Total Net Emissions Research Articles

Improving greenhouse gas emissions intensities of subtropical and tropical beef farming systems using Leucaena leucocephala

Leucaena leucocephala (leucaena) is a perennial legume shrub of subtropical regions that has forage characteristics favourable for livestock production, often delivering ruminant liveweight gains that are superior to most other forage systems. Recent work suggests that leucaena mitigates ruminant enteric methane emissions, implying that the shrub may also reduce greenhouse gas (GHG) emissions at the whole farm level. However, the high crude protein content of leucaena relative to endemic grasses can increase livestock urine nitrogen concentration and may increase soil nitrous oxide emissions, potentially offsetting benefits of enteric methane mitigation.Here we examine the effects of leucaena on emissions, production and profitability at the whole farm level by modelling a property in northern Australia, assuming enterprises that specialise in cattle breeding and finishing. To contrast leucaena with a baseline property with Rhodes grass, we modelled three equivalent leucaena scenarios by matching (1) annual average stocking rate, (2) total liveweight production or (3) net farm emissions with that of the baseline, assuming all animals had access to leucaena.To maintain average annual stocking rate or liveweight production, scenarios 1 and 2 carried 5% and 12% less cattle than the baseline because animals on leucaena grew faster and had greater liveweight. In contrast, the number of animals carried and liveweight production in scenario 3 increased by 15% and 31% relative to the baseline, respectively, due to enteric methane abatement and greater liveweight gains. Grazing of leucaena increased soil nitrous oxide emissions by more than 38% in all scenarios, but this did not substantially offset net emissions abatement because nitrous oxide constituted a far smaller proportion of emissions than did methane (<10% and >90%, respectively). In all scenarios, emissions intensity (net farm emissions per unit liveweight sold) caused by grazing leucaena was reduced by more than 23% relative to baseline emissions intensities.This work shows that whilst income from carbon offsets associated with grazing leucaena is small, leucaena has significant potential to increase both animal production and gross margin, whilst reducing emissions intensity. Provided net farm emissions are maintained or reduced, these results suggest that leucaena is conducive to sustainable intensification of beef production in subtropical grazing systems.

Spatial source attribution of measured urban eddy covariance CO2 fluxes

Interpretation of tower-based eddy covariance (EC) carbon dioxide flux (F C ) measurements in urban areas is challenging because of the location bias of EC instruments. This bias results from EC point measurements taken above a complex CO2 source/sink surface that is spatially heterogeneous at scales approaching or exceeding those of the turbulent flux source areas. This makes it difficult to accomplish traditional measurement objectives such as calculating spatially unbiased ecosystem-wide cumulative F C totals or objectively comparing F C during different environmental conditions (e.g., day vs. night or seasonal differences). This study uses a multiyear F C dataset measured over a residential area of Vancouver, BC, Canada from a 30-m flux tower in close proximity to a busy traffic intersection on one side. The F C measurements are analyzed using surface geospatial data and turbulent flux source area models to exploit location bias to develop methods to statistically model individual emissions and uptake processes in terms of environmental controls and surface land cover. The empirical relations between controls and measured F C are used to spatially and temporally downscale individual CO2 emissions/uptake processes that are then used to create high-resolution maps (20 m) and calculate ecosystem-wide F C at temporal resolutions of 30 min to 1 year. At this site, the modeled ecosystem-wide annual net F C total is calculated as 6.42 kg C m−2 year−1 with traffic emissions estimated to account for 68.8 % of the total net emissions. Building sources contribute 27.9 %, respiration from soil and vegetation is 5.5 %, respiration from humans 5.0 %, and photosynthesis offsets are −7.2 % of the annual net total. The statistical models developed here are then tested by direct comparison to independent EC measurements using land cover scalings derived from 30-min source area models. Results are also scaled to ecosystem-averaged land cover to compare results to independent emissions/uptake models.

