The global market for environmental sensing and monitoring technologies is expected to increase to $13 billion in 2014, with a compound annual growth rate (CAGR) of 5.2 percent, up from $9.1 billion in 2008 and an estimated $10.1 billion in 2009, according to a report published in June 2009 by BCC Research.Titled Environmental Sensing and Monitoring Technologies: Global Markets (IAS030A), the report discusses application areas for the largest share of the market: radon, GPS, remote sensing and new technologies. Worth $4.9 billion in 2008, this segment is estimated to grow to $5.1 billion in 2009 and to $6.8 billion in 2014, for a CAGR of 6.2 percent.Use of environmental sensors in places like this water-treatment facility is growing.The terrestrial sensing and monitoring application segment, representing the second largest share, was worth $2.6 billion in 2008 and is expected to grow to $2.7 billion in 2009 and to $3.4 billion in 2014, for a CAGR of 4.7 percent. The third largest segment, atmospheric sensing and monitoring, was worth $800 million in 2008 and is projected to increase to $1.5 billion in 2009 and to $1.8 billion in 2014, for a CAGR of 3.1 percent. Real-time warningBased on the rate of growth in revenues, the fastest-growing emerging areas include the application of photonics-based sensors for water processing and wastewater treatment as well as for photonic devices employed in biosensing, according to analyst Kevin Gainer, author of the report. For example, he said, in water processing, treatment and monitoring, many initiatives are being pursued to detect and classify pathogenic micro-organisms in liquids using multiangle light scattering and other photonics techniques.These methods also can detect and classify biological agents such as bacteria and bacterial spores as well as those including chemical, biotoxin and radiation agents, he said. Real-time warning in water treatment is a key operative trend in terms of uses of photonics-based applications, Gainer said. The application of in situ photonics sensor-based technologies can greatly reduce the time lag seen in standard laboratory analyses, which can take up to 72 hours per test. The remote sensing category encompasses many photonics-based techniques, while the “new technologies” category includes additional important photonics advances such as silicon photonic integrated circuits, he said. He noted that significant investment has been made in developing optical methods for the remote or stand-off detection of trace chemicals, environmental pollutants, chemical and biological agents – even high explosives. These techniques involve advanced laser remote sensing based on Raman scattering or laser-induced fluorescence from a target sample.Among the specific photonics techniques, fluorescence-based ones offer some of the most powerful molecular detection methods available, Gainer said. For optical fluorescence-based sensors, there are classes of nanoparticles that exhibit extremely enhanced photostability in fluorescence emission, enabling new types of sensors to be devised with extremely long operational lifetimes, he noted. He emphasized that other important photonics techniques are suitable for many applications, depending upon the contaminant being detected, the medium it is in, the distance from the sample and other variables.Nanotechnology is a principal driving force in the development of every type of sensor, including the class that one would consider photonics-based, Gainer said. A significant amount of research money is being spent on nanotech-based sensing techniques, he noted, as reported in the chapter discussing recent nanotechnology R&D initiatives funded by the Environmental Protection Agency in Washington. The drive to adopt nanobased methods stems from the fact that, assuming that all else is held constant, the detection limit of a sensor scale approximates the cube of its characteristic length. Real-time detection is a common feature of nanosensing technology and, relative to that, the nanosensors being developed by industry operate in the seconds-to-minutes range, he said.Sensing air pollutionPhotonics-based technologies will be key going forward in the area of air-sensing technologies and the networking of multiple units to measure air pollution at the street level, Gainer said. As an example of networked sensing already in place, he cited the UK-sponsored “Mobile Environmental Sensing System Across a Grid Environment.” He also noted that researchers from Siemens Corporate Technology in Munich, Germany, have developed a laser-supported technique for measuring carbon monoxide concentrations, adding that the method is much more reliable than conventional sensors.“Technological dynamism” was the term used by Gainer to describe developing technology, which ultimately drives what the sensors can do. Detection limits are falling, and sensitivity and specificity of the devices are improving, he said.The need to acquire reliable scientific data is another driving force in the environmental sensors business, he said. Scientists now require more sophisticated monitoring programs to detect ecological changes that are occurring as a result of climate change. Related to this is the need for monitoring programs that yield data meeting specific scientific standards and quality control procedures. The development of more large-scale monitoring systems such as remote sensing and satellite-based large-area sensors represents another trend in the sensors business, Gainer said. Mobile environmental systems are being increasingly tested and proposed for urban areas, he noted, adding that such systems can identify and monitor urban air pollution events. Correlations can be made between resulting data and levels of local transport or industrial activity. These “rapid sensor grids” can enable real-time decisions, so as to reduce the impact of poor air quality on people and the environment, he said.Finally, government spending is propelling the business, Gainer reported. He said government sensor research activity worldwide is significant and was enhanced recently in the US by the 2009 Economic Recovery Act, which provides millions of dollars to government agencies and laboratories for research on environmental monitors and sensors.Technologies and applicationsAmong photonics-related sensor technologies, laser-induced incandescence is useful for monitoring vehicular emissions and, for remote sensing of vehicle emissions, UV and IR techniques are commonly used, Gainer said. For monitoring the combustion of fossil fuels, one such technology, a multiparameter fiber optic sensing system, uses an aperiodic sapphire fiber grating as the sensing element.In the field of agricultural runoff monitoring, optical sensors for use with a visible-light laser excitation beam and a Raman spectroscopy detector can be used to detect chemical groups in an analyte. For industrial and mine waste disposal, an example is the use of optical fiber-mounted porous silicon photonic crystals for remote sensing of environmental toxins and volatile organic compounds. For ocean spills and dumping, IR/UV, microwave radiometers and imaging laser fluorosensors are all workable techniques, Gainer said.For monitoring climate change, optical spectroscopic methods that can measure trace amounts of a particular atom or molecule, such as oxygen, carbon dioxide or water vapor, are of relevance, he said. In other applications, changes in stress or pressure, such as in water pressure in upstream flash-flood monitors, can be detected by measuring the optical transmission through fiber Bragg gratings.