Biochar is seen as a cost-effective and easy to implement negative emission technology to sequester carbon dioxide and help to mitigate climate change. A Life cycle assessment (LCA) of slow pyrolysis using forest residues was conducted to study the environmental effects of biochar in Norway. The LCA was performed for biochar production at 350°C and 650°C for comparison and analysis of potential trade-offs. Co-products formed during pyrolysis (i.e. bio-oil and syngas) were assumed to be burnt for energy recovery and displace district heating produced from natural gas. SimaPro software has been used with EcoInvent as background system for the LCA and the ReCiPe impact assessment method was used for impacts characterization at midpoint level. Pyrolysis at 650°C showed an increased stable carbon yield by 24% than 350°C. Biochar at 650°C showed lower impacts for global warming, fossil resource scarcity impacts -2.34 compared to -1.46 kg CO2eq at 350°C and -0.037 vs 0.0024 kg oil eq. This is due to more stable carbon in the biochar produced at 650°C and more displaced district heating. For the other impact categories, biochar produced at 650°C showed slightly but larger impacts compared to 350°C, which is probably due to lower biochar yield at 650°C that requires more feedstock and more upstream inputs and emissions. The net climate mitigation potential for Norway at pyrolysis temperature 350 °C and 650 °C will be 1.1 Mt CO2 eq/yr and 1.3 Mt CO2 eq/yr respectively.