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  • 1.
    Brandao, Miguel
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering. IEA Bioenergy Task 38, Int Energy Agcy, Stockholm, Sweden.
    Kirschbaum, Miko U. F.
    Landcare Res, Palmerston North, New Zealand..
    Cowie, Annette L.
    IEA Bioenergy Task 38, Int Energy Agcy, Stockholm, Sweden.;Univ New England, NSW Dept Primary Ind, Armidale, NSW, Australia..
    Hjuler, Susanne Vedel
    Slangerup, Slangerup, Denmark.;COWI AS, Lyngby, Denmark..
    Quantifying the climate change effects of bioenergy systems: Comparison of 15 impact assessment methods2019In: Global Change Biology Bioenergy, ISSN 1757-1693, E-ISSN 1757-1707, Vol. 11, no 5, p. 727-743Article in journal (Refereed)
    Abstract [en]

    Ongoing concern over climate change has led to interest in replacing fossil energy with bioenergy. There are different approaches to quantitatively estimate the climate change effects of bioenergy systems. In the present work, we have focused on a range of published impact assessment methods that vary due to conceptual differences in the treatment of biogenic carbon fluxes, the type of climate change impacts they address and differences in time horizon and time preference. Specifically, this paper reviews fifteen different methods and applies these to three hypothetical bioenergy case studies: (a) woody biomass grown on previously forested land; (b) woody biomass grown on previous pasture land; and (b) annual energy crop grown on previously cropped land. Our analysis shows that the choice of method can have an important influence on the quantification of climate change effects of bioenergy, particularly when a mature forest is converted to bioenergy use as it involves a substantial reduction in biomass carbon stocks. Results are more uniform in other case studies. In general, results are more sensitive to specific impact assessment methods when they involve both emissions and removals at different points in time, such as for forest bioenergy, but have a much smaller influence on agricultural bioenergy systems grown on land previously used for pasture or annual cropping. The development of effective policies for climate change mitigation through renewable energy use requires consistent and accurate approaches to identification of bioenergy systems that can result in climate change mitigation. The use of different methods for the same purpose: estimating the climate change effects of bioenergy systems, can lead to confusing and contradictory conclusions. A full interpretation of the results generated with different methods must be based on an understanding that the different methods focus on different aspects of climate change and represent different time preferences.

  • 2. Ericsson, N.
    et al.
    Porsö, C.
    Åhlgren, S.
    Nordberg, Å.
    Sundberg, Cecilia
    Hansson, P. -A
    Time-dependent climate impact of a bioenergy system - methodology development and application to Swedish conditions2013In: Global Change Biology Bioenergy, ISSN 1757-1693, E-ISSN 1757-1707, Vol. 5, no 5, p. 580-590Article in journal (Refereed)
    Abstract [en]

    The area of dedicated energy crops is expected to increase in Sweden. This will result in direct land use changes, which may affect the carbon stocks in soil and biomass, as well as yield levels and the use of inputs. Carbon dioxide (CO2) fluxes of biomass are often not considered when calculating the climate impact in life cycle assessments (LCA) assuming that the CO2 released at combustion has recently been captured by the biomass in question. With the extended time lag between capture and release of CO2inherent in many perennial bioenergy systems, the relation between carbon neutrality and climate neutrality may be questioned. In this paper, previously published methodologies and models are combined in a methodological framework that can assist LCA practitioners in interpreting the time-dependent climate impact of a bioenergy system. The treatment of carbon differs from conventional LCA practice in that no distinction is made between fossil and biogenic carbon. A time-dependent indicator is used to enable a representation of the climate impact that is not dependent on the choice of a specific characterization time horizon or time of evaluation and that does not use characterization factors, such as global warming potential and global temperature potential. The indicator used to aid in the interpretation phase of this paper is global mean surface temperature change (ΔTs(n)). A theoretical system producing willow for district heating was used to study land use change effects depending on previous land use and variations in the standing biomass carbon stocks. When replacing annual crops with willow this system presented a cooling contribution to ΔTs(n). However, the first years after establishing the willow plantation it presented a warming contribution to ΔTs(n). This behavior was due mainly to soil organic carbon (SOC) variation. A rapid initial increase in standing biomass counteracted the initial SOC loss.

  • 3. Ericsson, N.
    et al.
    Sundberg, Cecilia
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Industrial Ecology.
    Nordberg, Å.
    Ahlgren, S.
    Hansson, P. -A
    Time-dependent climate impact and energy efficiency of combined heat and power production from short-rotation coppice willow using pyrolysis or direct combustion2017In: Global Change Biology Bioenergy, ISSN 1757-1693, E-ISSN 1757-1707, Vol. 9, no 5, p. 876-890Article in journal (Refereed)
    Abstract [en]

    A life cycle assessment of a Swedish short-rotation coppice willow bioenergy system generating electricity and heat was performed to investigate how the energy efficiency and time-dependent climate impact were affected when the feedstock was converted into bio-oil and char before generating electricity and heat, compared with being combusted directly. The study also investigated how the climate impact was affected when part of the char was applied to soil as biochar to act as a carbon sequestration agent and potential soil improver. The energy efficiencies were calculated separately for electricity and heat as the energy ratios between the amount of energy service delivered by the system compared to the amount of external energy inputs used in each scenario after having allocated the primary energy related to the inputs between the two energy services. The energy in the feedstock was not included in the external energy inputs. Direct combustion had the highest energy efficiency. It had energy ratios of 10 and 36 for electricity and heat, respectively. The least energy-efficient scenario was the pyrolysis scenario where biochar was applied to soils. It had energy ratios of 4 and 12 for electricity and heat, respectively. The results showed that pyrolysis with carbon sequestration might be an option to counteract the current trend in global warming. The pyrolysis system with soil application of the biochar removed the largest amount of CO2 from the atmosphere. However, compared with the direct combustion scenario, the climate change mitigation potential depended on the energy system to which the bioenergy system delivered its energy services. A system expansion showed that direct combustion had the highest climate change mitigation potential when coal or natural gas were used as external energy sources to compensate for the lower energy efficiency of the pyrolysis scenario.

