In response to the growing problems associated with road transport emissions, increasing emphasis is being placed on biofuels and bio-additives as a more ecological alternative to traditional fossil fuels. Biofuels, produced from renewable raw materials such as oil plants, cereals or organic waste, aim to reduce greenhouse gas emissions and limit the consumption of non-renewable raw materials. The introduction of additives to fuels can have a positive effect on reducing harmful substances in exhaust gases. Still, the effectiveness of this solution depends on many factors, such as the type of bio components and the design of the engines. The article discusses research on bio-additives impact on exhaust emissions, with particular emphasis on combustion processes and the formation of harmful substance emissions. It presents two complementary modelling methods: COPERT, which allows for estimating emissions in real conditions, and Diesel-RK, which simulates engine combustion processes for a detailed analysis of emission mechanisms. The combination of these tools allowed for a precise assessment of the impact of biofuels on pollutant emissions and may be an essential step towards optimising engine designs for more ecological solutions. Despite certain technological and economic limitations, using bio-additives to fuels can significantly reduce emissions from road transport, accelerating the implementation of global environmental protection and sustainable development goals.