Pesticides - Best Practice Guides



What is a Biobed?

As developed for pesticide handling areas, this is a specially excavated pit filled with a mixture of straw, soil and peat-free compost and turfed over. Research has shown that Biobeds are very effective at locking up and degrading pesticide residues which can arise from drips and splashes when filling sprayers and mixing pesticides. Subject to a Groundwater Authorisation (GWA), Biobeds can also be used for the disposal of dilute pesticide material from tank washings and wash water from cleaning the exterior of the sprayer. Biobeds are not the only solution to this problem and advice on other approaches is contained in the Best Practice Guide Pesticide Handling Areas.

Benefits of Biobeds

During research on biobeds point source pesticide contamination was applied to simulate multiple severe pollution incidents in the pesticide handling area in one spray day. Pesticide concentrations in excess of 100,000ppb were measured in the liquid entering the biobed. The biobed performed very effectively retaining and/or degrading the pesticides and reducing the concentrations to generally below 0.5ppb and often below the 0.1ppb EU standard set for pesticides in drinking water

Disposal of Washings

Biobeds are capable of handling spray washings, however application of pesticide washings to areas other than the crop or target area is regarded in law as disposal. Therefore where the intention is for washings to be discharged to the biobed the suitability of the site must be evaluated by the local environment agency by the user applying for a GWA. The agency will consider the local hydrogeological conditions, groundwater vulnerability and the nature of the biobeds intended use before granting the GWA.

Biobeds and Regulation

Both EA and SEPA recognise that lined biobeds offer significant environmental benefits over current practice. However, under the new Agricultural Waste Regulations (expected late 2005) the EA is proposing that lined Biobeds will be considered a waste recovery operation and made exempt from the regulations. This would mean that lined biobeds would not need to be licensed  but would need to be regisered with the EA. It is planned that the registration will be free and can be conducted online. Water from the biobed can be used for irrigation and sprayer washing without need for a Groundwater Authorisation , its disposal will also be exempt. The use of unlined biobeds for mixing and filling only is not encouraged by the EA.

Before building a biobed in Scotland a farmer must first check with SEPA. Whilst farmers in Northern Ireland should seek advice from the Environment and Heritage Service.

General Design Considerations

There are two basic designs for biobeds as illustrated opposite.

1: An Offset Biobed - this uses a bunded handling area which contains and intercepts all liquids. These are then directed to the biobed usually via a holding tank.

2: A Drive-Over Biobed is simply a system where all liquids fall directly onto a biobed.

Basic Design

The Biobed is a specially excavated pit 1-1.3m deep. The surface area dimensions of the Biobed depends on the nature and frequency of pesticide handling activities on the farm, and expert advice should be sought for this. As a general rule of thumb, if using the Offset design, the surface area of the Biobed should be approximately two-thirds of the area from which it is receiving run off. More details on the design and plumbing of the biobed can be found in the biobed Design Manual.

Biobed Mixture

Biobeds mixture consists of straw (50%), soil (25%) and compost (25%) and turfed over. After mixing the biobed constituent material it should be matured for approx. 6-8 weeks before placing it into the excavated pit. Annual topping up with pre-composted mixture will also be required.
Selecting a light, or medium, loamy soil enhances performance. Clay soils should be avoided as they can be difficult to mix and may hamper drainage. Sandy soils should also be avoided as they are too free draining and will not retain the pesticide residues adequately.

Water Management

Careful management of all the water entering a biobed is seen as critical to its long-term effectiveness in degrading pesticides. Sustained periods of water saturation can damage the beneficial microbes in the system. Preventing uncontaminated surface run off and rain water from buildings entering the biobed will help significantly. If necessary buffer tanks can be installed both on the route into and/ or out of the treatment system, with a view to providing a greater degree of control on the rate of liquid transfer.

Lined Biobeds

In most situations, the local Environment Agency will require a Biobed to be lined if it is to be used for wash down The latest research/designs on Biobeds has addressed rainwater management issue; historically this was a problem for lined biobeds where too much yard water drained into them and no thought had been given to their subsequent drainage. With suitable basic plumbing to assist in managing drainage of through flow, lined biobeds are a practical solution for wash down and subsequent disposal to a designated (GWA) area. Follow the advice in the biobed Design Manual if such as system is to be installed.

To find out more

This Guidance is due to be revised shortly with drawings and more detail on the management of Biobeds. Full details of the research will be published by the Environment Agency and Crop Protection Association shortly.

  • For information about GWA
    Scottish Environment Protection Agency (SEPA)
    Environment and Heritage Service for Northern Ireland (EHS)
    Environment Agency
  • For specialist advice on the design and construction of Biobeds contact
    ADAS Gleadthorpe
    Cranfield Centre for Eco Chemistry, Shardlow

For general advice on pesticides contact your local agronomist or crop protection distributor.


The advice in this Guide has been prepared after consultation with the UK environment agencies and leading researchers into pesticide handling areas. Research was funded by Defra, EA, CPA and SNIFFER.
This guide was produced by the Crop Protection Association as part of The Voluntary Initiative.
The Voluntary Initiative is a programme of measures agreed by Government to minimise the environmental impact of pesticides.

(C) Voluntary Initiative November 2004.

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