  • 4. Hammar, T.
    et al.
    Hansson, P. -A
    Sundberg, Cecilia
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Industrial Ecology.
    Climate impact assessment of willow energy from a landscape perspective: A Swedish case study2017In: Global Change Biology Bioenergy, ISSN 1757-1693, E-ISSN 1757-1707, Vol. 9, no 5, p. 973-985Article in journal (Refereed)
    Abstract [en]

    Locally produced bioenergy can decrease the dependency on imported fossil fuels in a region, while also being valuable for climate change mitigation. Short-rotation coppice willow is a potentially high-yielding energy crop that can be grown to supply a local energy facility. This study assessed the energy performance and climate impacts when establishing willow on current fallow land in a Swedish region with the purpose of supplying a bio-based combined heat and power plant. Time-dependent life cycle assessment (LCA) was combined with geographic information system (GIS) mapping to include spatial variation in terms of transport distance, initial soil organic carbon content, soil texture and yield. Two climate metrics were used [global warming potential (GWP) and absolute global temperature change potential (AGTP)], and the energy performance was determined by calculating the energy ratio (energy produced per unit of energy used). The results showed that when current fallow land in a Swedish region was used for willow energy, an average energy ratio of 30 MJ MJ-1 (including heat, power and flue gas condensation) was obtained and on average 84.3 Mg carbon per ha was sequestered in the soil during a 100-year time frame (compared with the reference land use). The processes contributing most to the energy use during one willow rotation were the production and application of fertilizers (~40%), followed by harvest (~35%) and transport (~20%). The temperature response after 100 years of willow cultivation was -6·10-16K MJ-1 heat, which is much lower compared with fossil coal and natural gas (70·10-16K MJ-1 heat and 35·10-16 K MJ-1 heat, respectively). The combined GIS and time-dependent LCA approach developed here can be a useful tool in systematic analysis of bioenergy production systems and related land use effects.

  • 5.
    Hansson, Julia
    et al.
    IVL Swedish Environm Res Inst, Climate & Sustainable Cities, Energy, Gothenburg, Sweden.;Chalmers Univ Technol, Dept Mech & Maritime Sci, Maritime Environm Sci, Gothenburg, Sweden..
    Berndes, Goran
    Chalmers Univ Technol, Dept Space Earth & Environm, Phys Resource Theory, Gothenburg, Sweden..
    Englund, Oskar
    Chalmers Univ Technol, Dept Space Earth & Environm, Phys Resource Theory, Gothenburg, Sweden..
    Mazzaro de Freitas, Flavio Luiz
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Sustainability Assessment and Management.
    Sparovek, Gerd
    Univ Sao Paulo, Dept Soil Sci, Piracicaba, SP, Brazil..
    How is biodiversity protection influencing the potential for bioenergy feedstock production on grasslands?2019In: Global Change Biology Bioenergy, ISSN 1757-1693, E-ISSN 1757-1707, Vol. 11, no 3, p. 517-538Article in journal (Refereed)
    Abstract [en]

    Sustainable feedstock supply is a critical issue for the bioenergy sector. One concern is that feedstock production will impact biodiversity. We analyze how this concern is addressed in assessments of biomass supply potentials and in selected governance systems in the EU and Brazil, including the EU Renewable Energy Directive (RED), the EU Common Agricultural Policy (CAP), and the Brazilian Forest Act. The analysis focuses on grasslands and includes estimates of the amount of grassland area (and corresponding biomass production volume) that would be excluded from cultivation in specific biodiversity protection scenarios. The reviewed assessments used a variety of approaches to identify and exclude biodiverse grasslands as unavailable for bioenergy. Because exclusion was integrated with other nature protection considerations, quantification of excluded grassland areas was often not possible. The RED complements and strengthens the CAP in terms of biodiversity protection. Following the RED, an estimated 39%-48% (about 9-11 Mha) and 15%-54% (about 10-38 Mha) of natural and non-natural grassland, respectively, may be considered highly biodiverse in EU-28. The estimated biomass production potential on these areas corresponds to some 1-3 and 1.5-10 EJ/year for natural and non-natural grassland, respectively (depending on area availability and management intensity). However, the RED lacks clear definitions and guidance, creating uncertainty about its influence on grassland availability for bioenergy feedstock production. For Brazil, an estimated 16%-77% (about 16-76 Mha) and 1%-32% (about 7-24 Mha) of natural and non-natural grassland, respectively, may be considered highly biodiverse. In Brazil, ecological-economic zoning was found potentially important for grassland protection. Further clarification of grassland definitions and delineation in regulations will facilitate a better understanding of the prospects for bioenergy feedstock production on grasslands, and the impacts of bioenergy deployment on biodiversity.

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