31 July 2019
By The KLH Team
Top 9 Ideas for a more Sustainable Food Factory Part 1
KLH Sustainability have a new project up our sleeve, working on something which has got us quite excited. While we can’t share the details just yet, us and our colleagues at Integrated Food Projects thought we would introduce some of our research and learnings on the biggest sustainability opportunities within food processing facilities.
Food processing facilities often have a much higher water and carbon footprint than other building types. This is not only due to their size but is also attributed to their energy-intensive equipment, such as cold storage and/or pasteurisation, and their strict food safety regimes for cleaning and sanitation.
Over the next two articles, we will explore nine key ideas and numerous sustainable design opportunities through which food factories can minimise environmental impact, improve working conditions and strive for carbon neutrality.
This first article focuses on all things carbon and climate change, while the second article will introduce sustainability themes less typical of factories, but that are quickly on the rise in the industry.
1. Energy demand reduction
Food factories are energy guzzlers requiring exceptional amounts of energy to mass-produce the food we see on the shelves. Their major energy hitters are processing equipment, including production lines’ operation and cleaning, and general factory operations, including space conditioning, ventilation and lighting. Each major contributor comprises many individual energy users, with diverse use profiles and requirements. And while quick wins on energy demand reduction can be identified by considering each contributor individually, greater energy efficiency opportunities arise when considering the full energy demand profiles of the factory, and when investigating the interdependencies among its significant energy uses.
Process energy demand reduction
Industrial production usually requires some form of process heating for activities such as distillation, evaporation, drying, etc. Process heating operations are responsible for approximately 70% of the manufacturing sector’s energy use, while the food industry is estimated to account for about 26% of the EU’s total energy consumption. Capturing waste heat can save money and energy, and can be achieved through various waste heat recovery (WHR) technologies. WHR systems consist of heat exchangers and can be built into a new plant or retrofitted to existing plants. It is estimated that, depending on the process, energy wastage from freezing and canning in fruit and vegetable processing is between 10% and 45%. With rising fuel costs, estimates show WHR payback periods are as low as 2-3 years. Additionally, use of economisers in boiler systems can increase the efficiency by 1% for every 5°C reduction of flue gas temperature. This indicates that the system’s fuel consumption can be reduced by 5–10% with a payback period of less than 2 years.
Other opportunities to reduce energy demand of the process heat include maximising utilisation, minimising evaporative losses through good insulation, metering, monitoring and regular maintenance.
Factory energy demand reduction
Factories are energy intensive buildings. They tend to be spaces of high volume, with sensitive temperature setpoints and high mechanical ventilation rates and lighting requirements, throughout their operating hours.
Warehouses and vehicle loading can be major sources of heat losses. While provision of lobbies and strip curtains, air locks, or insulated shutter doors can reduce heat loss, even greater benefits can be achieved by coupling vehicles to buildings by a dock seal, notably when coupled to a temperature-controlled loading bay or holding area.
Placing rooms with low temperature setpoints, or containing cold storage, adjacent to one another, or increasing internal wall insulation to minimise heat transfer, can lead to significant energy demand reductions, considering the 24/7 cooling requirements for key ingredients and products.
Careful and selective glazing positioning can provide significant wellbeing and energy benefits in large factory spaces. Rather than providing good levels of natural light throughout a facility (which given the higher U-values of glazing compared to solid walls can lead to significant reduction in thermal performance) it is sensible to prioritise glazing in areas where operatives are working, if food safety permits, such as packing areas and above engineer’s workstations, rather than areas of automated processing lines, where operatives are just passing through for quality checks.
2. Balanced energy distribution
Typically, factory cooling is provided using chillers, whose waste heat output would be rejected into the atmosphere, and heating is generated from a separate system, thereby creating an open jaw duplication of energy generation. Food factories have a unique energy characteristic: they generally require both heat and coolth in large quantities at the same time or within a reasonable buffer range. This presents the opportunity to introduce a closed loop waste-heat recovery system which uses the cooling waste heat to preheat air or water, and, consequently, reduce the factory’s heating demand.
Additional energy balancing opportunities comprise pre-cooling/heating of spaces at times of low power demand, such as during night shifts.
3. Low and zero carbon technologies
Factories are typically located in low density industrial areas with low-rise buildings, and good distribution links. The low density of their surrounds may prove ideal for large scale wind turbines, thereby improving the local renewable energy infrastructure, and offering a zero-carbon energy source for the factories.
Considering the sheer size and footprint of many factories, their extensive roof area is perfect for roof-mounted photovoltaic arrays. Coupling the PVs with a green roof can also improve the building thermal performance and provide a more thermally comfortable environment, therefore reducing winter heating and summer cooling needs and costs.
4. Hidden carbon
When we think of carbon, we usually think of gas and electricity consumption. Maybe, some of us think about cows farting too, as one tonne of methane has the same global warming potential (GWP) as 28 tonnes of carbon. But there are other colourless, odourless gases in buildings which we tend to overlook: refrigerants.
Modern cooling systems can use multiple refrigerants, with hydrofluorocarbons (HFCs) being the norm, since they replaced the pesky chlorofluorocarbons (CFCs), responsible for the ozone hole and banned under the Montreal Protocol 1987. However, these refrigerants often have a high GWP of over 1400, and even those deemed “low GWP”, such as the HFOs (Hydroflouro Olefins) often need to be blended with HFCs for commercial application thereby leading to coolants with a GWP of around 1000.
Of course, the GWP of the refrigerants is only an issue if they escape the system and leak into the atmosphere, but therein lies the problem, as annual gas leak rates in refrigeration systems can be around 25%!
Natural refrigerants such as ammonia and hydrocarbon with no or negligible GWP are available in commercial systems and can operate in temperature ranges far greater than their alternatives. The added benefit of this is that heat pump solutions using such refrigerants can operate in higher temperatures, and therefore, become more attractive for industrial installations.