Mitigating greenhouse gas fluxes from cultivated organic soils with raised water table

Cultivated organic soils are a remarkable source of greenhouse gases (GHG) in many countries. Keeping the ground water table as high as possible could lower the mineralization rate of the peat and thus the emissions of carbon dioxide (CO2) and nitrous oxide (N2O) from these soils. We studied the effect of raised water table on the emissions of N2O, CO2 and methane (CH4) from undisturbed peat soil profiles of six different Finnish cultivated organic soils during a 5-week outdoor mesocosm experiment. The aim was to determine an optimum water table that would enable grass cultivation but lower the net gas balance of the soil. Raised water table decreased the GHG emissions from each peat type ranging from weakly decomposed Sphagnum peat to highly humified Carex peat. Based on the results, the optimum water table would be 30 cm below the soil surface. The average reduction of the total net emissions with a raise of water table from a typical drainage depth of 70 to 30 cm was 42 % in the outdoors mesocosm experiment and 23 % at a constant temperature (+6 °C). The emissions of both CO2 and N2O declined and the net consumption of CH4 changed to net production as the water table rose. The results were confirmed by long-term measurements at one of the sampled sites. As a conclusion, we see that promoting drainage systems enabling raising of the ground water table and cultivation of crops capable of producing good yields also in wet conditions would be beneficial for the GHG mitigation in agriculture.

Comment on &amp;quot;Soil CO&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;, CH&amp;lt;sub&amp;gt;4&amp;lt;/sub&amp;gt; and N&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;O fluxes from an afforested lowland raised peat bog in Scotland: implications for drainage and restoration&amp;quot; by Yamulki et al. (2013)

Abstract. Yamulki and co-authors address in their recent publication the important issue of net emissions of greenhouse gases (GHGs) from peatlands where land use conversion has taken place. In their case, they studied conversion to forestry versus peatland restoration after a first rotation of plantation forestry. They monitored soil-derived fluxes of carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) using opaque chamber measurements on planted and unplanted control treatments (with or without drainage), and an unplanted plot within a restored (felled) block on former lowland raised bog. They propose that their measurements of greenhouse gas (GHG) emissions at these sites suggest that the total net GHG emissions, in 100 yr carbon dioxide equivalents, of the restored peat bog would be higher than that of the peat bog with trees. We believe there are a number of issues with the measurement, calculation and comparison of these greenhouse budgets that may invalidate this conclusion.

A generalized multistage optimization modeling framework for life cycle assessment-based integrated solid waste management

Solid waste management (SWM) is an integral component of civil infrastructure and the global economy, and is a growing concern due to increases in population, urbanization, and economic development. In 2011, 1.3 billion metric tons of municipal solid waste (MSW) were generated, and this is expected to grow to 2.2 billion metric tons by 2025. In the U.S., MSW systems processed approximately 250 million tons of waste and produced 118 Tg of CO2e emissions, which represents over 8% of non-energy related greenhouse gas (GHG) emissions, and 2% of total net GHG emissions. While previous research has applied environmental life cycle assessment (LCA) to SWM using formal search techniques, existing models are either not readily generalizable and scalable, or optimize only a single time period and do not consider changes likely to affect SWM over time, such as new policy and technology innovation. This paper presents the first life cycle-based framework to optimize—over multiple time stages—the collection and treatment of all waste materials from curb to final disposal by minimizing cost or environmental impacts while considering user-defined emissions and waste diversion constraints. In addition, the framework is designed to be responsive to future changes in energy and GHG prices. This framework considers the use of existing SWM infrastructure as well as the deployment and utilization of new infrastructure. Several scenarios, considering cost, diversion, and GHG emissions, are analyzed in a 3-stage test system. The results show the utility of the multi-stage framework and the insights that can be gained from using such a framework. The framework was also used to solve a larger SWM system; the results show that the framework solves in reasonable time using typical hardware and readily available mathematical programming solvers. The framework is intended to inform SWM by considering costs, environmental impacts, and policy constraints.

Optimal energy management of a micro-grid with renewable energy resources and demand response

With the introduction of smart energy grids and extensive penetration of renewable energy resources in distribution networks, Micro-Grids (MGs), which are comprised of various alternative energy resources and Advanced Metering Infrastructure (AMI) systems for better implementation of DR programs, are effectively employed. The design and development of Smart Energy Management Systems (SEMSs) for MGs are interesting and attractive research problems. In this paper a new SEMS architecture is presented to solve the multi-objective operation management and scheduling problem in a typical MG while considering different energy resource technologies, Plug-in Hybrid Electric Vehicles (PHEVs) and DR programs. The energy management problem is formulated as a constrained mixed integer nonlinear multi-objective optimization problem, in which the MG's total operating cost and net emissions must be minimized simultaneously. Three different optimization algorithms are used to solve the above mentioned problem and their outputs (Pareto optimal solutions) for the same problem are compared and analyzed.

