a better placeGuidance on using a lined biobed to dispose of agricultural waste consisting of non-hazardous pesticidesolutions or washings(Exemption 52)
Submitted: 27 April 2007
ADAS Project Code: XCH2001
Environment Agency ref: 30139296
Reported produced for: Prepared by:Lynsey Craig Dr Paul FoggEnvironment Agency ADAS UK LtdGoldway Way GleadthrorpeOrton Goldway Medan ValePeterborough MansfieldPE2 5ZR Nottinghamshire
NG20 9PF
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Table of contents
1 INTRODUCTION 3
2 LOCATION AND SITING 42.1 Risk to surface water 4
2.2 Risk to groundwater 4
2.3 Environment Impact Assessment 5
3 DESIGN AND CONSTRUCTION 63.1 Background 6
3.2 Preparation of Biomix 6
3.3 How big does the biobed need to be? 73.3.1 Should the biobed be covered to exclude rainfall? 8
3.4 Indirect Biobed 93.4.1 Handling area 93.4.2 Temporary storage 103.4.3 Transfer to the Biobed 113.4.4 Biobed construction 11
3.5 Direct Biobed 123.5.1 Biobed construction 12
3.5 Post treatment storage 13
4 OPERATION AND MANAGEMENT REQUIREMENTS 144.1 Handling area 14
4.2 Biobed 144.2.1 Routine maintenance 144.2.2 Long-term maintenance 144.2.3 Storage of exhausted biomix 14
4.3 Land spreading exhausted biomix 15
5 REFERENCES 16
APPENDIX I 17
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1. Introduction
‘Pesticides’ is a name that describes a range of products used to control insects,diseases and weeds. They include insecticides, fungicides, herbicides,molluscicides, plant growth regulators as well as bird and animal repellents androdenticides. You can use a biobed to treat non hazardous pesticide washings orsolutions from agriculture. However biobeds are not approved for use in thetreatment of veterinary medicines, including sheep dip.
Pesticides may be released to farmyard surfaces from spillages, leakages (Higginbotham et al., 1999)and from washing and cleaning tractors and sprayers (Ramwell et al., 2004, Ramwell et al., in press).Studies have shown that any pesticides deposited onto the yard surface may later be washed off tosurface water (Mason et al., 1999). Drainage to groundwater is also possible on permeable surfaces(Helweg, 1994). You can minimise these point source releases by changing your handling practices toreduce loss (Carter, 2000) as well as ensuring that sprayer operators are adequately trained andequipment is well maintained (Rose et al., 2001).
Because it is inevitable that some release will occur, we need to have systems in place that reduce theamount of pesticides that end up in water bodies. These systems need to be cost effective and simpleto operate. One way is to use a lined biobed to catch contaminated runoff and equipment wash water.In its simplest form, a biobed is a lined structure filled with biomix, a mixture of topsoil, compost andstraw. The biomix removes the pesticides from the contaminated water. The retained pesticides arethen degraded, and the treated water can be re-used (Fogg et al., 2003a, 2003b, 2004a, 2004b,2004c, Rose et al., 2004).
There are two main biobed systems. A lined indirect biobed where all filling, mixing and sprayerwashdown happens on an impermeable, bunded pesticide handling area. All liquid is diverted via asealed drainage system to a nearby biobed. The second biobed system is the lined direct biobed. Allfilling, mixing and sprayer washdown happens directly above the biobed with access provided by ametal grid and support frame. All liquid falls directly onto the biobed. You do not need a groundwaterauthorisation for either system.
