By applying a quantitative universal exergy method, the team provides a science-based tool for selecting combustion technologies that balance environmental performance with practical feasibility. These findings offer actionable guidance for policymakers and energy planners aiming to reduce gaseous emissions from agricultural and forestry waste.
Biomass combustion remains the most mature and widely used thermochemical conversion route for renewable energy, yet most environmental assessments have focused narrowly on greenhouse gas emissions using life cycle analysis. What has been missing is a systematic, side‑by‑side comparison of how different combustion methods—ranging from uncontrolled open burning to advanced boiler systems—affect the overall environmental burden. Exergy, a thermodynamic measure that accounts for both energy quantity and quality, has proven effective for unifying the assessment of multiple pollutants, but it had not previously been applied to compare distinct biomass combustion technologies.
A study (DOI: 10.48130/een-0025-0019) published in Energy & Environment Nexus on 28 January 2026 by Yaning Zhang’s team, Harbin Institute of Technology, analyzes 31 literature samples across four combustion categories—open burning, kW‑scale grate furnaces, MW‑scale grate furnaces, and CFBB—and found that CFBB consistently delivers the lowest environmental impact, while open burning is the most harmful.
The researchers employed a quantitative universal exergy method to assess PEI of four biomass combustion methods: open burning, kW‑scale grate, MW‑scale grate, and CFBB. For each of the 31 collected literature samples, emission factors for CO, CO₂, and NOx were calculated from reported mass or volume concentrations, using theoretical flue gas volumes and excess air coefficients. These emission factors were then converted into molar flows and multiplied by the standard chemical exergy of each pollutant—274.71 kJ/mol for CO, 19.48 kJ/mol for CO₂, and 88.90 kJ/mol for NOx—to yield the PEI in kJ per kg of fuel. To isolate the effect of combustion technology from fuel composition, the team further normalized the results to PEI per kilogram of carbon (for CO and CO₂) and per kilogram of nitrogen (for NOx). The analysis revealed that open burning produced the highest overall PEI (712–1,538 kJ/kg), driven by extremely high PEI values for CO (966–1,550 kJ/kg‑C), due to poor air‑fuel contact and incomplete combustion. In contrast, CFBB systems consistently delivered the lowest total PEI (450–841 kJ/kg) across a range of biomass types, with notably low CO and NOx emissions when denitrification equipment and staged air distribution were employed. MW‑scale grates showed intermediate performance, but the reciprocating grate led to a high PEI (516 kJ/kg) when burning high‑nitrogen biomass (2.183% N) because elevated furnace temperatures increased NOx formation. kW‑scale grates could achieve low PEI, but required excessive excess air ratios (1.6–5), reducing their cost‑effectiveness. Overall, the exergy‑based normalization method successfully ranked combustion technologies by environmental performance while controlling for fuel variability.
The authors conclude that CFBB is the superior technology for minimizing environmental impact from biomass combustion, while inclined reciprocating grates offer a viable alternative only for low‑nitrogen fuels. Open burning should be phased out where possible. Future work will expand the assessment to include particulates and heavy metals, and integrate techno‑economic analysis to identify optimal pathways for specific deployment scenarios.
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References
DOI
10.48130/een-0025-0019
Original Source URL
https://doi.org/10.48130/een-0025-0019
Funding Information
Financial support was provided by Heilongjiang Provincial Key R&D Program (Grant No. 2023ZX02C05), and Heilongjiang Provincial Key R&D Program 'Unveiling the Leader' Project (Grant No. 2023ZXJ02C04).
About Energy & Environment Nexus
Energy & Environment Nexus is a multidisciplinary journal for communicating advances in the science, technology and engineering of energy, environment and their Nexus.