Furniture Sector: Reducing Emissions To Air

Last updated: (February 2005)

Introduction

A variety of air emissions are a cause for concern in the furniture manufacturing sector. Air emissions are controlled because of their contribution to a number of global and local environmental effects, such as global warming, acid rain, ozone depletion, photochemical smog and neighbourhood nuisance.

This Reference Note provides a summary of relevant legislation and best practice for air emissions.

Information

Background

Air emissions which are potentially problematic for furniture manufacturers include:

• volatile organic compounds, particulate matter and odour from wood coating operation
• wood dust and noise from woodworking
• particulate matter, carbon monoxide, formaldehyde, hydrogen cyanide and hydrogen chloride from combustion.

The following sections break down air emissions according to legal requirements and provide information on accepted best practice within the sector.

Environmental Protection Act 1990 : Part I

This legislation controls wood dust, wood coating solvent and wood combustion emissions at sites above relevant thresholds. It also provides best practice advice in the form of the Process Guidance Notes.

Part I of the Environmental Protection Act makes it an offence to operate a prescribed process or use a prescribed substance without an authorisation. The processes which are subject to authorisation are listed in the Environmental Protection (Prescribed Processes and Substances) Regulations 1991 (Statutory Instrument 472) and fall into Part A and Part B.

Part A processes are subject to Integrated Pollution Control (IPC) – a regime which rarely applies to the furniture sector. Part B processes are subject to Local Air Pollution Control (LAPC) and this applies to hundreds of furniture companies. The LAPC system is regulated by various regional bodies:

• Local Authorities in England and Wales
• Scottish Environment Protection Agency in Scotland
• Environment and Heritage Service in Northern Ireland

Processes above the relevant threshold require authorisation. Authorised processes are obliged to use the principle of BATNEEC (Best Available Techniques Not Entailing Excessive Cost) to control the process. This is a balance between state-of-the-art management techniques and technology - and what an industrial sector can generally afford.

Process Guidance Notes lay down BATNEEC for each process. These notes were originally issued in 1991/1992, and are reviewed on a four-yearly basis. Notes such as PG1/12(95) were last re-issued in 1995, and are being reviewed in early 2000. PG6/33(97) is due for review in late 2000 and republication in mid 2001.

Guidance Notes of particular interest to the furniture sector include:

• PG1/12(95) Combustion of fuel manufactured from or comprised of solid waste in appliances between 0.4 and 3MW
• PG6/2(95) Manufacture of timber and wood based products
• PG6/33(97) Wood coating processes.

Regulators are under a duty to ‘have regard to’ these Guidance Notes, but they do have a degree of flexibility with regard to the interpretation of requirements at individual sites. Requirements may vary, depending on the particular locality and characteristics of an individual company (eg presence of sensitive residential areas close-by).

PG1/12(95) Combustion of Fuel Manufactured From or Comprised of Solid Waste in Appliances Between 0.4 and 3 MW

This Guidance Note applies to wood burning boilers between 0.4 and 3 MW, which roughly equates with a feed rate of 90 to 650 kg/hr. Such plant is expected to comply with the following emission limits:

*Emission limits for carbon monoxide for existing plant were suspended during the 1995 Guidance Note revision. These limits are agreed on a site basis according to the level that can be achieved under normal operating conditions.

Limits on formaldehyde, hydrogen chloride and hydrogen cyanide are applicable to sites burning certain board materials, eg:

• formaldehyde from chipboard, plywood, fibreboard and similar material
• hydrogen chloride where painted or PVC coated wood is burned
• hydrogen cyanide from melamine faced wood

Sites using boilers falling below the 0.4 MW threshold will still be required to ensure that dark smoke is not produced (requirement of the Clean Air Act 1993) and that fumes/particulates do not pose a nuisance to neighbours (requirement of EPA Part III). Boilers larger than 3 MW should fall under IPC control. However, most are attached to LAPC processes for the manufacture of timber and wood-based products, as a result of which both processes are controlled by the same regulator under LAPC.

