Analysis of landfill gas migration by use of autonomous gas monitoring platforms

Autonomous gas sensing platforms have been developed to facilitate the long-term continuous monitoring of landfill gas concentrations. The analysis of a municipal landfill site in Ireland forms part of an on-going collaboration with the Environmental Protection Agency in monitoring the migration of greenhouse gases, i.e. methane and carbon dioxide, emanating from the landfill site. Target gas concentrations were automatically recorded via infrared gas sensors calibrated for the respective gases, with this data being logged remotely every six hours to a central base-station. The autonomous platform with its web-based portal interface provides a flexible alternative to the existing labor-intensive, manual monitoring routines. Frequent occurrences of 70% v/v methane and 6% v/v carbon dioxide were substantially in breach of the regulatory limits of 1.5% v/v and 1.0% v/v, respectively. These excessive levels of gas migration were analyzed with respect to SCADA flare data, on-site measurements and meteorological data

Landfill gas monitoring network - development of wireless sensor network platforms

A wireless sensor network has been developed for the application of landfill gas monitoring, specifically sensing methane, carbon dioxide and extraction pressure. This collaborative work with the Irish Environmental Protection Agency has been motivated by the need to reduce greenhouse gas emissions as well as aiming to improve landfill gas management and utilisation. This paper describes the preliminary findings of an ongoing trial deployment of multiple sensing platforms on an active landfill facility; data has been acquired for nine months to date. The platforms have operated successfully despite adverse on-site conditions, with validity demonstrated by reasonably strong correlation with independent on-site measurements. The increased temporal and spatial resolution provided by distributed sensor platforms is discussed with regard to improving landfill gas management practice

Distributed chemical sensor networks for environmental sensing

Society is increasingly accustomed to instant access to real-time information, due to the ubiquitous use of the internet and web-based access tools. Intelligent search engines enable huge data repositories to be searched, and highly relevant information returned in real time. These repositories increasingly include environmental information related to the environment, such as distributed air and water quality. However, while this information at present is typically historical, for example, through agency reports, there is increasing demand for real-time environmental data. In this paper, the issues involved in obtaining data from autonomous chemical sensors are discussed, and examples of current deployments presented. Strategies for achieving large-scale deployments are discussed

The optimisation of a paired emitter-detector diode optical pH sensing device

With recent improvements in wireless sensor network hardware there has been a concurrent push to develop sensors that are suitable in terms of price and performance. In this paper a low cost gas sensor is detailed, and significant improvements in sensor characteristics have been achieved compared to previously published results. A chemical sensor is presented based on the use of low cost LEDs as both the light source and photodetector, coupled with a sensor slide coated with a pH sensitive colorimetric dye to create a simple gas sensor. Similar setups have been successfully used to detect both acetic acid and ammonia. The goal of this work was to optimise the system performance by integration of the sensing technique into a purposely deigned flowcell platform that holds the colorimetric slide and optical detector in position. The reproducibility of the sensor has been improved through this arrangement and careful control of deposited film thickness. The enhanced reproducibility between sensors opens the potential of calibration-free measurement, in that calibration of one sensor can be used to model the characteristics of all sensors in a particular batch

Web-based monitoring of gas emissions from landfill sites using autonomous sensing platforms

