Environmental Sensors in Waste Management

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Courtesy of CEST

Issue: As part of an increasing sentiment among European consumers that environmental protection is important, concern about the impact of landfill is growing. Sensor technology makes it possible to measure and control inputs to landfill sites and pollutants arising from them. However, the exploitation - or uptake - of such technology has been lower than expected in the waste management sector.
Relevance: Coordinated European science and technology policies can help improve exploitation of sensor technology, and lead to future development of more innovative waste management processes. Setting unambiguous targets for the release of pollutants from landfill sites, in both leachate and landfill gas, may aid uptake.

Market Pull - European Waste Management

Much of the cost of traditional (i.e. landfill and sewage plant) treatment methods comes from minimizing the nuisance for those living in the vicinity, i.e. odours, traffic, etc. This translates into higher costs for operators seeking planning permission. Improving detection of inputs and outputs of landfill sites can help landfill operators reduce this nuisance, and thus the 'not in my back yard' (NIMBY) resistance to such facilities. In addition, new waste management techniques such as composting and recycling will rely heavily on sensors to monitor and optimize processes. However, sensor research is being hampered by the lack of cooperation and cross-fertilization between researchers in the biological and medical sciences and those in micro electromechanical engineering and environmental sciences.

Initiatives in integrated waste management in the Netherlands and material reclamation in Austria, Sweden and elsewhere use sensors to develop innovative waste management practices. Worldwide, alternative waste treatment approaches such as bioremediation (the process by which living organisms are used to degrade hazardous organic contaminants or transform hazardous inorganic contaminants to environmentally safe levels in soils, subsurface materials, water, sludges, and residues) and other techniques such as 'living machines' are being developed, particularly in the US. However, until systems are developed in bulk, to develop sufficient economies of scale in large markets, there is no incentive to develop new waste management techniques. Therefore, there is a role to stimulate and coordinate harmonized research and development in waste management.

Generally, with a few exceptions, waste management in Europe tends not to be a highly technologically sophisticated industry. While companies use geologists and geophysicists in planning their sites, they are often fairly lacking in innovative development of technology to address operational barriers or generate new business. This is due, in part, to the culture of their major customer base, which tends to comprise mainly local authorities. These see waste treatment as part of a social service rather than an opportunity area for developing new technology-based business. These customers tend not to be very demanding, so there is little perceived competitive advantage in developing and implementing innovative technology.

Lately, the waste management industry has been focusing specifically on developing close customer relationships. There are a wide range of techniques and technologies in practice across the European Union. Some countries such as the UK and Germany rely heavily on landfill as the preferred technique for a combination of historical and geographical reasons. Other states focus on a combination of landfill, recycling and incineration. Bioremediation is another innovative approach, but is still a relatively immature technology. In terms of developing the European policy on innovative waste management, it is important to consider improving landfill management as part of an integrated waste management programme. This would focus on more than just concerns over charging levels and topsoil, looking rather at the inward gradient - so as to contain rather than disperse leachate - long-term leachate collection and treatment systems (pumping to tailings or sewers), contaminated land applications, and touch on the continuing debate over co-disposal, in light of draft EU directives on reducing biodegradable arisings in landfill sites.

Impacts of present and proposed levies, such as the landfill tax, proposed raw materials tax and packaging recovery legislation, on landfill operations may also be considered. Experiences from the construction industry, in recycling some waste and disposal of other waste as 'landscaping' material, can be evaluated, and the use of sensors in developing integrated and diverse waste management practices that include waste minimization, recycling, landfilling, composting and incineration assessed. The use of sensors for waste stream segregation may also be profitably assessed, including using aromatic compounds and electronic nose-based id systems, vision systems and magnetic segregation technologies. The role of sensors in reducing the environmental impact of transporting recycled/recyclable goods may also be considered.

