ارزیابی کارایی اقتصادی از فن آوری های انرژی زیستی در کاهش اثرات آب و هوایی و جایگزین سوخت فسیلی در اتریش با استفاده از روش های اقتصادی

The core issues of the Austrian energy policy agenda include reducing greenhouse gas (GHG) emissions and dependence on fossil fuels. Within this study, the costs of GHG mitigation and fossil fuel replacement (abatement costs) of established and upcoming bioenergy technologies for heat, electricity and transport fuel production are assessed. Sensitivity analyses and projections up to 2030 illustrate the effect of dynamic parameters on specific abatement costs. The results show that the abatement costs of wood-based heat generation technologies substituting oil-fired boilers and gas-fired heating plants, respectively, are in the range of −45 € per ton CO2-equivalent (€/t CO2-eq.) and −11 € per MW h higher heating value (€/MW hHHV) to 93 €/t CO2-eq. and 24 €/MW hHHV. Heating systems around 50 kW show the lowest abatement costs. For combined heat and power (CHP) plants, two different cases with regard to heat utilization are assumed. In an optimal mode (100% of generated heat displaces fossil fuel-based heat production), abatement costs of wood-based technologies, substituting electricity from modern combined cycle gas turbines, range from 5 €/t CO2-eq. and 1 €/MW hHHV to 201 €/t CO2-eq. and 38 €/MW hHHV. Representative values of typical CHP plants with a capacity of 1 MWel and more are in the magnitude of 50 €/t CO2-eq. and 10 €/MW hHHV. Under less favorable conditions (3000 heat full load hours per year), abatement costs of typical plants are around 100 €/t CO2-eq. and 17 €/MW hHHV higher. The costs of GHG mitigation and fossil fuel saving with established transport fuels (biodiesel and ethanol) range from 71 €/t CO2-eq. and 8 €/MW hHHV to 200 €/t CO2-eq. and 82 €/MW hHHV. For liquid fuels from lignocellulosis, abatement costs are estimated 147 €/t CO2-eq. and 38 €/MW hHHV to 240 €/t CO2-eq. and 59 €/MW hHHV. The abatement costs of synthetic natural gas are found to be significantly lower: 75 €/t CO2-eq. and 14 €/MW hHHV to 128 €/t CO2-eq. and 23 €/MW hHHV. The results suggest that heat generation and – given favorable conditions – CHP generation are the most cost-efficient options for reducing GHG emissions and fossil fuel dependence in Austria. A core advantage of CHP is higher quantities of abatement per unit of biomass used. In contrast, this is found to be the main drawback of synthetic transport fuels from wood.

Two of the major challenges of the European Union’s and Austria’s energy policy are to reduce greenhouse gas (GHG) emissions and dependence on fossil fuels [1]. Bioenergy is generally expected to make a significant contribution to these energy policy targets (see [2] or [3]). Not only because it currently (2008) has the highest share of all renewable energy sources in Austria (and the EU), but also due to its vast potentials and the fact that it can be used in all energy sectors: for heat-only production or combined heat and power (CHP) generation as well as for the production of biofuels.2 Furthermore, there is a wide variety of biomass fractions, technologies and plant sizes. Hence, there are numerous pathways for energy conversion from biogenic energy carriers, each of which has specific properties with regard to GHG mitigation, fossil fuel replacement and economics. 1.1. Biomass and fossil fuel consumption in Austria Biomass currently accounts for about 15% of the total primary energy consumption in Austria (all data about the current energy use stated here are based on [4] and [5], and refer to 2008 unless otherwise stated). Until the end of the 20th century, the use of bioenergy was virtually limited to heat generation (residential heating and process heat generation). Today biomass accounts for about 30% of the total energy demand for space and water heating. Despite the growing importance of renewable energy sources, fossil fuels account for more than 50% (heating oil: 74 PJ, natural gas: 76 PJ). Therefore, the use of biomass in the heat sector still holds the opportunity for substituting significant amounts of fossil fuels. Biomass has also become increasingly important for district heating, power generation and in the transport sector due to support schemes in recent years. About 38% of the district heat supply is currently based on biomass (25.5 PJ), with 17% coming from heating plants and 21% from CHP plants.3 The non-renewable production of district heat is dominated by natural gas: 32% of the total supply originate from natural gas CHP and 10% from heating plants. In the electricity sector the biomass share has increased from 3% in the late 1990s to 6.5% in 2008. Fossil-based electricity generation accounts for about 30% (with more than half of this coming from natural gas-fired power plants), the rest is primarily hydropower. As a consequence of obligatory quotas and tax incentives, the share of biofuels in road transport fuel consumption has increased from less than 1% in 2005 to 7% in 2009 [6]. The fossil fuel consumption in the transport sector accounts for about 300 PJ/a (about 75% diesel and 25% gasoline). 1.2. Objective Comparing GHG mitigation costs of different technologies is a commonly used approach for identifying efficient strategies for achieving climate policy targets (e.g. [7] and [8]). However, there is scarce literature comparing GHG mitigation costs of different bioenergy technologies, taking into account the wide range of plant sizes and variable operational characteristics, such as annual full load hours or heat utilization rates of CHP plants. The objective of this work is to assess GHG mitigation costs as well as costs arising from replacing fossil fuels with bioenergy technologies for the situation in Austria. Biomass and fossil fuel prices are based on specific data for Austria. Costs data were also preferably taken from studies referring to the situation in Austria (e.g. [9]) and the selection of technologies is based on which plant types and sizes are common in Austria. In addition, technologies which are likely to become more important in the future are taken into account. The results are to provide insight into the question of how limited biomass resources can be utilized in a most efficient way, and how bioenergy can contribute to the achievement of energy policy targets in a cost-efficient way for the specific case of Austria. In contrast to these and other publications on this topic (see Section 4), a core objective of this study is to highlight the influence of plant sizes and other (country-specific) parameters on the efficiency of bioenergy technologies for GHG mitigation and fossil fuel replacement. Furthermore, projections for technological developments, plant costs and fuel prices are used to assess trends up to 2030.

