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Developing sustainable management practices including appropriate residue removal and nitrogen (N) fertilization for bioenergy sorghum is critical. However, the effects of residue removal and N fertilization associated with bioenergy sorghum production on soil organic carbon (SOC) are less studied compared to other crops. The objective of our research was to assess the impacts of residue removal and N fertilization on biomass yield and SOC under biomass sorghum production. Field measurements were used to calibrate the DNDC model, then verified the model by comparing simulated results with measured results using the field management practices as agronomic inputs. Both residue removal and N fertilization affected bioenergy sorghum yields in some years. The average measured SOC at 0–50 cm across the treatments and the time-frame ranged from 47.5 to 78.7 Mg C ha−1, while the simulated SOC was from 56.3 to 67.3 Mg C ha−1. The high correlation coefficients (0.65 to 0.99) and low root mean square error (3 to 18) between measured and simulated values indicate the DNDC model accurately simulated the effects of residue removal with N fertilization on bioenergy sorghum production and SOC. The model predictions revealed that there is, in the long term, a trend for higher SOC under bioenergy sorghum production regardless of residue management.  相似文献   

3.
There is growing interest in understanding how storage or delayed emission of carbon in products based on bioresources might mitigate climate change, and how such activities could be credited. In this research we extend the recently introduced approach that integrates biogenic carbon dioxide (CO2) fluxes with the global carbon cycle (using biogenic global warming potential [GWPbio]) to consider the storage period of harvested biomass in the anthroposphere, with subsequent oxidation. We then examine how this affects the climate impact from a bioenergy resource. This approach is compared to several recent methods designed to address the same problem. Using both a 100‐ and a 500‐year fixed time horizon we calculate the GWPbio factor for every combination of rotational and anthropogenic storage periods between 0 and 100 years. The resulting GWPbio factors range from ?0.99 (1‐year rotation and 100‐year storage) to +0.44 (100‐year rotation and 0‐year storage). The approach proposed in this study includes the interface between biomass growth and emissions and the global carbon cycle, whereas other methods do not model this. These results and the characterization factors produced can determine the climate change benefits or impacts associated with the storage of biomass in the anthroposphere, and the subsequent release of biogenic CO2 with the radiative forcing integrated in a fixed time window.  相似文献   

4.
Harvesting crop residue needs to be managed to protect agroecosystem health and productivity. DAYCENT, a process-based modeling tool, may be suited to accommodate region-specific factors and provide regional predictions for a broad array of agroecosystem impacts associated with corn stover harvest. Grain yield, soil C, and N2O emission data collected at Corn Stover Regional Partnership experimental sites were used to test DAYCENT performance modeling the impacts of corn stover removal. DAYCENT estimations of stover yields were correlated and reasonably accurate (adjusted r 2?=?0.53, slope?=?1.18, p?<<?0.001, intercept?=?0.36, p?=?0.11). Measured and simulated average grain yields across sites did not differ as a function of residue removal, but the model tended to underestimate average measured grain yields. Modeled and measured soil organic carbon (SOC) change for all sites were correlated (adjusted r 2?=?0.54, p?<<?0.001), but DAYCENT overestimated SOC loss with conventional tillage. Simulated and measured SOC change did not vary by residue removal rate. DAYCENT simulated annual N2O flux more accurately at low rates (≤2-kg N2O-N ha?1 year?1) but underestimated when emission rates were >3-kg N2O-N ha?1 year?1. Overall, DAYCENT performed well at simulating stover yields and low N2O emission rates, reasonably well when simulating the effects of management practices on average grain yields and SOC change, and poorly when estimating high N2O emissions. These biases should be considered when DAYCENT is used as a decision support tool for recommending sustainable corn stover removal practices to advance bioenergy industry based on corn stover feedstock material.  相似文献   

5.
The cultivation of microalgae gained high attention within the last years because of their potential to substitute conventional bioenergy crops. To evaluate algal bioenergy production pathways already at an early stage, several life cycle assessment (LCA) studies have been performed, but their results and conclusions vary drastically. Against this background, this review gives a comparative analysis of 16 recent studies. To allow for a comparison, a meta-approach served to uniform the considered systems. System boundaries have been equalized and the energy return on investment (EROI) has been calculated for each study. Depending on the assumptions made on biomass productivity, lipid content, required energy, and the output of the system, the energetic performance was assessed. Large variations from 0.01 to 3.35 for the EROI could be derived.  相似文献   