The main concerns of waste management policy makers include cost-effectiveness technological feasibility of solutions. There are also vocal local groups who may have certain perspectives on which waste management techniques are used in certain areas. However, coordination of research initiatives and a sharing of best practice can help create markets of critical mass that let affordable, innovative waste management techniques come about. The creation of sensor-based solutions and common standards across the EU means that generally accepted methods can be developed with knowledge that there will be few standards-based barriers to development of large markets.

To develop and stimulate innovation in this area, another key role that policy makers could play is to help disseminate innovative, technology-based waste management policies and make the use of more sophisticated sensing technologies a self-reinforcing cycle. As more comes to be known about conditions associated with waste management, the public will take a greater interest. In turn, this will lead to more public will to fund and develop innovations in sensors for waste management use. Increasing levels of sensitivity allows society to know more, but also whets the appetite for more information.

This cycle can be reflected in the development of legislation for waste management. As sensors become more sensitive and selective, legislation to limit levels of toxic analyte becomes enforceable. This legislation can be used, in turn, to stimulate operators to invest in applying new sensor technology. The main emissions from landfill sites are methane, from biodegradable fill such as paper and kitchen waste, and toxins from slowly degrading plastics and other chemical compounds in appliances, as well as detergents, oils and heavy metals. The first of these, methane, has been addressed by upcoming EU limits on methane emissions from biodegradables, to conform to the non-fossil fuel obligations (NFFO) agreed in Kyoto.

The time is right for similar action regarding other analytes. These will require consensus over levels and types of compounds that can be measured, as well as on what constitute dangerous levels to both health and the ecosystem. Emissions caps and tradable permits, as in the case of global pollution issues such as greenhouse gas emissions, may not be appropriate for local emissions issues, such as toxic compounds from landfill sites. While there is an imperative to reduce overall emissions of dangerous analytes, point site pollution, such as that from landfill sites, most directly effects those living in the vicinity of the facility. While NIMBY can quickly become BANANA (build absolutely nothing anywhere near anything), a coherent policy would recognize the need for waste management facilities, but encourage sensor development to monitor, control and reduce the risk associated with their operation.

Price cap models, in which regulations on target levels of pollutant and analytes are fixed once, and firms are rewarded or penalized in proportion to how far above or below them they are, should be explored.

Technology Push - Innovative Sensors

There is need to stimulate and co-ordinate policy in both sensor research and landfill and waste management. Sensor research policy should assess the effect of innovations and technical solutions such as the uptake of microbial biodegradation of toxic xenobiotic chemical compounds, the remote tracking of airborne compounds such as organophosphates using electronic noses, enzyme-linked immunoassay (ELISA) kits, or enzyme-based biosensors and identifying compounds using 'lab on a chip' or 'DNA chips.' Application areas in landfill management, recycling, composting and contaminated land remediation are plentiful. In addition, further development requires more detailed knowledge of chemical interactions such as bonding. Here, there is much scope for the involvement of researchers in chemical and biotechnical engineering in the development process of novel sensors. The most promising research directions in this involve novel chemical sensor technology based on detecting the changes in a polymer, or series of polymers, due to the impinging of an analyte molecule. By detecting the degree of swelling of an array of several polymers, the type of analyte can be deduced.

A range of technologies has already been developed and more is under development. However, landfill sensors currently require a trade-off between selectivity, sensitivity, scope and price. Current systems are available which detect total organic content (TOC) levels in industrial effluent, which correlates directly with the biological oxygen demand (BOD). These can be easily adapted for use with landfill leachate. As legislation governing landfill and waste management becomes more stringent, simple monitoring of carbon for organic load on the environment, or simply presence of leachate within and below landfill sites, becomes less important. What is required, at low cost and in robust packages, are systems which detect certain specific hazardous analytes. Detection not only of the presence of gas or leachate, but also of the types of chemical compounds contained, as well as their concentrations, are required for effective landfill management.