Bioenergy is the most important renewable energy source used for GHG mitigation and fossil fuel replacement in Austria. With the increasing exploitation of sustainable biomass potentials, the question of how limited biomass resources can be utilized in a most efficient way is gaining in importance. In contrast to CCS, bioenergy can contribute to two major energy policy targets: reducing GHG emission and dependence on fossil fuels. The results of this work indicate that the economic efficiency of bioenergy for GHG mitigation and fossil fuel replacement vary widely for different plant types and applications. In the default case, the abatement costs among the technologies considered in this study are achieved with 50 kW-small-scale heating systems. Heating systems and plants generally show a good performance, with GHG mitigation costs of typically 0–50 €/t CO2-eq. and 10 €/MW hHHV when substituting oil-fired boilers and gas-fired heating plants, respectively. However, modern biomass heating systems under 15 kW show clearly higher abatement costs of up to 100 €/t CO2-eq. and 25 €/MW hHHV. In order to achieve high quantities of abatement with biomass CHP, it is essential that the heat output is utilized to a high degree. In practice, this is achieved by choosing suitable locations for CHP plants and appropriate dimensioning, so that annual full load hours above 6000 h/a [9]. In such cases, the abatement costs of most technologies account for less than 100 €/t CO2-eq. and 20 €/MW hHHV.17 Even lower abatement costs are possible with large-scale CHP plants; especially BIGCC is found to be a promising technology. Technological progress is assumed to lead to improved efficiencies of biomass CHP, resulting in enhanced competitiveness and reduced abatement costs. This is also true for 2nd generation biofuel production technologies. However, the results show that even if abatement cost with these technologies might decrease to about 50 €/t CO2-eq. and 10 €/MW hHHV, one major drawback remains: the quantity of GHG mitigation and fossil fuel saving per unit of biomass used is clearly lower than in the case of heat and especially CHP generation. A major drawback of currently established biofuel technologies is a high sensitivity of production costs to feedstock price variations. With regard to long-term bioenergy strategies, structural changes and the diffusion of other renewable energy technologies need to be taken into account. Residential heating is the energy sector where the most significant reductions in fossil fuel consumption and GHG emissions can be expected through enhanced energy efficiency and the deployment of other renewable energy technologies in the coming decades. Decreasing heat loads have a significant impact on the economic efficiency of biomass heating technologies, as those market segments where bioenergy systems are most economic shrink.18 A trend towards less annual load hours, which is sometimes expected due to enhanced building quality and global warming, also results in higher abatement costs of biomass heating systems. Still, as significantly reducing the residential heat demand by refurbishing the existing building stock will probably take several decades [31], and currently more than 50% of the residential heat demand in Austria is covered with fossil fuels, the use of biomass in the heat sector is considered a cost-efficient way of reducing GHG emissions and fossil fuel demand in the future energy system (cp. [35]). Biofuels are sometimes seen as the only short-term alternative for fossil fuels in the transport sector. However, as long as fossil fuels can be substituted cost-efficiently in the heat sector, it is questionable why efforts to reduce fossil fuel consumption should focus on the transport sector. Significant reductions in transport fuel demand are achievable with more efficient vehicles as well as by electrification. Still, liquid (or gaseous) transport fuels are indispensable for certain applications (e.g. ship and air traffic). Therefore a partial substitution of fossil transport fuels with biofuels is inevitable, albeit on the long term.