Higher Emission Factors Research Articles

Rapid growth of petroleum coke consumption and its related emissions in China

Petroleum coke, a non-environmentally friendly energy source, is gradually replacing other power fuels in China’s industrial enterprises because of its price advantage. Petroleum coke has high emission factors and thus emits more greenhouse gases (GHGs) and air pollutants than even raw coal. This study first examines the rapid growth of petroleum coke consumption in China since 2010 by industry sector and region and then estimates the petroleum coke-related emissions. We conclude that the total consumption of petroleum coke increased by 18.9% from 2010 to 2016 and that the industry final consumption for burning in boilers increased dramatically (by 158.2%). Petroleum coke-related CO2 emissions reached 28 million tonnes in 2016, whereas CH4 and N2O emissions totaled 870 and 143 tonnes, respectively. The increased use of petroleum coke will increase the urgency for the development of climate change mitigation and emissions reduction measures in China. We propose several possible policy suggestions for petroleum coke management and emissions control, such as strongly restricting the production and import of high-sulphur petroleum coke, as well as burning petroleum coke to provide power; more power plants and industrial kiln stoves/boilers should be equipped with efficient decontamination systems; the development of advanced industrial processes and the clean utilization of petroleum coke should be encouraged.

Particle and VOC emission factor measurements for anthropogenic sources in West Africa

Abstract. A number of campaigns have been carried out to establish the emission factors of pollutants from fuel combustion in West Africa, as part of work package 2 (“Air Pollution and Health”) of the DACCIWA (Dynamics-Aerosol-Chemistry-Cloud Interactions in West Africa) FP7 program. Emission sources considered here include wood (hevea and iroko) and charcoal burning, charcoal making, open trash burning, and vehicle emissions, including trucks, cars, buses and two-wheeled vehicles. Emission factors of total particulate matter (TPM), elemental carbon (EC), primary organic carbon (OC) and volatile organic compounds (VOCs) have been established. In addition, emission factor measurements were performed in combustion chambers in order to reproduce field burning conditions for a tropical hardwood (hevea), and obtain particulate emission factors by size (PM0.25, PM1, PM2.5 and PM10). Particle samples were collected on quartz fiber filters and analyzed using gravimetric method for TPM and thermal methods for EC and OC. The emission factors of 58 VOC species were determined using offline sampling on a sorbent tube. Emission factor results for two species of tropical hardwood burning of EC, OC and TPM are 0.98 ± 0.46 g kg−1 of fuel burned (g kg−1), 11.05 ± 4.55 and 41.12 ± 24.62 g kg−1, respectively. For traffic sources, the highest emission factors among particulate species are found for the two-wheeled vehicles with two-stroke engines (2.74 g kg−1 fuel for EC, 65.11 g kg−1 fuel for OC and 496 g kg−1 fuel for TPM). The largest VOC emissions are observed for two-stroke two-wheeled vehicles, which are up to 3 times higher than emissions from light-duty and heavy-duty vehicles. Isoprene and monoterpenes, which are usually associated with biogenic emissions, are present in almost all anthropogenic sources investigated during this work and could be as significant as aromatic emissions in wood burning (1 g kg−1 fuel). EC is primarily emitted in the ultrafine fraction, with 77 % of the total mass being emitted as particles smaller than 0.25 µm. The particles and VOC emission factors obtained in this study are generally higher than those in the literature whose values are discussed in this paper. This study underlines the important role of in situ measurements in deriving realistic and representative emission factors.

