Life cycle greenhouse gases,energy and cost assessment of automobiles using magnesium from Chinese Pidgeon process

Magnesium (Mg) has a great potential to reduce vehicle weight, fuel consumption, and greenhouse gas emissions. The Chinese Mg industry has developed rapidly since the 1990s. The output of Mg reached 700,000 tons in 2006, accounting for more than 70% of global Mg production. Most of Mg is produced in China through the Pidgeon process that has an intensive energy usage and generates a large amount of greenhouse gas (GHG) emissions, which may offset the potential advantage of using Mg parts in automobiles. It is critical to quantify the energy usage and GHG emissions through entire life cycle when the Mg are applied to automobiles. It is also essential to evaluate cost implications of the Mg parts application in automobiles and ensure it to be cost competitive. The objectives of this study are (1) Build a life cycle inventory (LCI) of Mg produced by Pidgeon process; (2) Establish an LCA model that can evaluate GHG emissions and energy usage for the Mg automotive application; (3) Estimate the cost implications of the Mg parts application in automobiles.An Mg LCI was built based on interviews and surveys and the GREET model was adapt for this study. The results indicated that, for each kilogram of Mg produced by Pidgeon process, GHG emissions and energy usage would be 27 kg CO₂eq and 280 MJ, which are five times higher than steel production. Replacing steel with 82 kg Mg on a base automobile would lower curb weight by 5.7%, but only reduce life cycle GHG emissions and energy usage by 0.8% and 1.3%. Scenario analyses indicated that potential reduction of life cycle GHG emissions and energy usage could reach to 15%, if secondary weight saving and a smaller engine were included. Cost analyses also show 18% reduction when the additional weight saving and a smaller displacement engine were included, under a 100,000 km driving distance and gasoline price at $1.0/l.     

Mitigation of greenhouse gas emissions by anaerobic digestion of cattle slurry

Biogas treatment of animal manures is an upcoming technology because it is a way of producing renewable energy (biogas). However, little is known about effects of this management strategy on greenhouse gas (GHG) emissions during fermentation, storage, and field application of the substrates compared to untreated slurries. In this study, we compared cattle slurry and cattle slurry with potato starch as additive during the process of fermentation, during storage and after field application. The addition of potato starch strongly enhanced CH₄ production from 4230 l CH₄ m⁻³ to 8625 l CH₄ m⁻³ in the fermenter at a hydraulic retention time (HRT) of 29 days. Extending the HRT to 56 days had only a small effect on the CH₄ production. Methane emissions from stored slurry depended on storage temperature and were highest from unfermented slurry followed by the slurry/starch mixture. Gas emissions from untreated and fermented slurry during storage were further analyzed in a pilot-scale experiment with different levels of covering such as straw cover, a wooden lid and no cover. Emissions of greenhouse gases (CH₄, N₂O, NH₃) were in the range of 14.3–17.1 kg CO₂ eq. m⁻³ during winter (100 day storage period) and 40.5–90.5 kg CO₂ eq. m⁻³ during summer (140 day storage period). A straw cover reduced NH₃ losses, but not overall GHG emissions, whereas a solid cover reduced CH₄ and NH₃ emissions. After field application, there were no significant differences between slurry types in GHG emissions (4.15–8.12 kg CO₂ eq. m⁻³ a⁻¹). GHG emissions from slurry stores were more important than emissions after field application. Co-digestion of slurry with additives such as starch has a large potential to substitute fossil energy by biogas. On a biogas plant, slurry stores should be covered gas-tight in order to eliminate GHG emissions and collect CH₄ for electricity production.     

Life-cycle environmental and economic impacts of energy-crop fuel-chains: an integrated assessment of potential GHG avoidance in Ireland

