Politicians and policymakers are searching for alternatives for current energy conversion systems in order to reduce environmental pollution whilst preserving scarce natural resources. When defining new alternatives it is important to find out how environmentally friendly and sustainable these alternatives are, and which of them will ensure a major improvement in environmental issue. To answer such questions the present work proposes a new type of indicator based on exergy life cycle data. Alternative energy routes towards different services and commodities are compared in terms of environmental impact and indirect natural resource costs. Two case studies are presented using data from the Ecoinvent database (v2.01 2007) to compare alternatives to petrol transport and fuel oil power generation. The alternative transport routes assessed were methanol and biogas fueled cars, and wind electricity in the case of power generation. (C) 2010 Elsevier Ltd. All rights reserved.