With the introduction of the Agricultural Waste Regulations in May 2006, lined biobeds are regardedas waste treatment systems, so they require a waste management licence. Biobeds built before May2006 have had a 12 month transition period, which expires in May 2007. In September 2006, inkeeping with the government’s commitment to minimise the administrative burden on farmers and tomake the widest use of exemptions, Defra and the Welsh Assembly consulted on a proposal for a newwaste management licensing exemption. This was for the disposal of agricultural waste consisting ofdilute pesticides washings into a lined biobed. The aim of the exemption is to improve themanagement of pesticide washings and reduce the risk of pollution from pesticide handling andequipment cleaning activities. A copy of the exemption is in Appendix I, with a copy of StatutoryInstrument No. 1156 The Waste Management (Miscellaneous Provisions) (England and Wales)Regulations 2007 available at http://www.opsi.gov.uk/si/si2007/uksi_20071156_en.pdf. Theexemption has a number of key provisions to ensure that any lined biobed is built, maintained andoperated in a way that will ensure that the pesticide washings are treated appropriately and that theactivity does not pollute or harm groundwater and/or surface waters. This includes the requirementsthat:
• There is secure storage of the dilute pesticide washings (only necessary for indirect systems)before treatment in the biobed.
• Every part of the area where the activity happens is surfaced with an impermeable pavementthat has a sealed drainage system so that all liquids are directed into the biobed.
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• The biobed is located in a secure place.
• The lining of the biobed is impermeable.
• The biobed is suitable for treating the waste.
• The biobed is covered with turf.
• The biobed material (biomix) is securely stored before spreading to land.
By registering an exemption you are saying that your biobed will not pose any significant risk to theenvironment. Following this guidance will help you achieve this.
This document explains what the requirements of the exemption mean in practice and covers thefollowing key areas:
• Location and siting
• Design and construction
• Operation and management requirements.
2. Location and siting
Biobeds may not be appropriate for all situations. There will be some locations that are not suitable.Before installing a biobed you MUST carefully consider whether the proposed site presents anunacceptable risk to surface water, groundwater and the nearby environment. The biobed must belocated in a secure1 place at least 10 metres away from any surface water and 50 metres from anyspring, well or borehole. It also has to be away from major access routes to prevent the trafficking ofpotentially contaminated material. As part of the site risk assessment, you should carefully considerwhat the environmental impact would be if part of the biobed system failed. You can use the followingnotes to decide how suitable your proposed site is. Please ensure that you keep a record of the riskassessment you conducted prior to installing a biobed, it should include details from the followingsections 2.1 – 2.3.
1 Definition of secure is that the activity taking place is under your control at all times.
2.1 Risk to surface water
You should draw a map of and / or record of all surface water bodies in and around your proposed site.There may already be such a map in an existing crop protection management plan. The biobed mustnot be located within 10 metres of any surface water body. If the drainage from the biobed or posttreatment irrigation area (section 3.6) could meet any underground field drains, you should interceptand / or divert the drainage.
2.2 Risk to groundwater
The Environment Agency has defined Source Protection Zones (SPZs) for all groundwater sources likewells, boreholes and springs that provide water for human consumption. These zones, which aremapped for all the largest sources, show the risk of contamination from any activities that might causepollution in the area. The closer the activity, the greater the risk. To assess the suitability of the
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proposed biobed site in terms of risk to ground water, you should follow this process to find the SPZsthat we have mapped in your area:
1. Use the link below to go to our web sitehttp://www.environment-agency.gov.uk/maps/info/groundwater/
2. Enter your post code under ‘What’s in your back yard’ and click ‘OK’
3. Under ‘ground water source protection zones’ click on ‘View map of results’. The map will showwhether your proposed location falls within one of the four source protection zones
Zone 1 (Inner protection zone) REDClosest to the source, and shows the most vulnerable groundwater.
Zone 2 (Outer protection zone) GREENThe outer zone covers areas at risk from pollution by pollutants that do not break downquickly.
Zone 3 (Total catchment) BLUEThe total area supplying water to the source.
Zone of special interest BROWNSometimes, a fourth zone is defined. This is usually where local conditions mean thatindustrial sites and other polluters could affect the groundwater source even though theyare outside the normal catchment area.
4. If the proposed location of the biobed falls within a SPZ 1 or 2 you would need to contact theEnvironment Agency National Agriculture Customer Help Line 0845 6033113 to determine thesuitability of the proposed site.