This paper combines life-cycle analyses and economic analyses for Miscanthus and willow heat and electricity fuel-chains in Ireland. Displaced agricultural land-uses and conventional fuels were considered in fuel-chain permutations. Avoided greenhouse gas (GHG) emissions ranged from 7.7 to 35.2 t CO₂ eq. ha⁻¹ a⁻¹. Most fuel-chain permutations exhibited positive discounted financial returns, despite losses for particular entities at a farm-gate processed-biomass price of €100 t⁻¹ dry-matter. Attributing a value of €10 t⁻¹ CO₂ eq. to avoided GHG emissions, but subtracting financial returns associated with displaced fuel supplies, resulted in discounted annual national economic benefits (DANEBs) ranging from −457 to 1887€ ha⁻¹ a⁻¹. Extrapolating a plausible combination of fuel-chains up to a national indicative scenario resulted in GHG emission avoidance of 3.56 Mt CO₂ eq. a⁻¹ (5.2% of national emissions), a DANEB of 167 M€, and required 4.6% of national agricultural land area. As cost-effective national GHG avoidance options, Miscanthus and willow fuel-chains are robust to variation in yields and CO₂ price, and appear to represent an efficient land-use option (e.g. compared with liquid biofuel production). Policies promoting utilisation of these energy-crops could avoid unnecessary, and environmentally questionable, future purchase of carbon credits, as currently required for national Kyoto compliance.     

Disaggregated greenhouse gas emission inventories from agriculture via a coupled economic-ecosystem model

Estimates of regional greenhouse gas emissions from agricultural systems are needed to evaluate possible mitigation strategies with respect to environmental effectiveness and economic feasibility. Therefore, in this study, we used the GIS-coupled economic-ecosystem model EFEM–DNDC to assess disaggregated regional greenhouse gas (GHG) emissions from typical livestock and crop production systems in the federal state of Baden-Württemberg, Southwest Germany. EFEM is an economic farm production model based on linear programming of typical agricultural production systems and simulates all relevant farm management processes and GHG emissions. DNDC is a process-oriented ecosystem model that describes the complete biogeochemical C and N cycle of agricultural soils, including all trace gases.Direct soil emissions were mainly related to N₂O, whereas CH₄ uptake had marginal influence (net soil C uptake or release was not considered). The simulated N₂O emissions appeared to be highly correlated to N fertilizer application (R² = 0.79). The emission factor for Baden-Württemberg was 0.97% of the applied N after excluding background emissions.Analysis of the production systems showed that total GHG emissions from crop based production systems were considerably lower (2.6–3.4 Mg CO₂ eq ha⁻¹) than from livestock based systems (5.2–5.3 Mg CO₂ eq ha⁻¹). Average production system GHG emissions for Baden-Württemberg were 4.5 Mg CO₂ eq ha⁻¹. Of the total 38% were derived from N₂O (direct and indirect soil emissions, and manure storage), 40% were from CH₄ (enteric fermentation and manure storage), and 22% were from CO₂ (mainly fertilizer production, gasoline, heating, and additional feed). The stocking rate was highly correlated (R² = 0.85) to the total production system GHG emissions and appears to be a useful indicator of regional emission levels.     

Modelling greenhouse gas emissions from European conventional and organic dairy farms

Agriculture is an important contributor to global emissions of greenhouse gases (GHG), in particular for methane (CH₄) and nitrous oxide (N₂O). Emissions from farms with a stock of ruminant animals are particularly high due to CH₄ emissions from enteric fermentation and manure handling, and due to the intensive nitrogen (N) cycle on such farms leading to direct and indirect N₂O emissions. The whole-farm model, FarmGHG, was designed to quantify the flows of carbon (C) and nitrogen (N) on dairy farms. The aim of the model was to allow quantification of effects of management practices and mitigation options on GHG emissions. The model provides assessments of emissions from both the production unit and the pre-chains. However, the model does not quantify changes in soil C storage.Model dairy farms were defined within five European agro-ecological zones for both organic and conventional systems. The model farms were all defined to have the same utilised agricultural area (50 ha). Cows on conventional and organic model farms were defined to achieve the same milk yield, so the basic difference between conventional and organic farms was expressed in the livestock density. The organic farms were defined to be 100% self-sufficient with respect to feed. The conventional farms, on the other hand, import concentrates as supplementary feed and their livestock density was defined to be 75% higher than the organic farm density. Regional differences between farms were expressed in the milk yield, the crop rotations, and the cow housing system and manure management method most common to each region.The model results showed that the emissions at farm level could be related to either the farm N surplus or the farm N efficiency. The farm N surplus appeared to be a good proxy for GHG emissions per unit of land area. The GHG emissions increased from 3.0 Mg CO₂-eq ha⁻¹ year⁻¹ at a N surplus of 56 kg N ha⁻¹ year⁻¹ to 15.9 Mg CO₂-eq ha⁻¹ year⁻¹ at a N surplus of 319 kg N ha⁻¹ year⁻¹. The farm N surplus can relatively easily be determined on practical farms from the farm records of imports and exports and the composition of the crop rotation. The GHG emissions per product unit (milk or metabolic energy) were quite closely related to the farm N efficiency, and a doubling of the N efficiency from 12.5 to 25% reduced the emissions per product unit by ca. 50%. The farm N efficiency may therefore be used as a proxy for comparing the efficiencies of farms with respect to supplying products with a low GHG emission.     

