New beginnings in solvent emissions
Simon Skentelbery and Eric Hartmann of OEH Group look at the development of a Solvent Management Plan (SMP) for operators of major industrial processes.
Operators of major processes and installations are coming under increasing pressure to abate process waste emissions (principally to air and water) using Best Available Technology (BAT). The question is, has the pendulum swung too far when such installations are pushed into commissioning expensive and, often, environmentally counter-productive end-of pipe technology simply because of ignorance of their situation and of the law?
Good examples can be found in sectors employing Volatile Organic Compounds (VOCs) such as solvents, as diluents for paints used in vehicle spraying, paint and ink manufacture, ink / varnish / adhesive coating / paint spraying. Traditionally, these sectors have had to comply with meeting the emission limits set under the Environmental Protection Act (EPA 1990) where discharge of VOCs had to be below 50 or 150mg/Nm3 or 20mg/Nm3 for chlorinated VOCs; depending on the tonnage of solvents used. The majority of such installations emit VOC concentrations of anywhere between 10 and 10,000mg/Nm3 from anywhere between 2-10 emission points, on average.
For most of these installations, the answer has been to look at emissions to air in isolation and try to meet compliance limits by commissioning thermal oxidisers or solvent recovery units.
Hidden or ‘indirect costs’ of these waste management methods include poor design or over specified performance capabilities, increased environmental noise, odour, unexpected operating failures (catalyst poisoning, etc). Many of the costs can be avoided if the site management works closely with the designers of the abatement plant and if the following questions are answered and the basic principles of design are followed:
- how does the process behave?
- what VOC species are used in the main processes and in the non-continuous processes?
- what unusual occurrences take place in the process?
- how many (solvent) material streams are there and how do they behave?
- are the production outputs likely to increase / decrease / change in the next one, two or five years?
- what are the prime sensitive receptors surrounding the site?
The legal situation as it currently stands is that solvent installations previously covered by the EPA 1990 need to comply with the Solvent Emissions Directive (SED). The directive was adopted by the EC on 11 March 1999 with the aim of reducing emissions of VOCs from industrial processes and is being implemented through EPA 1990 and the Integrated Pollution Prevention and Control (IPPC] Directive.
Compliance with the SED is complex and is tailored to fit different processes and whether these fall under the category of existing, existing but being varied, or simply new. With the exception of new processes where compliance has to be met before the start of the plant, the deadline for complying with SED for existing processes is no later than 31 October 2003.
SED offers existing installations two routes for compliance:
- meeting emissions limits that are similar to those specified under the EPA,
- meeting a total emission value.
Solvent Management Plan
With ink and coatings manufacture, for example, if the installation can demonstrate with confidence that the total VOC emissions consistently and regularly fall below three to five per cent of the total solvent used in the process, compliance is met. No abatement may be deemed necessary and the operator has the option to pursue other options for minimising solvent use and process related emissions. In addition, implementing a Solvent Management Plan (SMP) provides the requisite background data to demonstrate compliance.
It is OEH’s experience that several sectors, which may have hitherto believed that compliance may only be achieved by the application of an end-of-pipe solution in conjunction with stack emissions monitoring, can meet the required criteria set out in the SED by using a SMP.
Developing a SMP involves a mass balance to be calculated across the installation, where flows of material inputs are followed out of the process as product or waste streams. Carrying out a SMP is a methodical approach that clearly determines the input and output of materials to and from processes. This leads to simple and cost-effective compliance and more proactive waste management control and negates the need for emissions monitoring to be carried out, as long as conditions on the installation remain the same.
The use of SMPs also allows installation operators to gain good data on a macro scale that can be used for environmental benchmarking, development of Environmental Management Systems and Life Cycle Assessments.
So what approach should the operator take? These are the key steps:
- based on available data, decide whether there is an emissions problem to be addressed,
- approach the Local Authority (LA) to establish that in principle they would be amenable to the approach,
- draw a detailed input/output solvent (VOC) map of the process showing all the streams even if they do not form part of the main process,
- determine what are the point source (stack) and fugitive streams under all typical production patterns,
- calculate main discharges of VOC from all streams,
- compare total discharge versus total solvent inputs. Does this figure meet the minimum requirement of the SED?
- if yes, present the case to the LA and agree compliance parameters,
- if not, use data obtained for process alterations, materials (solvent) recovery or as a last resort, use of abatement plant,
- evaluate the proposals on a cost-benefit basis,
- select the most appropriate method of reducing emissions.
The process of correctly developing a SMP can be a complex issue. Obtaining the services of a consultant or setting staff time aside to carry out a SMP may cost the operator up to £20,000. However, this is a small expense if the operator was considering installing abatement at a cost of £500,000 without any consideration of what benefits carrying out a SMP might provide.
As a worst-case, should the SMP determine that some form of end-of-pipe abatement is required to help meet compliance, good data will be available to ensure the correct technology is chosen and that costly mistakes are avoided.
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