Steam cracking for the production of light olefins, such as ethylene and propylene, is the single most energyconsuming process in the chemical industry. This paper reviews conventional steam cracking and innovative olefin technologies in terms of energy efficiency. It is found that the pyrolysis section of a naphtha steam cracker alone consumes approximately 65% of the total process energy and approximately 75% of the total exergy loss. A family portrait of olefin technologies by feedstocks is drawn to search for alternatives. An overview of state-of-the-art naphtha cracking technologies shows that approximately 20% savings on the current average process energy use are possible. Advanced naphtha cracking technologies in the pyrolysis section, such as advanced coil and furnace materials, could together lead to up to approximately 20% savings on the process energy use by state-of-the-art technologies. Improvements in the compression and separation sections could together lead to up to approximately 15% savings. Alternative processes, i.e. catalytic olefin technologies, can save up to approximately 20%. q

A recent article 'Burden of proof: A comprehensive review of the feasibility of 100% renewable-electricity systems' claims that many studies of 100% renewable electricity systems do not demonstrate sufficient technical feasibility, according to the criteria of the article's authors (henceforth 'the authors'). Here we analyse the authors' methodology and find it problematic. The feasibility criteria chosen by the authors are important, but are also easily addressed at low economic cost, while not affecting the main conclusions of the reviewed studies and certainly not affecting their technical feasibility. A more thorough review reveals that all of the issues have already been addressed in the engineering and modelling literature. Nuclear power, which the authors have evaluated positively elsewhere, faces other, genuine feasibility problems, such as the finiteness of uranium resources and a reliance on unproven technologies in the medium-to long-term. Energy systems based on renewables, on the other hand, are not only feasible, but already economically viable and decreasing in cost every year.

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While most olefins (e.g., ethylene and propylene) are currently produced through steam cracking routes, they can also possibly be produced from natural gas (i.e., methane) via methanol and oxidative coupling routes. We reviewed recent data in the literature and then compared the energy use, CO 2 emissions and production costs of methane-based routes with those of steam cracking routes. We found that methane-based routes use more than twice as much process energy than state-of-the-art steam cracking routes do (the energy content of products is excluded). The methane-based routes can be economically attractive in remote, gas-rich regions where natural gas is available at low prices. The development of liquefied natural gas (LNG) may increase the prices of natural gas in these locations. Oxidative coupling routes are currently still immature due to low ethylene yields and other problems. While several possibilities for energy efficiency improvement do exist, none of the natural gas-based routes is likely to become more energy efficient or to lead to less CO 2 emissions than steam cracking routes do. r

The use of polymer materials for photovoltaic applications is expected to have several advantages over current crystalline silicon technology. In this paper, we perform an environmental and economic assessment of polymer-based thin film modules with a glass substrate and modules with a flexible substrate and we compare our results with literature data for multicrystalline (mc-) silicon photovoltaics and other types of PV. The functional unit of this study is ‘25 years of electricity production by PV systems with a power of 1 watt-peak (Wp)’. Because the lifetime of polymer photovoltaics is at present much lower than of mc-silicon photovoltaics, we first compared the PV cells per watt-peak and next determined the minimum required lifetime of polymer PV to arrive at the same environmental impacts as mc-silicon PV. We found that per watt-peak of output power, the environmental impacts compared to mc-silicon are 20–60% lower for polymer PV systems with glass substrate and 80–95% lower for polymer PV with PET as substrate (flexible modules). Also in comparison with thin film CuInSe and thin film silicon, the impacts of polymer modules, per watt-peak, appeared to be lower. The costs per watt-peak of polymer PV modules with glass substrate are approximately 20% higher compared to mc-silicon photovoltaics. However, taking into account uncertainties, this might be an overestimation. For flexible modules, no cost data were available. If the efficiency and lifetime of polymer PV modules increases, both glass-based and flexible polymer PV could become an environment friendly and cheap alternative to mc-silicon P

Chemical conversions have been a cornerstone of industrial revolution and societal progress. Continuing this progress in a resource constrained world poses a critical challenge which demands the development of innovative chemical processes to meet our energy and material needs in a sustainable way. This challenge forms the basis for this article. We report a method for quick preliminary assessment of chemical processes at the laboratory stage. The proposed method enables a review of chemical processes within a broader sustainability context. It is inspired by green chemistry principles, techno-economic analysis and some elements of environmental life-cycle assessment (LCA). This method evaluates a proposed chemical process against comparable existing processes using a multi-criteria approach that integrates various economic and environmental indicators. An effort has been made to incorporate quantitative and qualitative information about the processes while making the method transparent and easy to implement based on information available at an early stage in process development. The idea is to provide a data-based assessment tool for chemists and engineers to develop sustainable chemistry. This paper describes the method in detail and examines plausibility of the results. A biobased process for the production of but-1,3-diene has been analyzed using this method. This biobased process is compared with a conventional process for the production of but-1,3-diene from petroleum sources. The effects of uncertainty in the underlying model parameters and assumptions are also analyzed, along with the effect of system boundary selection on the assessment outcome. Analysis and testing of the method shows that it can be used as a valuable tool for sustainable process development

The production of bulk chemicals from biomass can make a significant contribution to solving two of the most urgent environmental problems: climate change and depletion of fossil energy. We analyzed current and future technology routes leading to 15 bulk chemicals using industrial biotechnology and calculated their CO 2 emissions and fossil energy use. Savings of more than 100% in nonrenewable energy use and greenhouse gas emissions are already possible with current state of the art biotechnology. Substantial further savings are possible for the future by improved fermentation and downstream processing. Worldwide CO 2 savings in the range of 500-1000 million tons per year are possible using future technology. Industrial biotechnology hence offers excellent opportunities for mitigating greenhouse gas emissions and decreasing dependence on fossil energy sources and therefore has the potential to make inroads into the existing chemical industry.