Abstract The loss of organic material into the aqueous and gas phases in the liquefaction of raw peat with ≈ 90 wt% moisture content has been studied. The raw material was treated with CO at an initial pressure of 5.5–8.3 MPa and a temperature of 300–350 °C in the presence of K 2CO 3. The yield of water, water-soluble and gas products depended on the operating conditions and the chosen input material. In the liquefaction of peat with 31 wt% oxygen content the loss of material into the aqueous and gas phases decreased with increases in the initial CO pressure and the reaction temperature. The loss of organic material from peat with a high oxygen content (≈ 40 wt%) was significant. This loss of organic material is a result of thermal decomposition and hydrolysis of the organic matter of the peat and elimination of low molecular weight gases and water-soluble compounds with high oxygen and low energy contents. The selective transfer of highly oxygenated components from the peat resulted in the formation of liquid and solid residual materials with low oxygen and high energy contents. Most of the energy content of the peat becomes concentrated in the liquid and solid products (toluene- or acetone-solubles and -insolubles). The loss of organic material from the peat into the aqueous and gas phases is not accompanied by significant energy losses from the raw material.