Caterers consume massive quantities of water, energy and cleaning chemicals, particularly on tasks such as warewashing and laundry. But many of the benefits go straight down the drain. Bruce Whitehall and David Clarke look at solutions that could save money and benefit the planet
As any dishwasher user should know, removing as much debris as possible from the dirty ware before putting it through the wash cycle ensures better results and better all-round efficiency. It can also help kitchens to be greener.
For Stowe School, catering for 800 covers daily near Milton Keynes in Buckinghamshire, equipment that removes the need to rewash plates has gone hand-in-hand with lower energy and detergent usage and reduced labour costs.
The school solved the problem of stubborn deposits such as dried cereal and egg yolk with a new Meiko flight dishwasher, which includes a pre-soak sink and a pre-wash section fed with recycled hot water from the rinse section. Catering manager Geoff Higgins estimates his detergent usage, aided by a CSS Top detergent-saving system, now amounts to 40 litres per week, a saving of 30% on the previous warewashing system. "At £30 per 20-litre container, that is a saving worth having," he comments.
His system also has a Meiko WP-4 heat pump, installed at an OGC (Office of Government Commerce) price of £5,533. For users of larger warewashing systems, the extra investment in a heat pump offers a way of trapping and recycling otherwise wasted heat and is probably the most tangible way to lower energy consumption in a typical kitchen. By continuously extracting hot air and steam from within and around the warewasher, it can preheat incoming cold water to around 70°C, eliminating the need for wash tank elements and requiring only a modest amount of power to boost the water to 85°C for the final rinse stage.
In independent tests, a Meiko K200VP rack transport dishwasher drawing 38.4kW of power has been found to require only 22.6kW when fitted with a Meiko WP4 6kW heat pump module and other energy-saving features.
Ken Winch, head of Ken Winch Design, is one of several food service design consultants who favours heat pumps. "The energy saving is shown back in the boilerhouse so it's ecologically right to install them," he said. "They produce hot water from what is otherwise waste water and - theoretically - there's also a knock-on effect on air conditioning."
Dishwasher maker Winterhalter agrees. Marketing manager Simon Aspin points out that by transferring hot, moist air, the heat pump on its conveyor rack machines operates as "radiator in reverse", pumping it back to the initial rinse prewash. The result is that the plates emerge cooler and the hot exhaust air is both cooled and demoisturised. "So effective is this cooling that in many sites it can actually cool the warewash area, acting as a secondary kitchen ventilation system," Aspin claims.
He estimates that a heat pump - list price £8,982 - can net savings of about 12kWh per day, while a more basic exhaust air heat recovery system - list price £2,148 - can cut energy requirement by up to 6kWh a day. The problem is that the person responsible for capital expenditure at many catering companies gets a bonus for purchasing at lowest price, while another person is responsible for actually operating the equipment. "They're coming at it from different directions, so the company loses out on significant long-term savings
as well as environmental benefits," Aspin points out.
Not all energy-saving issues associated with warewashing concern extra fitments. A significant contribution can be made by efficient, continuous filtering of debris from the wash water. Hobart claims that its machines fitted with Genius X four-stage filters can be run for extended periods without the need to change the water.
Thus Hobart's FX frontloading cabinet washer, which has a small (13-litre) tank, can operate at a typical water, energy and detergent cost as low as 22p per day. A similar capacity machine with a 20-litre tank made by a competitor costs slightly more (33p) for the first fill of the day but ends up costing £1.06 per day because of the energy, water, detergent and labour cost of having to drain and refill. In such a scenario, Hobart claims that its machine could save up to 2,500 litres of water per year and reduce costs by more than £300.
Another Hobart standard feature that can cut costs is the insulated four-sided hood on its pass-through dishwashers. This box-like enclosure around the washing process saves up to 3.5kWh per day, the manufacturer claims, compared with machines with three-sided hoods, which spill out a lot of the steam and heat when raised.
Optional fitments on larger Hobart warewashing system include heat pumps, exhaust heat recovery and a rinse water bypass system, which diverts 50% of the rinse water to the prewash, contributing to savings of up to 73,000 litres of water per annum.
Extra fitments can contribute significantly to better environmental performance but simply choosing the right equipment in the first place can gain savings, according to Malcolm Martin of Miele Professional. Miele pursues a "horses for courses" policy, with freshwater cabinet washers for smaller sites such as bed and breakfasts and gastropubs needing only a few wash cycles per day or the option of its new G8072 frontloader, featuring a double-walled cabinet, for optimum electricity and water consumption in high-turnover applications.
