Global Change Biology Bioenergy最新文献

Bioenergy from biofuels has the potential to slow growing atmospheric carbon dioxide concentrations by reducing fossil fuel use. However, growing bioenergy feedstocks is a land-intensive process. In the United States, the recent expansion of maize bioethanol has presented some environmental costs, prompting the development of several alternative bioenergy feedstocks. These feedstocks, selected in part for traits associated with ecosystem services, may provide opportunities for environmental benefits beyond fossil fuel displacement. We hypothesized that these bioenergy ecosystems will provide direct climatic cooling through their influence on carbon and radiative energy fluxes (i.e., through albedo). To test this hypothesis, we investigated the potential cooling effect of five current or potential bioenergy feedstocks using multi-year records from eddy covariance towers. Perennial feedstocks were carbon sinks, with an annual mean net ecosystem carbon balance (NECB) of −2.7 ± 2.1 Mg C ha⁻¹ for miscanthus, −0.8 ± 1.1 Mg C ha⁻¹ for switchgrass, and −1.4 ± 0.7 Mg C ha⁻¹ for prairie. In contrast, annual rotations were generally carbon sources, with an annual mean NECB of 2.6 ± 2.4 Mg C ha⁻¹ for maize-soy and 3.2 ± 2.1 Mg C ha⁻¹ for sorghum-soy. Using maize-soy as a baseline, conversion to alternative feedstocks increased albedo, inducing further cooling. This effect was strongest for miscanthus, with −3.5 ± 2.0 W m⁻² of radiative forcing, and weakest for sorghum, with −1.4 ± 1.4 W m⁻². When feedstock effects on carbon and albedo were compared using carbon equivalents, carbon fluxes were the stronger ecosystem effect, underscoring the role of perennial species as effective carbon sinks. This work highlights the impact of feedstock choice on ecosystem processes as an element of bioenergy land conversion strategies.

Understanding carbon (C) storage in different soil-sized fractions of perennial bioenergy crops enhances our knowledge of how these crops contribute to long-term soil organic carbon (SOC) storage, with positive implications for mitigating climate change through C sequestration. However, the extent to which perennial bioenergy crops contribute C in different soil-sized fractions remains unclear. Hence, this study investigated SOC contents under perennial bioenergy crops of Miscanthus (Miscanthus × giganteus L.), willow (Salix miyabeana L.), switchgrass (Panicum virgatum L.), and a successional site. We also quantified the C contribution of the bioenergy crops to different soil-sized fractions using the δ¹³C natural abundance technique. After 12 years of cultivation, SOC contents to 30 cm depth increased by 2.5% and 3.1% in willow and Miscanthus, respectively, but decreased by 3.7% in switchgrass compared to baseline SOC data. SOC stocks ranged from 5686 to 7002 g C m⁻² and were higher (p ≤ 0.050) in the successional site compared to switchgrass and willow, but not Miscanthus. Unlike switchgrass and willow, Miscanthus maintained SOC stocks comparable to the successional site even with annual biomass harvest. This implies that the ability of perennial bioenergy crops to influence SOC storage similar to regrowth vegetation on marginally productive cropland depends significantly on the crop species. Additionally, Miscanthus contained higher (p ≤ 0.013) SOC in micro-sized and silt + clay fractions at 20–30 cm depth compared to the 0–10 and 10–20 cm depths and contributed the most C in all three soil-sized fractions compared to switchgrass and willow. Our findings suggest that among the three bioenergy crops, Miscanthus has the greatest potential for long-term C storage and stabilization in deeper soil depths on marginally productive croplands. This holds true even with annual biomass harvesting and the absence of fertilization, making Miscanthus a valuable contributor to climate change mitigation.

The impacts of plastic, including carbon emissions and plastic pollution, have significant negative impacts on human well-being and the environment. Recent research suggests that these impacts could be mitigated by using biomass to create products with lower carbon emissions or that reduce pollution through biodegradation or composting. As the scale of the plastic problem is substantial, the amount of biomass required for mitigation could be large. Biomass may have benefits, but it also has risks, including the potential to cause significant land-use change. Land-use impacts are widely acknowledged in the literature on plastic mitigation but are often downplayed with assumptions that changes in policies, behaviors, agricultural productivity, and technology can ameliorate the most negative impacts. This paper reviews the assumptions made about land use in the literature on biomass-based plastics and plastic alternatives. Current studies generally make optimistic assumptions about land-use change or have limited ability to account for land-use change impacts. These assumptions, including technological and agricultural advancement, along with idealized feedstock sourcing, minimize potential land-use impacts. This paper demonstrates how reasonable projections based on the literature could require a considerable amount of biomass, equivalent to a 7%–13% increase in global crop demand in 2040. Further research investigating projections for biomass use and the assumptions in these estimates is required to better understand potential land-use impacts from bio-based plastic substitutes. This research is important for informing emerging policies, including the UN Treaty on plastic pollution. Establishing criteria and thresholds for the sustainability of bio-based alternatives, as well as identifying potential negative outcomes, will be crucial to avoid setting out on a path with significant unintended and potentially unavoidable consequences.

