Dutch space instrument TROPOMI discovers mega-emission garbage dumps New Scientist

In the search for unprecedented methane emissions, the Dutch space instrument TROPOMI made a major discovery at four garbage dumps in Argentina, India and Pakistan. The emissions from these four places are comparable in terms of climate impact to those of more than two million cars.

The garbage dumps in four world cities appear to emit on average twice as much methane as expected based on previous calculations. This was discovered by the Dutch space instrument TROPOMI, which searches for methane leaks and other large forms of emissions. Methane is odorless, colorless, and as a long-term greenhouse gas nearly thirty times as potent as CO2.

The finds were made at landfills in Argentina’s Buenos Aires, Delhi and Mumbai in India and Lahore in Pakistan. The garbage dump in Buenos Aires emits 28 tons of methane per hour. In terms of climate impact, this is comparable to the emissions of one and a half million cars. The other three garbage dumps also add up to almost the same impact as that of a million cars. The researchers published this information in Science Advances.

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Successful years

The largely Dutch space instrument, the TROPOspheric Monitoring Instrument (TROPOMI), previously detected methane leaks in American oil fields and thus mapped unprecedented emissions. ‘But I’ve never experienced an instrument that works so efficiently and also has so little degradation (decrease or lost functionality, ed.)’, says project manager and system engineer Ruud Hoogeveenwho participated in the TROPOMI project on behalf of SRON, the Dutch institute for space research.

Tropomic
TROPOMI and the ESA satellite it is mounted on (Sentinel-5 Precursor). Image: Wikimedia / SkywalkerPL / CC BY 3.0

The ESA satellite on which TROPOMI is mounted consists of, among other things, the solar panels, batteries and communication equipment. The lower part contains the spectrometers of TROPOMI where the measurements are taken. The ‘snowplow’ at the bottom radiates heat away to the room. This allows TROPOMI’s methane detector to function at a temperature of approximately 144 Kelvin (about 130 degrees Celsius below zero).

TROPOMI orbits our planet, from North Pole to South Pole, at an altitude of 824 kilometers. He looks down at a strip of earth 2,600 kilometers wide. He divides this into so-called ground pixels of 7 by 5.5 kilometers. ‘This is the first instrument with which we can map the entire world every day with reasonable resolution’, says Bram Maasakkerslead author of the landfill study.

tracing technique

Using a telescope, TROPOMI collects light that it divides into four different wavelength ranges: UV, visible light, near infrared and infrared. He does not only use these techniques for methane. For example, it also measures ozone, nitrogen dioxide and sulfur dioxide, to demonstrate, among other things, human and natural emissions. For methane, the instrument uses the infrared and near infrared regions.

Each gas absorbs light of specific wavelengths. You can then measure the light that a gas has absorbed with a spectrometer. This unique color absorption allows you to determine which gas it is. The gas then actually has a unique ‘bar code’ or ‘fingerprint’.

As soon as the researchers conclude from this data that there are increased emissions from certain areas, they will send the Canadian satellite GHGSat on it. This also makes circles around the earth and can therefore map all places almost every day. GHGSat then zooms in on the area where TROPOMI made an observation, to be able to determine very accurately where the methane comes from. ‘You can’t look at the whole earth and then also work with a magnifying glass. So we have the Canadian satellite for that,’ says Hoogeveen.

Provide a solution

Now that these finds are on the table, the question is what will happen to them. According to Maasakkers, it is the ‘low hanging fruit’ in tackling methane emissions. The cities could do a number of things, he says: ‘First of all, you can reduce the production of organic waste, separate it or compost it.’ In this way, much less methane ends up in the atmosphere.

‘And if you do mix the waste, you can still collect it and flare it or even use it usefully for, for example, your central heating boiler or gas stove’, continues Maasakkers. These appliances burn natural gas, which mainly consists of methane. ‘Then it could even be used commercially,’ adds Hoogeveen.

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