6.
Net benefits of bioenergy crops, including maize and perennial grasses such as switchgrass, are a function of several factors including the soil organic carbon (SOC) sequestered by these crops. Life cycle assessments (LCA) for bioenergy crops have been conducted using models in which SOC information is usually from the top 30 to 40?cm. Information on the effects of crop management practices on SOC has been limited so LCA models have largely not included any management practice effects. In the first 9?years of a long-term C sequestration study in eastern Nebraska, USA, switchgrass and maize with best management practices had average annual increases in SOC per hectare that exceed 2?Mg?C?year?1 (7.3?Mg?CO2?year?1) for the 0 to 150 soil depth. For both switchgrass and maize, over 50?% of the increase in SOC was below the 30?cm depth. SOC sequestration by switchgrass was twofold to fourfold greater than that used in models to date which also assumed no SOC sequestration by maize. The results indicate that N fertilizer rates and harvest management regimes can affect the magnitude of SOC sequestration. The use of uniform soil C effects for bioenergy crops from sampling depths of 30 to 40?cm across agro-ecoregions for large scale LCA is questionable.  相似文献   

7.
Lignocellulosic biomass is one of the most abundant yet underutilized renewable energy resources. Both anaerobic digestion (AD) and hydrothermal carbonization (HTC) are promising technologies for bioenergy production from biomass in terms of biogas and HTC biochar, respectively. In this study, the combination of AD and HTC is proposed to increase overall bioenergy production. Wheat straw was anaerobically digested in a novel upflow anaerobic solid state reactor (UASS) in both mesophilic (37 °C) and thermophilic (55 °C) conditions. Wet digested from thermophilic AD was hydrothermally carbonized at 230 °C for 6 hr for HTC biochar production. At thermophilic temperature, the UASS system yields an average of 165 LCH4/kgVS (VS: volatile solids) and 121 L CH4/kgVS at mesophilic AD over the continuous operation of 200 days. Meanwhile, 43.4 g of HTC biochar with 29.6 MJ/kgdry_biochar was obtained from HTC of 1 kg digestate (dry basis) from mesophilic AD. The combination of AD and HTC, in this particular set of experiment yield 13.2 MJ of energy per 1 kg of dry wheat straw, which is at least 20% higher than HTC alone and 60.2% higher than AD only.  相似文献   

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Journal of Plant Growth Regulation - In a controlled environment experiment, we studied how physiological changes in leaves during the vegetative phase regulate final grain yield of wheat crops in...  相似文献   

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Bioenergy crops have a secondary benefit if they increase soil organic C (SOC) stocks through capture and allocation below-ground. The effects of four genotypes of short-rotation coppice willow (Salix spp., ‘Terra Nova’ and ‘Tora’) and Miscanthus (M.?×?giganteus (‘Giganteus’) and M. sinensis (‘Sinensis’)) on roots, SOC and total nitrogen (TN) were quantified to test whether below-ground biomass controls SOC and TN dynamics. Soil cores were collected under (‘plant’) and between plants (‘gap’) in a field experiment on a temperate agricultural silty clay loam after 4 and 6 years’ management. Root density was greater under Miscanthus for plant (up to 15.5 kg m?3) compared with gap (up to 2.7 kg m?3), whereas willow had lower densities (up to 3.7 kg m?3). Over 2 years, SOC increased below 0.2 m depth from 7.1 to 8.5 kg m?3 and was greatest under Sinensis at 0–0.1 m depth (24.8 kg m?3). Miscanthus-derived SOC, based on stable isotope analysis, was greater under plant (11.6 kg m?3) than gap (3.1 kg m?3) for Sinensis. Estimated SOC stock change rates over the 2-year period to 1-m depth were 6.4 for Terra Nova, 7.4 for Tora, 3.1 for Giganteus and 8.8 Mg ha?1 year?1 for Sinensis. Rates of change of TN were much less. That SOC matched root mass down the profile, particularly under Miscanthus, indicated that perennial root systems are an important contributor. Willow and Miscanthus offer both biomass production and C sequestration when planted in arable soil.  相似文献   

