Sustainability assessment efficiency indicators

The authors stated that the sustainability assessment of biofuels shall be conducted through a multicriterial approach, and indicated a list of important issues to be investigated, such as the contribution to GHG emissions reduction land use and carbon stock changes induced by the growing demand for biofuels the efficiency of produced fertilizers the utilization of coproducts and residues the impact of biofuel production on water resources and soil, social, (e.g., food prices) and economic (i.e., production costs) issues. 

Pyrolysis of agricultural residue was experimentally assessed as a fuel production process for farm applications. A rotary kiln (3.4 m by 0.165 m I.D.) was used due to its ease of operation, commercial availability, low operating costs and ease of start-up and shutdown. Ground oat straw and corn stover at less than 10% moisture were pyrolysed in an indirectly fired continuous-flow rotary kiln located at the University of Sherbrooke. The principle products were char and gas, less than 1% of the feed mass was converted to tar. Calorific values were about 17 MJ/kg for the feed, 26 MJ/kg for the char, and 12 MJ/m3 for the gas. Calculations indicate that the thermal efficiency of a self-sustaining process would be around 65%. 

As mentioned previously the studied fermentation process to produce ethanol presents challenges in its process dynamics that exhibit oscillatory behavior, which affect process productivity and sustainabhity. To address these challenges, this section introduces a new sustainable process control framework that combines the biomimetic control strategy detailed earlier and the GREENSCOPE sustainabihty assessment tool. In this case study, the controlled variable is the concentration of product, Cp (see objective function defined earlier), and the dilution rate, Djn, is chosen as the manipulated variable. GREENSCOPE is employed to evaluate the sustainability performance of the system in open-loop and closed-loop operations. The obtained GITEENSCOPE indicator scores provide information on whether the implementation of the biomimetic controller for the fermentation process enables a more efficient and sustainable process operation. 

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