One of the strategies to ensure energy security and to mitigate climate change in the European Union (EU) is the establishment and the use of short rotation woody crops (SRWCs) for the production of ...renewable energy. SRWCs are cultivated in the EU under different management systems. Addressing the energy security problems through SRWCs requires management systems that maximize the net energy yield per unit land area. We assembled and evaluated on-farm data from within the EU, (i) to understand the relationship between the SRWC yields and spatial distribution of precipitation, as well as the relationship between SRWC yield and the planting density, and (ii) to investigate whether extensively managed SRWC systems are more energy efficient than their intensively managed counterparts. We found that SRWC yield ranged from 1.3 to 24tha−1y−1 (mean 9.3±4.2tha−1y−1) across sites. We looked for, but did not find a relationship between yield and annual precipitation as well as between yield and planting density. The energy inputs of extensively managed SRWC systems ranged from 3 to 8GJha−1y−1 whereas the energy ratio (i.e. energy output to energy input ratio) varied from 9 to 29. Although energy inputs (3–16GJha−1y−1) were larger in most cases than those of extensively managed SRWC systems, intensively managed SRWC systems in the EU had higher energy ratios, i.e. between 15 and 62. The low energy ratio of extensively managed SRWC systems reflected their lower biomass yield per unit area. Switching from intensively managed SRWC systems to extensively managed ones thus creates an energy gap, and will require more arable land to be brought into production to compensate for the yield loss. Consequently, extensification is not the most appropriate path to the success of the wide scale deployment of SRWC for bioenergy production in the EU.
The production of bioenergy in Europe is one of the strategies conceived to reduce greenhouse gas (GHG) emissions. The suitability of the land use change from a cropland (REF site) to a ...short-rotation coppice plantation of hybrid poplar (SRC site) was investigated by comparing the GHG budgets of these two systems over 24 months in Viterbo, Italy. This period corresponded to a single rotation of the SRC site. The REF site was a crop rotation between grassland and winter wheat, i.e. the same management of the SRC site before the conversion to short-rotation coppice. Eddy covariance measurements were carried out to quantify the net ecosystem exchange of CO2 (FCO2), whereas chambers were used to measure N2O and CH4 emissions from soil. The measurements began 2 years after the conversion of arable land to SRC so that an older poplar plantation was used to estimate the soil organic carbon (SOC) loss due to SRC establishment and to estimate SOC recovery over time. Emissions from tractors and from production and transport of agricultural inputs (FMAN) were modelled. A GHG emission offset, due to the substitution of natural gas with SRC biomass, was credited to the GHG budget of the SRC site. Emissions generated by the use of biomass (FEXP) were also considered. Suitability was finally assessed by comparing the GHG budgets of the two sites. CO2 uptake was 3512 ± 224 g CO2 m−2 at the SRC site in 2 years, and 1838 ± 107 g CO2 m−2 at the REF site. FEXP was equal to 1858 ± 240 g CO2 m−2 at the REF site, thus basically compensating for FCO2, while it was 1118 ± 521 g CO2 m−2 at the SRC site. The SRC site could offset 379.7 ± 175.1 g CO2eq m−2 from fossil fuel displacement. Soil CH4 and N2O fluxes were negligible. FMAN made up 2 and 4 % in the GHG budgets of SRC and REF sites respectively, while the SOC loss was 455 ± 524 g CO2 m−2 in 2 years. Overall, the REF site was close to neutrality from a GHG perspective (156 ± 264 g CO2eq m−2), while the SRC site was a net sink of 2202 ± 792 g CO2eq m−2. In conclusion the experiment led to a positive evaluation from a GHG viewpoint of the conversion of cropland to bioenergy SRC.
