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Scrubs up for food waste

The north west London prison is saving more than £20,000 a year composting its food waste while providing training and career opportunities for its inmates. Paul Tittle reports.

As well as porridge and indeed any other waste food item, Her Majesty’s Prison Wormwood Scrubs will now be turning all its food waste into compost. The prison service is more than used to being under the microscope when it comes to minimising operational costs. Many prisons up and down the country have already made huge strides, for example, in the area of food waste management by significantly reducing the volume of material that is collected through the use of food waste disposers and dewaterers.

However, HMP Wormwood Scrubs is going one step further by completely eliminating food waste collection, and subsequent landfill, and instead will compost the waste on site, saving themselves and the Ministry of Justice thousands of pounds every year. It will be using IMC’s “CompPod” to recycle all its food waste into compost. And as well as breakfast cereals, everything from fish and fruit to meat and vegetables will be collected and turned into compost.

At the end of last year, the Scrubs carried out a review of its food waste management policy with the main objectives of reducing associated costs and raising the bar on sustainability. One obvious area for potential savings was in food waste collection and landfill, which was costing the prison in the region of £20,000 every year. By taking the waste and composting it, they would gain an additional benefit of being able to use the material on the prison’s raised flower beds and hanging baskets.

Having explored the alternatives available, the prison was convinced of the environmental and financial benefits of implementing an on-site composting solution. However, there were a number of key challenges that first had to be met. Firstly, the solution had to be able to deal with approximately 2 metric tonnes of food waste produced each week from the prison’s kitchens. The equipment needed to be proven, robust and reliable and the waste needed to be processed without a high degree of intervention as it was envisaged that the prisoners themselves would play a large part in the composting process.

Secondly, the lack of available space in the prison’s kitchens for the food waste processing equipment, meant that any solution had to be housed elsewhere without incurring excessive building costs as this would prolong the eventual return on investment.

Once the review was completed, the Scrubs turned to IMC, which was already working closely with the majority of the prison service having deployed the company’s range of products, including Food Waste Disposers (FWDs), Dewaterers and In-Vessel Composters (IVCs), to more than 100 prisons in the UK.

IMC had already completed a field trial, that proved the economic viability of turning food waste into a high grade compost, at HMP Morton Hall in Lincolnshire – the prison now also plans to take on an IMC CompPod in the next few months.

During the 34 week trial - carried out by IMC in collaboration with Imperial College London - over 4,600Kg of food waste was processed. The food waste was converted into a high grade compost, through a combination of macerating and dewatering to homogenise and reduce the water content of the waste.  A carbon-rich bulking agent was added to achieve the correct carbon to nitrogen ratio and absorb excess water, before loading into a closed In-Vessel Composter. The vessel requires no external heating but achieves sufficiently high temperatures to ensure pathogenic depletion resulting in a high quality product that surpasses the standards of BSI PAS 100.

It was at the end of this trial that IMC developed the CompPod – after Imperial College, convinced of the trial results – tried to install the necessary composting equipment but couldn’t find the space. IMC suggested enclosing the equipment needed in a prefabricated building that could be craned into place on site – and the CompPod was born.

The bespoke-built self-contained building is designed to be a flexible solution to the treatment and processing of food waste generated by commercial caterers. The composting process takes 6-8 weeks and the system can be used within a variety of catering establishments such as restaurants and hotels, shopping centres, schools and universities as well as hospitals and stadia.

Imperial College London is already reaping the benefits and has to date saved over £100,000 in food waste treatment and disposal costs since its installation and is set to achieve a return on investment in just 16 months. No sooner had the CompPod been launched than it earned multiple awards including two 2010 Rushlight Awards (for green technology) - the ‘Organic Waste Award’ and overall ‘Waste Innovation Award’.

Using the learning gained from the Imperial College installation, it was clear that the CompPod could be a solution for The Scrubs.  IMC developed a stand-alone, prefabricated building designed to the prison’s requirements, which could be craned into position onto the footings situated close to the prison’s kitchens. The CompPod’s specifications are unique to HMP Wormwood Scrubs and take into account the extra security features required for prison use as well as ensuring it could be manoeuvred through the narrow prison gates. 

It is estimated that HMP Wormwood Scrubs will save over £20,000, a year by diverting the waste away from collection and landfill with the equipment paying for itself in less than four years. Government has been quick to see the advantages and successive Environment Ministers, including Lord Taylor of Holbeach (the current Government Spokesperson at the Department for Environment, Food and Rural Affairs) has praised IMC’s composting solution.

Lord Henley, until recently Parliamentary Under Secretary responsible for environmental regulation, publicly praised the on-site initiative for turning food waste into compost using IMC equipment at Wakehurst Place, Kew’s ‘Country Garden’, and applauded the practical and environmental benefits of the system.

IMC has had huge interest from large scale commercial caterers looking for a composting solution with a quick return on investment. But its use at the Scrubs has additional benefits. As the prisoners take ownership for the food waste management and composting process, IMC has developed in-depth training materials that will help ensure best practice and maximum compost yield. In parallel, the Ministry of Justice (MOJ) has developed a qualification, similar to an NVQ, that incorporates food waste composting within its content and for which IMC has provided much of the content. This could provide inmates with the opportunity to gain a qualification and a potential future career path when they leave prison. 

Paul Tittle is product manager at IMC

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