11.
Walnut decline caused by Phytophthora sp. occurred in an orchard in Sakarya province in Turkey. Affected young trees showed poor growth, leaf discolouration, root and crown rot and eventual death. A Phytophthora sp. isolated from necrotic taproots and crown tissues. The causal agent of the disease was identified as Phytophthora cinnamomi by morphological characteristics and comparing sequences of internal transcribed spacer (ITS) region. Upon conducting pathogenicity test, averaging 7.8‐cm‐long canker developed on basal stem within 2 weeks, while no cankers developed in the control plants.  相似文献   

12.
Spatial segregation of metabolism, such as cellular-localized CO2 fixation in C4 plants or in the cyanobacterial carboxysome, enhances the activity of inefficient enzymes by selectively concentrating them with their substrates. The carboxysome and other bacterial microcompartments (BMCs) have drawn particular attention for bioengineering of nanoreactors because they are self-assembling proteinaceous organelles. All BMCs share an architecturally similar, selectively permeable shell that encapsulates enzymes. Fundamental to engineering carboxysomes and other BMCs for applications in plant synthetic biology and metabolic engineering is understanding the structural determinants of cargo packaging and shell permeability. Here we describe the expression of a synthetic operon in Escherichia coli that produces carboxysome shells. Protein domains native to the carboxysome core were used to encapsulate foreign cargo into the synthetic shells. These synthetic shells can be purified to homogeneity with or without luminal proteins. Our results not only further the understanding of protein-protein interactions governing carboxysome assembly, but also establish a platform to study shell permeability and the structural basis of the function of intact BMC shells both in vivo and in vitro. This system will be especially useful for developing synthetic carboxysomes for plant engineering.A key enzyme in photosynthesis is the CO2 fixation enzyme ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco). Rubisco not only fixes CO2, resulting in carbon assimilation, but it can also fix O2, leading to photorespiration. Suppressing the unwanted oxygenase activity of Rubisco by sequestering Rubisco with a source of CO2 is Nature’s solution to this substrate discrimination problem. While C4 plants compartmentalize CO2 fixation in specific cells (Hibberd et al., 2008; Parry et al., 2011), cyanobacteria have evolved a specialized organelle composed entirely of protein to encapsulate Rubisco—the carboxysome.The carboxysome is just one type of bacterial microcompartment (BMC), widespread, functionally diverse bacterial organelles (Axen et al., 2014). All BMCs consist of an enzymatic core surrounded by a selectively permeable protein shell (Kerfeld et al., 2005; Tanaka et al., 2008; Chowdhury et al., 2014; Kerfeld and Erbilgin, 2015). While the encapsulated enzymes differ among functionally distinct BMCs, they share an architecturally similar shell composed of three types of proteins: BMC-H, BMC-T, and BMC-P forming hexamers, pseudohexamers, and pentamers, respectively (Kerfeld and Erbilgin, 2015). These constitute the building blocks of a self-assembling, apparently icosahedral shell with a diameter ranging from 40 to 400 nm (Shively et al., 1973a,b, 1998; Price and Badger, 1991; Bobik et al., 1999; Iancu et al., 2007, 2010; Petit et al., 2013; Erbilgin et al., 2014). Recent studies have also shown that in the biogenesis of BMCs an encapsulation peptide (EP) (Fan and Bobik, 2011; Kinney et al., 2012; Aussignargues et al., 2015; Jakobson et al., 2015), a short (approximately 18 residues) amphipathic α-helix mediates interactions between a subset of core protein and the shell (Fan and Bobik, 2011; Choudhary et al., 2012; Kinney et al., 2012; Lawrence et al., 2014; Lin et al., 2014; Aussignargues et al., 2015). Indeed, because they are self-assembling organelles composed entirely of protein, BMCs hold great promise for diverse applications in bioengineering and development of bionanomaterials (Frank et al., 2013; Chowdhury et al., 2014; Chessher et al., 2015; Kerfeld and Erbilgin, 2015); the key features of BMCs include selective permeability, spatial colocalization of enzymes, the establishment of private cofactor pools, and the potentially beneficial effects of confinement on protein stability. For example, introducing carboxysomes into plants could provide a saltational enhancement of crop photosynthesis (Price et al., 2013; Zarzycki et al., 2013; Lin et al., 2014; McGrath and Long, 2014).The β-carboxysome, which sequesters form 1B Rubisco, has been an important model system for the study of the structural basis of carboxysome function, assembly, and engineering (Kerfeld et al., 2005; Tanaka et al., 2008; Cameron et al., 2013; Aussignargues et al., 2015; Cai et al., 2015). Beta-carboxysomes assemble from the inside out (Cameron et al., 2013; Gonzalez-Esquer et al., 2015). Two proteins that are absolutely conserved and unique to β-carboxysomes, CcmM and CcmN, play essential roles in this process: CcmM crosslinks Rubisco through its C-terminal Rubisco small subunit-like domains (SSLDs; pfam00101); CcmM and CcmN interact through their N-terminal domains; and C-terminal EP of CcmN interacts with the carboxysome shell.Here we describe a system for producing synthetic β-carboxysome shells and encapsulating nonnative cargo. We constructed a synthetic operon composed of ccmK1, ccmK2, ccmL, and ccmO, genes encoding, respectively, two BMC-H proteins, a BMC-P protein, and a BMC-T protein of the carboxysome shell of the halotolerant cyanobacterium, Halothece sp. PCC 7418 (Halo hereafter). Recombinant shells composed of all four proteins were produced and purified. We also demonstrated that the terminal α-helices of CcmK1 and CcmK2 are not, as had been proposed (Samborska and Kimber, 2012), required for the shell formation, and that the synthetic shell is a single-layered protein membrane. Cargo could be targeted to the interior of the synthetic shells using either the EP of CcmN or the N-terminal domain of CcmM; the latter observation provides new insight into the organization of the β-carboxysome. Our results not only further the understanding of protein-protein interactions governing carboxysome assembly but also provide a platform to study carboxysome shell permeability. These results will be useful in guiding the design and optimization of carboxysomes and other BMCs for introduction into plants.  相似文献   

