In fact, algae represent an interesting alternative to the production of first or second generation biofuels, thanks to an high photosynthetic yield and hence, a lower land competition with food production and a better control of ground emissions. In addition, the ability to use CO2 directly from industrial emissions as a resource of carbon for the growth of microalgae is a promising feature for fluegas mitigation. Hence if used as an interface between biowaste and energy production, macroalage allows direct utilization of biowaste and, at the same time transforms negative environmental externalities into positive ones. A Life cycle assessment (LCA) is fundamental in order to optimize the overall process from the environmental point of view, addressing the attention on the environmental “hot spots” of the process. The LCA methodology is one of the best suitable instruments for understanding the environmental benefits and the share of non-renewable sources still needed for the process. It interest to investigate a transformation system coupling the anaerobic digestion of raw algae (for production of biogas and after upgrading methane as biofuel) and the algal production itself. The benefits can be focused also on the recirculation of the liquid fraction of the digestates toward the algal ponds and a significant fertilizers recycling. The purpose of this paper is to carried out an environmental assessment of the use of biogas from algae as a biofuel for the heat and electricity production on a cogeneration (CHP) unit (40kW) and compares it in case of natural gas/diesel supplies. All the biogas production from algae is reference to the pilot plant in Augusta (Italy) to be implemented within the framework of the FP7 project BioWALK4biofuels. Environmental and energy analysis will be carried out within the methodological framework of the LCA based on a ‘‘cradle to grave” inventory of emissions and resources consumption. The chosen method to assess the potential impacts is IMPACT2002+, described in Jolliet et al. (2003). Data about algal productivity and the methane yield production mainly coming from the project partners and technical literature. In this study, the anaerobic digestion of the marine macroalgae Ulva Prolifera has been taken into account.