High-resolution inversion of OMI formaldehyde columns to quantify isoprene emission on ecosystem-relevant scales: application to the southeast US

Abstract. Isoprene emissions from vegetation have a large effect on atmospheric chemistry and air quality. “Bottom-up” isoprene emission inventories used in atmospheric models are based on limited vegetation information and uncertain land cover data, leading to potentially large errors. Satellite observations of atmospheric formaldehyde (HCHO), a high-yield isoprene oxidation product, provide “top-down” information to evaluate isoprene emission inventories through inverse analyses. Past inverse analyses have however been hampered by uncertainty in the HCHO satellite data, uncertainty in the time- and NOx-dependent yield of HCHO from isoprene oxidation, and coarse resolution of the atmospheric models used for the inversion. Here we demonstrate the ability to use HCHO satellite data from OMI in a high-resolution inversion to constrain isoprene emissions on ecosystem-relevant scales. The inversion uses the adjoint of the GEOS-Chem chemical transport model at 0.25∘ × 0.3125∘ horizontal resolution to interpret observations over the southeast US in August–September 2013. It takes advantage of concurrent NASA SEAC4RS aircraft observations of isoprene and its oxidation products including HCHO to validate the OMI HCHO data over the region, test the GEOS-Chem isoprene oxidation mechanism and NOx environment, and independently evaluate the inversion. This evaluation shows in particular that local model errors in NOx concentrations propagate to biases in inferring isoprene emissions from HCHO data. It is thus essential to correct model NOx biases, which was done here using SEAC4RS observations but can be done more generally using satellite NO2 data concurrently with HCHO. We find in our inversion that isoprene emissions from the widely used MEGAN v2.1 inventory are biased high over the southeast US by 40 % on average, although the broad-scale distributions are correct including maximum emissions in Arkansas/Louisiana and high base emission factors in the oak-covered Ozarks of southeast Missouri. A particularly large discrepancy is in the Edwards Plateau of central Texas where MEGAN v2.1 is too high by a factor of 3, possibly reflecting errors in land cover. The lower isoprene emissions inferred from our inversion, when implemented into GEOS-Chem, decrease surface ozone over the southeast US by 1–3 ppb and decrease the isoprene contribution to organic aerosol from 40 to 20 %.

Analysis of clean coal technology in Nigeria for energy generation

An analysis of clean coal technologies for the recovery of energy from Nigerian coals was carried out. The coal mines studied are Onyeama, Ogwashi, Ezimo, Inyi, Amasiodo, Okaba, Lafia-Obi, Owukpa Owukpa, Ogboyoga and Okpara. The estimated reserves of the ten coal deposit amount to 2.1 Gt, which is about 84% of the total coal reserves of the country 2.5 Gt of coal Nigeria. The key clean coal technologies studied are Ultra-Supercritical Combustion (USC), Supercritical-Fluidised Bed Combustion (FBC), Integrated Gasification Combined Cycle (IGCC) and Coal bed Methane (CBM) and the results were compared with conventional subcritical pulverised fuel combustion (PF). The total potential energy recovery from these technologies are: PF 5800 TWh, FBC 7250 TWh, IGCC 7618 TWh, and USC 8519 TWh. This indicates an increase of about 31% in the total electricity generation if USC technology is used instead of the conventional sub-critical PF technology. About 39% of the total electricity generation of 8519 TWh from USC could come from Amasiodo coal deposit, making it the highest contributor to the total power generation. Inyi coal had a contribution of ∼1.5% making it the lowest contributor. The lowest CO2 emission factor was from Onyeama coal and was reduced from 1.0 kg CO2/kWh in PF to 0.68 kg CO2/kWh in USC. Oghwashi coal had the lowest energy and highest emission factor. There will be a need for the coal upgrading/beneficiation for optimal energy recovery.

Ultracompact Pseudowedge Plasmonic Lasers and Laser Arrays.

Concentrating light at the deep subwavelength scale by utilizing plasmonic effects has been reported in various optoelectronic devices with intriguing phenomena and functionality. Plasmonic waveguides with a planar structure exhibit a two-dimensional degree of freedom for the surface plasmon; the degree of freedom can be further reduced by utilizing metallic nanostructures or nanoparticles for surface plasmon resonance. Reduction leads to different lightwave confinement capabilities, which can be utilized to construct plasmonic nanolaser cavities. However, most theoretical and experimental research efforts have focused on planar surface plasmon polariton (SPP) nanolasers. In this study, we combined nanometallic structures intersecting with ZnO nanowires and realized the first laser emission based on pseudowedge SPP waveguides. Relative to current plasmonic nanolasers, the pseudowedge plasmonic lasers reported in our study exhibit extremely small mode volumes, high group indices, high spontaneous emission factors, and high Purell factors beneficial for the strong interaction between light and matter. Furthermore, we demonstrated that compact plasmonic laser arrays can be constructed, which could benefit integrated plasmonic circuits.