Executive Summary Numerous initiatives that are policy driven by national, European and global agencies target the preservation of our environment, human society’s health and our ecology. Ireland’s EPA 2020 Vision outlines a mandate to prepare for the unavoidable impact of climate change, the reduction of greenhouse gas (GHG) emissions, the control of air-emissions standards, the sustainable use of resources and the holding to account of those who flout environmental laws. These strategies are echoed in the Europe 2020: Resource-efficient Europe Flagship Initiative, which also advocates the creation of new opportunities for economic growth and greater innovation. The promotion of research and technical development is central to each of these strategies – specifically the achievement of accurate environmental monitoring technologies that will inform policy-makers and effect change. This is described in the EPA Strategic Plan 2013–2015 as the provision of ‘high quality, targeted and timely environmental data, information and assessment to inform decision making at all levels’. Specific to landfills, the Environmental Protection Agency’s (EPA) Focus on Landfilling in Ireland stipulates the management of landfill gas to eliminate environmental harm and public nuisance, to promote energy generation where possible and to avoid liabilities in site closure and aftercare. It was in this context that the EPA STRIVE programme granted funding for this research project on developing autonomous sensor platforms for the real-time monitoring of gases generated in landfill facilities. Managing landfill gas is one of the crucial operations in a landfill facility, where gases (primarily methane [CH4] and carbon dioxide [CO2] generated from the decomposition of biodegradable waste) are extracted and combusted in a flare or preferably an engine (as biogas fuel). These gases, classified as greenhouse gases (GHGs), also pose localised hazards due to fire risk and asphyxiation, and are indicative of odorous nuisance compounds. Gas-monitoring on site is conducted to (i) ensure against gas migration into the local environment and to (ii) maintain the thorough gas extraction and optimum composition for combustion. This is becoming more relevant because of the numerous landfill closures brought by Europe-wide changes in waste-management policy. Even for landfills no longer actively receiving waste, substantial gas generation remains ongoing for years and even decades. Despite diminished financial resources and reduced manpower, management of this gas must be maintained. Traditionally, monitoring involves taking manual measurements using expensive handheld equipment and requiring laborious travel over difficult and expansive terrain. Consequently, it is conducted relatively infrequently – typically once a month. These issues can be addressed by adopting distributed continuous monitoring systems. These low-cost remotely deployable sensor platforms offer a valuable complementary service to operators and the EPA. They enable easier adherence to their licence criteria, the prevention of expensive remediation measures and the potential boost in revenue from increasing energy production through the use of biogas. Challenges arise in terms of achieving a long-term monitoring performance in a harsh environment while maintaining accuracy, reliability and cost-effectiveness. To meet these challenges, this project developed cost- effective autonomous sensor platforms to allow long- term continuous monitoring of gas composition (methane and carbon dioxide) and extraction pressure. The project’s work represents one of the only developments of autonomous sensor technology in this space; the few other market alternatives tend to be expensive or difficult to implement for remotely deployable continuous monitoring. Beyond the development of a platform technology, the challenge was to apply this technology to the adverse environmental conditions. The project delivered a total of 14 autonomous sensor platforms in deployments involving Irish landfill sites, a Scottish landfill site and a Brazilian wastewater treatment plant. The analysis and interpretation of acquired data, coupled with local meteorological data and on-site operational data, provided the translation from raw environmental data to meaningful conclusions that could inform decision-making. This report presents a number of case studies to illustrate this. Characteristics of site gas dynamics could be identified; for example, it was possible to show if excessive gas concentrations in a perimeter well could be resolved by increasing the flare extraction rate for a particular well. Furthermore, the potential for quantifying methane generation potential at distributed locations within the landfill was identified in addition to diagnosing the effectiveness of the extraction network – hence aiding in field-balancing and landfill gas utilisation. The extensive wealth of data enabled by this platform technology will help better-informed decision-making and improve operational practices in managing gas emissions. In landfills, this signifies alleviating gas migration with perimeter monitoring and enhancing flare/ engine operation by evaluating gas quality at distributed locations within the gas field. While landfilling is becoming outmoded as a waste-management process, the need for continuous monitoring will be relevant for many years to come. Indeed, a number of existing facilities are considering retrofitting engines because of the significant potential for additional landfill gas utilisation being identified by Sustainable Energy Authority Ireland in 2010. Furthermore, the technology’s low-cost and autonomous nature would benefit the hundreds of historical and legacy landfills if any were deemed to be problematic in terms of their environmental impact. Beyond landfills, this work pertains to other applications within the waste sector, as demonstrated by measuring emissions from wastewater treatment plant lagoons. With some further development, this technology could apply to efforts in dealing with climate change (e.g. in evaluating GHG inventories), where applications include managed peatlands (one case study is presented in this report and future efforts could also be targeted at carbon sinks/storage) and agriculture (Ireland’s greatest contributor to GHGs). Further scope could also be pursued in air-quality monitoring, particularly relevant at present with 2013 being dubbed the ‘Year of Air’ by European leaders. Throughout this project, the commercial prospect of this technology was affirmed with positive feedback from landfill operators, environmental regulators and private consultancies. Continual technical developments and refinements in mechanical/electronic design delivered a platform with expanded functionality and reduced price-point, thus becoming more viable for scaled-up deployments and commercial feasibility. Ultimately, this innovative development shows good promise as a high-potential commercial venture, with this work continuing under Enterprise Ireland’s Commercialisation Fund