5. It is also important to take into account the location of wells, springs and boreholes that havenot had SPZs mapped, including those not producing water for human consumption. For this,you will need to make local enquiries within at least 50 metres of the proposed site.
6. Evidence of the risk assessment must be recorded to support your exemption.
If you do not have access to the internet, then contact the Environment Agency National AgricultureCustomer Help Line 0845 6033113 directly and they will help you assess the suitability of theproposed site.
2.3 Environment Impact Assessment
Biobeds can potentially cause harmful discharges. If you want to carry out an exempt activity, forexample install and operate a lined biobed or land spread used biomix within 250 metres of anenvironmental sensitive area or protected habitat, you will need to do an environmental impactassessment. Examples of environmentally sensitive areas or protected habitats include Sites ofSpecial Scientific Interest (SSSI), Candidate Special Areas of Conservation (cSAC), Special Areas ofConservation (SAC), Special Protection Area (SPA), sites as defined under the RAMSAR convention,Areas of Outstanding Natural Beauty (AONB). You can get more information on environmentallydesignated areas and sensitive habitats including location at http://www.jncc.gov.uk/. The purposeof the Environmental Impact Assessment (EIA) is to make sure that all possible risks around installingthe biobed are considered and that measures are put in place to manage the risks. This assessmentshould include a description of the measures that you would put in place to avoid, reduce and, ifpossible, remedy significant adverse effects. You should also cover the main alternative sites and thereason for selection, after taking into account possible environmental effects. The EIA is designed tobe a self assessment activity and you can do it by completing the questionnaire under the ImpactAssessment section in the exemptions pack.
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3. Design and construction
3.1 Background
Lined biobeds are designed to treat non-hazardous pesticide solutions. Examples include the spillsand drips that occur during handling and mixing pesticide solutions diluted to manufacturer’sstandards as well as equipment washings. However, biobeds are not a substitute for best practice andwe recommend that you make every effort to contain spills of concentrate chemical by using aninduction hopper and drip trays. Concentrated pesticide should NEVER be disposed of on the biobed.As a minimum, the first set of tank washings should be sprayed in the field, onto the intended target,subject to label guidelines. Under these use conditions the performance of the biobed technology iscurrently acceptable to us.
For further guidance on best practice – see the Defra Code of Practice for using Plant ProtectionProducts, ISBN 0-85521-170-9. You can download the Code of Practice athttp://www.pesticides.gov.uk/safe_use.asp?id=64 or you can get a free copy on CD, or a printedcopy for £15, from Defra publications:
Defra Publications,Admail 6000,LondonSW1A 2XX,(telephone 08459 55 6000).
Please quote product code PB11090 for the printed copy and PB11090CD for the CD version.
The design of biobeds must address the following key areas:
• An impermeable area, with a sealed drainage system on which all pesticide handling / mixingand equipment washdown activities take place (indirect system).
• Temporary storage capacity before treatment in the biobed (indirect system)
• A lined biobed. The liner must not have any seams which could result in seepage of thepesticide solution.
• A system that enables the treated water to be re-used.
• Storage and reuse of used biobed material.
The main principle of a biobed system is containment / treatment / re-use.
3.2 Preparation of biomix
The biobed is basically an organic filter system. Most pesticides will cling to organic matter. Thereforewhen runoff water contaminated with pesticides is directed through the biobed, the pesticides stick tothe organic material and ‘clean’ water is left. The pesticides left in the biobed are then broken down bymicro-organisms, (Fogg et al., 2003b). The organic filter or ‘biomix’ consists of a mixture of straw(wheat or barley), compost (preferably peat free) 2 and topsoil. The three parts should be mixed, 1part compost, 1 part topsoil and 2 parts straw, (Plate 1). Ideally the mix should be allowed to stand forbetween 30 and 90 days before being added to the biobed. This allows the composting process tostart to break down the straw, which makes it easier to create a homogenous mix. Note that it is moredifficult to create a good mix when using very wet clay texture soils.2 Using peat in the biomix is not encouraged as it is an unsustainable resource. A peat free substitute should be used ifpossible. Farmyard manure is not approved for use in the biobed. There is potential for waste peat based growing media tobe used in the biobed as well as composted green waste. However, both do not currently have approval for use in the biomix.
