Beyond Dictionaries: Machine-Learned Normalization of Emission Units in Information Extraction

Lisa Reichenbach, Simon Oehler, Malte Schierholz, Anna Steinberg Schulten


Abstract
Sustainability reports denote greenhouse gas emissions with heterogeneous unit strings, such as abbreviations, inconsistent formatting, and scale markers. In emission extraction pipelines, these units must be normalized to a common target, e.g. t CO2e, to enable reliable comparison and aggregation of emissions across companies, reporting years, scopes, and regions. We propose a hybrid normalization approach: If a raw unit string is not found in a curated dictionary, a machine learning classifier maps noisy unit strings to normalized emission-unit categories that can then be converted to the target unit. The classifier is trained using character-level TF-IDF, lightweight string features, and LLM-assisted data augmentation. On random-splits of the augmented dataset, an ensemble model achieves approximately 95% accuracy. Additional evaluation on rare real-world unit strings indicates that supervised fallback classifiers can handle out-of-dictionary variants in climate-related information extraction.
Anthology ID:
2026.climatenlp-1.10
Volume:
Proceedings of the 3rd Workshop on Natural Language Processing Meets Climate Change (ClimateNLP 2026)
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Tobias Schimanski, Aida Usmanova, Gaku Morio, Jingwei Ni, Kalyan Dutia, Seyed Saeid Vaghefi, Dominik Stammbach, Markus Leippold
Venues:
ClimateNLP | WS
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
132–142
Language:
URL:
https://aclanthology.org/2026.climatenlp-1.10/
DOI:
Bibkey:
Cite (ACL):
Lisa Reichenbach, Simon Oehler, Malte Schierholz, and Anna Steinberg Schulten. 2026. Beyond Dictionaries: Machine-Learned Normalization of Emission Units in Information Extraction. In Proceedings of the 3rd Workshop on Natural Language Processing Meets Climate Change (ClimateNLP 2026), pages 132–142, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Beyond Dictionaries: Machine-Learned Normalization of Emission Units in Information Extraction (Reichenbach et al., ClimateNLP 2026)
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PDF:
https://aclanthology.org/2026.climatenlp-1.10.pdf