Purpose: Ammonia (NH3) production is an energy-intensive process that is concentrated in a few countries at large-scale plants, mainly using the Haber-Bosch (HB) process. Local plants next to farmers can reduce environmental impacts, as well as reduce storage, shortage risks, and price volatility of fertilisers. Since local NH3 production is not cost-effective, we analyse how internalisation of environmental impacts into economic analyses could help to promote novel technologies for NH3 synthesis when supplied with renewable energy.
Methods: Mini-HB plants working at high pressure and temperature, as well as novel alternatives based on plasma reactors working at ambient conditions and using electricity from renewable sources, have been recently proposed for decentralised NH3 production. To evaluate the environmental performances of these alternative and traditional NH3 pathways, a life cycle assessment was performed to quantify the reduced emissions in each production process and the impacts of by-product utilisation, such as steam, oxygen, or carbon black. Different scales of storage and transportation, fuelled by traditional energy sources, were modelled to quantify the impacts of the simplified NH3 supply chains. A review of monetary valuation coefficients was performed to internalise the life cycle environmental impacts into the techno-economic analyses of NH3 production in Australia.
Results and discussion: Most of the estimated environmental costs were due to the carbon emissions of conventional plants and thermal plasma plants because of the use of fossil-based electricity. However, the high external costs associated with the photochemical oxidant formation and particulate matter affected the thermal plasma and non-thermal plasma (NTP) plants, costing in total 9,500 and 4,200 $/t NH3, respectively, due to the impacts of solar panels manufacturing. In contrast, electrolyser-HB plants obtained rates of 114 $/t NH3 because of the high energy efficiency and oxygen sales. In the future scenario for NTP-based plants, this alternative could also be competitive with rates of 222 $/t NH3. Additionally, the estimated total external costs for the conventional NH3 industry in Australia amounted to about US$5 billion per year.
Conclusions: Electrolyser-HB plants could be cost-effective in the short term due to the energy efficiency of HB processes. However, the HB process has reached its efficiency limits, while the NTP process still has room for improvement, as well as its production costs are lower at smaller scales. In addition, if monetised environmental costs are analysed for a whole industry, public administrations could be prompted to invest the expected savings in the promotion of these novel technologies.
Supplementary info
Purpose: Extensive agriculture activities for crop production have led to increasing environmental impacts that threaten to exceed environmentally safe limits. The purpose of this study is to analyze resource efficiency of the agri-food industry, considering the case of sugarcane production in Pakistan.
Methods: A holistic approach has been applied by determining the relevant impact categories and Sustainable Development Goals (SDGs), and linking them with Planetary Boundary-based Life Cycle Assessment (PB-LCA). Both the spatially generic and spatially resolved approaches were considered with application of different sharing principles.
Results and discussion: Application of different sharing principles showed high variations in the assigned share of the safe operating space values. When taking a spatially generic approach, most of the impacts (except marine eutrophication and water consumption) were within the safe operating space for equal per capita, economic, caloric, and grandfathering sharing principles. However, all the impacts exceeded their limits considering the agri-land sharing and land use impact surpassed its budget considering the grandfathering sharing. In the spatially resolved approach, most of the impact values surpassed the available budgets. Furthermore, the failure to attain the pertinent SDG targets from a PB-LCA perspective is indicated by the exceeding of safe operating space for relevant impact categories.
Conclusions: Overall, the production of sugarcane was found to be unsustainable, requiring urgent action to promote resource improvement and contain the impacts within safe limits. The developed framework enabled the evaluation of the SDGs using PB-LCA at the product level. The target-driven impact reduction values would help in achieving the targets and prioritizing the efforts by making informed decisions for reducing impacts within safe limits.
Supplementary information: The online version contains supplementary material available at 10.1007/s11367-023-02185-7.
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