The food industry (e.g. brewery, sugar factory, fruit and vegetable processing industry) generates significant amounts of organic waste. This waste has the potential for further conversion toward valuable products or by-products, simultaneously limiting disposal and offering added value materials. Furthermore, the use of waste is in line with the idea of circular economy (CE) leading to reduction of dependence on natural resources and mitigation of the environmental, social and economic impacts associated with the generation and disposal of food waste. In this study, the three types of food waste were investigated. There were rape cake, walnut shells, and maize cob. These wastes are organic lignocellulosic matter (c.a. 45% of C, 7% of H) with high potential for thermal conversion. The pyrolysis process (nitrogen atmosphere, 600 °C of temperature, 10 min of residence time) was carried out to convert these waste and produce biochar. The yield of pyrolysis was in the range of 22 to 25%. The biochars obtained for all the waste were carbon-rich material (even more than 80% of the C content for the walnut shells and maize cob) with a porous structure and high surface area. The biochars were then treated with chemicals (acidic (nitric acid) and alkaline (KOH, ammonia) treatments) to produce well-developed porous structure materials with enriched surface functional groups, which makes these materials with a very wide range of applications. The CO2 sorption capacities of biochars using adsorption isotherms were analysed for a wide pressure range. To evaluate the chemical composition, thermal behaviour, pore structure, surface chemistry, and physical properties of biochar, the following instrumental techniques were applied: EA, TGA, BET, SEM, and FTIR. The investigation of the adsorption properties of biochar derived from waste from the food industry holds significant promise for the valorisation of waste and resource efficiency. Through innovative research and technological advancements, biochar-based materials have the potential to address environmental challenges and bring about a more sustainable future.