Analysis of the routes for biomass processing towards sustainable development in the conceptual design step: Strategy based on the compendium of bioprocesses portfolio

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.

Sustainability analysis of orange peel biorefineries

Biorefineries are constantly evolving since new technological advances in enzyme and microbial processes are boosting research for producing new bio-based products. Nevertheless, the step towards real process implementation must overcome a series of stages based on process sustainability in the early design stages. Orange peel (OP) has been profiled as a potential raw material for producing different products. Few studies have estimated the sustainability of OP-based biorefineries considering the upstream influence on the final process performance. This research aims to perform the sustainability assessment of several OP valorization pathways based on experimental data applying the biorefinery concept. Steam distillation and polyphenolic compound extraction prior to saccharification and anaerobic digestion increase the process performance. A glucose concentration and biogas yield of 21.43 g/L (0.44 g/g OP, db) and 415 mL/g SV were obtained, respectively. An essential oil extraction yield of 1.17 g/100 g OP (db) with a d-limonene content of 91.62% was produced. Moreover, hesperidin, apigenin, and naringenin yields of 7.88 mg/g, 0.475 mg/g, and 0.675 mg/g were obtained. An OP-based biorefinery addressed to produce essential oil, polyphenolic compounds, and biogas with a processing 25 tons/day (wb) has a sustainability index of 66.88%, higher than the values obtained with lesser upstream stages. In conclusion, an integral OP upgrading leads to better enzymatic and anaerobic digestion performances, as well as, a high process sustainability.

Advances in the utilisation of carbon-neutral technologies for a sustainable tomorrow: A critical review and the path forward

Global industrialisation and overexploitation of fossil fuels significantly impact greenhouse gas emissions, resulting in global warming and other environmental problems. Hence, investigations on capturing, storing, and utilising atmospheric CO2 create novel technologies. Few microorganisms, microalgae, and macroalgae utilise atmospheric CO2 for their growth and reduce atmospheric CO2 levels. Activated carbon and biochar from biomasses also capture CO2. Nanomaterials such as metallic oxides, metal-organic frameworks, and MXenes illustrate outstanding adsorption characteristics, and convert CO2 to carbon-neutral fuels, creating a balance between CO2 production and elimination, thus zeroing the carbon footprint. The need for a paradigm shift from fossil fuels and promising technologies on renewable energies, carbon capture mechanisms, and carbon sequestration techniques that help reduce CO2 emissions for a better tomorrow are reviewed to achieve the world's sustainable development goals. The challenges and possible solutions with future perspectives are also discussed.