Smart grids (SGs) have a central role in the development of the global power sector. Cost-benefit analyses and environmental impact assessments are used to support policy on the deployment of SG ...systems and technologies. However, the conflicting and widely varying estimates of costs, benefits, greenhouse gas (GHG) emission reduction, and energy savings in literature leave policy makers struggling with how to advise regarding SG deployment. Identifying the causes for the wide variation of individual estimates in the literature is crucial if evaluations are to be used in decision-making. This paper (i) summarizes and compares the methodologies used for economic and environmental evaluation of SGs (ii) identifies the sources of variation in estimates across studies, and (iii) point to gap in research on economic and environmental analyses of SG systems. Seventeen studies (nine articles and eight reports published between 2000 and 2015) addressing the economic costs versus benefits, energy efficiency, and GHG emissions of SGs were systematically searched, located, selected, and reviewed. Their methods and data were subsequently extracted and analysed. The results show that no standardized method currently exists for assessing the economic and environmental impacts of SG systems. The costs varied between 0.03 and 1143M€/yr, while the benefits ranged from 0.04 to 804M€/yr, suggesting that SG systems do not result in cost savings The primary energy savings ranged from 0.03 to 0.95MJ/kWh, whereas the GHG emission reduction ranged from 10 to 180gCO2/kWh, depending on the country grid mix and the system boundary of the SG system considered. The findings demonstrate that although SG systems are energy efficient and reduce GHG emissions, investments in SG systems may not yield any benefits. Standardizing some methodologies and assumptions such as discount rates, time horizon and scrutinizing some key input data will result in more consistent estimates of costs and benefits, GHG emission reduction, and energy savings.
•Comparison of 40 bioenergy pathways to a fossil-fuel based CHP system.•Not all energy efficient pathways led to lower GHG emissions.•iLUC through intensification increased the total energy input and ...GHG emissions.•Fluidized bed technologies maximize the energy and GHG benefits of all pathways.•Perennial crops are in some cases better than residues on GHG emissions criteria.
Bioenergy (i.e., bioheat and bioelectricity) could simultaneously address energy insecurity and climate change. However, bioenergy’s impact on climate change remains incomplete when land use changes (LUC), soil organic carbon (SOC) changes, and the auxiliary energy consumption are not accounted for in the life cycle. Using data collected from Belgian farmers, combined heat and power (CHP) operators, and a life cycle approach, we compared 40 bioenergy pathways to a fossil-fuel CHP system. Bioenergy required between 0.024 and 0.204MJ (0.86MJth+0.14 MJel)−1, and the estimated energy ratio (energy output-to-input ratio) ranged from 5 to 42. SOC loss increased the greenhouse gas (GHG) emissions of residue based bioenergy. On average, the iLUC represented ∼67% of the total GHG emissions of bioenergy from perennial energy crops. However, the net LUC (i.e., dLUC+iLUC) effects substantially reduced the GHG emissions incurred during all phases of bioenergy production from perennial crops, turning most pathways based on energy crops to GHG sinks. Relative to fossil-fuel based CHP all bioenergy pathways reduced GHG emissions by 8–114%. Fluidized bed technologies maximize the energy and the GHG benefits of all pathways. The size and the power-to-heat ratio for a given CHP influenced the energy and GHG performance of these bioenergy pathways. Even with the inclusion of LUC, perennial crops had better GHG performance than agricultural and forest residues. Perennial crops have a high potential in the multidimensional approach to increase energy security and to mitigate climate change. The full impacts of bioenergy from these perennial energy crops must, however, be assessed before they can be deployed on a large scale.
•A full energy and GHG balance of bioelectricity from SRWC was performed.•Bioelectricity was efficient; it reduced GHG by 52–54% relative to the EU non-renewable grid mix.•Bioelectricity required ...1.1m2 of land kWh−1; land conversion released 2.8±0.2 t CO2eha−1.•SRWC reduced GHG emission when producing electricity during the 1st rotation period.
Short-rotation woody crops (SRWCs) are a promising means to enhance the EU renewable energy sources while mitigating greenhouse gas (GHG) emissions. However, there are concerns that the GHG mitigation potential of bioelectricity may be nullified due to GHG emissions from direct land use changes (dLUCs). In order to evaluate quantitatively the GHG mitigation potential of bioelectricity from SRWC we managed an operational SRWC plantation (18.4ha) for bioelectricity production on a former agricultural land without supplemental irrigation or fertilization. We traced back to the primary energy level all farm labor, materials, and fossil fuel inputs to the bioelectricity production. We also sampled soil carbon and monitored fluxes of GHGs between the SRWC plantation and the atmosphere. We found that bioelectricity from SRWCs was energy efficient and yielded 200–227% more energy than required to produce it over a two-year rotation. The associated land requirement was 0.9m2kWhe-1 for the gasification and 1.1m2kWhe-1 for the combustion technology. Converting agricultural land into the SRWC plantation released 2.8 ± 0.2tCO2eha−1, which represented ∼89% of the total GHG emissions (256–272gCO2ekWhe-1) of bioelectricity production. Despite its high share of the total GHG emissions, dLUC did not negate the GHG benefits of bioelectricity. Indeed, the GHG savings of bioelectricity relative to the EU non-renewable grid mix power ranged between 52% and 54%. SRWC on agricultural lands with low soil organic carbon stocks are encouraging prospects for sustainable production of renewable energy with significant climate benefits.
