s field. With strategic investment and collaboration, Australia could lead the world in building a sustainable, decentralized energy future.