Jerker Samuelsson

Quantification of multiple methane emission sources at landfills using a double tracer technique

A double tracer technique was used successfully to quantify whole-site methane (CH(4)) emissions from Fakse Landfill. Emissions from different sections of the landfill were quantified by using two different tracers. A scaled-down version of the tracer technique measuring close-by to localized sources having limited areal extent was also used to quantify emissions from on-site sources at the landfill facility, including a composting area and a sewage sludge storage pit. Three field campaigns were performed. At all three field campaigns an overall leak search showed that the CH(4) emissions from the old landfill section were localized to the leachate collection wells and slope areas. The average CH(4) emissions from the old landfill section were quantified to be 32.6 ± 7.4 kg CH(4)h(-1), whereas the source at the new section was quantified to be 10.3 ± 5.3 kg CH(4)h(-1). The CH(4) emission from the compost area was 0.5 ± 0.25 kg CH(4)h(-1), whereas the carbon dioxide (CO(2)) and nitrous oxide (N(2)O) flux was quantified to be in the order of 332 ± 166 kg CO(2)h(-1) and 0.06 ± 0.03 kg N(2)Oh(-1), respectively. The sludge pit located west of the compost material was quantified to have an emission of 2.4 ± 0.63 kg h(-1) CH(4), and 0.03 ± 0.01 kg h(-1) N(2)O.

Quantification of Greenhouse Gas Emissions from Windrow Composting of Garden Waste

Microbial degradation of organic wastes entails the production of various gases such as carbon dioxide (CO(2)), methane (CH(4)), nitrous oxide (N(2)O), and carbon monoxide (CO). Some of these gases are classified as greenhouse gases (GHGs), thus contributing to climate change. A study was performed to evaluate three methods for quantifying GHG emissions from central composting of garden waste. Two small-scale methods were used at a windrow composting facility: a static flux chamber method and a funnel method. Mass balance calculations based on measurements of the C content in the in- and out-going material showed that 91 to 94% of the C could not be accounted for using the small-scale methods, thereby indicating that these methods significantly underestimate GHG emissions. A dynamic plume method (total emission method) employing Fourier Transform Infra Red (FTIR) absorption spectroscopy was found to give a more accurate estimate of the GHG emissions, with CO(2) emissions measured to be 127 +/- 15% of the degraded C. Additionally, with this method, 2.7 +/- 0.6% and 0.34 +/- 0.16% of the degraded C was determined to be emitted as CH(4) and CO. In this study, the dynamic plume method was a more effective tool for accounting for C losses and, therefore, we believe that the method is suitable for measuring GHG emissions from composting facilities. The total emissions were found to be 2.4 +/- 0.5 kg CH(4)-C Mg(-1) wet waste (ww) and 0.06 +/- 0.03 kg N(2)O-N Mg(-1) ww from a facility treating 15,540 Mg of garden waste yr(-1), or 111 +/- 30 kg CO(2)-equivalents Mg(-1) ww.

Quantifying methane emission from fugitive sources by combining tracer release and downwind measurements – A sensitivity analysis based on multiple field surveys

Using a dual species methane/acetylene instrument based on cavity ring down spectroscopy (CRDS), the dynamic plume tracer dispersion method for quantifying the emission rate of methane was successfully tested in four measurement campaigns: (1) controlled methane and trace gas release with different trace gas configurations, (2) landfill with unknown emission source locations, (3) landfill with closely located emission sources, and (4) comparing with an Fourier transform infrared spectroscopy (FTIR) instrument using multiple trace gasses for source separation. The new real-time, high precision instrument can measure methane plumes more than 1.2 km away from small sources (about 5 kg h(-1)) in urban areas with a measurement frequency allowing plume crossing at normal driving speed. The method can be used for quantification of total methane emissions from diffuse area sources down to 1 kg per hour and can be used to quantify individual sources with the right choice of wind direction and road distance. The placement of the trace gas is important for obtaining correct quantification and uncertainty of up to 36% can be incurred when the trace gas is not co-located with the methane source. Measurements made at greater distances are less sensitive to errors in trace gas placement and model calculations showed an uncertainty of less than 5% in both urban and open-country for placing the trace gas 100 m from the source, when measurements were done more than 3 km away. Using the ratio of the integrated plume concentrations of tracer gas and methane gives the most reliable results for measurements at various distances to the source, compared to the ratio of the highest concentration in the plume, the direct concentration ratio and using a Gaussian plume model. Under suitable weather and road conditions, the CRDS system can quantify the emission from different sources located close to each other using only one kind of trace gas due to the high time resolution, while the FTIR system can measure multiple trace gasses but with a lower time resolution.