Wet‐Transfer of Freestanding Dense Colloidal Quantum Dot Films and Their Photonic Device Application

AbstractA method of wet‐transferring a densely packed colloidal quantum dot (CQD) film is reported herein. Layers of poly(vinyl alcohol) (sacrificial layer) and poly(methyl methacrylate) (temporary mechanical support) are spin‐coated below and above the CQD film, respectively; the two layers are eventually removed, resulting in a single CQD film on an alien substrate. CQD films as large as 1 cm × 1 cm are transferred to any substrate, including flexible and prepatterned ones, with very little mechanical or optical damage. The wet‐transfer method can be repeated to form a CQD heterostructure. A CQD distributed feedback (DFB) laser is also demonstrated by transferring a thick CdSe‐based CQD layer (for both optical gain and waveguiding) on top of a surface grating structure. The resultant CQD structure exhibits a single‐mode DFB lasing action, with a high spontaneous emission factor (β ≈ 10−3), owing to a strong vertical mode confinement and smooth surface morphologies on both sides of the CQD waveguide layer.

NOx emission calculations for bulk carriers by using engine power probabilities as weighting factors

ABSTRACTAn important marine pollution issue identified by the International Maritime Organization (IMO) is NOx emissions; however, the stipulated method for determining the NOx certification value does not reflect the actual high emission factors of slow-speed two-stroke diesel engines over long-term slow steaming. In this study, an accurate method is presented for calculating the NOx emission factors and total amount of NOx emissions by using the actual power probabilities of the diesel engines in four types of bulk carriers. The proposed method is suitable for all types and purposes of diesel engines, is not restricted to any operating modes, and is highly accurate. Moreover, it is recommended that the IMO-stipulated certification value calculation method be modified accordingly to genuinely reduce the amount of NOx emissions. The successful achievement of this level of reduction will help improve the air quality, especially in coastal and port areas, and the health of local residents.Implications: As per the IMO, the NOx emission certification value of marine diesel engines having a rated power over 130 kW must be obtained using specified weighting factor (WF)-based calculation. However, this calculation fails to represent the current actual situation. Effective emission reductions of 6.91% (at sea) and 31.9% (in ports) were achieved using a mathematical model of power probability functions. Thus, we strongly recommend amending the certification value of NOx Technical Code 2008 (NTC 2008) by removing the WF constraints, such that the NOx emissions of diesel engines is lower than the Tier-limits at any load level to obtain genuine NOx emission reductions.

Optimal energy supply structures for industrial food processing sites in different countries considering energy transitions

This study focuses on analysing the most energy efficient utility system supply structure in terms of carbon emissions, primary energy efficiency and energy costs. In the German food processing industry, the state-of-the-art technologies in the utility supply structure are a gas fired steam boiler for steam generation and ammonia chillers for chilled water generation. Low investment costs and its durability are attractive for industrial production sites. But, given the ongoing energy transition to renewable energy, opportunities to reduce emissions will become increasingly important. There are other energy supply options, such as Combined Heat and Power and Heat Pumps, that need to compete against the conventional energy supply systems. In the short-term, countries with presently high electricity Grid Emissions Factors (GEF) such as Germany and the USA, the use of decentralised CHP results in savings of primary energy and emissions. This option is less attractive for countries with already low GEF such as Norway. It is also less attractive in the long-term for countries like Germany as the on-going energy transition towards renewables is anticipated to decrease the current GEF by 50% in 2030. In these cases of low GEF, HP solutions provide the lowest emissions and highest primary energy efficiency.

