Botley treatment centre approved to produce biosolids for farms

25 June 2025 by CSG

A new sludge treatment centre in Hampshire has been certified to provide biosolids to local farms to be used as an alternative fertiliser to grow crops.

The CSG Botley treatment plant – which opened last year – has received certification from the Biosolids Assurance Scheme (BAS), meaning the biosolids produced from the sewage it receives can be safely used on farms growing crops to Red Tractor standards.

Biosolids are produced by treating sludge from the wastewater recycling process and are a valuable resource as they are rich in nitrogen, phosphorus and micronutrients.

CSG’s Botley plant is currently processing 25,000 gallons (114,000 litres) of raw sewage every day from off-mains households and businesses across Hampshire.

The waste management specialist aims to produce 400 tonnes of enhanced lime treated biosolids every year, offering local farmers a cost-effective and organic alternative to chemical fertilisers.

James Baxter, Agricultural Recycling Manager at CSG, said: “We are delighted to have achieved BAS accreditation, which was the goal when we launched this new £1.3 million treatment centre.

“We have already produced over 125 tonnes of biosolids which have been sent to local farms to be used as fertiliser. This accreditation means the biosolids can now be used on fields where Red Tractor standard food for humans is grown. This includes the food you buy in supermarkets.

“Part of the CSG ethos is to find innovative recycling and recovery techniques that reduce environmental impacts and the creation of high-quality biosolids is a fantastic example of that.”

CSG uses the latest centrifuge technologies to separate wastewater from solids to create a lightweight sanitised ‘cake’ which can be easily transported to farms.

Under the BAS programme, biosolids are tested to ensure they meet the required standards and regular audits take place to confirm ongoing compliance and quality.

The Botley treatment centre has boosted wastewater capacity in Hampshire for over 8,000 off-mains households every year.

The treatment plant accepts domestic wastewater from thousands of households, hotels and holiday parks in Hampshire and beyond, which are not connected to the mains and instead use septic tanks or cesspits.

CSG is a major national operator, dealing with 30,000 off-mains drainage households across the UK.

James added: “Facilities such as this in Botley are required to ease the wastewater capacity issues around the country. This plant has large capacity and is already making a significant difference.”

The Botley site is built to the latest specifications and is fully licensed and permitted by the Environment Agency.

CSG is a national industry-leader with headquarters in Fareham. The business has 650 employees and a 200-strong fleet. Along with wastewater haulage and processing, CSG specialises in chemical waste processing, wastewater engineering and industrial cleaning.