According to European Unions directive 2009/28/EC 20% of the European energy demand should be covered by renewable energy sources by 2020. In Austria, biogas has become a widespread technology for the production of renewable energy, which potentially has a share in meeting this goal. Unfortunately, biogas market growth in Austria remains more or less static due to economic reasons (increasing substrate costs) as well as process-related drawbacks in gas utilisation (quality requirements, waste heat utilisation). Nevertheless, companies of the energy intensive basic industry are permanently looking for possibilities to embed CO2-neutral technologies and renewable fuels in existing production processes. In the face of these circumstances, the paper deals with the areal combination of biogas plants and plants of the building materials industry (e.g. cement works) from the technical and economical point of view. The main benefits of such a combination are the direct thermal utilisation of unprocessed biogas as a valuable, CO2-neutral fuel for combustion processes for instance clinker burning and the utilisation of low temperature excess heat sources from cement works for fermenter heating. Additionally, a new process for the recovery of ammonia from liquid digestate to act as reducing-agent in off gas denitrification is experimentally investigated (ion exchanger-loop-stripping). Furthermore, an overall process model of combined biogas plants and cement works is developed (BioZem-Model) to determine the effects of a combination of both plants in terms of energetic efficiency, investment and operating costs, plant feasibility, greenhouse gas emission reduction and overall energy production costs. Results show, that the overall energetic efficiency of the combined plant system significantly increases compared to conventional plants. Concurrently energy production costs are reduced, turning biogas into a competitive source of energy without the need for federal sponsorship. Calculations show, that production costs in combined plants for plant sizes larger than 125 m³STP/h biogas are even lower than the actual market prize of natural gas. With the developed model, site specific questions like maximum substrate and transport costs for economical plant operation can be estimated. Thereby, the number of potential biogas plant sites increases and the role of biogas as CO2-neutral fuel in power supply can be strenghtened by the installation of sustainable energy systems.