بررسی فرایندهای تولید سوخت های انرژی زیستی و عملکرد اقتصادی نسل دوم با استفاده از سناریوهای بازار انرژی

In this paper performance assessment of second generation biofuel production using energy market scenarios and system-level performance indicators is proposed. During biofuel production a number of products and services can be co-generated while import of energy services (e.g. electricity and heat) in addition to the fuel supply may also be needed. This needs to be reflected by a well-defined performance indicator enabling a comparison between different process alternatives. A marginal production perspective is proposed in this study for the definition of a general energy performance indicator, recalculating all services to primary energy on a system level. The Energy Price and Carbon Balance Scenarios (ENPAC) tool developed at Chalmers is used for the definition of the energy system background. Thereby, a scenario-specific comparison of the processes’ thermodynamic, economic and carbon footprint performance is possible. The usefulness of the approach is illustrated for production of synthetic natural gas (SNG) from biomass. The shortcomings of common performance indicators are also discussed.

Significant increase of production of biofuels for transportation has sparked much debate among researchers and policy-makers. On the one hand, biofuels are seen as a powerful option for greenhouse gas (GHG) emission reduction, for reducing fossil fuel dependency, as well as for local job creation in rural areas [1] and their use is promoted by targets for a 20% renewable energy share within the transport sector by 2020 in the European Union [2]. In particular the concept of biorefineries – resulting in a spectrum of products using an integrated upgrading system – has become a promising concept for efficient production of biofuels [3]. On the other hand their impact on food production and prices as well as their climate change mitigation potential is uncertain, as evidenced by a number of studies that present contrasting results (see for example [4] and [5]). A general consensus is that there is a need for identification of sustainability criteria for biofuel production in order to be able to compare different alternatives on a common basis and to assess their actual potential regarding different aspects [6] and [7].

In this paper, a systematic way of evaluating the performance of biofuel production processes using energy market scenarios has been demonstrated. Using this approach, a multi-faceted evaluation is possible accounting for the energy and economic performance, as well as for the CO2 consequences within different possible future energy background. The three performance indicators thereby can be used as supporting tool for policy-makers. The method has been demonstrated for the example of SNG production process alternatives designed as stand-alone plant, or as integrated solutions to an existing CHP steam power plant. The energy performance on a system level of the integrated solutions is superior to the stand-alone alternative for all scenarios when aiming at a high level of thermal integration. The economic evaluation shows little to no profitable opportunities for SNG production from biomass in all scenarios. Additional policy support would be needed to render SNG production economically viable. The CO2 emissions for SNG production increase for all scenarios due to the underlying assumption of biomass combustion not being CO2 neutral and coal power plants being the reference user of biomass. Adopting the more conventional approach of considering CO2 emissions during biomass combustion to be negligible, the results are changed considerably showing a reduction of CO2 emissions by introducing SNG production for replacing natural gas