Techno-Economic Perspectives on Biofuel Futures – Modelling Transport Sector Strategies in an Energy System Context
Doctoral thesis, 2011
The high oil dependence and the continuous growth of energy use in the transport sector have in recent years triggered interest in transport biofuels as a measure to mitigate climate change and
improve energy security. This work aims to examine techno-economic interactions linked to
transport biofuel strategies in national and regional energy systems and their implications for the
cost-effective realisation of energy policy objectives. The work applies an explorative,
quantitative modelling approach, in which applications of the optimising energy system model
MARKAL are developed and utilised. The thesis is based on four papers. Paper I and Paper II
apply a regional perspective with the Västra Götaland region of Sweden as the geographical
focus. Paper I studies system aspects of biomass gasification technologies, and Paper II examines
the prospects for biogas from anaerobic digestion and the implications of different strategies for
gas distribution. Paper III and Paper IV model the Swedish road transport sector as an integrated
part of the national energy system. Paper III assesses the impact of transport fuel tax designs on
the competitiveness of different fuel and technology options, and Paper IV investigates potential
transport fuel pathways for oil reduction in the passenger car fleet.
Both at the regional and national scale, the results show that limitations in low-cost biomass
supply induce a trade-off between biomass use in the transport sector and biomass use in the
stationary energy system. The latter option is often a more energy-efficient way of reducing CO2
emissions. However, which is the more cost-effective measure depends on energy market
conditions in general and the oil price in particular. Higher energy service demands and more
stringent climate targets increase the incentives for energy-efficient resource utilisation. Such
development pushes biomass use towards stationary applications (heat and power) and increases
the competitiveness of energy-efficient vehicle technologies such as hybrids and electric vehicles.
However, in the medium term, transport fuel pathways based on biomass gasification show large
potential of being a cost-effective option for lowered oil dependence.
From a techno-economic perspective, biogas from anaerobic digestion is generally better used as
transport fuel than for heat and power generation. Due to limitations in local vehicle gas markets,
enhanced conditions for biogas distribution imply a somewhat higher cost-effective total biogas
utilisation but, in particular, a shift from biogas use in heat and power generation to biogas use in
the transport sector. An expansion of the natural gas grid implies possibilities of higher cost-effective
biogas utilisation levels due to increased opportunities for low-cost biogas distribution to
large potential markets. However, from a bioenergy perspective, a grid expansion also involves
risks due to increased competition from natural gas.
Transport fuel taxation provides important incentives for acceleration of the competitiveness of
energy-efficient vehicle technologies such as hybrids and electric vehicles. Tax exemptions
increase the attractiveness of biofuels from a vehicle user perspective, but can lead to increased
CO2 emissions in the stationary energy system. As a consequence, the CO2 abatement costs
associated with biofuel tax exemption policies can be high; however, cost reductions are possible
through concurrent schemes for vehicle energy efficiency. For a given CO2 reduction, the results
indicate (for a range of scenarios) that the incremental energy and technology costs of a complete
oil phase-out in the Swedish passenger car fleet are lower than about one-fourth of the current
governmental transport fuel tax revenues.
biogas
oil dependence
model
MARKAL
transport
CO2
optimisation
biofuel
HC1, Hörsalsvägen 14, Chalmers University of Technology
Opponent: Prof. Mark Howells, Department of Energy Technology, KTH Royal Institute of Technology, Sweden