There is not enough land for the current bioenergy production process because of its low annual yield per unit land. In the present paper, an integrated biomass production and conversion process for sustainable bioenergy is proposed and analyzed. The wastes from the biomass conversion process, including waste water, gas and solid are treated or utilized by the biomass production process in the integrated process. Analysis of the integrated process including the production of water hyacinth and digestion for methane in a tropical area demonstrates several major advantages of the integrated process. (1) The net annual yield of methane per unit land can reach 29.0 and 55.6 km3/h for the present and future (2040) respectively, which are mainly due to the high yield of water hyacinth, high biomethane yield and low energy input. The land demand for the proposed process accounts for about 1% of the world’s land to meet the current global automobile fuels or electricity consumption / (2) A closed cycle of nutrients provides the fertilizer for biomass production and waste treatment, and thus reduces the energy input / (3) The proposed process can be applied in agriculturally marginal land, which will not compete with food production. Therefore, it may be a good alternative energy technology for the future.