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Plate 1 Volumetric proportions of straw, peat (preferably peat free substitute) and topsoil
3.3 How big does the biobed need to be?
In order to achieve the required level of treatment the biobed should be at least 1.0 metre deep in thecentre (1.5 metres maximum) not including the turf layer, with a surface area of at least 1.0 metre2
used to treated each 1000 litres of liquid per year. During construction it is recommended to overfillthe biobed. For example, target depth 1.0 metre, fill to 1.25 metres. This will allow for initialsettlement. This means the dimensions of the biobed are dictated by:
• The annual volume of pesticide washings. The total volume of pesticide waste (not includingrainfall) being treated by a single biobed MUST not exceed 15,000 litres in any period of 12months
• Annual rainfall total. (1 mm of rainfall on 1 square metre is equivalent to 1 litre). Average rainfalldata can be obtained from http://www.metoffice.gov.uk/climate/uk/
• The size of the bunded handling area. This is dictated by the size of the sprayer. The handlingarea must be adequate to contain all liquids that drop from the sprayer and allow the sprayeroperator to work freely in all mixing, loading and water filling operations. Routine servicing ofthe sprayer should take place on the same site. Consideration of currently available equipmentand work routines suggest the following typical sizes (Table 1):
Table 1 Typical dimensions required for pesticide mixing / handling areas
Sprayer Type Overall length (metres) Overall width (metres)
Self propelled sprayer 7 5
Trailed 7 5
Mounted 4 5
The size of the bunded handling area is a compromise between containment, minimising the volumeof clean rainwater requiring treatment and maintaining the ability to work safely. The areas suggestedwill not allow for full boom unfolding. However, it is possible to modify the handling area for anindirect biobed to enable the boom to be fully extended (Plate 2).
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Plate 2 Indirect biobed system under construction. Bunded handling area in foreground, with a boom wash out section all draining to single collector. Background lined hole waiting
to be filled with biomix and secure intercept tank awaiting installation.
The following example shows how to calculate the size of an indirect biobed system.
Background information
1. Annual volume of pesticide waste and washings: 15,000 litres
2. Annual rainfall: 650 mm
3. Required area of pesticide handling area: 7 x 5 metres = 35 m2
Total volume of liquid requiring treatment: 15,000 litres of pesticide waste and washings plus 22,750litres of rainwater (650 mm x 35 m2) equals 37,750 litres3.
Based on a figure of 37,750 litres and the requirement for 1 m2 per 1000 litres, the biobed needs to be1.0 m deep and have a surface area of 38 m2. In practical terms, this would mean that the biobed as aminimum would be 6.0 metres wide x 6.5 metres long x 1 m deep.3 It is not necessary to include the area of the biobed when calculating the volume of rainwater intercepted by the biobed.This has already been taken into consideration in the 1 m2 requirement for every 1000 litres of liquid. For direct biobeds thesurface area is governed by the volume of spray waste and the physical dimensions of the sprayer.
3.3.1 Should the biobed be covered to exclude rainfall?The biobed itself should not be covered as this will affect the ability of the biobed to degradepesticides. However, there are benefits from limiting the volume of the clean rainwater entering thebiobed. Purpose built roof structures are unlikely to be cost effective. However, if an existing buildingwould allow the bunded handling area to be covered this would allow the overall size of the biobed tobe reduced significantly.
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3.4 Indirect biobed
The indirect biobed is a system where all pesticide mixing and handling happens on an impermeablesurface with a sealed drainage system. This directs runoff to an adjacent biobed, (Plate 3).
Plate 3 Indirect biobed. Sprayer is parked on impermeable handling area with runoff diverted onto an adjacent biobed
You should use the following construction details as a guide as to how to comply with the WasteManagement Licence exemption (52) when installing a lined indirect biobed.
