Sugarcane straw has become available in large quantities in the field due to transition from manual to mechanical harvesting. Straw can be used as fuel for cogeneration systems of sugarcane mills to increase surplus electricity for commercialization. However, the exploitation of straw potential is still limited due to some challenges related to its agricultural recovery and industrial processing. The retrofit (additional installation) of existing sugarcane mills to process straw is an alternative to reduce investment and to allow a gradual utilization of this biomass. In this work, techno-economic and environmental assessment of straw recovery through bale system to increase electricity export was assessed. Two scenarios with straw recovery and processing were defined to take advantage of an existing cogeneration system, considering its operation in the season and off-season periods. An increase of up to 57% on surplus electricity was achieved. Both scenarios resulted in economically feasible alternatives. However, results were very sensitive to the variations on electricity prices and straw costs. In terms of environmental benefits, the bioelectricity presented a great potential to mitigate greenhouse gas emissions compared with natural gas-based electricity. The higher electricity surplus also affects the carbon intensity of ethanol, which can lead to indirect gains when the Brazilian program for biofuels incentive is implemented.
Decarbonization programs are being proposed worldwide to reduce greenhouse gas (GHG) emissions from transportation fuels, using Life Cycle Assessment (LCA) models or tools. Although such models are broadly accepted, varying results are often observed. This study describes similarities and differences of key decarbonization programs and their GHG calculators and compares established LCA models for assessing 2G ethanol from lignocellulosic feedstock. The selected LCA models were GHGenius, GREET, JRC’s model, and VSB, which originated calculators for British Columbia’s Low Carbon Fuel Standard, California’s Low Carbon Fuel Standard, Renewable Energy Directive, and RenovaBio, respectively. We performed a harmonization of the selected models by inserting data of one model into other ones to illustrate the possibility of obtaining similar results after a few harmonization steps and to determine which parameters have higher contribution to closing the gap between default results. Differences among 2G ethanol from wheat straw were limited to 0.1 gCO2eq. MJ−1, and discrepancies in emissions decreased by 95% and 78% for corn stover and forest residues, respectively. Better understanding of structure, calculation procedures, parameters, and methodological assumptions among the LCA models is a first step towards an improved harmonization that will allow a globally accepted and exchangeable carbon credit system to be created.
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