Evaluating biochar extraction from waste tree stumps in different pyrolysis systems using life cycle analysis

With the growing global attention to climate change and reducing environmental pollution, it is necessary to look for sustainable technologies that help curtail carbon dioxide emissions and create useful products from waste. The hypothesis of this study was that recycling wood waste reduces the negative impact on the environment, and the biochar obtained during processing could be used to create secondary, environmentally friendly products. This study evaluated the environmental effects of biochar production using two pyrolysis reactors, UMT-3 PLUS EcoTeploOtbor (SC-1) and BIO-KILN-1 (SC-2), across various impact categories, including global warming potential (GWP), human toxicity (HT), freshwater aquatic ecotoxicity (FWE), marine aquatic ecotoxicity (MAE), and terrestrial ecotoxicity (TE). The functional unit for this study was defined as 1 ton of biochar, which allowed for meaningful comparisons between studies and ensures data reproducibility. SC-1 showed higher impacts, with preparation and processing of tree stumps (SBP) contributing 643.02 kg CO₂eq total GWP without carbon sequestration, 134.47 kg 1,4-DBeq to HT, and 347,097.03 kg 1,4-DBeq to MAE - 8.65% higher than SC-2. Carbon sequestration potential resulted in net negative GWP values: -2,036.98 kg CO₂eq for SC-1 and - 1,866.31 kg CO₂eq for SC-2. Chemical analysis confirmed heavy metals in biochar are within permissible limits, and most material accumulated on the 2 mm sieve, indicating suitability for further use, such as granulation.