3.4.1 Handling area1. Remove existing topsoil. Excavate site as necessary to allow the following construction:
2. The excavated site should be lined with approximately 150 mm of well compacted hardcore overwhich a sand blinding layer (approximately 25 mm) should be placed to protect a damp proofmembrane (dpm) of 1200g weight. A 150 mm thick, reinforced concrete slab should then be laidto falls of not less than 1:100. A concrete bund (300 mm wide x 100 mm high) should beconstructed around the entire perimeter of the slab (Figure 1).
3. The bunded concrete slab should have a drain, for example an ARCO type drain (100mm x100mm), installed in accordance with manufacturers instructions, which is connected to a silttrap, with removable cover, with a nominal capacity of 250 mm below inlet (Plate 4).
Sometimes it may be possible to modify an existing concrete area to form the bunded sealed areaneeded. You should make the following checks / modifications.
1. Check the concrete is in good condition, i.e. free from damage, pitting and cracks so that liquidcan not pass through. Also check that there is adequate fall (1:100).
2. Is there a drain present that can be intercepted to only take runoff from the mixing handlingarea? If not, you need to install one, for example an ARCO type drain. Cut the concrete along oneedge of the handling area (suiting the fall) to accept a 100 mm x 100 mm Arco type drain, andinstall in accordance with the manufacturer’s instructions. The drain should connect to a silttrap, with removable cover, with a nominal capacity of 250 mm below inlet.
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3. Construct bund edge of minimum 300 mm wide x 100mm high around the entire perimeter of thehandling area. The existing concrete surface may need to be roughened, including bondingagents or similar to accept the new concrete mix.
Figure 1 Section through concrete pesticide handling and washdown area
Plate 4 Concrete pesticide handling area with bund and ARCO type drainage system
3.4.2 Temporary storageAll run off from the pesticide handling / washdown area MUST drain, via the silt trap, to a securetemporary storage, constructed from seamless polyethylene or similar. Old single skin metal tanks arenot suitable. The pump switch levels must be set to ensure that no more than 1500 litres of waste isdeliberately stored. You may also need to allow some feedback in the tank for situations such aselectricity or pump failure, or excessive wet periods when the biobeds cannot be irrigated. If this is notaddressed, either the biobed will be over-irrigated and damaged, or the handling and washdown areasmay flood and overtop. The overall tank size will be determined by these two considerations. Undercertain conditions the tank may need to be bunded. These will depend on the potential environmentalrisks associated with tank failure. As part of the exemption registration process we will assess therisks associated with the proposed site. Bunded tanks will be required for sites deemed to be ‘highrisk’. The tank should be sited near the lined biobed. Precise construction details for installing thistank will vary with design. You should be guided by the manufacturer. You must ensure that theconnection between the silt trap and storage tank is secure, so that NO leakage can occur.
INDIRECT SYSTEMSection through concrete pesticide handling and mixing intercept area
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3.4.3 Transfer to the biobed
It is important to distribute the liquid held in temporary storage evenly over the biobed using the fullsurface area. This has been successfully achieved using low cost drip irrigation. These systems have alow pressure demand (nominally 7 metres head) and can be driven by a submersible pump, fitted witha float switch and installed into the base of the temporary storage tank. Pumps with a nominalcapacity of 50 litres per minute @ 6.5 metres head (approx. 200 watt motor) would be suitable. Flowrates from the emitters on this type of irrigation are typically 1 – 2 litres per hour and should be spacedat 0.25 – 0.4 metres, with the main lines spaced at a similar distance. The system should beinspected regularly for signs of damage and loose joints.
3.4.4 Biobed constructionThe exact design of the biobed can be adapted to meet specific local requirements. For example,while most biobed systems will be based around an excavated hole in the ground, a sealed aboveground tank based biobed could be used where the volume of liquid requiring treatment is low. Anabove ground system may also have a lower environmental risk, as it can be inspected. For this reasonit may represent an acceptable reduction of risk in vulnerable groundwater areas. However, the biobedMUST be sealed, be at least 1.0 metres deep and have a minimum surface area of 1 m2 for every 1000litres of liquid requiring treatment. The following detail describes a typical biobed system.
