• Energy Research

Limiting global warming to well below 2°C and pursuing efforts to limit it to 1.5°C, as agreed in the 2015 Paris Agreement, requires global carbon neutrality by mid-century at the latest. The corresponding carbon budget is decreasing steadily and significantly. To phase out carbon emissions in line with the specified temperature target, countries are formulating their mitigation efforts in their long-term low greenhouse gas emission development strategies (LT-LEDS). However, there are no standardized specifications for preparing these strategies, which is why the reports published to date differ widely in terms of structure and scope. To consider the multiple facets of reaching net-zero from a systemic perspective as comprehensively as possible, the authors propose the Net-Zero-2050 System: A novel, transferrable systems approach that supports the development of national endeavors toward carbon neutrality. The Net-Zero-2050 System is defined by three interconnected components: The Carbon-Emission-Based System, the surrounding Framing System and a set of system boundaries. For both systems levels, IPCC approaches were used as a basis and were then adjusted and supplemented by Net-Zero-2050. We suggest applying the Net-Zero-2050 System—beyond the project environment—in carbon emission based contexts at different levels. Especially at the national level, this would improve the comparability of the different national strategies to achieve carbon neutrality.

In its latest assessment report the IPCC stresses the need for carbon dioxide removal (CDR) to counterbalance residual emissions to achieve net zero carbon dioxide or greenhouse gas emissions. There are currently a wide variety of CDR measures available. Their potential and feasibility, however, depends on context specific conditions, as among others biophysical site characteristics, or availability of infrastructure and resources. In our study, we selected 13 CDR concepts which we present in the form of exemplary CDR units described in dedicated fact sheets. They cover technical CO2 removal (two concepts of direct air carbon capture), hybrid solutions (six bioenergy with carbon capture technologies) and five options for natural sink enhancement. Our estimates for their CO2 removal potentials in 2050 range from 0.06 to 30 million tons of CO2, depending on the option. Ten of the 13 CDR concepts provide technical removal potentials higher than 1 million tons of CO2 per year. To better understand the potential contribution of analyzed CDR options to reaching net-zero CO2 emissions, we compare our results with the current CO2 emissions and potential residual CO2 emissions in 2050 in Germany. To complement the necessary information on technology-based and hybrid options, we also provide an overview on possible solutions for CO2 storage for Germany. Taking biophysical conditions and infrastructure into account, northern Germany seems a preferable area for deployment of many concepts. However, for their successful implementation further socio-economic analysis, clear regulations, and policy incentives are necessary.

Abstract Bio-based carbon dioxide removal (CDR) encompasses a wide range of (i) natural sink enhancement concepts in agriculture and on organic soils including peatlands, and in forestry, (ii) bio-based building materials, and (iii) bioenergy production with CO2 capture and storage (BECCS), which are also expected to contribute to the German climate neutrality target. While the concepts vary in CO2 removal dynamics, long-term CO2 removal potential, in specific costs and many other factors, a common database is crucial to compare and discuss the different options. To cover this gap, we provide standardised factsheets with many aspects from economics, resource base and environmental impacts to social and political implications. When comparing those concepts, we find different dynamics of their development until 2045: For CO2 removal rates from the atmosphere, natural sink enhancement concepts are characterised by gradually increasing rates, followed by a saturation and potentially a decrease after few decades; forest-related measures ramp up slowly and for construction projects and bioenergy plants, annually constant removal rates are assumed during operation which drop to zero afterwards. The natural sink enhancement concepts and some long-lived materials could be deployed immediately, whilst BECCS and ramping up construction materials still face legal and political barriers. The expenses for removing 1 t CO2 from the atmosphere were found to be between 8 and 520 € t CO2-1. All concepts investigated could theoretically be scaled up to remove over 1 million tons of CO2 during 25 years, suggesting they can become part of a portfolio of CDR measures.