A national landfill methane budget for Sweden based on field measurements, and an evaluation of IPCC models

Seven Swedish landfills were investigated from 2001 to 2003. On each landfill, ameasure of the total methane production was calculated from data on: (1) methane emissions (leakage); (2) methane oxidation and (3) from gas recovery. Methane emissions were determined via a tracer gas (N2O) release-based remote sensing method. N2O and CH4 were measured with an Fourier Transform infrared detector at a distance of more than 1 kmdownwind from the landfills. Methane oxidation in the landfill covers was measured with the stable carbon isotope method. The efficiency in gas recovery systems proved to be highly variable, but on an average, 51% of the produced landfill gas was captured. A first-order decay model, based on four fractions (waste from households and parks, sludges and industrial waste), showed that the use of a degradable organic carbon fraction (DOCf) value of 0.54, in accordance with the default value for DOCf of 0.50 in the latest IPCC model, gave an emission estimate similar to the official national reports.

Measurements of industrial emissions of alkenes in Texas using the solar occultation flux method

Solar occultation flux (SOF) measurements of alkenes have been conducted to identify and quantify the largest emission sources in the vicinity of Houston and in SE Texas during September 2006 as part of the TexAQS 2006 campaign. The measurements have been compared to emission inventories and have been conducted in parallel with airborne plume studies. The SOF measurements show that the hourly gas emissions from the large petrochemical and refining complexes in the Houston Ship Channel area and Mount Belvieu during September 2006 corresponded to 1250 +/- 180 kg/h of ethene and 2140 +/- 520 kg/h of propene, with an estimated uncertainty of about 35%. This can be compared to the 2006 emission inventory value for ethene and propene of 145 +/- 4 and 181 +/- 42 kg/h, respectively. On average, for all measurements during the campaign, the discrepancy factor is 10.2(+ 8,-5) for ethene and 11.7(+ 7,-4) for propene. The largest emission source was Mount Belvieu, NE of the Houston Ship Channel, with ethene and propene emissions corresponding to 440 +/- 130 kg/h and 490 +/- 190 kg/h, respectively. Large variability of propene was observed from several petrochemical industries, for which the largest reported emission sources are flares. The SOF alkene emissions agree within 50% with emissions derived from airborne measurements at three different sites. The airborne measurements also provide support to the SOF error budget.

Quantification of methane emissions from 15 Danish landfills using the mobile tracer dispersion method

Whole-site methane emissions from 15 Danish landfills were assessed using a mobile tracer dispersion method with either Fourier transform infrared spectroscopy (FTIR), using nitrous oxide as a tracer gas, or cavity ring-down spectrometry (CRDS), using acetylene as a tracer gas. The landfills were chosen to represent the different stages of the lifetime of a landfill, including open, active, and closed covered landfills, as well as those with and without gas extraction for utilisation or flaring. Measurements also included landfills with biocover for oxidizing any fugitive methane. Methane emission rates ranged from 2.6 to 60.8 kg h(-1), corresponding to 0.7-13.2 g m(-2)d(-1), with the largest emission rates per area coming from landfills with malfunctioning gas extraction systems installed, and the smallest emission rates from landfills closed decades ago and landfills with an engineered biocover installed. Landfills with gas collection and recovery systems had a recovery efficiency of 41-81%. Landfills where shredder waste was deposited showed significant methane emissions, with the largest emission from newly deposited shredder waste. The average methane emission from the landfills was 154 tons y(-1). This average was obtained from a few measurement campaigns conducted at each of the 15 landfills and extrapolating to annual emissions requires more measurements. Assuming that these landfills are representative of the average Danish landfill, the total emission from Danish landfills were calculated at 20,600 tons y(-1), which is significantly lower than the 33,300 tons y(-1) estimated for the national greenhouse gas inventory for 2011.

Quantification of NO2 and SO2 emissions from the Houston Ship Channel and Texas City industrial areas during the 2006 Texas Air Quality Study

In August-September 2006, as part of the Second Texas Air Quality Study, NO2 and SO2 emissions from the Houston Ship Channel and Texas City industrial areas were quantified using mobile mini-differential optical absorption spectroscopy instruments. The measured NO2 emissions from the Houston Ship Channel and Texas City industrial areas were 2542 and 452 kg h(-1), respectively, yielding NOx emissions 70% and 43%, respectively, above the reported inventory values. Quantified SO2 emissions from the Houston Ship Channel area were 1749 kg h(-1) and were found to be 34% above the values reported in the inventory. Short-term variability of NO2 and SO2 emissions was found at the Houston Ship Channel. On 31 August 2006, a plume was detected at the HSC during three consecutive measurements, yielding a HCHO flux of 481 kg h(-1). This event has been mainly attributed to photochemical production.

