Technoeconomic analysis and life cycle assessment of sugarcane biorefineries considering different time horizons

Ethanol production from cellulosic feedstocks, known as 2^nd generation ethanol (E2G) process, presents a great potential for reducing both ethanol production cost and greenhouse gases (GHG) emissions since agricultural residues can be used as feedstock.

This study aimed at the quantification of the economic and environmental impacts considering current and future scenarios of sugarcane biorefineries, taking into account not only improvements on industrial process but also on biomass production. The used assumptions were supported by companies in Brazil and abroad related to cellulosic ethanol production chain. For instance, increased efficiencies and lower residence times for pretreatment, enzymatic hydrolysis and fermentation as well as higher sugarcane yields and introduction of energy cane (a high fiber variety of cane) were considered.

As a result of the economic assessment of these scenarios, ethanol production cost was estimated for different time horizons. In the short term, E2G presents a higher cost compared to the 1^st generation ethanol (E1G); however, in the long term, E2G becomes quite competitive, presenting considerably lower production cost.

In addition, Life Cycle Assessment (LCA) showed that both E1G and E2G can reduce GHG emissions by more than 80% when compared to gasoline. Considering that sugarcane biorefinery products, ethanol and electricity, are replacing gasoline and the average Brazilian electricity grid, respectively, the annual mitigation would be between 11 and 35 metric tons of greenhouse gases (CO₂eq) per planted hectare. These results are aligned with the commitment of the Brazilian Government in its Intended Nationally Determined Contribution (INDC) to COP 21.