Environmental consequences of different beef production systems in the EU

The aim of this paper is to examine the environmental consequences of beef meat production in the EU, using a life cycle approach. Four beef production systems were studied – three from intensively reared dairy calves and one from suckler herds. According to the results of the analysis, the contributions from the production of 1 kg beef meat (slaughter weight) to global warming, acidification, eutrophication, land use and non-renewable energy use were lower for beef from dairy calves than from suckler herds (16.0–19.9 versus 27.3 kg CO₂e, 101–173 versus 210 g SO₂e, 622–1140 versus 1651 g NO₃e, 16.5–22.7 versus 42.9 m²year, and 41.3–48.2 versus 59.2 MJ, respectively). The breakdown analysis helped identify the key areas in the “cradle to farm gate” beef production system where sustainable management strategies are needed to improve environmental performance. The study also included a sensitivity analysis to preliminarily estimate GHG emissions from beef production systems if land opportunity cost and land use change related to grazing and feed crop production for beef were taken into account. If so, the contribution from the production of 1 kg beef to global warming would increase by a factor of 3.1–3.9, based on a depreciation period of 20 years. This highlights the importance of taking into account the impacts of land use in assessing the environmental impacts of livestock production.     

Methane,nitrous oxide and ammonia emissions during storage and after application of dairy cattle slurry and influence of slurry treatment

Slurries are a significant source of CH₄, NH₃ and N₂O emissions to the atmosphere. The research project aimed at quantifying CH₄, NH₃ and N₂O emissions from liquid manure stores and after manure application under field conditions. The influence of the manure treatment options “no treatment”, “slurry separation”, “anaerobic digestion”, “slurry aeration” and “straw cover” on the emission level was investigated. Approximately 10 m³ of differently treated slurry were stored in pilot scale slurry tanks. Emissions were followed for c. 80 days. After the storage period, slurries were applied to permanent grassland. Greenhouse gas emissions from slurry were mainly caused by methane emissions during storage and by nitrous oxide emissions after field application of manures. Mitigation of GHG emissions can be achieved by a reduction in slurry dry matter and easily degradable organic matter content. Ammonia emissions mainly occurred after field application. Untreated slurry emitted 226.8 g NH₃ m⁻³ and 92.4 kg CO₂ eq. m⁻³ (storage and field application). Slurry separation (liquid fraction and composting of the solid fraction) resulted in NH₃ losses of 402.9 g m⁻³ and GHG losses of 58.5 kg CO₂ eq. m⁻³. Anaerobic digestion was a very effective means to reduce GHG emissions. 37.9 kg CO₂ eq. m⁻³ were lost. NH₃ emissions were similar to those from untreated slurry. Covering the slurry store with a layer of chopped straw instead of a wooden cover increased NH₃ emissions to 320.4 g m⁻³ and GHG emissions to 119.7 kg CO₂ eq. m⁻³. Slurry aeration nearly doubled NH₃ emissions compared to untreated slurry. GHG emissions were reduced to 53.3 kg CO₂ eq. m⁻³.     

Greenhouse gas emissions from production and use of used cooking oil methyl ester as transport fuel in Thailand

Biodiesel, produced from various vegetable and/or animal oils, is one of the most promising alternative fuels for transportation in Thailand. Currently, the waste oils after use in cooking are not disposed adequately. Such oils could serve as a feedstock for biodiesel which would also address the waste disposal issue. This study compares the life cycle greenhouse gas (GHG) emissions from used cooking oil methyl ester (UCOME) and conventional diesel used in transport. The functional unit (FU) is 100 km transportation by light duty diesel vehicle (LDDV) under identical driving conditions. Life cycle GHG emissions from conventional diesel are about 32.57 kg CO₂-eq/FU whereas those from UCOME are 2.35 kg CO₂-eq/FU. The GHG emissions from the life cycle of UCOME are 93% less than those of conventional diesel production and use. Hence, a fuel switch from conventional diesel to UCOME will contribute greatly to a reduction in global warming potential. This will also support the Thai Government's policy to promote the use of indigenous and renewable sources for transportation fuels.     

