Initially, in order to identify the current practices of LCA in the forestry and wood energy sectors and to derive a reproducible, precise and harmonized methodological proposal, two review studies, including meta-analyses were conducted and an initial proposal for a harmonized assessment methodology proposed. Subsequently, in order to apply the methodology onto the case study region of Bavaria, LCA studies for both the provision of wood from Bavarian forests (KLEIN ET AL. 2015) (not covered in this dissertation) and the energetic utilization for heat, as well as the impacts of the entire heating sector and shifts in these impacts through e.g. policy, were analyzed. In a last step, to complete the evaluation of the direct systems emissions identified in publications three, mitigation effects through the displacement of other energy carriers with wood were assessed (FIGURE 1). The following section presents these publications.
Figure 1 Overview of publications in the context of this dissertation. The red line depicts the case study application.
Method development
Systematic review of LCA in the forestry sector
[Publication 1]
Systematic review of LCA for wood energy services
[Publication 2]
Method application
Environmental impacts of raw wood provision in Bavaria
[Klein et al. 2015]
Environmental impacts of energy provision by wood heating systems
in the Bavarian heating mix [Publication 3]
Benefits and burdens outside the primary system boundary
Mitigation of environmental impacts through wood use for
energy services [Publication 4]
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2.1. Publication 1: 20 years of Life Cycle Assessment (LCA) in the forestry sector: state of the art and a methodical proposal for the LCA of forest production
Daniel Klein, Christian Wolf, Christoph Schulz, Gabriele Weber-Blaschke
2015, International Journal of Life Cycle Assessment. DOI: 10.1007/s11367-015-0847-1 Abstract
Although methodologies for the LCA of forest production have been conducted since the early 1990s, consistent and comprehensive LCA studies are still lacking for the forestry sector. In order to support better comparability between LCA studies, we analyzed the problems and differences by conducting a descriptive and quantitative analysis of existing LCA studies of forest production. Important issues were, among others, the goal of the studies, system boundaries, functional units, impact categories and involved processes. In addition, a quantitative analysis in respect to the impact on Global Warming (GW) published by individual studies was performed. The studies showed large differences between methodical assumptions and their subsequent results. For GW, a range between 2.4–59.6 kg CO2-eq. * m−3 over bark from site preparation to forest road delivery and 6.3–67.1 kg CO2-eq.
* m−3 over bark from site preparation to plant gate or consumer delivery could be identified.
Results varied as a function of the included processes and decisive assumptions, e.g., regarding productivity rates or fuel consumption of machineries. Raw wood products are widely declared as “carbon neutral,” but the above-mentioned results show that absolute carbon neutrality is incorrect, although the GW is low compared to the carbon storage of the raw wood product (range of C-emitted/C-stored in wood is 0.008–0.09 from forest to plant gate or consumer). Thereby, raw wood products can be described as “low emission raw materials” if long-term in situ carbon losses by changed forest management or negative direct or indirect land use change effects (LUC, iLUC) can be excluded. In order to realize improved comparisons between LCA studies in the forestry sector in the future, we propose a methodical approach regarding the harmonization of system boundaries, functional units, considered processes, and allocation assumptions.
Contribution
Daniel Klein is the main author of the publication. Christian Wolf co-developed the systematic review protocol and methodological proposal and is responsible for the deduction of system visualization as well as the joint interpretation of the results and discussion parts of this study. Christoph Schulz and Gabriele Weber-Blaschke supported the development of the study in respect to the conceptualization and redacted the publication.
2.2. Publication 2: Systematic review and meta-analysis of Life Cycle Assessments for wood energy services
Christian Wolf, Daniel Klein, Gabriele Weber-Blaschke, Klaus Richter 2015, Journal of Industrial Ecology. DOI: 10.1111/jiec.12321
Abstract
Environmental impacts of the provision of wood energy have been analyzed through Life Cycle Assessment (LCA) techniques for many years. Systems for the generation of heat, power, and combined heat and power (CHP) differ, and methodological choices for LCA can vary greatly, leading to inconsistent findings. We analyzed factors that promote these findings by conducting a systematic review and meta-analysis of publically available LCA studies for wood energy services. The systematic review investigated crucial methodological and systemic factors, such as system boundaries, allocation, and technologies, for transformation and conversion of North American and European LCA studies. Meta-analysis was performed on published results in the impact category Global Warming (GW). A total of 30 studies with 97 systems were incorporated. The studies exhibit great differences in their systemic and methodological choices, as well as their functional units, technologies, and subsequent outcomes. A total of 44 systems for the generation of power, with a median impact on GW of 0.169 kg CO2-eq. * kWhel-1, were identified. Results for the biomass fraction, i.e. the emissions associated with the share of biomass in co-combustion systems, show a median impact on GW of 0.098 kg CO2-eq. * kWhel−1. A total of 31 systems producing heat exhibited a median impact on GW of 0.040 kg CO2-eq. * kWhth−1. With a median impact on GW of 0.066 kg CO2-eq. * kWhel+th−1, CHP systems show the greatest range among all analyzed wood energy services. To facilitate comparisons, we propose a methodological approach for the description of system boundaries, the basis for calculations, and reporting of findings, which can support the development of a bioenergy product category rule (PCR).
