Biosolids and the need for Potash

Sludge Regulations 1989

These regulations enact the European Directive (on the protection of the environment, and in particular of the soil, when sewage sludge is used in agriculture, 86/278/EEC). This was the first soil protection directive. The main provisions of the 1989 Regulations require that:

• All soils must be sampled and the results must be available before the first application of biosolids, and be resampled thereafter when heavy metals could have accumulated.
• Biosolids must not be applied to agricultural land when the concentrations of certain heavy metals in the soil (lead, cadmium, mercury, copper, zinc, and nickel) are greater than specified limits, according to soil pH.
• The rate at which heavy metals in biosolids may be added to soil is restricted.
• Biosolids must not be applied if the soil pH is below 5.0.
• Restrictions on use of different materials and harvest intervals for different crops must be adhered to, see Safe Sludge Matrix, page 3.
• Biosolids application rates must take account of the fertiliser needs of the rotation; the use of biosolids must not impair soil quality nor pollute ground or surface waters.

The farmer or landowner must provide the biosolids producer/supplier with relevant information about the application of other materials to the land. The biosolids producer/supplier must provide information to the farmer or landowner about the nutrients and heavy metals applied in the biosolids.

Cross-compliance

Statutory Management Requirement No. 3 (SMR 3) requires compliance with the Sludge (Use in Agriculture) Regulations 1989 and the Code of Practice for Agricultural Use of Sewage Sludge. HMSO, London 1996. The biosolids supplier will ensure that SMR 3 is observed and also SMR 4 (Nitrate Vulnerable Zones), as far as biosolids are concerned.

Use of biosolids can be considered to contribute to the requirement to maintain the land in 'Good Agricultural and Environmental Condition' (GAEC) because it improves soil structure, builds soil organic matter and increases water infiltration rate and resistance to soil erosion.

Stakeholder agreement

In the latter part of the 1990s, ADAS facilitated discussions between the British Retail Consortium, Country Land and Business Association, Environment Agency, National Farmers’ Union, Department of Environment Transport and Regions, Ministry of Agriculture Fisheries and Food, Water UK and other stakeholders to review the Regulations and agree additional requirements that would enable the use of biosolids on farmland to be welcomed by all parties as part of sustainable development. The Agreement on the method of working came into force on 31st December 1998. All agreed that the existing Regulations dealt with chemical risks adequately. Measures were agreed to further control the risk of disease transmission compared with the Regulations. Sludge treatment was to be based on HACCP (Hazard Analysis and Critical Control Point) principles, with two classes of treated sludge and defined rules on how they could be used. With this additional control and with FACTS training for advisors, all parties agreed that using biosolids to complete nutrient cycles and conserve organic matter is part of sustainable development. Conservation and recycling of phosphate by using biosolids to complement mineral fertiliser is especially relevant to sustainability; the phosphate industry estimates that the world’s reserves will be exhausted in between 100 and 300 years at the current rate of exploitation, depending on price.

The agreement was published by ADAS as the 'Safe Sludge Matrix'; it affects all applications of biosolids to agricultural land. Defra planned to revise the Sludge Regulations to embembody the provisions of the Agreement and published a consultation in 2001, but revision now looks unlikely.

The Agreement on sludge treatment is:

Untreated sludge
Not permitted on land for food crops since 1999, nor for non-food crops since 2005.

Conventionally treated biosolids
These are biosolids that have undergone biological, chemical or heat treatment to reduce the fermentability and possible health hazards. The commonest treatment is anaerobic digestion. Conventional treatment ensures that at least 99% of pathogens have been destroyed.

Enhanced treated biosolids
These are biosolids subjected to treatment that virtually eliminates any pathogens. These materials will be free from Salmonella and the treatments will destroy 99.9999% of all pathogens.