Circular economy models of sugarcane biorefinery towards carbon neutrality and environmental sustainability

Abstract

Sugarcane biorefineries convert sugarcane waste into bioproducts, requiring assessment for environmentally viable processing. This study compared the life cycle environmental impacts, environmental damage costs, and circularity of sugarcane biorefinery scenarios: a base case with pre-harvest cane trash burning and sugar and ethanol production; a modified one with improved energy efficiency; and three bioproduct scenarios producing bagasse-based biobutanol or biochar for bioenergy scenario, lactic or acetic acid for biochemicals, and cane trash-derived cellulose nanofibers or soil conditioner for biomaterials. Bioproduct scenarios assumed green cane harvesting. Life cycle assessment followed a cradle-to-gate scope, with a functional unit of 1 tonne of cane processed (t_c). Damage to human health ranged from 7.72 × 10⁻⁴ to 2.85 × 10⁻³ disability-adjusted life years/t_c; ecosystem from 4.85 × 10⁻⁶ to 9.15 × 10⁻⁶ species.year/t_c; resource scarcity from 10 to 60 United States dollar 2013/t_c; total damage costs from 2,100 to 5,410 Thai Baht/t_c, and circularity from 0.44 to 0.52. Bioproduct scenarios, except cellulose nanofibers, had lower environmental damage costs than the base case. Biorefinery circularity aligned closely with the highest-value product in each scenario. Biochemical (Lactic acid) was the best overall, with the lowest environmental damage cost and resource scarcity damage, relatively low human health and ecosystem damage, and a high circularity score of 0.5. Biomaterial (Cellulose nanofibers) was the worst due to its highest damage cost from the highest fossil resource scarcity, accounting for over 95 % of resources scarcity damage in all scenarios, and high-water consumption, despite minimum human health damage from the lowest fine particulate matter formation, leading contributor to human health damage mainly from cane burning and biomass electricity, and a high circularity of 0.52. The modified base case was slightly better than the base case across all metrics. Bioproduct scenarios increased circularity; however, higher circularity did not always correlate better environmental performance.