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This study compares energy savings and greenhouse gas (GHG) emission reductions of biobased polymers with those of bioenergy on a per unit of agricultural land-use basis by extending existing life-cycle assessment (LCA) studies. In view of policy goals to increase the energy supply from biomass and current efforts to produce biobased polymers in bulk, the amount of available land for the production of nonfood crops could become a limitation. Hence, given the prominence of energy and greenhouse issues in current environmental policy, it is desirable to include land demand in the comparison of different biomass options. Over the past few years, numerous LCA studies have been prepared for different types of bio-based polymers, but only a few of these studies address the aspect of land use. This comparison shows that referring energy savings and GHG emission reduction of biobased polymers to a unit of agricultural land, instead of to a unit of polymer produced, leads to a different ranking of options. If land use is chosen as the basis of comparison, natural fiber composites and thermoplastic starch score better than bioenergy production from energy crops, whereas polylactides score comparably well and polyhydroxyalkaonates score worse. Additionally, including the use of agricultural residues for energy purposes improves the environmental performance of bio-based polymers significantly. Moreover, it is very likely that higher production efficiencies will be achieved for biobased polymers in the medium term. Biobased polymers thus offer interesting opportunities to reduce the utilization of nonrenewable energy and to contribute to GHG mitigation in view of potentially scarce land resources.  相似文献   