Global implications of biomass and biofuel use in Germany – Recent trends and future scenarios for domestic and foreign agricultural land use and resulting GHG emissions

The global land area required to meet the German consumption of agricultural products for food and non-food use was quantified, and the related greenhouse gas (GHG) emissions, particularly those induced by land-use changes in tropical countries, were estimated. Two comprehensive business-as-usual scenarios describe the development corridor of biomass for non-food use in terms of energetic and non-energetic purposes. In terms of land use, Germany was already a net importer of agricultural land in 2004, and the net additional land required by 2030 is estimated to comprise 2.5–3.4 Mha. This is mainly due to biofuel demand driven by current policy targets. Meeting the required biodiesel import demand would result in an additional GWP of 23–37 Tg of CO₂ equivalents through direct and indirect land-use changes. Alternative scenario elements outline the potential options for reducing Germany's land requirement, which reflect future global per capita availability.     

Effect of straw addition on nitrous oxide and methane emissions from stored farmyard manures

Stored solid manure heaps can be a significant source of nitrous oxide (N₂O) and methane (CH₄) emissions. The manure characteristics influence emissions and solid manure heaps can be managed to promote aerobic decomposition during storage. Increasing the carbon (C) content of the manure heap with high-C additives, such as straw, may provide the opportunity for N₂O and CH₄ emission reduction. Greenhouse gas (GHG) emissions from conventionally produced farmyard manure (FYM) have been quantified, but there is little data on emissions from organically produced FYM. N₂O and CH₄ emissions were measured using a small-scale storage method from FYM collected from organic and conventional dairy units under a range of storage conditions with and without extra straw addition.The organic and the conventional FYM were similar in composition except for the higher C and dry matter content in the organic FYM and in the FYM with added straw. This resulted in mean total emissions of N₂O and CH₄ being lower from the organic (27 g N t⁻¹) than the conventional FYM (52 g N t⁻¹) and from the treatments with straw added (32 g N t⁻¹) than those without (47 g N t⁻¹). The initial C:N ratio and dry matter content of the stored FYM were the most important factors affecting N₂O and CH₄ emissions although the FYM temperature also affected CH₄ emissions. Adding high-C additives, such as straw could be a promising strategy for reducing GHG emissions because it influences the dry matter content, C:N ratio and aeration of the manure. The small-scale FYM storage method were shown to be a reliable and an easy method to quantify emissions under a range of environmental conditions and manure manipulations and so develop effective manure management practices to reduce GHG emissions.     

Mitigation of greenhouse gas emissions in European conventional and organic dairy farming

Dairy farming is the largest agricultural source of the greenhouse gases methane (CH₄) and nitrous oxide (N₂O) in Europe. A whole-farm modeling approach was used to investigate promising mitigation measures. The effects of potential mitigation measures were modeled to obtain estimates of net greenhouse gas (GHG) emissions from representative dairy model farms in five European regions. The potential to reduce farm GHG emissions was calculated per kg milk to compare organic and conventional production systems and to investigate region and system specific differences. An optimized lifetime efficiency of dairy cows reduced GHG emissions by up to 13% compared to baseline model farms. The evaluation of frequent removal of manure from animal housing into outside covered storage reduced farm GHG emissions by up to 7.1%. Scraping of fouled surfaces per se was not an effective option since the reduction in GHG emissions from animal housing was more than out-weighed by increased emissions from the storage and after field application. Manure application by trail hose and injection, respectively, was found to reduce farm GHG emissions on average by 0.7 and 3.2% compared to broadcasting. The calculated model scenarios for anaerobic digestion demonstrated that biogas production could be a very efficient and cost-effective option to reduce GHG emissions. The efficiency of this mitigation measure depends on the amount and quality of organic matter used for co-digestion, and how much of the thermal energy produced is exploited. A reduction of GHG emissions by up to 96% was observed when all thermal energy produced was used to substitute fossil fuels. Potential measures and strategies were scaled up to the level of European regions to estimate their overall mitigation potential. The mitigation potential of different strategies based on a combination of measures ranged from −25 up to −105% compared to baseline model farms. A full implementation of the most effective strategy could result in a total GHG emission reduction of about 50 Mt of carbon dioxide (CO₂) equivalents per year for conventional dairy farms of EU(15) comparable to the defined model farms.     