Climate change threatens long-term soil health because of increased severity and frequency of drought periods. Applying biochar to soils before a drought can increase non-biochar soil carbon (C) and water storage over the long term and sustain crop yield. However, the on-farm benefit of buried solid biochar and applied liquid biochar at low rates remains uncertain. This study examined the effects of two novel biochar-based soil amendments on soil C, water storage and crop yield. The biochar-based amendments included a biochar reactive barrier (RB) made by layering wood-based biochar, straw mulch and cow manure into a series of open surface trenches, and a liquid biochar mineral complex (BMC) applied twice, at low rate (200 kg ha⁻¹) to one side of RB (fertilised area), while the other side of RB received no treatments (non-fertilised area). Moisture concentration within the RB ranged from 6.76% up to 56.68% after large rainfall, more than double the surrounding soils and gradually started migrating from the RB outwards. Soil within 50 cm distance of the RB showed a 24.5% increase in non-biochar soil C compared with soil at 600 cm distance of the RB, 2.54% versus 2.04%, respectively, in the non-fertilised area, which was supported with lowering soil microbial activity. Pasture yield increase was associated with liquid BMC fertiliser rather than proximity to the RB. Pasture yield was 44% higher in the fertilised area compared with the non-fertilised area 27.89 t ha⁻¹ versus 19.31 t ha⁻¹. Approximately 158 kg CO₂e was removed from the atmosphere for each cubic meter of RB and an annual removal of 150 kg CO₂e ha⁻¹ was estimated by liquid BMC application. Income earned by increased yield was still profitable even though applied liquid BMC could cost between USD 400–520 ha⁻¹ including shipping costs. Overall, our study suggested biochar-based RB and BMC fertilisers can effectively increase soil moisture retention while building non-biochar soil C storage in the surrounding soil. The adoption of biochar-based techniques has the potential to improve drought resilience while increasing soil C in wide range of non-irrigated cropping systems.

Carbon dioxide removal technologies such as bioenergy with carbon capture and storage (BECCS) are required if the effects of climate change are to be reversed over the next century. However, BECCS demands extensive land use change that may create positive or negative radiative forcing impacts upstream of the BECCS facility through changes to in situ greenhouse gas fluxes and land surface albedo. When quantifying these upstream climate impacts, even at a single site, different methods can give different estimates. Here we show how three common methods for estimating the net ecosystem carbon balance of bioenergy crops established on former grassland or former cropland can differ in their central estimates and uncertainty. We place these net ecosystem carbon balance forcings in the context of associated radiative forcings from changes to soil N₂O and CH₄ fluxes, land surface albedo, embedded fossil fuel use, and geologically stored carbon. Results from long term eddy covariance measurements, a soil and plant carbon inventory, and the MEMS 2 process-based ecosystem model all agree that establishing perennials such as switchgrass or mixed prairie on former cropland resulted in net negative radiative forcing (i.e., global cooling) of −26.5 to −39.6 fW m⁻² over 100 years. Establishing these perennials on former grassland sites had similar climate mitigation impacts of −19.3 to −42.5 fW m⁻². However, the largest climate mitigation came from establishing corn for BECCS on former cropland or grassland, with radiative forcings from −38.4 to −50.5 fW m⁻², due to its higher plant productivity and therefore more geologically stored carbon. Our results highlight the strengths and limitations of each method for quantifying the field scale climate impacts of BECCS and show that utilizing multiple methods can increase confidence in the final radiative forcing estimates.

We estimate the U.S. potential to convert biomass into liquid hydrocarbons for fuel and chemical feedstocks, assuming massive low-carbon external heat and hydrogen inputs. The biomass is first a carbon feedstock and only secondarily an energy source. This analysis is done for three estimates of available biomass derived from the 2023 U.S. Department of Energy/U.S. Department of Agriculture “Billion-Ton Report” and two augmented cases with maximum annual production of 1326, 4791, 5799, 7432, and 8745 million barrels of diesel fuel equivalent per year for the five cases. Constraints, such as assuring long-term soil sustainability by recycling nutrients and some carbon back to soils, result in production being 70%–80% of these numbers. The U.S. currently consumes about 6900 million barrels of diesel fuel equivalent per year. Long-term estimates for U.S. hydrocarbon consumption are between 50% and 75% of current consumption. External hydrogen additions for the conversion processes in the five cases are, respectively 25, 91, 111, 142, and 167 million tons of hydrogen per year. The system is strongly carbon negative because of carbon and nutrient recycling to soils to improve soil productivity.