A pit should be excavated to contain the biomix. This can be a shape to suit any tank or lining system.Successful biobed operation has been found with soil side slopes of 30-35°. These should be blindedwith 25 mm sand, over which a geotextile membrane of 190 grams per square metre should be laid.The hole should then be lined with a material of a type suitable for a small reservoir. This liner shouldbe 1.5 mm thick and be constructed from a synthetic material, it should be in one piece and notcontain any seams as this could allow seepage of pesticide solution. The liner needs a bonded outletpoint, able to accommodate a 100 mm outlet. You should consult the manufacturer before orderingthe bonded outlet as its construction will depend on the angle of the soil side slopes.
The bonded outlet MUST be installed according to the manufacturer’s guidelines, as, again, if it is notsealed correctly this could result in the biobed being unfit for use. The outlet should be installed at thelowest point of the excavation, compatible with the site layout. This outlet allows the rapid transportof the treated water for final distribution or re-use. A coil (approx. 5metres) of 100mm perforateddrainage pipe should then be laid into the base of the biobed (on-top of the liner) and connected tothe drain intake to prevent the biomix material clogging the pipe (Figure 2). The lined hole should thenbe filled with biomix (section 3.2) and covered with turf. If you are not going to use the biobedimmediately, adding the turf layer should be delayed to allow for the addition of fresh biomix after aninitial settlement period. The turf layer MUST be in place before pesticides are added to the biobed.
Figure 2 Section through lined biobed system
DRIVE OVER SYSTEMDrive over grid cover Biobed sectionBiobed section also suits Indirect System
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3.5 Direct biobed
With a direct biobed system the sprayer is parked over the top of the biobed, intercepting directly anyspill, drips and washings (Plate 5).
3.5.1 Biobed constructionThe direct biobed system is simpler in principle as it uses gravity to advantage and the containment ofliquids is confined to only one area. However, unlike the indirect system, it is unlikely that any existingfacility would be suitable for modification, so you will probably need a new construction.
It is important to emphasise the need for best practice when filling your sprayer directly over a biobed.We recommend that every effort should be made to contain spills of concentrate chemical by using aninduction hopper and drip trays. Concentrated pesticide should NEVER be disposed of on the biobed.
The biobed is constructed as described in section 3.4.4. However, to allow vehicles access to thebiobed, you need a grid over the surface. This grid needs to comply with all health and safetyrequirements both in terms of an operator handling concentrated pesticides and the support of a fullyloaded sprayer. A 40 mm x 100 mm steel mesh is recommended (Plate 6). All liquids as well as soil /mud from tyres should be able to pass vertically through the grid and onto the biobed. The grid willalso require removable sections, to allow for maintenance of the biobed. The grid will need to besupported with end and side foundations. These will need a firm sub-base to lay the concrete over.We recommend that you liaise with the grid supplier over the anchorage system for the grid. Wherepossible you should be able to approach the biobed from any direction to allow complete freedom inany working routine. The direct biobed system should not accept liquids, other than those fromvertically above. Therefore a bund, similar to that for the indirect biobed intercept area (section 3.4.1)should be installed, with a raised bund edge of minimum 300mm x 100mm (Figure 2).
Plate 5 Direct biobed system. The sprayer is parked on top of the metal grid such that that all spills, drips and washings are intercepted directly by the biobed.
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Plate 6 Example of grid construction used to allow access to direct biobed systems
3.6 Post treatment storage
Biobeds are classed as waste recovery systems. This means it’s necessary to re-use the treated water.Possible re-use options include irrigation or use as the carrier for pre-crop total herbicide applications.Research is ongoing to evaluate these options. If the treated water is to be used for irrigation, thisMUST be applied to a vegetated area, that is neither frozen or water logged, is at least 10 metres fromany watercourse and 50 metres from any spring, well or borehole. You should fully consider anddocument the presence of any underground drainage systems. Irrigation must be applied at a rate sothere is no surface runoff generated. A drip irrigation system as described in section 3.4.3 would besuitable. In order to collect the treated water the biobed drain outlet should be connected to a secondtemporary storage tank. The tank should accommodate 1500 litres storage capacity and of a type andinstallation as described in section 3.4.2.