Benefit assessment of cost, energy, and environment for biomass pyrolysis oil

This study used life cycle assessment (LCA) to clarify the feasibility and potential effects of a new type of bioenergy by evaluating the cost, energy, and environmental efficiency of biomass pyrolysis oil in the production and usage stages. An annual yield of 10,000 t of pyrolysis oil processed with the raw material of Cryptomeria residue was selected as the evaluated target. We used life cycle inventory and effect assessment to evaluate the advantages and disadvantages associated with the production of the new bioenergy. GaBi®4 software and the Eco-indicator 95 system were selected for the evaluation. The resulting calculated specific cost of pyrolysis oil production was NT$11,758/m3 pyrolysis oil (NT$1 = US$0.034 in October 2012), and pyrolysis oil with its byproduct could provide the energy of 36,019 MJ/m3 pyrolysis oil. The output–input energy ratio is approximately 13.2, indicating the high energy efficiency of pyrolysis oil. In terms of the environmental aspect, the total net carbon emission is 176.6 kg CO2/m3 pyrolysis oil. Using pyrolysis oil and the biochar byproduct to replace fuel oil and coal can produce a reduction of approximately 2835 kg CO2/m3 pyrolysis oil (0.079 kg CO2/MJ) of greenhouse gas emissions. The environmental impact indicator is 0.105 Pt, which is much lower than the fuel oil energy-equivalent. These findings suggest that pyrolysis oil produced from Cryptomeria residue yields enhanced energy and environmental efficiency. However, the production cost is higher than that of existing fossil fuels.

Assessment of the biomass energy potentials and environmental benefits of Jatropha curcas L. in Southwest China

Jatropha curcas L. (JCL) is believed to be the most promising tree species used to produce biodiesel in China. Due to its abundant marginal land resource and good meteorological conditions, Southwest China is the major region to develop JCL. With Southwest China being taken as the study area in this paper, multi-factor comprehensive analysis is used to identify marginal land resources suitable to JCL plantation and make suitability assessment, thus obtaining their spatial distribution, suitability degree and total amount. With life cycle analysis (LCA), the life cycle net energy and greenhouse gas emission reduction capacity of marginal land resources with different suitability degrees used to produce biodiesel are investigated. Based on the research results, the life cycle model is expanded to obtain the potentiality of total net energy production and greenhouse gas emission reduction of large-scale plantation of JCL in southwest China. The results show that the area of land resources suitable and moderately suitable for JCL plantation is 1.99 × 106 ha and 5.57 × 106 ha, respectively. If all of these land resources are put into use, the maximum net production potential of biodiesel from JCL would be 1.51 × 108 GJ/a, and the total greenhouse gas emission reduction capacity 1.59 × 107 t/a in Southwest China.

Cradle-to-gate inventory of wood production from Australian softwood plantations and native hardwood forests: Carbon sequestration and greenhouse gas emissions

Life cycle assessment provides a useful means of estimating environmental impacts associated with different materials and production systems and is increasingly being used to assess net greenhouse gas (GHG) emissions. Here we report on a cradle-to-gate inventory of wood production, focussing on GHG emissions associated with wood from softwood plantations and regrowth hardwood native forests across Australia. The inventory was primarily based on data provided by forest growers, managers and contractors across seven large case study regions. Modelling was used to combine data from different operations, account for upstream processes associated with the production of fuel and materials used, and to estimate total GHG emissions associated with the production of high- and low-value sawlogs, pulplogs, woodchips and other logs. We considered only the case of managing established forests for wood production, where the C stock of these forests could be considered to be constant over the long-term. Emissions were expressed in terms of m3 product (i.e. functional unit) and were allocated to products on an economic basis. Total GHG emissions associated with wood production, harvest and transport were 25.9 (SD 8.0) kg carbon dioxide equivalent (CO2-e) m−3 for an average plantation softwood log and 70.6 (SD 1.8) kg CO2-e m−3 for an average native hardwood log. The largest contributors to total emissions per unit wood production in softwood plantations were log haulage (37%) and harvesting (21%), whilst in native hardwood forests they were slash burning (46%) and log haulage (23%). Sensitivity analyses indicated that the amount of forest residues burnt in native hardwood forests had a relatively large influence on CO2-e emissions while wood density had a large impact on net carbon sequestration for both native hardwood and plantation softwood logs, indicating that improving estimates of these should be a priority. Estimated net carbon sequestered in an average plantation softwood log was 761 (SD 27) kg CO2-e m−3 and in an average native hardwood log it was 902 (SD 162) kg CO2-e m−3. Total net GHG emissions (assuming no net biogenic emissions) represented 3.3% and 7.3% of the estimated carbon content of an average log for plantation softwood and native hardwood, respectively. Thus, logs from sustainably managed forests delivered to downstream processing plants represent significant net stores of carbon and have potential to substitute for more GHG-intensive raw materials.

