The increase of ship’s energy utilization efficiency and the reduction of greenhouse gas emissions have been high lightened in recent years and have become an increasingly important subject for ship designers and owners. The International Maritime Organization (IMO) is seeking measures to reduce the CO2emissions from ships, and their proposed energy efficiency design index (EEDI) and energy efficiency operational indicator (EEOI) aim at ensuring that future vessels will be more efficient. Waste heat recovery can be employed not only to improve energy utilization efficiency but also to reduce greenhouse gas emissions. In this paper, a typical conceptual large container ship employing a low speed marine diesel engine as the main propulsion machinery is introduced and three possible types of waste heat recovery systems are designed. To calculate the EEDI and EEOI of the given large container ship, two software packages are developed. From the viewpoint of operation and maintenance, lowering the ship speed and improving container load rate can greatly reduce EEOI and further reduce total fuel consumption. Although the large container ship itself can reach the IMO requirements of EEDI at the first stage with a reduction factor 10% under the reference line value, the proposed waste heat recovery systems can improve the ship EEDI reduction factor to 20% under the reference line value.

Technical and operational energy efficiency measures for ships, such as the energy efficiency design index (EEDI) and ship energy efficiency management plan (SEEMP), aim to improve the energy efficiency of international shipping. Studies show that absolute emissions from international shipping will increase despite their mandatory application. For this reason, it is important to assess the impact on the effectiveness of the application of mandatory efficiency measures on future emissions. Further measures are being developed at the International Maritime Organization to control emissions from ships, in particular greenhouse gases (GHG) that contribute to climate change. In January 2019, a system of collecting fuel consumption data by ships (Ship Fuel Oil Consumption Database) was introduced.

Energy efficiency measures promoted by the IMO Maritime Environment Protection Committee, initially as facultative, then as mandatory, show strong preventive character. The mandatory use of energy efficiency measures by ships as well as the development of energy efficiency management policies by shipping companies contributes to climate protection and adaptation to climate change.

Obligation to use the best available technology (BAT) in the protection of the environment is envisaged in many international treaties. It is not only legal, but also moral obligation. Treaties concluded under the auspices of the International Maritime Organization (IMO) that aim at the protection of the environment and the prevention of pollution from ships, enshrine the precautionary principle which encompasses the obligation to use the best available technology. Many IMO treaties consider technological development, some of them even drive it, however, not all standards are based on the best and the newest solutions. The discussion at the IMO’s Marine Environment Protection Committee regarding the energy efficiency design index demonstrates the impact of political and economic interests on the text of adopted standards. The Initial IMO strategy on the reduction of greenhouse gas emissions from ships identifies levels of ambitions consistent with the Paris Agreement. In the shipping industry this will be achieved, if the adopted standards were based on the best available technology.