Due to the important role of ammonia as a fertilizer in the agricultural industry and its promising prospects as an energy carrier, many studies have recently attempted to find the most environmentally benign, energy efficient, and economically viable production process for ammonia synthesis. The most commonly utilized ammonia production method is the Haber-Bosch process. The downside to this technology is the high greenhouse gas emissions, surpassing 2.16 kgCO2-eq/kg NH3 and high amounts of energy usage of over 30 GJ/tonne NH3 mainly due to the strict operational conditions at high temperature and pressure. The most widely adopted technology for sustainable hydrogen production used for ammonia synthesis is water electrolysis coupled with renewable technologies such as wind and solar. In general, a water electrolyzer requires a continuous supply of pretreated water with high purity levels for its operation. Moreover, for production of 1 tonne of hydrogen, 9 tonnes of water is required. Based on this data, for the production of the same amount of ammonia through water electrolysis, 233.6 million tonnes/yr of water is required. In this paper, a critical review of different sustainable hydrogen production processes and emerging technologies for sustainable ammonia synthesis along with a comparative life cycle assessment of various ammonia production methods has been carried out. We find that through the review of each of the studied technologies, either large amounts of GHG emissions are produced or high volumes of pretreated water is required or a combination of both these factors occur.

Carbon Capture and Utilization (CCU) is an emerging technology field that can replace fossil carbon value chains, and that has a significant potential to achieve emissions mitigation or even "negative emissions"-however in many cases with challenging technology feasibility and economic viability. Further challenges arise in the decision making for CCU technology research, development, and deployment, in particular when allocating funding or time resources. No generally accepted techno-economic assessment (TEA) standard has evolved, and assessment studies often result in "apples vs. oranges" comparisons, a lack of transparency and a lack of comparability to other studies. A detailed guideline for systematic techno-economic (TEA) and life cycle assessment (LCA) for CCU technologies was developed; this paper shows a summarized version of the TEA guideline, which includes distinct and prioritized (shall and should) rules and which allows conducting TEA in parallel to LCA. The TEA guideline was developed in a co-operative and creative approach with roughly 50 international experts and is based on a systematic literature review as well as on existing best practices from TEA and LCA from the areas of industry, academia, and policy. To the best of our knowledge, this guideline is the first TEA framework with a focus on CCU technologies and the first that is designed to be conducted in parallel to LCA due to aligned vocabulary and assessment steps, systematically including technology maturity. Therefore, this work extends current literature, improving the design, implementation, and reporting approaches of TEA studies for CCU technologies. Overall, the application of this TEA guideline aims at improved comparability of TEA studies, leading to improved decision making and more efficient allocation of funds and time resources for the research, development, and deployment of CCU technologies.

The intended audience for this document are practitioners that want to learn how to create comprehensible and consistent techno-economic assessments and life cycle assessments in the CCU field. These practitioners may come from academia, industry or government and may work in technology assessment and technology research and development, or funding, they may be part of the CCU community, the TEA community or the LCA community. Readers of TEA and LCA, such as investors, policy Part A: General Assessment Principles Part B: TEA guidelines Part C: LCA guidelines PART A: GENERAL ASSESSMENT PRINCIPLES TEA & LCA Guidelines for CO2 Utilization 8makers or funding decision makers are not the intended audience for these TEA and LCA guidelines, but may use this document to understand the challenges and pitfalls for TEA and LCA. A.2.4 Limitations of this documentThese guidelines have been developed to enable consistent and comparable LCA and TEA studies for CCU. They are not intended to serve as an assessment standard or rulebook. Instead they are meant to help practitioners to conduct sound assessments efficiently, avoid common mistakes and to derive meaningful results that can be compared to other studies. This document serves as an addition to conventional existing standards (in particular for LCA) and literature and does not replace any chemical engineering, economics or project planning principles. However, since the guidelines aim to enhance the comparability and transparency of studies, the LCA guidelines are more restrictive than the general ISO-framework. In some cases, there may be need to add further tasks to the ones discussed in this guideline since they are important to a specific study. Such additions are not excluded by the present guideline. However, the guidelines provide a consistent methodological core for conducting all LCA and TEA CCU studies.This document is intended as the first step of a longer framework development process. TEA and LCA remain two separate approaches in this document as is common in current assessment practice in academic literature and industry. However, a combined approach is in strong demand to include trade-offs in decision making. The integration of TEA and LCA into one singular study is a next major development step that is subject to future work. This document provides some initial guidance to those who wish to carry out an integrated TEA & LCA study, however many facets of the integration process are still to be determined. A.2.5 The guidelinesThe guidelines for TEA are presented in part B of this document and LCA in part C. At the end of each guideline chapter there is a box listing rules that these guidelines recommend. The box contains three categories, shall, should and may:TEA & LCA Guidelines for CO2 Utilization 9TEA & LCA Guidelines for CO2 Utilization 14 A.4.2.4 GuidelinesGuideline A.1 -Technology maturity Shall 1) Technology maturity shall be defined in each assessment -first for each system element and second for the overall product system 2) The maturity of the over...

A feature article describing the fundamental characteristics and emerging applications of micro technology in the field of synthetic chemistry.

Several inexpensive and non-toxic solvents with low vapour pressures were investigated for their suitability as alternative solvents for the absorption of carbon dioxide from flue gas. The solvents include poly(ethylene glycol)s, poly(ethylene glycol) ethers, poly(ethylenimine) and glycerol-based substances. Solvent properties such as thermal stability, solubility of carbon dioxide and selectivity over nitrogen were investigated in a systematic study using a thermogravimetric analyser. Absorption results are reported for pure carbon dioxide and nitrogen as well as a mixture of both gases. Desorption and long-term sorption behaviour are also discussed. Glycerol and poly(ethylene glycol)s show a high solubility of carbon dioxide. Due to the high viscosity of the solvent, carbon dioxide absorption in poly(ethylenimine) is very slow in spite of the presence of favourable amine groups. PEG 300 was found to be the best solvent in this study and shows a high carbon dioxide solubility as well as good selectivity over nitrogen. The advantages of high stability, low solvent loss and low desorption energy of PEG 300 may outweigh its lower absorption capacity compared to the state-of-the-art solvent monoethanolamine, making it a potentially advantageous solvent for industrial carbon dioxide absorption processes.