The objective of this contribution is to perform the sustainable mixed-integer linear programming (MILP) synthesis of biogas processes based on life cycle assessment (LCA). An aggregated model previously developed by authors for the efficient optimisation of biogas processes has been upgraded with LCA, using the novel concept of eco-profit. Eco-profit is defined as the difference between burdening (eco-cost) and unburdening (eco-benefit) the environment, where eco-cost and eco-benefit calculations are based on LCA. The advantage of eco-profit is that it is expressed as a monetary value. Therefore. eco-profit and economic profit can be merged together and the preferred solutions are those with maximal total profit. The single-and multi-objective optimisations were performed on a model of the biogas production processes. Within the former, economic, eco- and total profit were maximised separately and, within the latter, maximisation of economic profit vs. eco-profit was introduced. All the results obtained from single- and multi-criteria optimisation show that biogas production is a sustainable alternative that provides an important eco-profit. (c) 2012 Elsevier Ltd. All rights reserved.