The increasing amount of plastic waste generation has become an important concern for the chemical industry and government agencies due to high disposal and environmental leakage rates. Chemical recycling is a promising technology due to the potential reduction of pollutant emissions and the establishment of a circular economy through the production of monomers and fuels. However, there is scarce information on industrial scale processes of this technology and their energetic, economic, and environmental performance. Therefore, the present process modeling study presents a novel multiproduct pyrolysis-based refinery for the conversion of 500 tonnes/day of waste high-density polyethylene (HDPE). The products obtained from the modeled refinery were chemical grade ethylene and propylene, an aromatics mixture, and low-and high-molecular weight hydrocarbon mixtures (MWHCs). Part 1 of this study focuses on the energetic and economic evaluation of the refinery and the potential effects of heat integration. The energy efficiency was 68% and 73% for the base case and the heat integrated refinery, respectively. The net present values (NPVs) were 367 and 383 million U.S. dollars (MM USD), for the base case and the heat integrated process, respectively. These results suggest energetic and economic sustainability of the design and its promising application on an industrial scale.

Thermal degradation of plastics is a promising technology for addressing the waste management issues of landfill disposal, while obtaining useful products. Primary thermal degradation of polymers usually yields a large quantity of high molecular weight compounds with a limited applicability, making necessary a secondary degradation to improve the product quality. In this study, pyrolysis vapors from waste high density polyethylene (HDPE) were subjected to secondary degradation by varying the temperature and vapor residence time (VRT) in the reaction zone of a new two-stage micropyrolysis reactor (TSMR) attached to a commercial micropyrolysis unit. Temperature and VRT variations showed a strong effect on the product distribution, with low temperature (625 °C) and short VRT (1.4 s) producing a wide range of gases and liquid products and with high temperature (675 °C) and long VRT (5.6 s) producing mostly hydrocarbon gases and mono- and polyaromatics. The results showed a good agreement with previously reported product distributions for larger-scale pyrolysis reactors and were well explained by known degradation mechanisms.

Life-cycle assessment (LCA) has been applied to many biofuel and bioenergy systems to determine potential environmental impacts, but the conclusions have varied. Different methodologies and processes for conducting LCA of biofuels make the results difficult to compare, in-turn making it difficult to make the best possible and informed decision. Of particular importance are the wide variability in country-specific conditions, modeling assumptions, data quality, chosen impact categories and indicators, scale of production, system boundaries, and co-product allocation. This study has a double purpose: conducting a critical evaluation comparing environmental LCA of biofuels from several conversion pathways and in several countries in the Pan American region using both qualitative and quantitative analyses, and making recommendations for harmonization with respect to biofuel LCA study features, such as study assumptions, inventory data, impact indicators, and reporting practices. The environmental management implications are discussed within the context of different national and international regulatory environments using a case study. The results from this study highlight LCA methodology choices that cause high variability in results and limit comparability among different studies, even among the same biofuel pathway, and recommendations are provided for improvement.

The growing generation of plastic waste (PW) is placing severe burdens in the terrestrial and marine environments due to its inappropriate management at end of life. Governments are aware of this situation and have proposed production bans or initiatives to minimize the amount of PW that is landfilled and encourage recycling or energy recovery. Circular economy is a strategy that reuses PW to produce new polymers while avoiding its disposal and displacing the use of virgin materials. This study reports on a refinery design that employs fast pyrolysis of waste high-density polyethylene and downstream separations to obtain monomers, aromatics, and hydrocarbon fuels. This study focuses on a life cycle carbon footprint analysis (CFA) and the effects of regional electricity grids on cradle-to-gate greenhouse gas emissions using process simulation for life cycle assessment inputs. The effects of heat integration on greenhouse gas (GHG) emissions were investigated in scenarios, as well as the investigation of parameter sensitivity and uncertainty. The CFA results show that the GHG emissions of ethylene, propylene, and aromatics mixture (1.08, 1.10, and 1.16 kg CO2 equiv/kg, respectively) are equal to or less than those of fossil products when heat integration is included assuming U.S. average electricity grid. The evaluation of regional electricity grids on GHG emissions for all products was conducted for 50 states in the U.S.

The present work presents a first characterization of the oil from the Moringa (Moringa oleifera) kernel as a potential candidate for biodiesel production. Moringa is an indigenous tree in the Yucatan Peninsula in Mexico, where there is a nascent biodiesel industry. Several extraction methods are compared in terms of the extraction yields, including solvent extraction (n-hexane and ethanol), and supercritical extraction (Sc-CO 2 ). The results are also compared against previously reported data. For supercritical extraction pressures of 200 to 400 bar and temperatures of 40˚C and 60˚C were tested. Gas Chromatography analysis reveals that the main fatty acids in Moringa oil are oleic acid (69%), palmitic acid (10%) and stearic acid (8%).