Mitigation of methane emission from an old unlined landfill in Klintholm, Denmark using a passive biocover system

Methane generated at landfills contributes to global warming and can be mitigated by biocover systems relying on microbial methane oxidation. As part of a closure plan for an old unlined landfill without any gas management measures, an innovative biocover system was established. The system was designed based on a conceptual model of the gas emission patterns established through an initial baseline study. The study included construction of gas collection trenches along the slopes of the landfill where the majority of the methane emissions occurred. Local compost materials were tested as to their usefulness as bioactive methane oxidizing material and a suitable compost mixture was selected. Whole site methane emission quantifications based on combined tracer release and downwind measurements in combination with several local experimental activities (gas composition within biocover layers, flux chamber based emission measurements and logging of compost temperatures) proved that the biocover system had an average mitigation efficiency of approximately 80%. The study showed that the system also had a high efficiency during winter periods with temperatures below freezing. An economic analysis indicated that the mitigation costs of the biocover system were competitive to other existing greenhouse gas mitigation options.

Gas production, composition and emission at a modern disposal site receiving waste with a low-organic content

AV Miljø is a modern waste disposal site receiving non-combustible waste with a low-organic content. The objective of the current project was to determine the gas generation, composition, emission, and oxidation in top covers on selected waste cells as well as the total methane (CH(4)) emission from the disposal site. The investigations focused particularly on three waste disposal cells containing shredder waste (cell 1.5.1), mixed industrial waste (cell 2.2.2), and mixed combustible waste (cell 1.3). Laboratory waste incubation experiments as well as gas modeling showed that significant gas generation was occurring in all three cells. Field analysis showed that the gas generated in the cell with mixed combustible waste consisted of mainly CH(4) (70%) and carbon dioxide (CO(2)) (29%) whereas the gas generated within the shredder waste, primarily consisted of CH(4) (27%) and nitrogen (N(2)) (71%), containing no CO(2). The results indicated that the gas composition in the shredder waste was governed by chemical reactions as well as microbial reactions. CH(4) mass balances from three individual waste cells showed that a significant part (between 15% and 67%) of the CH(4) generated in cell 1.3 and 2.2.2 was emitted through leachate collection wells, as a result of the relatively impermeable covers in place at these two cells preventing vertical migration of the gas. At cell 1.5.1, which is un-covered, the CH(4) emission through the leachate system was low due to the high gas permeability of the shredder waste. Instead the gas was emitted through the waste resulting in some hotspot observations on the shredder surface with higher emission rates. The remaining gas that was not emitted through surfaces or the leachate collection system could potentially be oxidized as the measured oxidation capacity exceeded the potential emission rate. The whole CH(4) emission from the disposal site was found to be 820 ± 202 kg CH(4)d(-1). The total emission rate through the leachate collection system at AV Miljø was found to be 211 kg CH(4)d(-1). This showed that approximately ¼ of the emitted gas was emitted through the leachate collections system making the leachate collection system an important source controlling the overall gas migration from the site. The emission pathway for the remaining part of the gas was more uncertain, but emission from open cells where waste is being disposed of or being excavated for incineration, or from horizontal leachate drainage pipes placed in permeable gravel layers in the bottom of empty cells was likely.

Emission measurements of alkenes, alkanes, SO2, and NO2 from stationary sources in Southeast Texas over a 5 year period using SOF and mobile DOAS

A mobile platform for flux measurements of VOCs (alkanes and alkenes), SO2, and NO2 emissions using the Solar Occultation Flux (SOF) method and mobile differential optical absorption spectroscopy (DOAS) was used in four different studies to measure industrial emissions. The studies were carried out in several large conglomerates of oil refineries and petrochemical industries in Southeast and East Texas in 2006, 2009, 2011, and 2012. The measured alkane emissions from the Houston Ship Channel (HSC) have been fairly stable between 2006 and 2011, averaging about 11,500kg/h, while the alkene emissions have shown greater variations. The ethene and propene emissions measured from the HSC were 1511kg/h and 878kg/h, respectively, in 2006, while dropping to roughly 600kg/h for both species in 2009 and 2011. The results were compared to annual inventory emissions, showing that measured VOC emissions were typically 5-15 times higher, while for SO2 and NO2 the ratio was typically 0.5-2. AP-42 emission factors were used to estimate meteorological effects on alkane emissions from tanks, showing that these emissions may have been up to 35-45% higher during the studies than the annual average. A more focused study of alkene emissions from a petrochemical complex in Longview in 2012 identified two upset episodes, and the elevation of the total emissions during the measurement period due to the upsets was estimated to be approximately 20%. Both meteorological and upset effects were small compared to the factor of 5-15, suggesting that VOC emissions are systematically and substantially underestimated in current emission inventories.