Decomposition Analysis on the Air Pollutant Baseline Emission Factors in China's Power Sector

Air pollution is one of the major problem in China's power sector. This paper calculates the baseline emission factor in the power sector and uses the index decomposition method to analyze the variation trend of the emission factor. For the SO2, the simple average baseline emission factor is 1.15kg/MWh. The east China has the highest emission factor and the central has the lowest number. As for the NOx, the simple average is 1.76kg/MWh, the northeast China has the highest emission factor, and the South China has the lowest emission factor. And the decomposition analysis takes into account three driving factors: pollution control technology level, fuel mix and power structure. The variation from 2005 to 2013 of the SO2 baseline emission factor is mostly influenced by the pollutant control technology improvement, and fuel mix in thermal power industry makes small contribution on the emission reduction and the influence brought by fuel mix varies a lot among different regions. As for the variation of NOx emission factor from 2007 to 2013, the technology level causes biggest variation too. The fuel mix also makes some positive contribution on east and central China. And the power structure don’t have significant influence on the variation of both SO2 and NOx baseline emission factor.

Nitrogen removal and nitrous oxide emission from a step-feeding multiple anoxic and aerobic process

ABSTRACTThe multiple anoxic and aerobic (AO) process is an advanced biological nitrogen-removal process, and nitrous oxide (N2O) emission might affect its sustainable application. Nitrogen removal and N2O emission in a step-feeding multiple AO sequencing batch reactor (SBRS) was examined, in comparison with a one-feeding sequencing batch reactor (SBRO). Nitrogen removal was enhanced by 12.6% in SBRS compared to the removal percentage of 75.8% in SBRO. Activated sludge in SBRs possessed a higher N2O emission factor during nitrification, denitrification and simultaneous nitrification and denitrification (SND) than in SBRO. A high N2O emission factor was observed during SND in both reactors, with the emission factor of 4.38% in SBRS and 4.66% in SBRO. More N2O emission occurred in the presence of nitrite. Bacteroidetes and Proteobacteria dominated in both SBRS and SBRO. A similar abundance of Thauera, Dechloromonas and Zoogloea possible for denitrification was observed in SBRS and SBRO. Moreover, nosZ from Proteobacteria dominated in both SBRS and SBRO, with dominating genus of Acidovorax, Ralstonia, Thauera and Marinobacter.

How the user can influence particulate emissions from residential wood and pellet stoves: Emission factors for different fuels and burning conditions

For a common household wood stove and a pellet stove we investigated the dependence of emission factors for various gaseous and particulate pollutants on burning phase, burning condition, and fuel. Ideal and non-ideal burning conditions (dried wood, under- and overload, small logs, logs with bark, excess air) were used. We tested 11 hardwood species (apple, ash, bangkirai, birch, beech, cherry, hickory, oak, olive, plum, sugar maple), 4 softwood species (Douglas fir, pine, spruce, spruce/fir), treated softwood, beech and oak wood briquettes, paper briquettes, brown coal, wood chips, and herbaceous species (miscanthus, Chinese silver grass) as fuel. Particle composition (black carbon, non-refractory, and some semi-refractory species) was measured continuously. Repeatability was shown to be better for the pellet stove than for the wood stove. It was shown that the user has a strong influence on wood stove emission behavior both by selection of the fuel and of the burning conditions: Combustion efficiency was found to be low at both very low and very high burn rates, and influenced particle properties such as particle number, mass, and organic content in a complex way. No marked differences were found for the emissions from different wood species. For non-woody fuels, much higher emission factors could be observed (up to five-fold increase). Strongest enhancement of emission factors was found for burning of small or dried logs (up to six-fold), and usage of excess air (two- to three-fold). Real world pellet stove emissions can be expected to be much closer to laboratory-derived emission factors than wood stove emissions, due to lower dependence on user operation.