Soil CO&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt; CH&amp;lt;sub&amp;gt;4&amp;lt;/sub&amp;gt; and N&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;O fluxes from an afforested lowland raised peatbog in Scotland: implications for drainage and restoration

Abstract. The effect of tree (lodgepole pine) planting with and without intensive drainage on soil greenhouse gas (GHG) fluxes was assessed after 45 yr at a raised peatbog in West Flanders Moss, central Scotland. Fluxes of CO2 CH4 and N2O from the soil were monitored over a 2-yr period every 2 to 4 weeks using the static opaque chamber method in a randomised experimental block trial with the following treatments: drained and planted (DP), undrained and planted (uDP), undrained and unplanted (uDuP) and for reference also from an adjoining near-pristine area of bog at East Flanders Moss (n-pris). There was a strong seasonal pattern in both CO2 and CH4 effluxes which were significantly higher in late spring and summer months because of warmer temperatures. Effluxes of N2O were low and no significant differences were observed between the treatments. Annual CH4 emissions increased with the proximity of the water table to the soil surface across treatments in the order: DP &lt; uDP &lt; uDuP &lt; n-pris with mean annual effluxes over the 2-yr monitoring period of 0.15, 0.64, 7.70 and 22.63 g CH4 m−2 yr−1, respectively. For CO2, effluxes increased in the order uDP &lt; DP&lt; n-pris &lt; uDuP, with mean annual effluxes of 1.23, 1.66, 1.82 and 2.55 kg CO2 m−2 yr−1, respectively. CO2 effluxes dominated the total net GHG emission, calculated using the global warming potential (GWP) of the three GHGs for each treatment (76–98%), and only in the n-pris site was CH4 a substantial contribution (23%). Based on soil effluxes only, the near pristine (n-pris) peatbog had 43% higher total net GHG emission compared with the DP treatment because of high CH4 effluxes and the DP treatment had 33% higher total net emission compared with the uDP because drainage increased CO2 effluxes. Restoration is likely to increase CH4 emissions, but reduce CO2 effluxes. Our study suggests that if estimates of CO2 uptake by vegetation from similar peatbog sites were included, the total net GHG emission of restored peatbog would still be higher than that of the peatbog with trees.

The timber and energy biomass potential of intensively managed cloned Norway spruce stands

AbstractWe used ecosystem model simulations to study the timber and energy biomass potential offered by intensively managed cloned Norway spruce stands. More specifically, we analysed how the use of cloned trees compared with non‐cloned trees, together with thinning, nitrogen (N) fertilisation and rotation length (from 60 to 100 years), affects the annual mean production of timber (i.e., saw logs, pulpwood) and energy biomass (i.e., stumps and harvesting residuals in the final felling) and its economic profitability [annual mean of net present value (NPV) with a 2% interest rate]. Furthermore, we employed a life cycle analysis/emission calculation tool to assess the total net CO2 emissions per unit of energy (kg CO2 MW h−1) produced based on energy biomass. We found that both the annual mean production of timber and the NPV increased substantially, regardless of the management regime, if cloned trees with an annual growth increase of up to 30% compared with non‐cloned trees were used in regeneration. In general, the use of a short rotation with N fertilisation clearly increased the annual mean of the NPV. Consequently, the use of cloned trees also clearly increased the annual mean production of energy biomass and decreased the total net CO2 emissions per unit of energy produced based on energy biomass. However, the total annual net CO2 emissions were the lowest if a long rotation was used with N fertilisation. To conclude, the use of cloned trees together with intensive management could potentially be highly beneficial for the cost‐efficient and sustainable production of timber and energy biomass in an integrated way.