Contribution
Christian Wolf was responsible for the study design, carried out the assessment and wrote the article. Daniel Klein supported the statistical analyses for the meta-analyses, provided valuable input towards the system description template and redacted the publication.
Gabriele Weber-Blaschke and Klaus Richter supported the development of the study in respect to its concept, research structure and level of detail, and contributed to the editing process.
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2.3. Publication 3: Environmental effects of shifts in a regional heating mix through variations in the utilization of solid biofuels
Christian Wolf, Daniel Klein, Klaus Richter, Gabriele Weber-Blaschke
2016, Journal of Environmental Management. DOI: 10.1016/j.jenvman.2016.04.019 Abstract
Solid biofuels, i.e. wood, play an important role in present and future national and global climate change mitigation policies. Wood energy, while displaying favorable properties in respect to the mitigation of climate change also exhibits several drawbacks, such as potentially high emission of particulate matter on a regional scale and with regional impacts.
To assess the environmental effects of shifts in the heating mix, emission factors of the comprising energy carriers and the Bavarian heating mix were determined. Through the application of regionalized substitution percentiles the environmental effects caused by shifts in the amount of final energy provided by solid biofuels could be identified. For this purpose, four scenarios, based on political and scientific specifications were assessed. In 2011 a total amount of 663.715 TJ of final energy was used for the provision of heat in Bavaria, with solid biofuels exhibiting the third largest share of 12.6%. Environmental effects were evaluated through LCA calculating the indicator values for Global Warming (GW), particulate matter emissions (PM), freshwater eutrophication (ET), acidification (AC) and the non-renewable primary energy consumption (PE). The heating mix in Bavaria (baseline) caused emissions of 49.6 Mt CO2-eq. * yr−1 (GW), 14,555 t of PM2.5-eq. * yr−1 (PM), 873.4 t P-eq. * yr−1 (ET), and 82.299 kmol H+ eq. * yr−1 (AC), for which 721,745 TJ of primary energy were expended.
Current policies entail a GHG reduction potential of approx. 1 Mt CO2-eq. * yr−1 while increasing the amount of energy wood by 15%. The maximum, hypothetical share of solid biofuels for the heating mix cannot surpass 25%, while the climate change mitigation performance of the current use of solid biofuels is approx. 6.4 Mt CO2-eq. * yr−1. GHG-emissions would be 13% higher and PM GHG-emissions 77% lower without this energetic use of wood. The results aid in the definition of the current and future role of wood energy in the study region of Bavaria.
Contribution
Christian Wolf was responsible for the study design, carried out the assessment and wrote the article. Daniel Klein provided data for the evaluation of wood production and redacted the publication. Gabriele Weber-Blaschke and Klaus Richter supported the development of the study in respect to the structure and conceptual approach and critically reviewed and guided the editing process.
2.4. Publication 4: Mitigating environmental impacts through the energetic use of wood: Regional displacement factors generated by means of substituting non-wood heating systems
Christian Wolf, Daniel Klein, Klaus Richter, Gabriele Weber-Blaschke
2016, Science of the Total Environment. DOI: 10.1016/j.scitotenv.2016.06.021 Abstract
Wood biomass, especially when applied for heating, plays an important role for mitigating environmental impacts such as climate change and the transition towards higher shares of renewable energy in national or regional energy mixes. However, the magnitude of mitigation benefits and burdens associated with wood use can vary greatly depending on regional parameters such as the displaced fossil reference or heating mix. Therefore, displacement factors, considering region-specific production conditions and substituted products are required when assessing the precise contribution of wood biomass towards the mitigation of environmental impacts. We carried out Life Cycle Assessments (LCA) of wood heating systems for typical conditions in Bavaria and substitute energy carriers with a focus on climate change and particulate matter emissions. In order to display regional effects, we created weighted displacement factors for the region of Bavaria, based on installed capacities of individual wood heating systems and the harvested tree species distribution.
The study reveals GHG displacements between −57 g CO2-eq.∗ MJ−1 of useful energy through the substitution of natural gas with a 15 kW spruce pellets heating system and
−165 g CO2-eq.∗ MJ−1 through the substitution of power utilized for heating with a modern 6 kW beech split log heating system. It was shown that the GHG mitigation potentials of wood utilization are overestimated through the common use of light fuel oil as the only reference system. We further propose a methodology for the calculation of displacement factors which is adaptable to other regions worldwide. Based on our approach it is possible to generate displacement factors for wood heating systems which enable accurate decision-making for project planning in households, heating plants, communities and also for entire regions.
Contribution
Christian Wolf was responsible for the study design, carried out the assessment and wrote the article. Daniel Klein provided data for the evaluation of wood production and redacted the publication. Gabriele Weber-Blaschke and Klaus Richter supported the development of the study in respect to the structure and conceptual approach and critically reviewed and guided the editing process.