Optimal energy supply structures for industrial sites in different countries considering energy transitions: A cheese factory case study

This present study focuses on analysing the most efficient utility energy supply structure in terms of primary energy efficiency, carbon emissions and energy costs. In the German dairy industry, separate conversion with gas fired steam boiler, and cooling with ammonia chillers are the-state-of-the-art technologies. It is attractive due to its robustness and low investment costs. But given the ongoing energy transition to renewable energy, opportunities to reduce emissions will become increasingly important. There are other energy supply options, such as Combined Heat and Power (CHP) and Heat Pumps (HP), that if implemented need to compete against the conventional energy supply systems. One option is CHP to provide cogenerated electricity and heat while cooling remains supplied by ammonia chillers. In countries with high electricity Grid Emissions Factors (GEF) such as Germany and the USA, the use of decentralised CHP results in savings of primary energy and emissions. However, this option is less attractive for countries with low GEF such as France and Norway, and for places like Germany where the energy transition lowering its GEF by 50 % in 2030. In these cases, HP solutions provide the lowest emissions and highest primary energy efficiency.

Dynamic hysteresis in a coherent high-β nanolaser

The quest for an integrated light source that promises high energy efficiency and a fast modulation for high-performance photonic circuits has led to the development of room-temperature telecom-wavelength nanoscale lasers with a high spontaneous emission factor β. The coherence characterization of this type of laser using the conventional measurement of output light intensity versus input pump intensity is inherently difficult due to the diminishing kink in the measurement curve. We demonstrate that the transition from incoherent to coherent emission of a high-β pulse-pump metallo-dielectric nanolaser can be determined by examining the width of a second-order intensity correlation peak that shrinks below and broadens above the threshold. Our photon fluctuation study, the first ever reported for this type of nanolaser, confirms the validity of this measurement technique. Additionally, we show that the width variation above the threshold results from the delayed threshold phenomenon, providing the first observation of dynamical hysteresis in a nanolaser.

The content and emission factors of heavy metals in biomass used for energy purposes in the context of the requirements of international standards

The aim of this work was to study the content of seven heavy metal factors within different biomasses. The potential environmental effects associated with the release of these elements into the atmosphere were also studied by determining the emission factors for each of biomass. 31 samples of biomass which were classified into four groups, i.e.: wood biomass, herbaceous biomass, fruit biomass and aquatic biomass and analyzed with use of ICP-OES spectrometer. Performed results were analyzed in the context of the requirements of international standards, described in the EN ISO 17225:2014. Higher heavy metal contents than the limits described in the EN ISO 17225:2014 standard were detected within some of the studied biomass samples. Importantly, this is also related to the products available on the market, i.e., wood pellets or wood chips. Among the detected trace elements, the largest limit exceedance was for lead (wood chips from a rubber tree, pomace oil and palm kernel shells) and arsenic (Sea Balls). The highest emission factors were determined for the herbaceous, fruit and aquatic biomass. However, the wood chips studied were characterized by relatively high emission factors for each heavy metal. A comparison of the emission factors calculated for the studied biomass samples and for coal revealed that the total emission of heavy metals during the combustion of wood pellets and wood chips was lower than that calculated for hard coal.

Carbon accounting of material substitution with biomass: Case studies for Austria investigated with IPCC default and alternative approaches

There is evidence that the replacement of carbon-intensive products with bio-based substitutes (‘material substitution with biomass’) can be highly efficient in reducing greenhouse gas (GHG) emissions. Based on two case studies (CS1/2) for Austria, potential benefits of material substitution in comparison to fuel substitution are analysed. GHG savings are calculated according to default IPCC approaches (Tier 2 method assuming first-order decay) and with more realistic approaches based on distribution functions. In CS1, high savings are achieved by using wood residues for the production of insulating boards instead of energy. The superiority of material substitution is due to the establishment of a long-term carbon storage, the high emission factor of wood in comparison to natural gas and higher efficiencies of gas-fired facilities.The biomass feedstock in CS2 is lignocellulosic ethanol being used for bio-ethylene production (material substitution) or replacing gasoline (fuel substitution). GHG savings are mainly due to lower production emissions of bio-ethylene in comparison to conventional ethylene and significantly lower than in CS1 (per unit of biomass consumed). While CS1 is highly robust to parameter variation, the long-term projections in CS2 are quite speculative.To create adequate incentives for including material substitution in national climate strategies, shortcomings of current default accounting methods must be addressed. Under current methods the GHG savings in both case studies would not (fully) materialize in the national GHG inventory. The main reason is that accounting of wood products is confined to the proportion derived from domestic harvest, whereas imported biomass used for energy is treated as carbon-neutral. Further inadequacies of IPCC default accounting methods include the assumption of exponential decay and the disregard of advanced bio-based products.