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4. Operation and management requirements
Biobeds are intended to be low cost systems that require only minimal technical and managementinputs. However, some maintenance is needed to make sure the system performs well. In order to beable to show that the biobed is being operated and maintained according to best practice, you shouldkeep a log book. This should include construction details as well as routine maintenance records, forexample when the biobed was topped up, silt traps cleaned, the biomix replaced and date spread toland.
4.1 Handling area
The pesticide handling area (section 3.4.1) should need only limited maintenance. The drains shouldbe kept clear of sediment and the sediment trap should be cleaned as required to ensure rapidtransport of liquid to temporary storage and subsequently the biobed. Certain pesticides stick stronglyto soil. Therefore soil that accumulates on the handling area may be contaminated with pesticides.Vehicles other than the sprayer should not have routine access over the handling area ascontaminated soil may be transported off the site. You should regularly clean the handling area withany soil placed directly onto the surface of the biobed.
4.2 Biobed
4.2.1 Routine maintenanceThe biobed is filled with biomix, which over time will decompose and compact. To keep the biobedperforming well, an average minimum depth of 1.0 metre MUST be maintained. In order to achieve this,the biobed will need to have fresh biomix added every year. The top-up biomix should be prepared asdescribed in section 3.2. The turf layer can then be removed, the fresh biomix added and the turfreplaced. Alternatively, the turf layer may be left in-situ, the fresh biomix added and then re-turfed.
4.2.2 Long-term maintenanceData on the long-term performance of the different biobed systems operated under UK conditions islimited. Research is ongoing and results will be made publicly available. However, the scientificliterature suggests that the biomix should work effectively for five to eight years (Torstensson 2000,Castillo MdP and Torstensson in press). Based on this information the biobed matrix MUST bereplaced after five years. Excavation to remove the used biomix must be done with great care to avoiddamaging the liner. While the biobed is empty, the construction should be carefully examined and anydefects repaired.
4.2.3 Storage of exhausted biomixThe biomix must be stored securely4 on the farm for a minimum of 12 months, but not more than 36months, before land spreading. The biomix must not be stored within 10 metres of a surfacewatercourse or 50 metres of any spring, well or borehole. If stored on an impermeable surface, forexample concrete, any runoff should be collected and irrigated to vegetated land, that is neither frozennor water logged. It MUST be at least 10 metres from any watercourse and 50 metres from any spring,well or borehole. You should give full consideration to the presence of any underground drainagesystems and this should be documented. In-field storage is subject to the same site risk assessmentfor surface and ground water as described on sections 2.1 and 2.2. No more than 50 m3 may be storedat any one time.
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4 The biomix MUST be stored in such a way that it does not become a ‘point source’ of pollution. Research is ongoing in orderto assess the potential environmental risks from storing exhausted biomix.
4.3 Land spreading exhausted biomix
Used biomix may be spread to land, as long as this results in benefit to agriculture5 or ecological6
improvement. It is subject to the following restrictions:
1. You must either be the occupier of the land, have the consent of the occupier to carry out theactivity or be otherwise entitled to carry out the activity.
2. The land is at least 10 metres from a watercourse and 50 metres from a spring, well or borehole.
3. At the start of treatment and at any time during the treatment the land has not been frozen for 12 or more hours during the 24 hours prior.
4. The land is not waterlogged, flooded or snow-covered.
5. The application does not exceed 50 tonnes per hectare in any period of 12 months.
6. You make an allowance for the available nitrogen, total phosphate and total potash in the wastewhen working out fertiliser requirements.