Clauses of the Guidance Note

• 1-9 Introduction.
• 10-11 Upgrade of existing processes should have been conducted by 1 October 1995.
• 12-18 Emission limits as outlined above.
• 19-32 Monitoring requirements. The Guidance Note recommends a number of monitoring requirements, eg continuous indicative monitoring for particulate, continuous monitoring for carbon monoxide and either oxygen or carbon dioxide where material other than untreated timber is burned.
• 33-43 Materials handling. These clauses aim to ensure that no loose dust is allowed to escape from the extraction system. If dust is spilled, as is inevitable, it should be cleaned up as soon as possible.
• 44-47 Combustion process details.
• 48-54 Chimney and exhaust height details.
• 55-58 General operational requirements such as the need for maintenance, training and good housekeeping.

It should be noted that PG1/12(95) is being revised in early 2000 and should be republished later in the year. In addition, Europe is currently considering two Directives of relevance to combustion.

The Hazardous Waste Incineration Directive is currently thought to be unlikely to impact upon wood burning if the timber contains no preservatives.

The Waste Incineration Directive contains an exclusion for wood waste, except where it contains heavy metals or halogenated organic compounds, eg PVC. Thus, any plant burning PVC (eg PVC faced melamine or PVC based edge lipping) will have to segregate PVC residues and landfill them, as the emission limits associated with the Directive are unattainable for wood burning boilers.

In reality, it is good practice to avoid PVC combustion in wood burning boilers. The material releases hydrogen cyanide which attacks and degrades the insides of boiler plant, leading to a reduction in operating efficiency and the need for frequent repair.

PG6/2(95) Manufacture of Timber and Wood Based Products

Sites likely to use more than 1,000 m³ of timber in any 12 month period are required to hold a PG6/2(95) authorisation. The threshold figure increases to 10,000 m³ if the wood is purely sawed, i.e. not sanded or drilled etc. The main aim of this legislation is to ensure the correct extraction and collection of wood dust to prevent environmental harm and nuisance to neighbours.

Very few sites have problems with this Guidance Note, due to its duplication of other legal requirements. Wood dust needs to be efficiently extracted from the workplace in order to comply with health and safety legislation. Once extracted, dust must be kept secure in order to comply with the Duty of Care for waste.

The main operational change involved in compliance is the switch from cyclones to bag filters, as required by Clauses 6-8. The intention is to increase the efficiency of wood dust capture. Other upgrade conditions involve the fitting of appropriate alarms and malfunction mechanisms to the extraction system.

Clauses of the Guidance Note

• 1-5 Introduction.
• 6-8 Upgrade of existing processes by 1 October 1996, except the replacement of cyclones - which is by 1 October 2000 for processes where total exhaust volume air flow exceeds 300 m³ /min and by 1 October 2003 in all other cases. Replacement of cyclones may not be needed if wood is processed with a moisture content over 20% - clause 22.
• 9-15 Monitoring. Where exhaust flow is under 300 m³/min, monitoring should not be needed. If flow is above this figure, cyclones should have alarms which warn of malfunction and continuous monitoring may be needed on the exhausts of bag filters if there are frequent problems. All sites should instruct operators to conduct regular visual assessment of emissions to identify and correct problems at an early stage.
• 16-24 Materials handling. These clauses aim to ensure that no loose dust is allowed to escape from the extraction system. If dust is spilled, it should be cleaned up as soon as possible. Alarms are recommended for silos to identify overfilling and blockage. Collection vehicles should have side windows or sensors to warn of overfilling. All filter bags should be replaced at least every four years and replacement should be recorded.
• 25 Process vents should have no restrictions at the final opening.
• 26-29 General operations. Outlines the need for maintenance, training and good housekeeping. Malfunctions should be corrected promptly and recorded in a logbook.

