Analysis of planetary boundaries and economic assessment for waste valorization in the context of a biorefinery: case study of the corn value chain in Sucre, Colombia.

The environmental impact generated by the excessive use of energy and petrochemical products has become a current problem addressed by considering the valorization of waste from a value chain (VC) under the biorefinery concept. At a global level, international organizations have proposed different tools to control the environmental impact of VC. Life cycle analysis (LCA) is the most representative tool. However, the LCA results do not allow defining a VC impact in a territory. The planetary boundaries (PB) approach contextualizes the results of an LCA with the maximum limits allowed for a defined activity. This research aimed to propose and apply a methodology integrating the LCA and PB approach (PBA-LCA). For this, waste valorization under the biorefinery concept was considered. The conceptual process analysis, economic optimization of biorefineries, LCA, and PB approach tools were combined and applied to a representative case study (the corn VC in Sucre, Colombia). First, the corn VC was analyzed to define different valorization alternatives for corn stover (CS). The valorization alternatives were simulated and evaluated using Aspen Plus V9.0., Aspen Economic Analyzer V9.0., and SimaPro V8.3. The LCA impact categories were used to define the PB. The economic optimization of CS biorefineries resulted in the technical and economic limitations of the cellulose valorization fraction due to high capital and operating costs. Moreover, the production of xylitol from CS presented the best economic results with a payback period of 2 years and an NPV of US$26.04 million. The LCA results demonstrated the advantages of using CS in agricultural activities. In the biorefinery, the split of CS scenarios for biorefineries had a higher environmental impact. The inclusion of the valorization stage increases to 5 and 15 times the impact on climate change and freshwater use boundaries, respectively. Finally, the PB results demonstrated the advantage of CS current use. On the other hand, the PB analysis determined the appropriate CS split with a biorefinery/mulching ratio of 70%/30% to be implemented in Sucre, Colombia. In conclusion, the results demonstrated the need to contextualize the results of an LCA with the PB in a given region to analyze the processes' environmental viability.