Energy Potential and Thermochemical Characterization of Sorghum Bicolor and Pennisetum Purpureum Compartments for Bioenergy Generation

Why It Matters

Sorghum’s superior fuel characteristics make it a viable, low‑ash bioenergy feedstock for Sub‑Saharan rural power, while elephant grass requires management to mitigate ash‑related combustion issues.

Key Takeaways

• Sorghum stems have the highest calorific value of all compartments
• Elephant grass leaves contain 9.27% ash, limiting direct burn
• Lignin content strongly boosts calorific value (r = 0.92)
• Ash content sharply reduces energy output (r = ‑0.95)

Pulse Analysis

The quest for renewable heat sources in the Southern Hemisphere has intensified as Sub‑Saharan nations seek to curb fossil‑fuel dependence and improve rural energy access. Agricultural residues are attractive because they are abundant, locally sourced, and can be integrated into existing farming systems. Sorghum bicolor and Pennisetum purpureum, two fast‑growing cereals, have emerged as candidates, prompting detailed thermochemical profiling to gauge their suitability for large‑scale bioenergy projects.

Laboratory analyses revealed that sorghum outperforms elephant grass on key fuel metrics. Across leaves, stems, and whole plants, sorghum’s calorific value consistently exceeded that of elephant grass, with stems delivering the peak energy density. Moreover, sorghum’s ash content stayed well below the 5% threshold that typically hampers combustion efficiency, whereas elephant grass leaves approached 9.3% ash, posing slagging and fouling risks. Statistical testing confirmed a robust positive link between lignin concentration and heating value, and an inverse relationship between ash and energy output, underscoring the chemical drivers of performance.

These findings carry strategic implications for policymakers and investors. Sorghum’s favorable profile positions it as a low‑maintenance, high‑yield biofuel that can be cultivated on marginal lands, supporting energy security without competing with food crops. For elephant grass, targeted agronomic practices—such as selective harvesting of stems and ash‑reduction treatments—could unlock its biomass potential. Scaling up sorghum‑based combustion systems could reduce rural reliance on diesel generators, lower greenhouse‑gas emissions, and stimulate agro‑industrial value chains across the region.