Balancing of greenhouse gas emissions and economic efficiency for biogas-production through anaerobic co-fermentation of slurry with organic waste

Using the organic fraction of municipal solid waste (OFMSW) for biogas production might contribute to greenhouse gas mitigation, but emissions linked with biogas production can reduce these beneficial effects. Therefore the emissions of NH₃, CH₄ and N₂O and costs caused by treating OFMSW by co-fermentation with slurry were calculated in detail from literature data, and strategies for reducing emissions were evaluated. Emission factors were calculated for single gases during storage and after application. The sensitivity of the calculations concerning the organic dry matter content of OFMSW, retention time and CH₄-yield was analyzed. The anaerobic co-fermentation of OFMSW increased biogas yields and contributed to the reduction of CO₂ emissions with 32 to 152 kg CO₂ t⁻¹ organic waste depending on application and storage techniques used for the fermentation residues. Considering a payment of 0.1 €/kWh for the electricity produced, the costs for utilization of OFMSW in slurry based biogas plants were calculated to range between 34 and 38 € t⁻¹. Measures for mitigating greenhouse gas emissions by covering the fermentation residue stores proved to be more cost effective with 3–31 € t⁻¹ CO₂ compared to immediate harrowing or injecting the residues during field application.     

Potential carbon sequestration in China’s forests

Forests are believed to be a major sink for atmospheric carbon dioxide. There are 158.94 million hectares (Mha) of forests in China, accounting for 16.5% of its land area. These extensive forests may play a vital role in the global carbon (C) cycle as well as making a large contribution to the country’s economic and environmental well-being. Currently there is a trend towards increased development in the forests. Hence, accounting for the role and potential of the forests in the global carbon budget is very important.In this paper, we attempt to estimate the carbon emissions and sequestration by Chinese forests in 1990 and make projections for the following 60 years based on three scenarios, i.e. “baseline”, “trend” and “planning”. A computer model F-CARBON 1.0, which takes into account the different biomass density and growth rates for the forests in different age classes, the life time for biomass oxidation and decomposition, and the change in soil carbon between harvesting and reforestation, was developed by the authors and used to make the calculations and projections. Climate change is not modelled in this exercise.We calculate that forests in China annually accumulate 118.1 Mt C in growth of trees and 18.4 Mt in forest soils, and release 38.9 Mt, resulting in a net sequestration of 97.6 Mt C, corresponding to 16.8% of the national CO₂ emissions in 1990. From 1990 to 2050, soil carbon accumulation was projected to increase slightly while carbon emissions increases by 73, 77 and 84%, and net carbon sequestration increases by −21, 52 and 90% for baseline, trend and planning scenarios, respectively. Carbon sequestration by China’s forests under the planning scenario in 2000, 2010, 2030 and 2050 is approximately 20, 48, 111 and 142% higher than projected by the baseline scenario, and 8, 18, 34 and 26% higher than by the trend scenario, respectively. Over 9 Gt C is projected to accumulate in China’s forests from 1990 to 2050 under the planning scenario, and this is 73 and 23% larger than projected for the baseline and trend scenarios, respectively. During the period 2008–2012, Chinese forests are likely to have a net uptake of 667, 565 and 452 Mt C, respectively, for the planning, trend and baseline scenarios. We conclude that China’s forests have a large potential for carbon sequestration through forest development. Sensitivity analysis showed that the biggest uncertainty in the projection by the F-CARBON model came from the release coefficient of soil carbon between periods after harvesting and before reforestation.     

Palm oil and the emission of carbon-based greenhouse gases

The current use of South Asian palm oil as biofuel is far from climate neutral. Dependent on assumptions, losses of biogenic carbon associated with ecosystems, emission of CO₂ due to the use of fossil fuels and the anaerobic conversion of palm oil mill effluent currently correspond in South Asia with an emission of about 2.8–19.7 kg CO₂ equivalent per kg of palm oil. Using oil palm and palm oil processing wastes for the generation of energy and preventing further conversion of tropical forest into oil palm plantations by establishing new plantations on non-peaty degraded soils can, however, lead to large cuts in the emission of carbon-based greenhouse gases currently associated with the palm oil lifecycle.     