15.
Crop residues like corn (Zea mays L.) stover perform important functions that promote soil health and provide ecosystem services that influence agricultural sustainability and global biogeochemical cycles. We evaluated the effect of corn stover removal from a no-till, corn-soybean (Glycine max (L.) Merr) rotation on soil greenhouse gas (GHG; CO2, N2O, CH4) fluxes, crop yields, and soil organic carbon (SOC) dynamics. We conducted a 4-year study using replicated field plots managed with two levels of corn stover removal (none; 55 % stover removal) for four complete crop cycles prior to initiation of ground surface gas flux measurements. Corn and soybean yields were not affected by stover removal with yields averaging 7.28 Mg ha?1 for corn and 2.64 Mg ha?1 for soybean. Corn stover removal treatment did not affect soil GHG fluxes from the corn phase; however, the treatment did significantly increase (107 %, P?=?0.037) N2O fluxes during the soybean phase. The plots were a net source of CH4 (~0.5 kg CH4-C ha?1 year?1 average of all treatments and crops) during the generally wet study duration. Soil organic carbon stocks increased in both treatments during the 4-year study (initiated following 8 years of stover removal), with significantly higher SOC accumulation in the control plots compared to plots with corn stover removal (0–15 cm, P?=?0.048). Non-CO2 greenhouse gas emissions (945 kg CO2-eq ha?1 year?1) were roughly half of SOC (0–30 cm) gains with corn stover removal (1.841 Mg CO2-eq ha?1 year?1) indicating that no-till practices greatly improve the viability of biennial corn stover harvesting under local soil-climatic conditions. Our results also show that repeated corn stover harvesting may increase N loss (as N2O) from fields and thereby contribute to GHG production and loss of potential plant nutrients.  相似文献   

16.
We analyzed the effects of management on the economic profitability of forest biomass production and carbon neutrality of bioenergy use in Norway spruce (Picea abies L. Karst) stands under the changing climate. We employed a forest ecosystem model and life cycle assessment tool. In particular, we studied the effects of thinning, nitrogen fertilization, and rotation length on: (1) the production of timber and energy biomass, and its economic profitability (net present value), (2) carbon stock in the forest ecosystem and carbon balance in forestry, and (3) carbon dioxide (CO2) emissions from the use of biomass in energy production. Results showed that the current Finnish baseline management with and without nitrogen fertilization resulted in the highest mean annual timber production and net present value (NPV) for long rotations (60 to 80 years), regardless of climate scenario. Mean annual production of energy biomass was enhanced by increasing stocking by 20–30 % compared to the baseline management, and/or use of nitrogen fertilization. Such management gave lower CO2 emissions per unit of energy compared to the baseline management, as the carbon stock in the forest ecosystem and the carbon balance in forestry increased. Overall, the carbon neutrality and net present value were, on average, the highest in the baseline management or with a 20 % increase in stocking, with nitrogen fertilization and 60- to 80-year rotation lengths, regardless of the climate applied. However, it was not possible to simultaneously maximize the NPV of forest biomass production and the carbon neutrality of bioenergy use.  相似文献   

17.

Background

The healthcare sector is a significant contributor to global carbon emissions, in part due to extensive travelling by patients and health workers.

Objectives

To evaluate the potential of telemedicine services based on videoconferencing technology to reduce travelling and thus carbon emissions in the healthcare sector.

Methods

A life cycle inventory was performed to evaluate the carbon reduction potential of telemedicine activities beyond a reduction in travel related emissions. The study included two rehabilitation units at Umeå University Hospital in Sweden. Carbon emissions generated during telemedicine appointments were compared with care-as-usual scenarios. Upper and lower bound emissions scenarios were created based on different teleconferencing solutions and thresholds for when telemedicine becomes favorable were estimated. Sensitivity analyses were performed to pinpoint the most important contributors to emissions for different set-ups and use cases.

Results

Replacing physical visits with telemedicine appointments resulted in a significant 40–70 times decrease in carbon emissions. Factors such as meeting duration, bandwidth and use rates influence emissions to various extents. According to the lower bound scenario, telemedicine becomes a greener choice at a distance of a few kilometers when the alternative is transport by car.

