Sugar-to-What? An Environmental Merit Order Curve for Biobased Chemicals and Plastics.

The chemical industry aims to reduce its greenhouse gas emissions (GHGs) by adopting biomass as a renewable carbon feedstock. However, biomass is a limited resource. Thus, biomass should preferentially be used in processes that most reduce GHG emissions. However, a lack of harmonization in current life cycle assessment (LCA) literature makes the identification of efficient processes difficult. In this study, 46 fermentation processes from literature are harmonized and analyzed on the basis of their GHG reduction compared with fossil benchmarks. The GHG reduction per amount of sugar used is defined as Sugar-to-X efficiency and used as a performance metric in the following. The analyzed processes span a wide range of Sugar-to-X efficiencies from -3.3 to 6.7 kg of CO2 equiv per kg of sugar input. Diverting sugar from bioethanol production for fuels to the fermentation and bioconversion processes with the highest Sugar-to-X efficiency could reduce the chemical industry's GHG emissions by an additional 130 MT of CO2 equiv without requiring any more biobased feedstocks.

Sustainable Conversion of Carbon Dioxide: An Integrated Review of Catalysis and Life Cycle Assessment.

CO2 conversion covers a wide range of possible application areas from fuels to bulk and commodity chemicals and even to specialty products with biological activity such as pharmaceuticals. In the present review, we discuss selected examples in these areas in a combined analysis of the state-of-the-art of synthetic methodologies and processes with their life cycle assessment. Thereby, we attempted to assess the potential to reduce the environmental footprint in these application fields relative to the current petrochemical value chain. This analysis and discussion differs significantly from a viewpoint on CO2 utilization as a measure for global CO2 mitigation. Whereas the latter focuses on reducing the end-of-pipe problem "CO2 emissions" from todays' industries, the approach taken here tries to identify opportunities by exploiting a novel feedstock that avoids the utilization of fossil resource in transition toward more sustainable future production. Thus, the motivation to develop CO2-based chemistry does not depend primarily on the absolute amount of CO2 emissions that can be remediated by a single technology. Rather, CO2-based chemistry is stimulated by the significance of the relative improvement in carbon balance and other critical factors defining the environmental impact of chemical production in all relevant sectors in accord with the principles of green chemistry.

Environmental potential of carbon dioxide utilization in the polyurethane supply chain.

Potential environmental benefits have been identified for the utilization of carbon dioxide (CO2) as a feedstock for polyurethanes (PUR). CO2 can be utilized in the PUR supply chain in a wide variety of ways ranging from direct CO2 utilization for polyols as a PUR precursor, to indirect CO2 utilization for basic chemicals in the PUR supply chain. In this paper, we present a systematic exploration and environmental evaluation of all direct and indirect CO2 utilization options for flexible and rigid PUR foams. The analysis is based on an LCA-based PUR supply chain optimization model using linear programming to identify PUR production with minimal environmental impacts. The direct utilization of CO2 for polyols allows for large specific impact reductions of up to 4 kg CO2-eq. and 2 kg oil-eq. per kg CO2 utilized, but the amounts of CO2 that can be utilized are limited to 0.30 kg CO2 per kg PUR. The amount of CO2 utilized can be increased to up to 1.7 kg CO2 per kg PUR by indirect CO2 utilization in the PUR supply chain. Indirect CO2 utilization requires hydrogen (H2). The environmental impacts of H2 production strongly affect the impact of indirect CO2 utilization in PUR. To achieve optimal environmental performance under the current fossil-based H2 generation, PUR production can only utilize much less CO2 than theoretically possible. Thus, utilizing as much CO2 in the PUR supply chain as possible is not always environmentally optimal. Clean H2 production is required to exploit the full CO2 utilization potential for environmental impact reduction in PUR production.