From eyes in space to hands on the ground: Using remote sensing to mitigate methane emissions from Africa’s waste sector
Solid waste management is a major source of greenhouse gases, accounting for roughly 11% of worldwide anthropogenic methane emissions. Waste methane is created when organic material we throw away – from food scraps to trimmed trees – ends up in dumps and landfills around the world and is left to decay, buried deep under piles of waste. In such oxygen-free conditions, organic waste is consumed by bacteria that convert the carbon found in them into methane. Methane is a powerful greenhouse gas, more than 80 times more potent than carbon dioxide over a 20-year period. The rapid increase of methane concentration in the atmosphere is responsible for about half a degree Celsius of global warming so far. But there is hope: since methane stays in the atmosphere only for a few years, if we stop methane emissions now, the benefits will be tangible in just a few years. Reducing methane pollution is an essential, first-line tool to slow global warming and avoid near-term impacts.
As one of the world’s fastest-growing regions, Africa’s waste generation is expected to triple by 2050. This increase will be mainly driven by the rapid increase of the continent’s population and the improvement of economic standards, often associated with increased consumption and an increased volume of waste. Poor waste management practices in the region are also the source of other detrimental impacts on human health, including bad air quality and groundwater pollution. This makes solving the waste management challenge crucial. The waste management systems in the region are as diverse as the continent itself, encompassing a diverse range of production, collection, and disposal practices, defying simple blanket solutions. Instead, any approach should be guided by a holistic understanding of the waste management challenge and recognize the local nature of any effective solution.
Methane measurements have a crucial role to play in both raising awareness and driving data-informed decisions. As methane is an invisible and odorless gas, measurements can help focus stakeholders’ attention on the methane issue and make it a key consideration in all waste management decisions. In addition, methane emission measurements can help stakeholders understand emissions from various facilities in their waste management infrastructure and, in this way, help them improve operational practices and design appropriate, effective mitigation measures. Finally, measurements can help monitor the progress of implementing these mitigation efforts, guide the improvement of their efficiency, and help understand best practices that can inform mitigation efforts in other jurisdictions.
Fortunately, the number of technologies to monitor and quantify methane emissions is increasing rapidly. Driven by the rise of key enabling technologies — such as miniaturized electronics, artificial intelligence (AI), and low-cost access to space — methane monitoring using sensors mounted on cars, planes, drones, and even satellites is becoming increasingly accessible, as outlined in our recent blog post.
Spaceborne methane sensing instruments, in particular, have a unique role to play as they have the potential to transform the measurement landscape. Thanks to their global reach and centralized processing, satellites can provide data in areas with limited access to instrumentation. Thanks to their ability to provide comparable data in many parts of the world, they highlight areas that require attention, can support the first attempts to integrate methane measurement data in the decision process, and kindle the local development of expertise, processes, and understanding.
Satellites reveal widespread emissions from waste facilities across Africa
With this in mind, CATF analyzed several waste management sites in Africa, to highlight the magnitude of the continent’s methane emission challenge. These measurements also aimed to help us understand the capabilities of state-of-the-art satellite methane sensors to monitor these emissions and explore the ways that satellite data can support methane mitigation efforts on the ground. To do that, we commissioned GHGSat, a leading commercial provider of spaceborne methane measurements, to monitor methane emissions in 13 sites in West, Central, and Eastern Africa, including both active and decommissioned dump sites and landfills.1 The measurement campaign operated from February to October 2023; most sites were targeted twice.
Our initial observations reveal how widespread the waste methane challenge is. Satellites detected emissions from 7 of the 13 large dumpsites monitored, with average emission rates ranging from 400kg/h to 2700kg/h. Interestingly, while most of the monitored sites are open dumps, the largest emissions were detected over a modern sanitary landfill near Abidjan in Cote d’Ivoire that started receiving waste less than five years ago. While further observations are needed to understand this dynamic, it suggests that methane management should become a major consideration in all efforts to manage waste across the continent.
| Pays | Nearby City | Average Emissions2 (kg/h) |
|---|---|---|
| Cote d’ Ivoire | Abidjan | 2700 |
| Angola | Luanda | 2400 |
| Kenya | Nairobi | 1900 |
| Ethiopia | Addis Ababa | 1100 |
| Cameroon | Duala | 900 |
| Mozambique | Maputo | 500 |
| Tanzania | Dar-es-Salaam | 400 |
The sites where satellites failed to detect emissions are equally interesting. In total, our satellites did not observe emissions in 6 sites. We know from previous studies that all waste sites emit some methane, and that the absence of satellite detection does not necessarily mean there are no emissions. To further support this fact, we visited two of these sites in Ghana – in Accra and Kumasi – to check for methane emissions. To do this, we used our gas analyzer, a highly sensitive portable methane-measuring instrument that uses a diode laser to detect tiny variation in methane concentration in the ambient air. As expected, the analyzer detected elevated methane concentrations on and around the sites, confirming our assumption that these sites are emitting methane even if undetected from space. The reasons why satellites did not detect emissions could vary:
- Emissions from landfills might be diffuse, coming from the entire site surface, while satellites are better at detecting concentrated sources;
- Strong winds in the region could quickly dilute the emitted methane, again making it hard for the satellite to detect; or
- The weather in the region (atmospheric temperature, pressure, recent rain, etc.) could reduce emissions at the moment of satellite observations.
Whatever the reason, it is clear that, in the long run, satellites cannot be the only sources of methane measurements for the waste sector. Instead, a multi-tiered observing system — including instruments on the ground, air, and space — is needed to guide effective mitigation efforts.
Advanced methane monitoring technologies propel global emission mitigation efforts
CATF is leveraging the initial batch of data collected by GHGSat to identify practical ways that methane measurements can accelerate and support mitigation action. In this direction, we are engaging with key regional partners, including policymakers, monitoring agencies, and scientists, to pinpoint specific scenarios where this data can catalyze impactful mitigation efforts. For example, we are working with local researchers in Mozambique to quantify the climate and health co-benefits that can be gained by implementing better waste management strategies in Maputo. We employ a ground-based gas analyzer as an educational tool during field visits with policymakers and waste management practitioners. These sessions are designed to give these stakeholders a firsthand understanding of methane emissions, fostering a deeper understanding and sparking crucial conversations about necessary actions. Through these integrated approaches, we aim to bridge the gap between data collection and actionable mitigation, ensuring that increased data availability will lead to accelerated methane mitigation.
The rise of new monitoring technologies is the outcome of years of public and private funded investment, the tireless work of countless scientists, and the drive of committed teams and funders. Due to these efforts, we are at the brink of a data revolution, where data for methane emissions will be global and readily available to raise awareness and help governments implement and monitor effective mitigation measures. What lies ahead is an uphill path to bring the data to the hands of those who have the opportunity to act and, thus, enabling them to design and implement effective mitigation pathways.
1 The selection of sites was informed by the advice of Braam Maasakkers and Ilse Aben, senior scientists with Netherlands Institute for Space Research (SRON).
2 The reported emissions are the average over all available measurements (ranging from 1 to 3). Observations with no detections have been considered to represent zero emissions, which is an underestimation; therefore, the reported numbers could have a negative bias. The results have been rounded.