Conclusions

Telemedicine is a potent carbon reduction strategy in the health sector. But to contribute significantly to climate change mitigation, a paradigm shift might be required where telemedicine is regarded as an essential component of ordinary health care activities and not only considered to be a service to the few who lack access to care due to geography, isolation or other constraints.  相似文献   

18.
Reed canarygrass, Phalaris arundinacea L., produces high biomass yields in cool climates and wetlands. The number and timing of harvests during a growing season directly affect biomass yield and biofuel quality. In order to determine optimum harvest management, seven cultivars of reed canarygrass were planted in field experiments at Ames, IA; McNay, IA; and Arlington, WI in the upper Midwestern USA and harvested once in autumn or in winter, twice in spring + autumn or spring + winter, or three times during the season as hay. Biomass yield varied considerably among harvest treatments, locations, and years, ranging up to 12.6 Mg ha?1. Dry matter percentage ranged from 37% for spring-harvested biomass to 84% for overwintered biomass. The three harvest hay and two harvest spring + autumn managements produced the highest biomass yield compared to other systems, but the advantage, if any, of hay management was small and probably does not justify the cost of additional fieldwork. More mature biomass, such as that found in the single harvest systems, had higher fiber concentrations. Overwintered biomass had superior biofuel quality, being low in P, K, S, and Cl and high in cell wall concentration. However, winter harvest systems had lower yield than autumn harvest and in some years, no harvest was possible due to lodging from snow compaction. The main limitation of a two harvest system is the high moisture content of the late spring/early summer biomass.  相似文献   

19.
Fire influences carbon dynamics from local to global scales, but many uncertainties remain regarding the remote detection and simulation of heterogeneous fire effects. This study integrates Landsat-based remote sensing and Biome-BGC process modeling to simulate the effects of high-, moderate-, and low-severity fire on pyrogenic emissions, tree mortality, and net ecosystem production. The simulation area (244,600 ha) encompasses four fires that burned approximately 50,000 ha in 2002–2003 across the Metolius Watershed, Oregon, USA, as well as in situ measurements of postfire carbon pools and fluxes that we use for model evaluation. Simulated total pyrogenic emissions were 0.732 Tg C (2.4% of equivalent statewide anthropogenic carbon emissions over the same 2-year period). The simulated total carbon transfer due to tree mortality was fourfold higher than pyrogenic carbon emissions, but dead wood decomposition will occur over decades. Immediately postfire, burned areas were a simulated carbon source (net C exchange: −0.076 Tg C y−1; mean ± SD: −142 ± 121 g C m−2 y−1). As expected, high-severity, stand-replacement fire had disproportionate carbon impacts. The per-unit area effects of moderate-severity fire were substantial, however, and the extent of low-severity fire merits its inclusion in landscape-scale analyses. These results demonstrate the potential to reduce uncertainties in landscape to regional carbon budgets by leveraging Landsat-based fire products that account for both stand-replacement and partial disturbance.  相似文献   

20.
Biomass for bioenergy is debated for its potential synergies or tradeoffs with other provisioning and regulating ecosystem services (ESS). This biomass may originate from different production systems and may be purposefully grown or obtained from residues. Increased concerns globally about the sustainable production of biomass for bioenergy has resulted in numerous certification schemes focusing on best management practices, mostly operating at the plot/field scale. In this study, we compare the ESS of two watersheds in the southeastern US. We show the ESS tradeoffs and synergies of plantation forestry, i.e., pine poles, and agricultural production, i.e., wheat straw and corn stover, with the counterfactual natural or semi-natural forest in both watersheds. The plantation forestry showed less distinct tradeoffs than did corn and wheat production, i.e., for carbon storage, P and sediment retention, groundwater recharge, and biodiversity. Using indicators of landscape composition and configuration, we showed that landscape planning can affect the overall ESS supply and can partly determine if locally set environmental thresholds are being met. Indicators on landscape composition, configuration and naturalness explained more than 30% of the variation in ESS supply. Landscape elements such as largely connected forest patches or more complex agricultural patches, e.g., mosaics with shrub and grassland patches, may enhance ESS supply in both of the bioenergy production systems. If tradeoffs between biomass production and other ESS are not addressed by landscape planning, it may be reasonable to include rules in certification schemes that require, e.g., the connectivity of natural or semi-natural forest patches in plantation forestry or semi-natural landscape elements in agricultural production systems. Integrating indicators on landscape configuration and composition into certification schemes is particularly relevant considering that certification schemes are governance tools used to ensure comparable sustainability standards for biomass produced in countries with variable or absent legal frameworks for landscape planning.  相似文献   

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