PG6/33(97) Wood Coating Processes

This Guidance Note sets out the control regime for sites likely to use more than 5 tonnes of organic solvent in any 12 month period. Organic solvents give rise to volatile organic compounds (VOCs), which are organic compounds that evaporate easily at ambient temperatures. VOCs are controlled because they contribute to photochemical smog, some are toxic and cancer causing, some contribute to high level (stratospheric) ozone depletion and most contribute to global warming. The controls in PG6/33(97) can be split into two:

• Final compliance options
• Other clauses.

Final compliance options

All authorised solvent users must choose one final compliance option. This should have been in place by April 1999 for sites using >15 tonnes of solvent, whilst sites using 5 to 15 tonnes users have until 2007. The options are:

• Compliant coatings – all coatings used must have a solvent content not more than that specified in Clause 20, eg 435 g/l VOC for clear coatings applied by spray, roller or dipping techniques. Many sites are finding it difficult to switch to compliant coatings throughout their operation.
• Abatement technology to reduce VOC emission levels below 50 mg/m³ (>15 tonnes) or to below 150 mg/m³ (5 to 15 tonnes). Certainly for larger users, the emission limit could only be reached via the use of unrealistically expensive "bolt on" abatement plant, e.g. incinerators.
• Mass balance approach (also known as the 'bubble’ approach) with which sites will be deemed to comply where they have achieved a level of solvent usage below their ‘target emission’. Such limits are related to the solids content of coatings, which allows flexibility in accordance with varying levels of production. They are calculated as follows:

• 0. 5 to 15 tonnes users can apply up to 1.6 times as much solvent as solids, ie 1:1.6 (and they are allowed until 2007 to achieve such a ratio or better)
  1. 15 tonnes and upwards users can apply the same amount of solvent as solids, ie 1:1 (and should have achieved such a ratio or better by April 1999)

The mass balance is the approach that the majority of sites favour due to its relative flexibility and cost effectiveness. It allows the use of low solvent coatings where they are practical, with the retention of solvent based coats where essential.

Other clauses

All authorised processes should have complied with all other clauses of the Guidance Note by April 1999. Such clauses include:

• 24 Solvent inventory - records should be kept of the amount of solvent used
• 45 Spray efficiency - conventional spray equipment must be replaced by high efficiency types such as high volume low pressure or airless air assisted
• 47-52 Cleaning operations - must be reviewed. Where possible, water or less volatile solvents should be used for cleaning spray lines etc
• 58-67 Chimney heights and dispersion considerations
• 68-72 General operational requirements relating to the need for maintenance, training and good housekeeping.

Best practice

This section provides a short overview of solvent reduction best practice. More detailed information is available in a variety of ETBPP publications, eg GG177 Reducing solvent use in the furniture sector. Relevant documents are listed at the back of this Reference Note.

When confronted with the need to comply with the wood coating regime, many sites have immediately started altering the composition of their traditional coatings, with a view to developing low solvent alternatives. However, there are many essential steps that must be taken prior to such action in order to reduce unnecessary solvent usage – thereby minimising the degree of reformulation required. Five important steps are listed below:

i. Compilation of a solvent inventory: effective solvent management can only occur if measurement has taken place to show which coatings contribute most solvent. With substances such as thinners, further measurement is likely to be needed to show how much is used for thinning, cleaning and stripping. This breakdown can go further still, with the recording of which sprayers use most thinners and coatings per unit of production. Best operating practices should be identified, documented and adopted as the standard operating procedure.
ii. Reduction of unnecessary cleaning solvent: experience shows that up to 30% of solvent use can be due to thinners. Benchmarking shows that thinners in efficient companies should not exceed 5% of total solvent usage.
iii. Reduction of unnecessary thinners: suppliers provide coatings with the correct viscosity for use in normal circumstances. Users should ensure that thinners are not added out of habit or due to a need to compensate for poor spraying technique. Where viscosity is a problem due to low temperature, trials of in-line heaters should be conducted. These attach to spray systems and maintain a consistent coating temperature throughout the day, eg 40^oC.
iv. Reduction of unnecessary fugitive losses/improved housekeeping: when coating tins are left without lids on, solvent will evaporate. Consequently, operators will add more thinners to correct the viscosity. Training and supervision of housekeeping can prevent this waste and improve the consistency of finish.
v. Implementation of effective application techniques: research has shown that many supposedly high transfer efficiency spray systems are used in a less than optimum manner. Typical transfer efficiencies being achieved range from 40% to 55%. Thus 45% to 60% of all coatings are not ending up on the furniture! Those using high volume low pressure guns should ensure air cap (atomisation) pressure is <10psi. Those using air assisted airless systems should ensure fluid pressure is kept as low as recommended by the manufacturer.

