The food industry is facing some big challenges, one of which is the need to reduce carbon emissions and cut energy costs. The sector accounts for around 12% of industrial energy consumption today. Energy use for refrigeration equipment currently accounts for 10% of greenhouse emissions, with around 16% of power consumption in the UK being attributed to refrigeration central systems, air conditioning and heat pump applications.

When setting out on a carbon reduction journey, engineers in the food sector first need to understand the power consumption of their current refrigeration system and what refrigerants are used. How is heat generated and how is cooling maintained? It is advisable to arrange for an audit to be undertaken at the outset to gather all the data needed to have a good understanding of the existing system. Consider talking to a specialist in the design, installation, servicing and maintenance of industrialrefrigeration systems, such as Seaward Refrigeration, to help you collate all the information needed to achieve this.

The next step would be to look at the refrigerants being used. I would always advise a move to natural refrigerants, such as ammonia, depending of course on the operating envelopes of the system.Ammonia (R717) is a natural refrigerant – it is also the best thermodynamic refrigerant – offering the highest efficiency and it is more cost effective when compared with synthetic refrigerants. It also has zero global warming potential (GWP).

It is, however, vital to ensure that ammonia is properly installed in refrigeration systems because it is toxic. It is important to understand that ammonia cannot be offered as a drop-in replacement for synthetic refrigerants. It will require a new installation because synthetic refrigerant systems are a lower category of installation, whereas ammonia (R717) will be graded as a category four assembly.

The system will also need to conform to Pressure Equipment Directive (PED) legislation – thepressure requirements of ammonia are different to those of synthetic systems.

On the plus side, ammonia-based refrigeration systems typically have a lifespan in excess of 30 years, so it will offer a more sustainable solution.

Legislation is also driving a move to natural refrigerants and many enterprises are making the move in a bid to meet their own corporate social responsibility (CSR) goals.

Heat recovery

With the food industry being one of the largest consumers of energy, the harvesting of rejected heat for hot water generation and other efficiency enhancements should also be considered.

The biggest wins in food sector heat recovery applications are to be found in large central plants – large cold stores or dairy processes, for example – where both heat and cooling is required as part of the process.

Rather than use a gas or LPG-fired boiler to generate heat, it is possible instead to harvest heat from the central refrigeration system and then pump it up to a pressure to enable it to generate low pressurehot water up to +95°C, making overall production processes more efficient.

Most dairies, for example, will require a steam boiler using either LPG or natural gas to generate heat for pasteurisation. In addition, it requires a cooling system at the start of the process to cool incomingmilk, and also at the end of the process, after pasteurisation, to once again cool the milk before bottling. With two cooling sources in the process it is possible to harvest the rejected heat from theseand reuse in the pasteurisation process, eliminating the need for a steam boiler and offering huge energy savings. Many other food processes will, to some degree, require both heating and cooling operations, where heat transfer could offer energy savings. In most applications

it is possible to create handshake points in the plant for space heating, air source heating, and water source heating.

So, for food processors looking to reduce their carbon footprint, putting a focus on cooling and heating operations can be a good place to start the journey.