Search

Ammonia (NH3) emissions can negatively affect ecosystems and human health, so they should be monitored and mitigated. This study presents methodology for the estimation of uncertainties in NH3 emissions measurements using the solar occultation flux (SOF) method. The reactive nature of NH3 makes its measurement challenging, but SOF offers a reliable open-path passive method which utilizes solar spectrum data, thereby avoiding gas adsorption within the instrument. To compute NH3 gas fluxes, horizontal and vertical wind speed profiles, as well as plume height estimates and spatially resolved column measurements, are integrated. A unique aspect of this work is the first-time description of plume height estimations derived from ground and column NH3 concentration measurements aimed at uncertainty reduction. Initial validation tests indicated measurement errors between −31 % and +14 % on average, which was slightly larger than the estimated expanded uncertainty ranging from ± 12 % to ± 17 %. Application of the methodology to assess emission rates from farms of various sizes showed uncertainties between ± 21 % and ± 37 %, generally influenced by systematic wind uncertainties and random errors. The method demonstrates the capacity to measure NH3 emissions from both small (∼ 0.5–1 kg h−1) and large (∼ 100 kg h−1) sources in high-density farming areas. Generally, the SOF method provided an expanded uncertainty below 30 % in measuring NH3 emissions from livestock production, which could be further improved by adhering to best application practices. This paper's findings offer the potential for broader applications, such as measuring NH3 fluxes from fertilized fields and in the oil and gas sector. However, these applications would require further research to adapt and refine the methodologies for these specific contexts.

In August and September 2020, three different measurement methods for quantifying methane (CH4) emissions from leaks in urban gas distribution networks were applied and compared in Hamburg, Germany: the "mobile", "tracer release", and "suction"methods. The mobile and tracer release methods determine emission rates to the atmosphere from measurements of CH4 mole fractions in the ambient air, and the tracer release method also includes measurement of a gaseous tracer. The suction method determines emission rates by pumping air out of the ground using soil probes that are placed above the suspected leak location. The quantitative intercomparison of the emission rates from the three methods at a small number of locations is challenging because of limitations of the different methods at different types of leak locations. The mobile method was designed to rapidly quantify the average or total emission rate of many gas leaks in a city, but it yields a large emission rate uncertainty for individual leak locations. Emission rates determined for individual leak locations with the tracer release technique are more precise because the simultaneous measurement of the tracer released at a known rate at the emission source eliminates many of the uncertainties encountered with the mobile method. Nevertheless, care must be taken to properly collocate the tracer release and the leak emission points to avoid biases in emission rate estimates. The suction method could not be completed or applied at locations with widespread subsurface CH4 accumulation or due to safety measures. While the number of gas leak locations in this study is small, we observe a correlation between leak emission rate and subsurface accumulation. Wide accumulation places leaks into a safety category that requires immediate repair so that the suction method cannot be applied to these larger leaks in routine operation. This introduces a sampling bias for the suction method in this

Ambitious methane (CH4) emission mitigation represents one of the most effective opportunities to slow the rate of global warming over the next decades. The oil and gas (O&G) sector is a significant source of methane emissions, with technically feasible and cost-effective emission mitigation options. Romania, a key O&G producer within the EU, with the second highest reported annual CH4 emissions from the energy sector in the year 2020 (Greenhouse Gas Inventory Data - Comparison by Category, 2022), can play an important role towards the EU's emission reduction targets. In this study, we quantify CH4 emissions from onshore oil production sites in Romania at source and facility level using a combination of ground- and drone-based measurement techniques. Measured emissions were characterized by heavily skewed distributions, with 10% of the sites accounting for more than 70% of total emissions. Integrating the results from all site-level quantifications with different approaches, we derive a central estimate of 5.4 kg h-1 per site of CH4 (3.6 %-8.4 %, 95% confidence interval) for oil production sites. This estimate represents the third highest when compared to measurement-based estimates of similar facilities from other production regions. Based on our results, we estimate a total of 120 kt CH4 yr-1 (range: 79-180 kt yr-1) from oil production sites in our studied areas in Romania. This is approximately 2.5 times higher than the reported emissions from the entire Romanian oil production sector for 2020. Based on the source-level characterization, up to three-quarters of the detected emissions from oil production sites are related to operational venting. Our results suggest that O&G production infrastructure in Romania holds a massive mitigation potential, specifically by implementing measures to capture the gas and minimize operational venting and leaks.