Pollution Prevention and Control Act 1999

EPA Part I is currently being replaced by PPC due to the requirements of a European Directive. In real terms, the initial impact on LAPC processes will be mainly administrative. ‘Authorisations’ will be called ‘permits’ and BATNEEC replaced by BAT – though the DETR suggests that the terms will have very similar implications. In addition, Process Guidance Notes will gradually introduce new considerations such as noise, waste minimisation and energy efficiency.

Environmental Protection Act 1990 - Part III, Statutory Nuisance

Statutory nuisance can be defined as an emission, action or premises which is prejudicial to health or a nuisance. ‘Nuisance’ is defined as an unlawful interference with someone's enjoyment of their land.

In the case of furniture manufacturers, some of the more common statutory nuisances will be:

• odour resulting from solvent-based coating operations
• noise due to extraction plant or vehicles
• dust escaping from extraction systems, eg due to splitting filter bags
• smoke from malfunctioning wood burning boilers.

Where the degree of nuisance warrants such action, regulators may serve an abatement notice requiring the cessation of the nuisance - with failure to do so being an offence.

One of the problems with nuisance is that it is largely a function of the perception of the recipient. For example, noise is sound which is not desired by the recipient - one man’s music can be another man’s nuisance. In addition, perception of nuisance is affected by other variables such as:

• Presence of activities with nuisance-causing potential.
• Proximity of neighbours.
• Sensitivity of neighbours: industrial units will generally be less sensitive than residential areas. The latter will be more sensitive outside of office hours, eg night-time and early morning and during the summer when windows are open etc.
• Prevailing winds: in the UK winds will generally originate in the south west, thereby carrying any pollutants towards areas located north east of manufacturing sites.
• Barriers across pollution pathways, eg screening fences.

Such a record will help the site to identify recurring problems. It will also demonstrate to regulators that the site has taken the complaint seriously, looked into the matter and, if appropriate, has taken remedial action.

Clean Air Act, 1993

This Act makes it an offence to emit ‘dark smoke’, ie smoke darker than shade 2 of a Ringelmann Chart, from any trade premises. Therefore, it imposes some degree of control on small wood-burning boilers which fall below the local authority control threshold, as well as making yard fires illegal. One defence of note is where a furnace is being lit from cold and all reasonable steps have been taken to minimise emissions.

Unless the contrary is proven, an emission of dark smoke is deemed to have taken place if material is burned which is likely to give rise to the emission of dark smoke. Therefore, this closes a loophole due to night-time burning where dark smoke cannot be seen!

Legislation

• Environmental Protection Act 1990 – Part I
• PG1/12(95) Combustion of fuel manufactured from or comprised of solid waste in appliances between 0.4 and 3 MW
• PG6/2(95) Manufacture of timber and wood based products
• PG6/33(97) Wood coating processes.
• Pollution Prevention and Control Act 1999
• Environmental Protection Act 1990 – Part III
• Clean Air Act 1993

The future

It must be remembered that air emission legislation and best practice is always developing. Legal changes in the near future include:

• Review of PG1/12(95) and PG6/2(95) due to be republished in 2000
• Review of PG6/33(97) due to be republished in 2001
• Implementation of PPC requirements which will replace the EPA Part I
• Implementation of the EU Solvent Emissions Directive (not expected to have a major impact on PG6/33(97))
• Finalisation and implementation of EU Waste Incineration Directive