Improving and disaggregating N2O emission factors for ruminant excreta on temperate pasture soils

Cattle excreta deposited on grazed grasslands are a major source of the greenhouse gas (GHG) nitrous oxide (N2O). Currently, many countries use the IPCC default emission factor (EF) of 2% to estimate excreta-derived N2O emissions. However, emissions can vary greatly depending on the type of excreta (dung or urine), soil type and timing of application. Therefore three experiments were conducted to quantify excreta-derived N2O emissions and their associated EFs, and to assess the effect of soil type, season of application and type of excreta on the magnitude of losses. Cattle dung, urine and artificial urine treatments were applied in spring, summer and autumn to three temperate grassland sites with varying soil and weather conditions. Nitrous oxide emissions were measured from the three experiments over 12months to generate annual N2O emission factors. The EFs from urine treated soil was greater (0.30–4.81% for real urine and 0.13–3.82% for synthetic urine) when compared with dung (−0.02–1.48%) treatments. Nitrous oxide emissions were driven by environmental conditions and could be predicted by rainfall and temperature before, and soil moisture deficit after application; highlighting the potential for a decision support tool to reduce N2O emissions by modifying grazing management based on these parameters. Emission factors varied seasonally with the highest EFs in autumn and were also dependent on soil type, with the lowest EFs observed from well-drained and the highest from imperfectly drained soil. The EFs averaged 0.31 and 1.18% for cattle dung and urine, respectively, both of which were considerably lower than the IPCC default value of 2%. These results support both lowering and disaggregating EFs by excreta type.

Gaseous emissions from compressed natural gas buses in urban road and highway tests in China

The natural gas vehicle market is rapidly developing throughout the world, and the majority of such vehicles operate on compressed natural gas (CNG). However, most studies on the emission characteristics of CNG vehicles rely on laboratory chassis dynamometer measurements, which do not accurately represent actual road driving conditions. To further investigate the emission characteristics of CNG vehicles, two CNG city buses and two CNG coaches were tested on public urban roads and highway sections. Our results show that when speeds of 0–10km/hr were increased to 10–20km/hr, the CO2, CO, nitrogen oxide (NOx), and total hydrocarbon (THC) emission factors decreased by (71.6±4.3)%, (65.6±9.5)%, (64.9±9.2)% and (67.8±0.3)%, respectively. In this study, The Beijing city buses with stricter emission standards (Euro IV) did not have lower emission factors than the Chongqing coaches with Euro II emission standards. Both the higher emission factors at 0–10km/hr speeds and the higher percentage of driving in the low-speed regime during the entire road cycle may have contributed to the higher CO2 and CO emission factors of these city buses. Additionally, compared with the emission factors produced in the urban road tests, the CO emission factors of the CNG buses in highway tests decreased the most (by 83.2%), followed by the THC emission factors, which decreased by 67.1%.

Estimation of long-term environmental inventory factors associated with land application of sewage sludge

