Alternatives to climate changing blowing agents (e.g. chlorofluorocarbons) and petroleum sourced raw materials (e.g. polyether polyols) are very attractive in the polyurethane (PU) foam industry. We explore a series of CO2 adducts from a branched polyethylenimine (bPEI) alkylated with C-4 to C-16 alkyl glycidyl ethers. These adducts can serve as CO2 releasing blowing agents during the exothermic polymerisation of PUs. A 13% alkylation of the bPEI amine groups enhances the dispersibility of the resultant CO2 adducts into the PU foaming mixtures containing a castor oil-derived polyol. In particular, the CO2 adduct with a C-8 alkyl (2-ethylhexyl) side chain possesses the best dispersibility and is among the most effective in decreasing the foam density. It generates PU foams whose density and compressive strength are almost suitable for thermal insulation of underground steel pipes. This is the first report showing that PU foams from biomass polyols can be blown by CO2 adducts that are environmentally neutral. (C) 2017 Elsevier Ltd. All rights reserved.