Transport biofuel futures in energy economy modeling: a review.

The high oil dependence and the growth of energy use in the transport sector have increased interest in alternative fuels as a measure to mitigate climate change and improve energy security. More ambitious energy and environmental targets and larger use of alternative energy in the transport sector increase system effects over sector boundaries, and while the stationary energy sector (e.g., electricity and heat generation) and the transport sector earlier to large degree could be considered as separate systems with limited interaction, integrated analysis approaches now grow in importance. In recent years, the scientific literature has presented an increasing number of energy-economic systems analysis modeling studies treating the transport sector as an integrated part of the energy system and/or economy. Many of these studies provide important insights regarding transport biofuels. The work summarizes and analyzes input data and transport biofuel-related results of 29 peer reviewed scientific journal articles presenting studies based on different energy-economic models. About half of the studies apply a global perspective and about half a regional or national perspective. Examples of models and model frameworks that are used in the studies included in the review are PRIMES, MARKAL, TIMES, AIM/Enduse, POLES, GCAM, GET and REDGEM70. The studies apply medium-term to long-term perspectives, with time horizons in most cases ending between 2040 and 2100. Most of the studies show low to intermediate market shares, with levels below 40% at the end of the studied time horizons for climate policy scenarios. Biofuels are to a higher degree seen in medium-term than in long-term model results. In the latter case, many of the models instead favor hydrogen or electricity-based transport options as competition for limited amounts of biomass increases with more stringent emission targets. Besides transport biofuels, energy efficient vehicle technologies, such as plug-in hybrids and, in the longer term, fuel cell vehicles, are an essential part in many of the model scenarios meeting future stringent climate targets