Land application of sewage sludge has a number of advantages over other alternatives, but is also associated with environmental impacts. To make proper assessments of different sludge treatments, it is crucial to have reliable estimates of emissions after the application of different sludge types. However, because of the complexity of the agricultural production system, it is difficult to estimate emissions consistently under different conditions. In the current paper, a mechanistic agro-ecosystem model was calibrated to be able to simulate different sludge types stabilized using different techniques. Subsequently, 100 year model simulations were used to provide emission factors as well as harvest and carbon sequestration factors (collectively called environmental inventory factors) under a variety of environmental conditions. Environmental inventory factors were calculated under both high crop response conditions (i.e. when nitrogen was limiting) and low crop response conditions (i.e. when nitrogen was not limiting). The average high response nitrogen harvest factor over the tested environmental conditions was ranging from 0.06 to 0.30 for the different sludge types included. This means that if an additional 1 kg of nitrogen is applied with sludge, between 0.06 and 0.30 kg additional nitrogen is harvested. This is considerably lower than for mineral fertilizer with an average value of 0.63. The low response harvest factors were considerably lower, ranging from 0.03 to 0.13. The emission factor for nitrous oxide nitrogen was ranging from 0.024 to 0.034, consistently being higher under high response conditions. For nitrogen leaching to the groundwater, the high response emission factor ranged from 0.20 to 0.50 for the different sludge types while the low response were slightly higher ranging from 0.18 to 0.55. The average carbon sequestration factor across the different environmental conditions ranged from 0.03 to 0.05 for the different sludge types. In conclusion, the approach using an agro-ecosystem model to estimate inventory factors associated with land application of sludge under varying conditions proved very powerful and would have been virtually impossible by experimental means.

Timing and amplitude jitter in a gain-switched multimode semiconductor laser

The differences in timing jitter between a gain-switched single-mode semiconductor laser and a gain-switched multimode semiconductor laser are examined using rate equations that include Langevin noise. The timing jitter in a gain-switched multimode semiconductor laser is found to be effectively suppressed by a decrease in the coherence time of the amplified spontaneous emission (ASE) based on a broad bandwidth of multimode oscillation. Instead, fluctuations in the ASE cause amplitude jitter in the pulse components of the respective modes. A pulse train of gain-switched pulses from a multimode semiconductor laser with timing jitter is equivalently simulated by assuming a high spontaneous emission factor and a short coherence time of the ASE in the single-mode semiconductor laser rate equations.

Methane, nitrous oxide and ammonia emissions from an Australian piggery with short and long hydraulic retention-time effluent storage

In the Australian pork industry, manure is the main source of greenhouse gases (GHG). In conventional production systems, effluent from sheds is transferred into open anaerobic ponds where the effluent is typically stored for many months, with the potential of generating large quantities of GHG. The present study measured methane (CH4), nitrous oxide (N2O) and ammonia (NH3) emissions from a conventional anaerobic effluent pond (control), a short hydraulic retention-time tank (short HRT, mitigation) and from the animal housing for a flushing piggery in south-eastern Queensland, over two 30-day trials during summer and winter. Emissions were compared to determine the potential for a short HRT to reduce emissions. Average CH4 emissions from the pond were 452 ± 37 g per animal unit (AU; 1 AU = 500 kg liveweight) per day, during the winter trial and 789 ± 29 g/AU.day during the summer trial. Average NH3 emissions were 73 ± 8 g/AU.day during the winter trial and 313 ± 18 g/AU.day during the summer trial. High emission factors during summer will be temperature driven and influenced by the residual volatile solids and nitrogen (N) deposited in the pond during winter. Average NH3 emissions from the piggery shed were 0.707 ± 0.050 g/AU.day and CH4 emissions were 0.344 ± 0.116 g/AU.day. The N2O concentrations from both the pond and shed were close to, or below, the detection limits. Total emissions from the short HRT during the winter and summer trials, respectively, were as follows: CH4 10.65 ± 0.616 mg/AU.day and 4108 ± 473 mg/AU.day; NH3-N 1.15 ± 0.07 mg/AU.day and 29.8 ± 2.57 mg/AU.day; N2O-N 0.001 ± 0.00052 mg/AU.day and 5.9 ± 0.321 mg/AU.day. On the basis of a conservative analysis of CH4 emissions relative to the inflow of volatile solids, and NH3 and N2O emissions as a fraction of the excreted N, GHG emissions were found to be 79% lower from the short-HRT system. This system provides a potential mitigation option to reduce GHG emissions from conventional pork production in Australia.