Renewable energy in the minerals industry: a review of global potential

This paper examines the major minerals producing countries and the potential that local energy mix and renewable energy resources have for lowering the impact of the industry, with respect to carbon dioxide emissions. Furthermore, it seeks to estimate the potential for new technologies, energy efficiency and demand-side measures to reduce emissions. Of total carbon dioxide emissions, 71% arise from fossil fuels used in thermal applications and 29% from indirect electricity generation. We find the highest theoretical potential for reduction of emissions from thermal applications is from the increased use of renewable biofuels and charcoal instead of fossil fuels (up to 46% of total industry net emissions), while conversion of various applications to use renewable hydrogen may reduce emissions by 28%. Electricity generation emissions could be “substantially reduced” by switching to electricity generation from cleaner sources, with hydropower a key potential contributor (reduction of 22% of total industry emissions). Solar thermal and electrical production may only be capable of 2–7% reduction in the industry's emissions.

Greenhouse gas emissions from the EU livestock sector: A life cycle assessment carried out with the CAPRI model

This study presents detailed product-based net emissions of main livestock products (meat, milk and eggs) at national level for the whole EU-27 according to a cradle-to-gate life-cycle assessment, including emissions from land use and land use change (LULUC). Calculations were done with the CAPRI model and the covered gases are CH4, N2O and CO2. Total GHG fluxes of European livestock production amount to 623–852MtCO2-equiv., 182–238MtCO2-equiv. (28–29%) are from beef production, 184–240MtCO2-equiv. (28–30%) from cow milk production and 153–226MtCO2-equiv. (25–27%) from pork production. According to IPCC classifications, 38–52% of total net emissions are created in the agricultural sector, 17–24% in the energy and industrial sectors. 12–16%MtCO2-equiv. are related to land use (CO2 fluxes from cultivation of organic soils and reduced carbon sequestration compared to natural grassland) and 9–33% to land use change, mainly due to feed imports. The results suggest that for effective reduction of GHG emissions from livestock production, fluxes occurring outside the agricultural sector need to be taken into account. Reduction targets should address both the production side as defined by IPCC sectors and the consumption side. An LCA assessment as presented here could be a basis for such efforts.

Estimating greenhouse gas emissions from soil following liquid manure applications using a unit response curve method

Quantitative information is critical in policy making related to the roles of agriculture in greenhouse gas (GHG) emissions. A Unit Response (UR) curve method was developed in this study for modeling GHG emissions from soil after liquid manure applications. The emission sources (soils and liquid manures) are conceptualized as a set of linear cascaded chambers with equal storage-release coefficients, or two sets of cascaded chambers in parallel, each set having equal storage-release coefficients. The model is based on a two-parameter gamma distribution. Three parameters in this model denote the number of cascaded chambers, the storage-release coefficient, and the multiplier (referring to the total net emissions) added to the gamma distribution function. These parameters can be expressed as functions of site-specific background fluxes without applications of manure/fertilizer. The method was assessed with emissions data from five fields in Washington State. The results showed that at the WSU and Lynden sites, the average excess CH4 emissions due to manure applications were 0.39 and 0.17kg CH4–Cha−1, respectively; the average excess CO2 emissions were 216.50 and 25.20kg CO2–Cha−1, respectively; and the average excess N2O were 0.37 and 0.03kg N2O–Nha−1, respectively. The UR method may fill the gaps between field measurements, simple emission factor (EF) method, and complex process-oriented models. This method has the potential to be used for estimating additional GHG emissions due to manure/fertilizer applications.

Evaluating a 3-D transport model of atmospheric CO&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt; using ground-based, aircraft, and space-borne data

