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Aerial View of a Houses

City - Frequently asked questions

Which Greenhouse gasses (GHG) are you measuring?

We measure CO2 (carbon dioxide) emissions and CH4 (methane) emissions.

What type of GHG monitoring sensors do you use? 

Everimpact uses a sensor solution that combines CO2, temperature and humidity sensors. The CO2 sensors perform continuous monitoring (as opposed to threshold monitoring) using NDIR technology (Non Dispersive Infra Red) and have a high accuracy (+/- 3%). The sensor solution transmits the data using the LoRaWAN network. They are powered by batteries which last at least 5 years, so very little maintenance is required.

Do you measure Air quality?

We can add Air quality monitoring (AQM) sensors to our core Carbon emissions monitoring solution for cities but we do not provide Air quality monitoring only.

How accurate is the GHG data Everimpact measures?

Our CO2 sensors perform continuous monitoring in real time and have a high accuracy. For Satellite data, the horizontal resolution of measurements obtained from the OCO2 satellite is 2km2, that Everimpact further downscales to 20m using Copernicus Sentinel 2. The accuracy of CO2 concentration measurement provided by spectrometer embarked in OCO2 satellite in 0,8 ppm (atmospheric baseline concentration averages 400 ppm). This represents a step change vs the way City emissions are currently calculated, often in excel spreadsheets using assumptions.

Do you need both satellites and sensors to measure GHG emissions?

Yes. Ground sensors provide precise measurements every 15s (with accuracy of +/- 3 ppm). Satellite provide higher precision but at low spatial resolution (2 km2) and low revisit time (every 2 weeks). Combining the two data flows provides high spatial resolution and near real time frequency with high accuracy as satellite data allow to recalibrate ground sensor network data flow.

Once you start measuring a city’s GHG emissions, how long does it take to establish a baseline against which to assess emissions reductions or sequestration?

It  takes about a year of emissions monitoring to get a baseline against which to assess carbon emission reduction (or sequestration). 

How are GHG monitoring sensors installed in a city?

Sensors are attached on the city's poles at 3-4 meters high (ex: lamp posts, bridge pillars etc). Their installation takes less than 10 minutes each and the municipality usually has an installation team that Everimpact can train very easily.

How long does it take to install GHG monitoring sensors in a city?

With a typical city of approximately 200 km2 and 150k habitants, it takes about a week to install 70-80 sensors.

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