Evidence of rich microbial communities in the subsoil of a boreal acid sulphate soil conducive to greenhouse gas emissions

The largest areas of acid sulphate (AS) soils in Europe are located in Finland, where 67,000–130,000 ha of AS soils are in agricultural use. In addition to their acidifying effects on waters, AS soils might be a significant source of greenhouse gases. In this pilot research, carbon and nitrogen content and microbial activity were studied in an AS and a non-AS soil. Large carbon and nitrogen stocks (110 Mg C_org ha^?1 and 15 Mg N_tot ha^?1) as well as high substrate induced respiration (33 μg CO₂–C g^?1h^?1) were found in the C horizons of the AS soil but not in the non-AS soil. High microbial activity in these horizons of the AS soil was further confirmed by the measurement of dehydrogenase activity, basal respiration, the numbers of culturable bacterial cells, and the ratio of culturable to total numbers of cells. Still, the denitrifying enzyme activity was very low in the anaerobic horizons of the AS soil, indicating the prevalence of microbes other than denitrifiers. We suspect that the microbial community originated with the genesis of AS soil and has been supported by the large stocks of accumulated carbon and mineral nitrogen in the C horizons. If these permanently water-saturated subsoils are exposed to oxygen and their microbial activity consequently increases, large carbon and nitrogen stocks are likely to be mobilised, resulting in increased emission of greenhouse gases. Additional studies of boreal AS soils are needed to assess their potential contribution to increases in greenhouse gas fluxes at the local, regional, and global scales.     

Wood materials used as a means to reduce greenhouse gases (GHGs): An examination of wooden utility poles

There has been growing concern over the build-up of greenhouse gase(GHGs) in the atmosphere, particularly carbon dioxide (CO₂), as acause of global warming. The IPCC Third Assessment Report (2001) suggests two ways in which the choice of materials could berelevant. First, some materials, particularly wood, have the advantage thatthey continue to hold carbon (C)in their cells even after being convertedto products. The implications of this feature are well researched. Second,an area that is not well researched relates to the different energyrequirements for producing similar products made with different materials. Using the findings of recent research, this paper compares the energyrequirements and C emissions of manufacturing a product using wood withthat of other materials. The case study of utility poles demonstrates thepositive C and global warming consequences of the lower energyrequirements of wood in the U.S., compared to other materials such assteel or concrete. It demonstrates that GHG emissions associated withutility poles are a small but significant percent of total US annual emissions. Wood utility poles are associated with GHG emission reductions of 163Terragrams (Tg) of CO₂ when compared with steel poles. This isabout 2.8 percent of US annual GHG emissions, which are estimated atabout 5.28 Petragrams (Pg) of CO₂ annually. Thus, the use ofwooden utility poles rather than steel results in a small but significantreduction in total US emissions.     

Nitrous oxide emissions from organic and conventional crop rotations in five European countries

Nitrous oxide (N₂O) emissions from agriculture are currently estimated from N inputs using emission factors, and little is known about the importance of regional or management-related differences. This paper summarizes the results of a study in which N₂O emission rates were recorded on 15–26 occasions during a 12-month period in organic and conventional dairy crop rotations in five European countries (Austria, Denmark, Finland, Italy, UK). A common methodology based on static chambers was used for N₂O flux measurements, and N₂O data were compiled together with information about N inputs (from fertilizers, N₂ fixation, atmospheric deposition and excretal returns), crop rotations and soil properties. Organic rotations received only manure as N fertilizer, while manure accounted for 0–100% of fertilizer N in conventional rotations. A linear regression model was used to examine effects of location, system and crop category on N₂O emissions, while a second model examined effects of soil properties. Nitrous oxide emissions were higher from conventional than from organic crop rotations except in Austria and, according to the statistical analysis, the differences between locations and crop categories were significant. Ammonium was significantly related to N₂O emissions, although this effect was dominated by observations from a grazing system. Despite the limited number of samplings, annual emissions were estimated by interpolation. Across the two systems and five locations there was a significant relationship between total N inputs and N₂O emissions at the crop rotation level which indicated that annually 1.6 ± 0.2% (mean ± standard error) of total N inputs were lost as N₂O, while there was a background emission of 1.4 ± 0.3 kg N₂O-N ha⁻¹ year⁻¹. Although this measurement program emphasized system effects at the expense of high temporal resolution, the results indicate that N input is a significant determinant for N₂O emissions from agricultural soils.     