Abstract. We evaluate the GEOS-Chem atmospheric transport model (v8-02-01) of CO2 over 2003–2006, driven by GEOS-4 and GEOS-5 meteorology from the NASA Goddard Global Modeling and Assimilation Office, using surface, aircraft and space-borne concentration measurements of CO2. We use an established ensemble Kalman Filter to estimate a posteriori biospheric+biomass burning (BS + BB) and oceanic (OC) CO2 fluxes from 22 geographical regions, following the TransCom-3 protocol, using boundary layer CO2 data from a subset of GLOBALVIEW surface sites. Global annual net BS + BB + OC CO2 fluxes over 2004–2006 for GEOS-4 (GEOS-5) meteorology are −4.4 ± 0.9 (−4.2 ± 0.9), −3.9 ± 0.9 (−4.5 ± 0.9), and −5.2 ± 0.9 (−4.9 ± 0.9) PgC yr−1, respectively. After taking into account anthropogenic fossil fuel and bio-fuel emissions, the global annual net CO2 emissions for 2004–2006 are estimated to be 4.0 ± 0.9 (4.2 ± 0.9), 4.8 ± 0.9 (4.2 ± 0.9), and 3.8 ± 0.9 (4.1 ± 0.9) PgC yr−1, respectively. The estimated 3-yr total net emission for GEOS-4 (GEOS-5) meteorology is equal to 12.5 (12.4) PgC, agreeing with other recent top-down estimates (12–13 PgC). The regional a posteriori fluxes are broadly consistent in the sign and magnitude of the TransCom-3 study for 1992–1996, but we find larger net sinks over northern and southern continents. We find large departures from our a priori over Europe during summer 2003, over temperate Eurasia during 2004, and over North America during 2005, reflecting an incomplete description of terrestrial carbon dynamics. We find GEOS-4 (GEOS-5) a posteriori CO2 concentrations reproduce the observed surface trend of 1.91–2.43 ppm yr−1 (parts per million per year), depending on latitude, within 0.15 ppm yr−1 (0.2 ppm yr−1) and the seasonal cycle within 0.2 ppm (0.2 ppm) at all latitudes. We find the a posteriori model reproduces the aircraft vertical profile measurements of CO2 over North America and Siberia generally within 1.5 ppm in the free and upper troposphere but can be biased by up to 4–5 ppm in the boundary layer at the start and end of the growing season. The model has a small negative bias in the free troposphere CO2 trend (1.95–2.19 ppm yr−1) compared to AIRS data which has a trend of 2.21–2.63 ppm yr−1 during 2004–2006, consistent with surface data. Model CO2 concentrations in the upper troposphere, evaluated using CONTRAIL (Comprehensive Observation Network for TRace gases by AIrLiner) aircraft measurements, reproduce the magnitude and phase of the seasonal cycle of CO2 in both hemispheres. We generally find that the GEOS meteorology reproduces much of the observed tropospheric CO2 variability, suggesting that these meteorological fields will help make significant progress in understanding carbon fluxes as more data become available.

Sustainable biochar to mitigate global climate change.

Production of biochar (the carbon (C)-rich solid formed by pyrolysis of biomass) and its storage in soils have been suggested as a means of abating climate change by sequestering carbon, while simultaneously providing energy and increasing crop yields. Substantial uncertainties exist, however, regarding the impact, capacity and sustainability of biochar at the global level. In this paper we estimate the maximum sustainable technical potential of biochar to mitigate climate change. Annual net emissions of carbon dioxide (CO2), methane and nitrous oxide could be reduced by a maximum of 1.8 Pg CO2-C equivalent (CO2-Ce) per year (12% of current anthropogenic CO2-Ce emissions; 1 Pg=1 Gt), and total net emissions over the course of a century by 130 Pg CO2-Ce, without endangering food security, habitat or soil conservation. Biochar has a larger climate-change mitigation potential than combustion of the same sustainably procured biomass for bioenergy, except when fertile soils are amended while coal is the fuel being offset.

Counting carbon on the farm: Reaping the benefits of carbon offset programs

R educing anthropogenic greenhouse gas (GHG) emissions is the greatest environmental challenge facing society over the coming decades (NAS 2005). Although the largest global source of emission stems from the use of fossil fuels, land use, including agriculture, is the second greatest contributor to increasing GHG concentrations in the atmosphere, accounting for about 30% of total net emissions (IPCC 2007). The majority of these land use emissions are associated with deforestation and land conversion, mainly in the tropics; however, in the United States, agriculture contributes around 7% of total emissions (EPA 2007). The three main GHGs of concern—carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O)—are all emitted through various agricultural activities, with the CH4 and N2O dominating agricultural emissions in the United States. However, agriculture has the capacity to not only significantly reduce its own emissions, but also to offset CO2 emissions from other sectors of the economy via carbon sequestration (CAST 2004; Paustian et al. 2006). By employing practices that increase organic matter content (about half of which is carbon) of soils, it is estimated that as much as 50 to 200 million t C per year of carbon offsets could be produced by US agriculture (Lal et al.…

Above ground biomass changes in the mountain birch forests and mountain heaths of Finnmarksvidda, northern Norway, in the period 1957–2006

