PhD defence: Per Eduard Robert Bjerager

Per Eduard Robert Bjerager defends his thesis,

Climate roadmaps meeting a global warming target of 1.5 °C including afforestation with short rotation forestry and harvest of wood for production of hydrogen bioenergy with carbon capture and storage

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Associate Professor Niclas Scott Bentsen

Assessment Commitee:
Dr. Jörg Schweinle, Thünen – Germany
Associate Professor Miguel Mendonça Reis Brandão, KTH Royal Institute of Technology, Stockholm – Sweden
Associate Professor Inge Stupak (chair), IGN

The risk of dangerous climate change led to the Paris Agreement in 2015, with the aim of keeping global warming well below 2°C and pursuing efforts to limit global warming to 1.5°C above pre-industrial levels. In 2018, the Intergovernmental Panel on Climate Change (IPCC) presented pathways for meeting the 1.5°C target through different combinations of land based CO2-removal by afforestation and/or energy crops combined with carbon capture and storage (BECCS).
This thesis explores an alternative concept for mitigating climate change through phase out and removal of CO2. The concept builds on CO2-removal via afforestation with short rotation forestry (SRF) and harvest of wood for a supply chain with BECCS, which is based on energy conversion by gasification to hydrogen and CO2, hereafter “forest-hydrogen”. The overall research question was: What levels of afforestation with harvest of wood for BECCS, globally, in terms of area and productivity of the afforestation, are needed to deliver CO2-removals at the same magnitudes and timing as the IPCC pathways. The question was answered by developing a modeling framework to design four climate roadmaps with combined strategies for CO2-remvoal through the forest-hydrogen supply chain and phasing out of anthropogenic CO2-emission meeting a remaining CO2-budget of 350 Gt between 2018 and 2100.
Only one of the climate roadmaps may be realizable, and it represents transitions of land-use and energy systems on a global scale: It is assumed that afforestation of 600 million ha is finalized in 2068, and that investments in innovative SRF increase the average land productivity from 10 Mg/(ha·yr) in 2020 to 15 Mg/(ha·yr) in 2100. Transitions of energy systems are assumed to phase-out fossil CO2-emmisions by 2050 due to substitution with primary CO2-neutral energy sources and secondary with forest-hydrogen by BECCS. The forest hydrogen supply chain has between 2018 and 2100 a cumulative CO2-storage in forest of 144 Gt and in geological formations by BECCS of 431 Gt. A main driver for realization of the climate roadmap is the production forest-hydrogen by BECCS, which have an energy-specific CO2-storage of 136 g/MJ.

A digital version of the PhD thesis can be obtained from the PhD secretary