To obtain the range of selectivity, sensitivity, detection of concentration, robustness and price applications of this type require, so-called sensor fusion may be the answer. This takes the outputs of a range of different sensors, and, via clever data processing, builds a picture of the types and concentrations of the analytes present. A major cost driver for many landfill operators is the employment of personnel to monitor conditions using the sensors developed. However, this can be replaced by developing smart arrays of sensors which monitor remotely, and then download data, either via land lines or mobile communications, to a monitoring base station. The bandwidth requirements of such a system can be minimized by signalling to the operator only when concentration levels fall outside pre-defined parameters.

The Specification Process for Sensors

A lack of harmonization of the specifications for sensors, typified by different companies in the same sector having different specifications for the same sensor, has hindered uptake and lead to a fragmented market. Thus small volumes of product tend to be produced, the unit price is high, new product development is beyond the means of most producers, compatibility with national and international standards is doubtful and the chances of building an export market are low. Generally, markets are built on standards, thus the technology moves faster than the standards, fragmentation occurs and technology is unavailable at reasonable prices. By pooling requirements, the resulting economies of scale mean companies can ensure that the technology that can meet their requirements will be developed affordably. Engaging users and vendors in the development process is also an important factor in ensuring real needs are met.

Standards lag behind sensor technology and are often hijacked by strong companies seeking to protect vested interests, leading to failure to achieve the best possible price/performance ratio, and delay in the purchasing decision until the standards have caught up. Standards often represent the evolution of public concern and interest over issues. As standards evolve, more detailed information can be obtained and public interest often increases.

Conclusions - Improving the Technology Exploitation

Several policy-level changes can improve the uptake of sensor technology in the waste management industry by aligning the technology-push with market-pull. An increased level of communication between developers of waste management policy and the science base in sensors, including both biological and electro-mechanical researchers, would result in both areas becoming more competitive and effective. The aim would be to ensure that the development of waste management policy is founded on sound science and a realistic appraisal of the technologies that will be available tomorrow for sensing and detection in waste management. In addition, an understanding of the emerging market opportunities in waste management can ensure that the research into the science of sensing can be drawn towards application areas that will represent the significant market opportunities of tomorrow.

Increased collaboration between the organizations responsible for collecting and disposing of waste - currently local authorities, or public/private combinations known as local authority waste disposal companies (LAWDCs)- across Europe could help to stimulate the development of innovative waste management practices, as well as offer the opportunity to benchmark best practice. The International Council for Local Environmental Initiatives (ICLEI) is one such organization attempting to build global networks on the local level. Significant lessons can be learned from Japanese efforts in this area, such as experiments in composting sludge from wastewater treatment plants prior to landfilling. Networks linking local authorities directly already exist. Some of these could be used to catalyse such collaboration.

One of the main factors in facilitating development of robust markets for environmental sensing and monitoring technology for landfill sites will be a clear consensus on toxicology of species and compounds that may emerge from such sites. There are clear threats in terms of local communities and, possibly, surface and groundwater contamination. There are also clear threats to traditional sewage treatment works if they become overloaded with industrial-strength pollutants, after, for example, heavy rainfall over landfill sites, that can cause sewage plant failure. Here, there is clear opportunity for the uptake of remote sensing and data logging and downloading devices in order to signal such threats to sewage treatment plants. However, until there is clear understanding of toxicology and associated risks --at local, regional and global levels-- of compounds arising from landfill sites, the case for taking up and developing sensors, in order to offset the costs of environmental hazard insurance premiums, will remain difficult to make.

A successful collaborative project could help users, vendors and legislators understand each others’ needs, position and constraints. It would form a shared view of the priorities for application of sensor technology, of how price/performance trade-offs work in specifying each solution and of who needs to be involved to achieve this. It would also catalyse relevant government and legislative groups, as well as industry, to align existing standards and legislation, in order to work towards a realistic view of how legislation would need to change in order to accommodate new thinking on toxicology and risk associated with arisings from landfill sites, both in operation and post-closure. A winning list of promising technologies to detect the target compounds identified during this process can lead to debate around price/performance trade-offs. This will then influence decision makers responsible for determining the type of analyte that needs to be monitored at landfill sites and the concentration levels deemed to be acceptable.

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