Environmental Impacts of Using Hydrogen for Defossilizing Industrial Specialty Glass Production

The glass industry is part of Germany's energy-intensive industry. Today, mostly fossil energy carriers are used to produce the high temperatures needed, e.g., to melt the raw materials. One option to push defossilisation is the use of green hydrogen in the furnace. The strictest requirements regarding a steady heat supply has the specialty glass production. The hydrogen can be produced on-site in an electrolyzer, using not only the hydrogen for combustion but also the co-produced oxygen in the oxyfuel process. Alternatively, hydrogen can be produced off-site in a large scale electrolyzer to facilitate economy of scale. For transport and distribution of this hydrogen different options are available. Besides conventional high-pressure trailers a rather new option are liquid organic hydrogen carriers (LOHC), which allow hydrogen to be transported and stored at a higher volumetric density and to be treated in the same way as conventional fossil fuels. Temperatures necessary to separate the hydrogen from the LOHC after transport can be provided using waste heat from the glass melt. Another promising future option is the repurposed use of today's natural gas pipelines. Environmental impacts of this example of the so-called sector coupling shifting from conventional fossil-based combustion to the use of electrochemically produced hydrogen in combination with a transformation of the German grid mix towards renewable electricity - is being investigated by the means of a Life Cycle Assessment (LCA). The main objective is to evaluate which hydrogen-based solution to produce specialty glass has the least impact on climate change in a time frame from 2020 till 2050. Furthermore, the trade-offs for other environmental impacts are analysed. The results indicate that all hydrogen-based options offer a huge potential to lower greenhouse gas emissions in 2050 compared to today's fossil-based production. When local conditions permit an on-site hydrogen production this is the best option for hydrogen use in the glass production.