Carbon footprint of sugar produced from sugarcane in eastern Thailand

Carbon footprint (CFP) of sugar produced from sugarcane in eastern Thailand was estimated from greenhouse gas emissions (CO₂, CH₄, and N₂O) during the sugarcane cultivation and milling process. The use of fossil fuels, chemical and organic fertilizer and sugarcane biomass data during cultivation were collected from field surveys, questionnaires and interviews. Sugar mill emissions, fossil fuel utilization and greenhouse gas emission from wastewater treatments were included. The results show that sugar production has a carbon footprint of 0.55 kg CO₂e kg^?1 sugar. This carbon footprint was a sum of 0.49 kg CO₂e kg^?1 sugar from sugarcane cultivation and 0.06 kg CO₂e kg^?1 sugar from the milling process. For the cultivation part, most of the GHGs emissions were from fertilizer, fossil fuel use and biomass burning. The CFP in eastern Thailand is sensitive to the type of data selected for calculation and of variations of farm inputs during sugarcane cultivation. There was no significant difference of CFP among farm sizes, although small farms tended to give a relatively higher CFP than that of medium and large farms.     

Greenhouse gas mitigation with scarce land: The potential contribution of increased nitrogen input

Agricultural lands have been identified to mitigate greenhouse gas (GHG) emissions primarily by production of energy crops and substituting fossil energy resources and through carbon sequestration in soils. Increased fertilizer input resulting in increased yields may reduce the area needed for crop production. The surplus area could be used for energy production without affecting the land use necessary for food and feed production. We built a model to investigate the effect of changing nitrogen (N) fertilizer rates on cropping area required for a given amount of crops. We found that an increase in nitrogen fertilizer supply is only justified if GHG mitigation with additional land is higher than 9–15 t carbon dioxide equivalents per hectare (CO₂-eq._./ha). The mitigation potential of bioenergy production from energy crops is most often not in this range. Hence, from a GHG abatement point of view land should rather be used to produce crops at moderate fertilizer rate than to produce energy crops. This may change if farmers are forced to reduce their N input due to taxes or governmental regulations as it is the case in Denmark. However, with a fertilizer rate 10 % below the economical optimum a reduction of N input is still more effective than the production of bioenergy unless mitigation effect of the bioenergy production exceeds 7 t carbon dioxide (CO₂)-eq._./ha. An intensification of land use in terms of N supply to provide more land for bioenergy production can only in exceptional cases be justified to mitigate GHG emissions with bioenergy under current frame conditions in Germany and Denmark.     

The influence of long term trends in pollutant emissions on deposition of sulphur and nitrogen and exceedance of critical loads in the United Kingdom

In the United Kingdom, as with other European countries, land-based emissions of NO_x and SO₂ have fallen significantly over the last few decades. SO₂ emissions fell from a peak of 3185 Gg S in 1970 to 344 Gg S in 2005 and are forecast by business-as-usual emissions scenarios to fall to 172 Gg by 2020. NO_x emissions were at a maximum of 951 Gg N in 1970 and fell to 378 by 2005 with a further decrease to 243 Gg N forecast by 2020. These large changes in emissions have not been matched by emissions changes for NH₃ which decreased from 315 Gg N in 1990 to 259 in 2005 and are forecast to fall to 222 by 2020. The Fine Resolution Atmospheric Multi-pollutant Exchange model (FRAME) has been applied to model the spatial distribution of sulphur and nitrogen deposition over the United Kingdom during a 15-year time period (1990–2005) and compared with measured deposition of sulphate, nitrate and ammonium from the national monitoring network. Wet deposition of nitrogen and sulphur was found to decrease more slowly than the emissions reductions rate. This is attributed to a number of factors including increases in emissions from international shipping and changing rates of atmospheric oxidation. The modelled time series was extended to a 50-year period from 1970 to 2020. The modelled deposition of SO_x, NO_y and NH_x to the UK was found to fall by 87%, 52% and 25% during this period. The percentage area of sensitive habitats in the United Kingdom for which critical loads are exceeded is estimated to fall from 85% in 1970 to 37% in 2020 for acidic deposition and from 73% to 49% for nutrient nitrogen deposition. The significant reduction in land emissions of SO₂ and NO_x focuses further attention in controlling emissions from international shipping. Future policies to control emissions of ammonia from agriculture will be required to effect further significant reductions in nitrogen deposition.