7. The application is carried out in accordance with any requirements imposed by the ActionProgramme for Nitrate Vulnerable Zones (England and Wales) Regulations 1998, (currentlyunder review).
5 There are several types of benefit to agriculture that could be derived from the land spreading of exhausted biomix. Forexample the replacement for inorganic fertiliser to provide nutrients such as nitrogen and phosphorus. The addition oforganic matter may improve the capacity of the soil to hold water, or its porosity, stability, tilth and workability. Overall theland spreading activity should result in the improvement of soil condition which in some way results in the land supporting orincreasing crop yield6 Ecological improvement may be assessed by whether or not that activity results in the maintenance of habitats and theirbiodiversity where these would otherwise deteriorate, or the provision of new habitats for wildlife and the development orrestoration of existing habitats to give greater biodiversity and sustainability.
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References
Carter A, How pesticides get into water – and proposed reduction measures.Pesticide Outlook 11 (4): 149-157 (2000)
Castillo MdP, Torstensson L, The effect of the biomixture age on pesticidedecomposition in biobeds Pest Manag. Sci. (in press).
Fogg P, Boxall ABA and Walker A. Degradation of pesticides in biobeds: The effect of concentration and pesticide mixtures. Journal of Agriculture andFood Chemistry 51(18); 5344-5349 (2003a)
Fogg P, Boxall ABA, Walker A and Jukes AA. Pesticide Degradation in a “biobed”composting substrate. Pest Manag. Sci. 59: 527-537 (2003b)
Fogg P, Boxall ABA, Walker A and Jukes A. Degradation and leaching potentialin biobed systems. Pest Manag. Sci. 60:645-654 (20044a)
Fogg P, Boxall ABA, Walker A and Jukes A. Leaching of pesticides from biobeds:effect of biobed depth and water loading. Journal of Agricultural and FoodChemistry 52(18);6217-6223 (2004b)
Fogg P, Boxall ABA, Walker A and Jukes A. The effect of different soil typeson the leaching potential and degradation of pesticides in biobed.Journal of Agricultural and Food Chemistry 52(18);5643-56 (2004c)
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Environment Agency Biobed Full Guidance 17
Appendix I
52.
(1) The disposal of agricultural waste consisting of non-hazardous pesticide solution or washings ina lined biobed at the place of production of the waste if –
(a) every part of the place upon which the activity is carried out is surfaced with animpermeable pavement provided with a sealed drainage system so that all liquids aredirected into the biobed;
(b) the biobed is located at a secure place at least –
(i) 10 metres from a watercourse; and
(ii) 50 metres from a spring, well or borehole;
(c) the lining of the biobed is impermeable;
(d) the biobed is suitable for treatment of the waste;
(e) the biobed is covered with turf; and
(f) the total quantity of waste being treated does not exceed 15,000 litres in any period oftwelve months.
(2) The secure covered storage of not more than 1500 litres of waste at the place where it isintended to be treated in a biobed in reliance on the exemption in sub-paragraph (1).
(3) The treatment of land used for agriculture with agricultural waste consisting of biobed materialwhere such treatment results in benefit to agriculture or ecological improvement if –
(a) the biobed material is stored securely for 12 months before it is spread;
(b) the biobed material consists of a mixture of straw, compost and biologically active soil;
(c) the land is at least –
(i) 10 metres from a watercourse; and
(ii) 50 metres from a spring, well or borehole;
(d) at the start of the treatment and at any time during the treatment –
(i) the land has not been frozen for 12 or more hours during the preceding 24 hours; and
(ii) the land is not waterlogged, flooded or snow-covered;
(e) the activity is carried out in accordance with any requirement imposed by an actionprogramme under the Action Programme for Nitrate Vulnerable Zones (England and Wales)Regulations 1998; and
(f) the total quantity of waste used does not exceed 50 tonnes per hectare in any period of12 months.
(4) The secure storage at the place of production of waste that is intended to be used in reliance ofthe exemption in sub-paragraph (3) if –
(a) no more than 50 cubic metres is stored at any one time; and
(b) no waste is stored more than three years.
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