The capacity to produce switchgrass efficiently and cost-effectively across diverse environments can be pivotal in achieving the short- and medium-term Sustainable Aviation Fuel targets set by the U.S. Department of Energy. This study evaluated the economic performance of forage- and bioenergy-type switchgrass cultivars and their response to N fertilization under diverse marginal environments across the US Midwest that included Illinois (IL), Iowa (IA), Nebraska (NE), and South Dakota (SD). Data Envelopment Analysis (DEA) was used to evaluate the efficiency of 23 Decision-Making Units (DMUs)—cultivar types and N fertilization rate combinations—while a cost–benefit analysis calculated their profitability over 5 years. Results showed that two energy-type cultivars—“Independence” and “Liberty”—were superior economically to the forage cultivars. Independence performed best with the highest profit margin when fertilized at 56 kg N ha⁻¹, particularly in the US hardiness zone 6a (Urbana, IL). Liberty exhibited the highest profit margins in hardiness zone 5b (Madrid, IA, and Ithaca, NE) at 56 kg N ha⁻¹ and showed exceptional profitability with 28 kg N ha⁻¹ in hardiness zone 6b (Brighton, IL). Switchgrass cultivar “Carthage” showed better efficiency score and profitability results in hardiness zone 4b (South Shore, SD) at 56 kg N ha⁻¹. The profit trends observed in current study sites may indicate broader patterns across similar US hardiness zones. This study provides valuable insights for decision-makers to optimize input strategies for biomass production of bioenergy switchgrass to meet renewable energy demands.

Wood use generates technosphere carbon credits (TCCs) through avoided fossil-based emissions and net sequestration of carbon into the technosphere (harvested wood products and geological storage). We investigated how large and uncertain TCCs of wood use per carbon harvested are considering the current and alternative ways of using wood, and the effects of the decarbonization of societies over 25-, 50-, and 100-year time horizons. We applied stochastic simulation and scenario analysis using Finnish market structure as a baseline to demonstrate the use of the TCC calculator created. The mean value of TCCs of wood use were between 0.2 and 0.5 t_C/t_C with an uncertainty range from 0.1 to 0.8 t_C/t_C, depending on the scenario. The uncertainties were mainly concerned with the extent to which (1) fossil-based emissions are avoided through substitution (displacement factors) and (2) fossil-based raw materials are substituted (substitution rates). Assumptions on the decarbonization of societies reduced TCCs of wood use significantly over time. TCCs of wood use can be increased by directing wood into uses that substitute fossil-intensive materials and have a long lifetime, such as construction materials, and increasing energy recovery and avoiding emitting carbon at the end of life of harvested wood products by carbon capture and storage. However, they were very likely to be considerably lower than forest carbon debits resulting from harvesting additional wood for substitution under all considered circumstances and under a wide but reasonable range of stochastic parameter values. Thus, the result emphasizes the need to reduce overall consumption of goods to mitigate climate change.

Fossil fuel subsidy reform(s) support the deployment of low-carbon technologies, yet fossil fuel subsidies remain stubbornly high, while money allocated by governments to renewable energy continues to grow. In the transport sector, this tension is observed between biofuels that still rely on national policies and gasoline/diesel subsidies. Using a global Computable General Equilibrium (CGE) model, we study how phasing out gasoline and diesel subsidies would impact global biofuel mandates. We find that where they are implemented, Fossil Fuel Subsidy Reforms increase biofuel competitiveness and lower the cost of achieving the mandates. The fiscal benefit is therefore twofold with savings on fossil and bio-based energy subsidies. In a multilateral reform scenario, we simulate the rise in fiscal revenue from phasing out the fossil fuel subsidies to be 25% higher when the avoided spending on biofuels' support is accounted for. In the rest of the world, however, the biofuel targets become costlier to achieve as the price of fossil fuels drops. Considering that global biofuel 2030 targets are achieved, governments' support for biofuel falls by $6 billion in regions phasing gasoline and diesel subsidies but increases by $600 million in the rest of the world.

Rising global temperatures underscore the urgent need to understand the complex interplay between greenhouse gas (GHG) emissions and climate change. This study investigates the relationships between GHG emissions and key environmental factors in China from 1990 to 2019, focusing on the role of forest ecosystems and soil management practices. Utilizing FAOSTAT and World Development Indicators data, we analyze the connections between total GHG emissions and factors such as biomass burning (BM), net stock change (NSC), fertilizer application (FERT), and manure application (MA) in soils. Employing impulse response analysis and Robust Least Squares Estimation with transformed logarithmic independent parameters, we find strong positive correlations between GHG emissions and both BM (coefficient 0.82) and FERT (coefficient 0.95). Robust Least Squares Estimation further confirms the significant influence of BM (coefficient 0.85) and FERT (coefficient 1.01) on GHG emissions. Notably, the interaction between precipitation (PPT) and NSC significantly impacts GHG emissions, with a negative coefficient (−0.58) for “PPT * NSC”. In contrast, the interaction between PPT and FERT significantly impacts GHG emissions, with a positive coefficient (0.29) for “PPT * FERT.” Furthermore, a unidirectional causality is observed from GHGs to BM (coefficient 6.31). These findings highlight the critical roles of BM, fertilizer use, and PPT patterns in driving GHG dynamics and underscore the potential of forest management strategies, particularly those focused on NSC, to mitigate climate change. This research provides valuable insights for promoting a sustainable balance between human activities and the vital role of forests in maintaining a healthy environment.