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Emission control: NPL's emissions measurement team has to reconcile regulatory and technology demands, and it's not always going to be easy.

Out in the back car park at the National Physical Laboratory at Teddington in west London a couple of weeks ago was a big pantechnicon lorry full of scientific kit. The lorry isn't often there--it's usually out and about across the UK and bevond--and it's not exactly new, though a lot of the equipment inside is pretty much state of the art. But it is unique.

It's the uniqueness that Rod Robinson, principal research scientist in the environmental measurements group at NPL, stresses. No one else, so far, has put together a transportable lidar (the light-based equivalent of radar) system that can fire off a series of infrared beams to analyse the emissions of gases from stacks and whole factories into the atmosphere and then to pinpoint the amount of gas and where it's coming from. It can pick up concentrations of gases such as methane down to 10 to 50 parts per billion over a plume 50m wide, and can be used on landfill sites it's well as in industry.

It's a hugely useful mobile lab and much in demand. But there's only the one. NPL is building another, Robinson says, "and the market should grow. But a market with only one supplier isn't really going to grow as it should."

That kind of market uncertainty seems to be almost endemic in emissions measurement where the drivers of technology development and regulatory regimes don't always seem to proceed hand in hand in an entirely orderly direction. NPL, as the custodian of the nation's measurement systems, has an important role in developing, evaluating and disseminating new technology, in evoking standards and in regulatory compliance and that's a lot of masters to be serving.

Robinson's group is concerned largely with measurement of gases and particulates, and those can be in the form of emissions that are ducted away from industrial sites through stacks and flues and those that are more diffuse and could come from leaks or from "unstructured" operations such as landfill sites.

There's also a big role on the verification of instrumentation. "We got involved with the instrumentation and automation trade association Gambica to develop a certification scheme for instruments used in emission monitoring and that became the MCERTS scheme, was harmonised with the German equivalent and standardised across Europe," Robinson says.

So the group now runs test facilities for type approval, where emissions monitors are calibrated against the reference methods stipulated in European directives--with NPL also having significant input into the development of the reference methods. "Some of the work is looking at the performance of these methods and how to improve them," he says.

The legislative driver for all of this verification and certification work is the EU Industrial Emissions Directive which specifies the performance of instruments based on a percentage of the limit values for particular gases. There's a technology link-up in here as well through the best available technology (BAT) reference documents.

But, Robinson says, there can sometimes be a bit of a disconnect in this area, where regulatory demands push further ahead than the technology that implements or monitors it, or where new technologies emerge that do things slightly differently. There's a system of "equivalence" where if a new measurement technology' can demonstrate that it is equal to or better than the existing standard then it can be used "and this is to stop the standards being a block to innovation".

But Robinson can then cite a specific example where the system isn't quite in tune. Many of the requirements specify instruments that use chemical methods to detect and measure gases, but increasingly they are being challenged by technology that, like the kit in the pantechnicon, uses optical and spectroscopic methods. "So we've now got an issue where for hydrogen chloride the approved chemical method measures chlorides in total, but the optical spectre method measures HCI itself," he says. It'll get resolved, but it's a disconnect.

The big "political" area where these disconnects between regulation, measurement and technology come together is in the hot topic of greenhouse gases, and Robinson's group now feeds in to the Centre for Carbon Measurement that NPL has set up to address the measurement issues here. There's new work out on reconciling the divergence between regulations that specify the measurement of gas concentrations and the bigger picture needed to know the cumulative impact.

This is all an evolving area, and markets and directions take time to settle down. In the mean time, there are unique facilities and unique expertise providing answers. If only the questions could be a bit clearer.

Pluming marvellous: NPL's lorry-based lab can plot a gas plume on to a map
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Title Annotation:Test & Measurement
Author:Pullin, John
Publication:Environmental Engineering
Date:Dec 1, 2013
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