The idea of a “green port” is becoming increasingly popular worldwide in the seaport industry, indicating a heightened dedication to environmental sustainability. However, there is a growing concern among the international community regarding the expansion of port facilities and the environmental impact of emissions from shipping. Thus, as the primary driver of climate change, CO2 emissions must be carefully controlled. African ports have had difficulties implementing the greening of ports project due to economic, technological, socio-cultural, legal, topographical, and fiscal constraints. To counteract the effects of climate change, several port authorities have implemented tactics related to the greening project, which is a smart concept. Concerning African ports’ current condition ‒ namely, their deficiency in port infrastructure ‒ is this proposal beneficial or detrimental? In this context, this paper has employed the GM (1, 1) grey forecasting model to predict the future carbon dioxide (CO2) emissions of the port from 2023 to 2040, using Mombasa Port as a case study and as one of the African ports that have implemented green port initiatives. The aim is to compare the “before” and “after” implementation conditions of green port policies in the Mombasa Port, utilizing the port’s CO2 emissions from 2009 to 2022 as the available data. Therefore, the data was separated into two sets: “before implementation”, i.e., from 2009-2015, and “after implementation”, i.e., from 2016-2015. The average relative error of the GM (1, 1) for both “before implementation” and “after implementation”, based on the study’s CO2 emission forecasts, is less than 10%. For the next 18 years, the GM (1, 1) model predicted continued increases in CO2 emissions based on the data from “before implementation”, whereas the data from “after implementation” showed a decrease in CO2 emissions. This observation confirmed our initial assumption that, based on data from the years 2016-2022, the CO2 emission forecast value for 2040 must be lower than that of 2040 based on data from the years 2009-2022. Furthermore, this paper also highlighted some key achievements realized through the successful implementation of the Green Port Policy program by the Kenya Ports Authority at Mombasa Port. By improving and modernizing Mombasa Port, this initiative also marks the beginning of a new era in Africa that is focused on environmental sustainability.