Poplar (Populus spp.) and willow (Salix spp.) short rotation coppice (SRC) are attractive feedstock for conversion to renewable electricity. Site managers typically optimize biomass production at ...their sites. However, maximum biomass production does not necessarily equate an optimal CO2 balance, water use and energy production. This is because many operational actions consume water and energy and emit CO2, either on-site or off-site. Coupling a land surface model (ORCHIDEE-SRC) with life cycle assessment enabled us to determine the optimal management for SRC in Belgium. We simulated 120 different management scenarios for each of two well-studied Belgian SRC sites (i.e. Boom and Lochristi). Simulated soil carbon changes suggested substantial carbon losses of 20–30 Mg ha−1 over a time period of 20 years, which were within observation-based uncertainty bounds. Results showed that in Belgium, which has a temperate maritime climate, optimal management of SRC has a rotation cycle of two years without irrigation. Energy inputs for this optimal management were 5.2 GJ ha−1 yr−1 for the Boom site and 5.3 GJ ha−1 yr−1 for the Lochristi site, while the biomass yields at Boom and Lochristi were 9.0 Mg ha−1 yr−1 and 9.4 Mg ha−1 yr−1, respectively. The energy ratio (i.e., ratio of bioelectricity output to cumulative energy input) for this optimal management was 12, on average. Planting density turned out to be unimportant, while rotation length turned out to be most important to obtain the highest energy ratio and still maintain high biomass yield. Scenarios with high energy-input generated more bioenergy outputs, but the energy gains did not compensate for the increased energy inputs. Reductions in energy consumption per unit of bioenergy output should target the agricultural stage since it accounted for the largest energy share in the production chain.
•Water use, CO2 and energy balance of SRC were compared across managements regimes in Belgium using a modelling approach.•Variation in planting densities from 5000 to 15000 trees ha−1 showed no effect on SRC yields.•Irrigation benefits biomass production, but is energetically too costly to apply.•High energy ratios proved that SRC-based electricity production is energy efficient.•Optimal rotation length was two years without irrigation.
There is an ongoing debate regarding the influence of the source location of pollution on the fate of pollutants and their subsequent impacts. Several methods have been developed to derive ...site-dependent characterization factors (CFs) for use in life-cycle assessment (LCA). Consistent, precise, and accurate estimates of CFs are crucial for establishing long-term, sustainable air pollution abatement policies. We reviewed currently available studies on the regionalization of non-toxic air pollutants in LCA. We also extracted and converted data into indices for analysis. We showed that CFs can distinguish between emissions occurring in different locations, and that the different methods used to derive CFs map locations consistently from very sensitive to less sensitive. Seasonal variations are less important for the computation of CFs for acidification and eutrophication, but they are relevant for the calculation of CFs for tropospheric ozone formation. Large intra-country differences in estimated CFs suggest that an abatement policy relying on quantitative estimates based upon a single method may have undesirable outcomes. Within country differences in estimates of CFs for acidification and eutrophication are the results of the models used, category definitions, soil sensitivity factors, background emission concentration, critical loads database, and input data. Striking features in these studies were the lack of CFs for countries outside Europe, the USA, Japan, and Canada, the lack of quantification of uncertainties. Parameter and input data uncertainties are well quantified, but the uncertainty associated with the choice of category indicator is rarely quantified and this can be significant. Although CFs are scientifically robust, further refinements are needed before they can be integrated in LCA. Future research should include uncertainty analyses, and should develop a consensus model for CFs. CFs for countries outside Europe, Japan, Canada and the USA are urgently needed.
•A summary of CFs for acidification, eutrophication and tropospheric ozone is made.•Comparison of CFs is performed and uncertainties in CFs are identified and classified.•Estimates of CFs vary substantially across studies.•Uncertainties related to modeler's choice are not quantified and can be significant.•CFs for regions outside Europe and USA is needed as well as a consensus model for CFs.
