Glycerol conversion into chemicals and fuel additives is pursued to valorise a burgeoning by-product in the bioenergy sector. To this aim, heterogeneous catalysts have been developed that enable, in many cases, efficient and green transformations. Still, the evaluation of the environmental and economic footprint that would be associated with their large-scale application has often been neglected, limiting their commercial attractiveness. Furthermore, the impact of integrating different glycerol upgrading routes within a biorefinery, which is highly instrumental to determine the effective sustainability and profitability of biodiesel production from vegetable oils, has not been assessed. Here, the manufacture of the most relevant chemical derivatives of glycerol is considered, i.e., lactic acid, acrylic acid, glycerol carbonate, propanediols, epichlorohydrin and allyl alcohol. State-of-the-art catalysts for each upgrading route are briefly reviewed. Based on their performances, processes are rigorously modelled and relevant indicators, the global warming potential, the cumulative energy demand and the operating costs, quantified by life-cycle analysis. Glycerol-based processes are generally found more attractive than the conventional technologies nowadays applied for the production of the same chemicals, among which the paths to lactic acid and glycerol carbonate are particularly promising. In addition, the process variables mostly contributing to the environmental and cost metrics are identified. Accordingly, future studies should target further optimisation mainly in relation to selectivity, solvent volatility, reactants ratio and catalyst stability. Finally, the processes are integrated simulating a prospective glycerol biorefinery and the advantages deriving from the exchange of heat between the different routes quantified. If the glycerol feed is split equally among all routes the CO₂ emissions and energy requirements are decreased by 15 and 32%, respectively, and the profit is increased by 5% as compared to the sum of the individual glycerol-based processes. In order to minimise the ecological impact of the biorefinery, glycerol should be rather divided in an 80 : 20 mass ratio among 1,2-propanediol and glycerol carbonate production, which are expected to have a significant market size. The innovative approach outlined in this work holds potential to guide both fundamental chemical research and process design in the development of CO₂ and other bio-refineries.

Recently, lactic acid has emerged as one of the most relevant platform molecules for the preparation of bio-chemicals. Due to the limited productivity of sugar fermentation, the dominant industrial technology practiced for its manufacture, new chemocatalytic processes are being developed in order to meet the expected demand for this intermediate. The Lewis-acid catalysed isomerisation of dihydroxyacetone has attracted particular interest. If the reaction is performed in water, lactic acid is attained directly, while if alcohol is used as the solvent, the desired product can be obtained upon subsequent hydrolysis of the alkyl lactates formed. Herein, we (i) demonstrate tin-containing MFI zeolites prepared by scalable methods as highly active, selective and recyclable catalysts able to operate in concentrated dihydroxyacetone aqueous and methanolic solutions, and (ii) reveal by life cycle analysis that a process comprising the enzymatic production of dihydroxyacetone from crude glycerol and its chemocatalytic isomerisation in methanol is advantageous for the production of lactic acid compared to glucose fermentation in terms of both sustainability and operating costs. In particular, we demonstrate that the reduced energy requirements and CO₂ emissions of the cascade process originate from the valorisation of a waste feedstock and from the high performance and recyclability of the zeolite catalyst and that the economic advantage is strongly determined by the comparably low market price of glycerol. It is also shown that the bio-/chemocatalytic route remains ecologically and economically more attractive even if the purity of glycerol is as low as 38%.

The chemical industry is increasing its efforts to reduce the environmental burdens of chemical production. One focus is to implement energy-efficient processes and green technologies early in the process design to maximize environmental efficiency and to reduce costs. However, as data on many chemical products are scarce, many sustainability studies are hampered by the lack of information on production processes, and chemicals are often neglected or only crudely estimated. Models that estimate production data and environmental burdens can be vital tools to aid sustainability efforts. In addition, they are useful for the environmental assessment of chemicals without access to production data, i.e. in supply-chain management or for the assessment of products using chemicals as materials. Using mass and energy flow data on the petrochemical production of 338 chemicals, we developed models that can estimate key production parameters directly from the molecular structure. The data sources were mostly production data provided by industrial partners, extended by data from the ecoinvent database. The predicted parameters were the Cumulative Energy Demand (CED), the Global Warming Potential (GWP), the Eco-indicator 99 score, a Life Cycle Assessment (LCA) method, and the electricity and heat use over the production cycle. Model outputs include a measure of the prediction uncertainty. The median relative errors of the models were between 10% and 30%, within acceptable ranges for estimations. The modelled parameters offer a thorough insight into the environmental performance of a production process and the model estimates can be of great service in process design, supply-chain management and environmental assessments of chemical products in the early planning and design stages where production data are not available.

Over the past few years, bio-succinic acid from renewable resources has gained increasing attention as a potential bio-derived platform chemical for the detergent/surfactant, ion chelator, food and pharmaceutical markets. Until now, much research was undertaken to lower the production costs of bio-succinic acid, however a multicriteria sustainability evaluation of established and upcoming production processes from a technical perspective is still lacking in the scientific literature. In this study, we combine metabolic engineering with the most mature technologies for the production of bio-succinic acid from sugar beet and lignocellulosic residues. Downstream technologies such as reactive extraction, electrodialysis and ion exchange are investigated together with different upstream technologies such as neutral pH level-, acidic- and high sugar fermentation including metabolically engineered E. coli strains. Different biorefinery concepts are evaluated considering technical, economic, environmental and process hazard aspects in order to gain a broad sustainability perspective of the technologies. The results reveal that energy integration is a key factor for biorefinery concepts in order to be economically reasonable and to achieve lower environmental impacts compared to the conventional production from non-renewable resources. It was found that metabolically engineered E. coli with resistance at the acidic pH level in the fermentation together with reactive extraction in the purification presents the most environmentally competitive technology. However, E. coli strains with resistance at high sugar concentrations together with reactive extraction are revealed to present the most economically competitive technology for the production of bio-succinic acid. Moreover, both technologies are flagged for higher process hazards and require the right measures to enhance process safety and mitigate environmental loads and worker exposure.