Keeping control of emissions

Air emissions control has long been a priority for processing industries, notably the pharmaceutical sector, which uses a wide range of organic solvents in the manufacture of its products.

Volatile organic compounds (VOCs) or solvents are commonly used in a range of pharmaceutical manufacturing processes, including chemical synthesis, fermentation, extraction, formulation and finishing of products. Emissions can typically occur in a number of process areas – from reactor vents, storage tanks and vacuum pumps – and the VOCs most regularly used include hexane, methyl chloride, dichloromethane, methanol, ethyl acetate, acetone, toluene, xylene, triethylamine, tetrahydrofurane, butyl acetate and isopropanol.

European targets Tightening environmental legislation in Europe continues to drive standards in emissions control and the latest figures published by the UK Department of the Environment, Food and Rural Affairs (DEFRA) show that emissions of non-methane VOCs fell by 52% between 1990 and 2002 to 1.186 million tonnes – just within the target set by the EU National Emission Ceilings Directive. One of the main reasons for the recent success in reducing solvent emissions is developments in emissions control technology and in particular in cryogenic condensation systems, which have evolved significantly since their introduction in the late 1980s. These systems started life as large-scale units that were suited only to a relatively small number of major installations with processes operating at high gas flow rates. Since then, cryogenic condensation systems have evolved to become highly efficient, continuous single unit systems, which are flexible enough to operate at smaller plants, with processes using low gas flow rates. The simplicity of these new single-unit systems means that, with minimal training, they can be easily adapted by onsite operatives to meet variables such as flow rates, temperature variations, solvent types and loading concentrations. This is particularly advantageous in pharma manufacturing, where swift alterations are often necessary to get new drugs into production as quickly as possible. These new generation cryogenic condensation systems are also capable of enhancing a plant's overall sustainability by recovering the solvents in a pure form, so that they can be reused. These developments mean that cryogenic condensation systems are now suited to a much broader range of processing applications than before. They can bring efficiency benefits too, which can compare favourably to some of the more traditional abatement solutions. For example, carbon bed technology is a traditional means of abatement that uses a process of adsorption onto activated carbon to manage the recovery of solvents used as part of gas processes. However, these systems produce VOC contaminated waste that requires disposal at designated landfill sites. Recent Landfill Tax hikes in the UK have encouraged plant managers in the pharmaceutical and chemical industries to review their use of carbon bed abatement systems and many are considering onsite systems. In addition, the Landfill Directive has banned the mixing of hazardous and general waste. As a consequence, the number of sites licensed for the disposal of hazardous waste is expected to fall sharply, forcing landfill costs still higher. The latest guidance for solvent-using industries, as set out by Envirowise, reminds managers that they should consider various factors when selecting an appropriate emissions control solution. For example, they should consider the nature of the air stream, the properties of the solvent concerned and the specific application. In particular, the advice states that condensation methods of solvent recovery using coolants and refrigerants are highly suitable for organic solvents with reasonably high boiling points. Cryogenic condensation systems using liquid nitrogen are ideal for solvents with lower boiling points, particularly where liquid nitrogen is used elsewhere on site.

Efficient solution While the new generation cryogenic condensation systems are already providing an increasingly cost-effective and efficient solution, pharmaceutical manufacturers are also looking for long term solutions that will enable them to stay one step ahead of environmental legislation. The EC Solvents Directive (1999/12/EC), adopted by the UK in 2002, has set a goal for the reduction of solvent emissions in Europe by 67% by 2007. While most new installations are affected immediately, all installations will be required to fully comply by 31 October, 2007. Adding to this legislative pressure, the ongoing roll-out of the Integrated Pollution Prevention and Control (IPPC) regulations in the UK is helping to establish best available technologies designed to help processing industries to reduce their impact on the environment. Furthermore, a new EU-wide pollution inventory, called the European Pollutant Emission Register, was published last year in response to the 1996 EU Directive on IPPC. The inventory allows industries to compare their environmental performance and identifies the UK as one of the main sources of VOC emissions, including benzene, hydrogen cyanide, dichloromethane and non-methane VOCs. This new inventory has significantly increased the transparency of VOC emissions and is likely to encourage many to keep their emissions control systems under review. Until now emissions limits have been set by industry and emissions control has been effectively self-regulated. But how long can this last? At the moment, self-regulated emissions limits are 20mg/m3 for Class 1 solvents – a benchmark set by TA Luft, the German Technical Directive for Air Pollution Abatement. In the near future, however, it is likely that emissions limits could be set even lower and some solvent-users are already working towards the goal of zero emissions.

Speed to market To meet these new standards of environmental efficiency, further enhancements in cryogenic condensation technology – and indeed other abatement technologies – will undoubtedly be necessary. These enhancements will also play an important role in helping the pharmaceutical manufacturers of today to remain competitive in the future, taking their new products to market as quickly as possible. It is vital that those involved in developing and applying new technologies work closely with industry as environmental management partners. In doing so, UK-based manufacturers will be able to profit from more efficient and sustainable solutions in the future.