Contribution of waste treatment plants to future energy systems
What contribution can waste treatment plants make to the energy systems of the future? bifa is investigating this question in a current study. Options for sector coupling in the electricity sector are considered, but also the more extensive use of heat and biogas. The use of carbon dioxide (Carbon Capture and Utilisation, CCU) is also taken into account.
The study is being commissioned by the German Environment Agency (Umweltbundesamt – UBA) and financed with federal funds. Initial results were presented by bifa at the Berlin Waste Management and Energy Conference 2021 (Thiel N., Schönemann M., Dietz W. and Rommel W.: Sector coupling at waste treatment plants – options and success factors).
What does the study contain?
Data from electricity-generating waste treatment plants in Germany were aggregated as a basis. Already implemented examples of sector coupling at waste treatment plants are examined. Electricity-based sector coupling aims at the production of fuels such as hydrogen, methane and diesel or of basic chemicals such as methanol and ammonia. As a first step, the production paths have hydrogen production by means of electrolysis in common. Both electrolysis with a polymer electrolyte membrane and alkaline electrolysis are mature technologies in the single-digit megawatt range.
Methane and methanol production are also considered, starting from the hydrogen produced and incorporating carbon dioxide from flue gas. While electrolysis currently achieves efficiencies of 71-74 %, catalytic methanation is at 56 % and methanol production at approx. 52 %, calculated in each case with the calorific value of the products for electricity use at the electrolyser.
Results of the current study
The computational simulation of hydrogen production at a thermal waste treatment plant shows significant influences on economic efficiency and climate gas emissions. Scenarios and sensitivities are calculated. For hydrogen production, the results indicate that the current energy-economy boundary conditions only allow profitability if sales revenues can be achieved that are significantly above the current price level of hydrogen produced on a large scale from natural gas. For the climate balance, it should be noted that although sector coupling replaces fossil production paths, the electricity used is no longer fed into the grid. This means that electricity has to be generated elsewhere, which in turn causes greenhouse gas emissions.
Waste treatment plants offer good conditions for sector coupling as well as starting points for the use of the products in the municipal environment, e.g. in local public transport. Whether hydrogen or methane, methanol or other demanded downstream products are ultimately to be produced is the subject of the current study. The economic and ecological boundary conditions will change significantly in the coming years. Influencing factors include the CO2 price, the increasing share of renewable energies in the electricity mix and the need for grid stabilisation measures. Public sector actors in particular are called upon to invest in climate protection measures to secure the future. Sector coupling at waste treatment plants can make a contribution here.
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Dr. Wolfram Dietz