The development of low-cost, robust, reproducible optical chemical sensors using inkjet printing

The optical sensor industry is forseen to be- come a $4 billion market worldwide within 10 years. This projected figure suggests the incorporation of wireless sensor networks into our daily lives. In order to achieve this, many hardware requirements have already been met, with many of the world’s top university in- volved in wireless "mote" development. The objective of this study is to prove that inkjet printed sensors will be compatible with these motes in terms of both accuracy and more im- portantly reproducibility

Remote monitoring of landfill gases from solid waste landfill

Landfill gas is primarily made up from Methane (CH4) and Carbon Dioxide (CO2). Global methane emissions from landfill are estimated to be between 30 and 70 million tonnes each year. Methane makes landfill gas explosive when it is present in the 5-15% concentration range. Landfill directives state that licensed landfills in the UK and Ireland should never exceed a concentration of 1% for CH4 and 1.5% for CO2, at perimeter borehole wells[1]. However, the EPA has cited large noncompliance with suggested targets [2]. This is partly due to the single point nature of the CH4 and CO2 sampling, and also the low sampling frequency. This research group has developed a dual autonomous CH4 and CO2 sensor, and has successfully run extensive field trials over the last 2 years. Currently using the system, three live data streams are being populated logging methane and carbon dioxide values in real-time on three different landfill sites

Ultra low cost LED based gas sensing

Over the last number of years a movement has taken place where conventional point-to-point grab sampling style sensors have slowly been phased out in favor of in situ autonomous sensors. Autonomous sensors provide a better insight into the monitored parameter delivering more data points in a less manual fashion. Over the next ten years, it’s predicted that gas sensors will become smaller, consume less power and exhibit much improved performance, and be of substantially reduced cost [1]. Optical sensors certainly are in pole position in terms of development having already met many of the criteria. The authors present a low cost (< €1) sensing platform. Two L.E.D’s are setup as a light sensor (emitter,detector), where the light passing from the emitter to detector L.E.D is modulated by a chemically selective colorimetric film, providing an indirect chemical measurement (this sensing setup is visible in Figure 1). Our presented experimental setup has exhibited a limit of detection in the p.p.b region (0.001145 mg/L or 12 ppb) [2], as well as demonstrating a 95% recovery within 30 seconds of contaminant exposure [2] (example exposures visible in Figure 2). This work has been done utilizing a bromophenol blue based dye, which was inkjet printed to created reproducible optical pH sensitive slides. However, the target of the device can be tuned by varying the colorimetric coating composition

Landfill Gas Monitoring Network Development of Wireless Sensor Network Platforms

Abstract: A wireless sensor network has been developed for the application of landfill gas monitoring, specifically sensing methane, carbon dioxide and extraction pressure. This collaborative work with the Irish Environmental Protection Agency has been motivated by the need to reduce greenhouse gas emissions as well as aiming to improve landfill gas management and utilisation. This paper describes the preliminary findings of an ongoing trial deployment of multiple sensing platforms on an active landfill facility; data has been acquired for nine months to date. The platforms have operated successfully despite adverse on-site conditions, with validity demonstrated by reasonably strong correlation with independent on-site measurements. The increased temporal and spatial resolution provided by distributed sensor platforms is discussed with regard to improving landfill gas management practice