Biosolids are nutrient rich and benefit soil in many ways - especially by increasing the organic matter in the soil.
This stabilises and improves soil structure (reducing the risk of soil erosion), increasing water-holding capacity and workability. This helps plant root development with the benefit of increased crop yields.
Higher levels of organic matter increase life within the soil from microbial activity to earthworms, helping to lock carbon into the soil. Using biosolids also reduces the need for inorganic fertilisers which are often produced in energy-intensive processes.
Biosolids replace soil nutrients essential for plant growth. They mainly provide nitrogen and phosphate, but also contain sulphur, magnesium, potassium and other trace elements, which are not found in manufactured fertilisers. In summary, the benefits of biosolids application to agricultural land are:
• Improved soil structure
• Increased water retention capability
• Increased life in soil (from microbes to earthworms)
• Increased carbon sequestration
These lead to . . . .
• Less soil work and energy required
• Increased crop yields and reduced risk of yield loss
• Maintaining soil structure and nutrient levels
• Reduced risk of diffuse pollution
• A natural provision of nutrients
• Greenhouse gas reductions
The National Farmers Union
“We support the recycling of treated biosolids to agricultural land in accordance with The Safe Sludge Matrix and Code of Agricultural Practice. We recognise biosolids as a useful resource that can help farmers supply nutrients to their crops, improve soil condition and substitute for the use of conventional fertilisers.”
The Environment Agency
“We believe that in most cases recycling to agricultural land represents the Best Practicable Environmental Option for managing treated sewage sludge (bioresources) arising from sewage treatment.
The addition of sludge bioresources to agricultural land benefits the soil in the form of nutrients and organic matter that would otherwise have to be supplied through alternative fertilisers and soil conditioners.”
FACTS AND FIGURES
• In the UK three million tonnes of biosolids are applied annually to agricultural land. Around 150,000 hectares of agricultural land receive biosolids annually with most applied to arable crop land.
• In 2018, we applied 110,000 tonnes of enhanced treated biosolids on to land in the north east of England.
• Biosolids make up less than 5% of the total organic material going to agricultural land. The remainder of organic material applied to land consists of farm animal manure (83%) compost (7%) and industrial organic material (5%).
• The carbon offset from avoided manufacture of nitrogen fertiliser as a result of biosolids application in the north east of England is approximately 2,100 tonnes of carbon dioxide a year.