Birch forests cover large areas of the northern Fennoscandia and the mountain birch ( Betula pubescens ssp. czerepanovii) often forming the altitudinal and Arctic forest and tree lines. Interpreting the factors leading to landscape changes in mountain birch forest involves disturbance from anthropogenic use and climate as important factors. Using vegetation maps based on aerial photographs and satellite images from 7 years in combination with statistical data and ground estimation data of biomass in the period 1957–2006, we were able to assess the transitions among mountain heaths and different types of forest, the displacement of the altitudinal forest line and hence the change in biomass. The tree biomass as well as the growing stock for birch in Finnmarksvidda doubled in the period 1957–2006. Only lichen biomass has been significantly reduced in the period 1957 to 2000, with a subsequent slight increase of lichen biomass in the period 2000 to 2006. The results presented in this paper show significant and positive relationships between measured tree biomass and the increase in reindeer population in the period 1957–2006 in the study area. The hypothesis concerning the removal of the “lichen barrier effect” by heavy reindeer grazing which leads to increased success for birch seeds to germinate and sprout is therefore considered to be valid. However, also, climate change effects like increased precipitation, moth attacks, freezing and thawing events during winter and long-transported air pollution (e.g. nitrogen) may also have reinforced the changes in biomass. Climatic variables from regional weather stations for the period 1955–2006 did not, however, reveal any consistent change except for that the increased snow depth had a negative impact on the reindeer population while increase in snow depth hindering the reindeer in grazing seemed to have a positive impact on the lichen biomass. The ongoing development of increased forest cover and hence elevated forest line will lead to reduction of open habitats, and hence decreased grazing accessibility for the reindeer. The effects on forestry and carbon sequestration are also discussed, and here one of the suggestions is to let the northern birch forests act as carbon sinks contributing to the reduction of total net emission of CO 2 in the Nordic countries. Land use like reindeer husbandry has shown to strongly affect relationships between ecological processes like tree-growth and climate. Moreover, reindeer husbandry is such a widespread human activity in the arctic and boreal region that it might affect the global carbon budget.

Measurement of the heat of smoldering combustion in straws and stalks by means of simultaneous thermal analysis

Abstract In order to investigate reaction heat of agro-stalks smoldering, wheat straw, corn stalk, cotton stalk, millet straw, sorghum stalk and sweet potato rattan powder were smoldered and pyrolyzed in a simultaneous thermal analyzer (STA). The samples were placed in a platinum crucible (∅5 mm×5 mm) with a lid (with a ∅1 mm hole) on a high-accuracy differential scanning calorimetry–heat capacity (DSC-cp) holder in the furnace of an STA and heated from 303 to 1073 K at a heating rate of 10 K min−1. Sweeping gas with a flow rate of 25 ml min−1 was air and nitrogen during smoldering and pyrolysis, respectively. Results showed that the heat emission characteristic of the smoldering process differed remarkably from the pyrolysis process. Based on the analysis of the DSC curves, oxidative polymer degradation heat and char oxidation heat were obtained from experimental data. It showed that the oxidative polymer degradation heat of the agro-stalks is more than 6.92 MJ kg−1 consumed matter, higher than that of cellulose paper. And char oxidation heat is around 23 MJ kg−1 consumed matter, similar to that of cellulose paper, but higher than that of cigarette. Total net heat emission of smoldering in STA was also obtained. These data can be used as reference data in analyzing smoldering of agro-stalks under similar conditions.

The potential role of hydrogen energy in India and Western Europe

We used the TIMER energy model to explore the potential role of hydrogen in the energy systems of India and Western Europe, looking at the impacts on its main incentives: climate policy, energy security and urban air pollution. We found that hydrogen will not play a major role in both regions without considerable cost reductions, mainly in fuel cell technology. Also, energy taxation policy is essential for hydrogen penetration and India's lower energy taxes limit India's capacity to favour hydrogen. Once available to the (European) energy system, hydrogen can decrease the cost of CO 2 emission reduction by increasing the potential for carbon capture technology. However, climate policy alone is insufficient to speed up the transition. Hydrogen diversifies energy imports; especially for Europe it decreases oil imports, while increasing imports of coal and natural gas. For India, it provides an opportunity to decrease oil imports and use indigenous coal resources in the transport sector. Hydrogen improves urban air quality by shifting emissions from urban transport to hydrogen production facilities. However, for total net emissions we found a sensitive trade-off between lower emissions at end-use (in transport) and higher emissions from hydrogen production, depending on local policy for hydrogen production facilities.