The Paris Agreement promotes forest management as a pathway towards halting climate warming through the reduction of carbon dioxide (CO
) emissions
. However, the climate benefits from carbon ...sequestration through forest management may be reinforced, counteracted or even offset by concurrent management-induced changes in surface albedo, land-surface roughness, emissions of biogenic volatile organic compounds, transpiration and sensible heat flux
. Consequently, forest management could offset CO
emissions without halting global temperature rise. It therefore remains to be confirmed whether commonly proposed sustainable European forest-management portfolios would comply with the Paris Agreement-that is, whether they can reduce the growth rate of atmospheric CO
, reduce the radiative imbalance at the top of the atmosphere, and neither increase the near-surface air temperature nor decrease precipitation by the end of the twenty-first century. Here we show that the portfolio made up of management systems that locally maximize the carbon sink through carbon sequestration, wood use and product and energy substitution reduces the growth rate of atmospheric CO
, but does not meet any of the other criteria. The portfolios that maximize the carbon sink or forest albedo pass only one-different in each case-criterion. Managing the European forests with the objective of reducing near-surface air temperature, on the other hand, will also reduce the atmospheric CO
growth rate, thus meeting two of the four criteria. Trade-off are thus unavoidable when using European forests to meet climate objectives. Furthermore, our results demonstrate that if present-day forest cover is sustained, the additional climate benefits achieved through forest management would be modest and local, rather than global. On the basis of these findings, we argue that Europe should not rely on forest management to mitigate climate change. The modest climate effects from changes in forest management imply, however, that if adaptation to future climate were to require large-scale changes in species composition and silvicultural systems over Europe
, the forests could be adapted to climate change with neither positive nor negative climate effects.
A life cycle assessment was performed to quantify and compare the energetic and environmental performances of hydrogen from wheat straw (WS-H2), sweet sorghum stalk (SSS-H2), and steam potato peels ...(SPP-H2). Inventory data were derived from a pilot plant. Impacts were assessed using the impact 2002+ method. When co-product was not considered, the greenhouse gas (GHG) emissions were 5.60kg CO2eq kg−1H2 for WS-H2, 5.32kg CO2eq kg−1H2 for SSS-H2, and 5.18kg CO2eq kg−1H2 for SPP-H2. BioH2 pathways reduced GHG emissions by 52–56% compared to diesel and by 54–57% compared to steam methane reforming production of H2. The energy ratios (ER) were also comparable: 1.08 for WS-H2, 1.14 for SSS-H2 and 1.17 for SPP-H2. A shift from SPP-H2 to WS-H2 would therefore not affect the ER and GHG emissions of these BioH2 pathways. When co-product was considered, a shift from SPP-H2 to WS-H2 or SSS-H2 decreased the ER, while increasing the GHG emissions significantly. Co-product yield should be considered when selecting BioH2 feedstocks.
Winter oilseed rape (WOSR) is the main crop for biodiesel in the EU, where legislation demands at least 50% savings in greenhouse gas (GHG) emissions as compared to fossil diesel. Thus industrial ...sectors search for optimized management systems to lower GHG emissions from oilseed rape cultivation. Recently, pyrolysis of biomass with subsequent soil amendment of biochar has shown potentials for GHG mitigation in terms of carbon (C) sequestration, avoidance of fossil based electricity, and mitigation of soil nitrous oxide (N2O) emissions. Here we analyzed three WOSR scenarios in terms of their global warming impact using a life cycle assessment approach. The first was a reference scenario with average Danish WOSR cultivation where straw residues were incorporated to the soil. The others were biochar scenarios in which the oilseed rape straw was pyrolysed to biochar at two process temperatures (400 and 800 °C) and returned to the field. The concept of avoided atmospheric CO2 load was applied for calculation of C sequestration factors for biochar, which resulted in larger mitigation effects than derived from calculations of just the remaining C in soil. In total, GHG emissions were reduced by 73 to 83% in the two biochar scenarios as compared to the reference scenario, mainly due to increased C sequestration. The climate benefits were higher for pyrolysis of oilseed rape straw at 800 than at 400 °C. The results demonstrated that biochar has a potential to improve the life cycle GHG emissions of oilseed rape biodiesel, and highlighted the importance of consolidated key assumptions, such as biochar stability in soil and the CO2 load of marginal grid electricity.
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•Two scenarios were analyzed of including biochar in Danish oilseed rape cultivation.•Carbon sequestration factors for two generic biochars were derived for use in LCA.•Carbon sequestration effects dominated the GHG mitigation in biochar scenarios.•Biochar effects on soil emissions of N2O had limited impact on total GHG mitigations.•Well-defined key assumptions on biochar degradation and grid electricity are crucial.
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