Methane is a potent greenhouse gas contributing to climate change. Reliable data for methane emissions from the waste management sector are paramount in terms of providing national methane budgets and developing climate mitigation efforts. This study quantified total methane emissions and characterised temporal as well as operational emission patterns at five commercial composting plants in Denmark. Methane emissions were measured over a one-year period, using the tracer gas dispersion method. The results show that methane emission rates ranged from 8.0 ± 0.1 to 42.5 ± 1.5 kg CH4 h−1 and were significantly affected by factors including the type of feedstock and composting technology, treated feedstock mass, operational patterns and season. The results indicate that the highest methane emission factors were obtained at the combined anaerobic digestion and open windrow composting plant (4.51–5.21 kg CH4 Mg−1 wet garden/park waste (GPW) and food waste), followed by open windrow plants co-composting GPW, sewage sludge and straw (3.49–3.76 kg CH4 Mg−1 wet feedstock). The lowest methane emission factors were found at open windrow composting plants treating GPW (1.56–3.24 kg CH4 Mg−1 wet feedstock). Emissions tended to be higher when measurements were performed during working hours, in comparison to when they were measured after the plant closed for the day. At one plant, emissions were measured monthly over one year, and emissions were about 50% higher in spring and summer in comparison to autumn and winter.

Regeringen har en målsætning om at nedbringe udledningen af drivhusgasser som kuldioxid (CO2), metan (CH4) og lattergas (N2O) i Danmark. Haveaffald har et potentiale for at bidrage til disse mål. Nærværende projekt, ”Reduktion af klimagasser fra behandling af haveaffald i Danmark”, er i den forbindelse igangsat af Miljøstyrelsen og udarbejdet af COWI. Projektet er opdelt i følgende tre arbejdspakker og publikationer: 1: Markedsundersøgelse af haveaffald i Danmark: Reduktion af klimagasser fra behandling af haveaffald i Danmark Del 1: Markedskortlægning. Refereret til i rapporten som "Arbejdspakke 1" (Guldberg, Henriksen, Schjødt-Hansen, & Graasbøll, 2022). 2: Teknisk rapport til undersøgelse af emissionsfaktorer for kompostering og oplagring af finstof i Danmark: Reduktion af klimagasser fra behandling af haveaffald i Danmark Del 2: Emissionsfaktorer for behandling af haveaffald i Danmark. Refereret til i rapporten som "Arbejdspakke 2". 3: Undersøgelse af alternative teknologier til kompostering: Reduktion af klimagasser fra behandling af haveaffald i Danmark Del 3: Alternative teknologier til behandling af haveaffald i Danmark. Refereret til i rapporten som "Arbejdspakke 3". Nærværende rapport er Arbejdspakke 2, som har til formål at undersøge de klimamæssige konsekvenser ved kompostering af haveaffald samt ved oplagring af finstof til direkte udspredning på marker i Danmark. Rapporten danner grundlag for en genberegning af Danmarks nationale emissionsopgørelser for kompostering lavet af Nationalt Center for Miljø og Energi (DCE), hvor følgende emissionsfaktorer er benyttet: 3,19 kg CH4 og 0,23 kg N2O pr. ton VV haveaffald håndteret (Nielsen, et al., 2022). Emissionsfaktorerne er benyttet på den totale mængde haveaffald modtaget til behandling (964.000 ton i 2020). Genberegningen foretages på basis af de målinger, der er foretaget undervejs i proj

In total, 69 biogas plants representing 59 % of Danish biogas production participated in a national effort to reduce methane (CH4) emission. Measurements in terms of total plant CH4 emissions, quantification of emissions from point sources, leak surveys and conceptual design plans to mitigate emissions were performed. Plant-level CH4 emission rates varied between 1.3 and 81.2 kg CH4 h−1, and CH4 losses expressed in percentages of production varied between 0.3 and 40.6 %. Agricultural plants generally had lower CH4 loss rates compared to wastewater treatment plants. Biogas plants with a smaller gas production emitted a larger fraction of their production compared to larger plants, which was partly explained by the absence of gas collection from digestate storage tanks at smaller plants. A very commonly observed source of emission was pressure relief valves, where this source of leakage was observed at 53 % of the plants. A national emission factor (sum of CH4 emissions/sum of CH4 productions) was determined at 2.5 % for the Danish biogas production, whereof it was 2.1 % for agricultural biogas production and 6.7 % for biogas production at wastewater treatment plants. Measurements of total CH4 emissions at six plants performed before and after implementation of mitigating actions showed that emissions were reduced by 46 % by carrying out relatively minor technical fixes and adjustments. An economic evaluation showed that, in some cases, mitigating actions could be economically beneficial for the biogas plant (positive net present value over a 10 year time frame), due to an increase in revenue.