Martin points out that basic education can significantly lower wastage over time - for example, encouraging staff to fill each load to maximum capacity, which is particularly pertinent on machines able to take double-stacked racks. Fitment of auto-dosing equipment also helps by eliminating the guesswork of manually adding cleaning chemicals.
Miele also offers various energy-saving features on its laundry equipment for restaurants and hotels. Features such as reverse action on tumble dryers can, the company says, cut energy usage by 15% compared with single rotation, while electronic monitoring of residual moisture also trims costs by shutting down machines when the preset degree of dryness is reached, and is especially useful if a rotary ironer is to be used for finishing.
Unnecessary use of energy and water, and chemical wastage are not the only "green" issues associated with kitchen services. At the Center Parcs resort in Sherwood Forest, Nottinghamshire, a sewage overflow into the garden of one of the villas was attributed to a build-up of fat in the main drainage system. It's difficult to control what guests put down the drains of a villa during their stay but Center Parcs - which makes a selling point of its natural woodland setting, healthy menus and accreditation to the ISO14001 environmental auditing standard - decided to install a Greasebeta unit in its main kitchen and another in its Sports Café. These compact units automatically dose naturally-occurring bacteria into the waste water to "digest" fats, oil and grease and keep drains running freely. Larger Biogester units have since gone into two of the site's sewage pumping stations.
Technical services maintenance manager Kevin Bonsor attributes significant cost savings to the installation, thanks to fewer breakdowns. "We no longer find ourselves in the position of having to close down the kitchens in order to unblock the drains and deep clean every time a problem occurs, when loss of revenue could be substantial."
The commercial dishwasher is one of the most labour-saving devices in the commercial kitchen and is probably one of the most expensive to run, so it makes sense when considering energy efficiency and sustainability to look at the wash-up. All dishwashers require four components to work successfully - water, energy, detergents and time, all of which are expensive. Any savings which can be engineered will save money and increase the economic, environmental and social bottom line.
The calculation for heating a set amount of water over a given time cannot change; the amount of energy required will always remain constant. Therefore the technology required for making dishwashing more efficient is to improve the insulation on the machine to maximise the heat generated, reduce the amount of water required per cycle, and recover the wasted heat that is discharged to the atmosphere and the drains. In addition, the removal of any dissolved minerals will ensure that the machine stays efficient.
Water that's high in dissolved minerals, specifically calcium and magnesium, is described as hard. Hard water is not a health risk, but a nuisance because of its tendency to cause mineral build-up in pipework and on heating elements, which reduces the efficiency of the system.
Together with the poor performance of detergents and rinse agents when using hard water compared with soft water, it makes water treatment a necessity. It's worth noting that the cost of detergents and rinse agents over a five- to seven-year period can easily amount to the original price of the dishwasher.
To obtain good results, you have to use clean water, so it's worth looking at machines with an effective filtration and wash system incorporating antiblocking jets, as these will on average consume 30% less water while significantly improving the quality of the wash. This will save on the energy to heat the water as well as providing considerable savings on both detergents and rinse agents. The higher throughputs provided by incorporating the improved wash will also help to minimise labour costs.
When considering a pass-through, single-rack machine, it's worth considering a fully enclosed insulated hood as this offers potential savings of up to 3kW. The hood should remain enclosed on all four sides when lifted to prevent steam venting on to the back wall and ceiling. This means that no ventilation canopy is required, but the area will require 30 air changes per hour.
Drain heat recovery is normally found on pass-through single-rack machines, when fresh rinse water is heated from 15°C to 45°C using waste heat from the machine drain water. The rinse water is drained from the machine through a pipe enclosed within the water inlet pipe and heat from the rinse drain pipe is transferred to the incoming cold water. This provides savings on average
of between 4kW and 6kW.
Heat exchangers are usually found on rack conveyor and flight machines and comprise a system using cooling coils, where steam is drawn efficiently from the wash chamber. The heat recovered through a contraflow principle is used to heat the fresh water intake up to 50°C, saving about 9kW.
A heat-recovery system based on heat pump technology gives three advantages: no direct connection is required to the ventilation system, the system recovers up to 59% of the energy used by the machine, and it improves the working environment. The cool air leaving the outlet is between 13°C and 19°C can be passed back into the room.
Source: David Clarke is a professional member of the Foodservice Consultants Society International UK and a committee member of the Catering for a Sustainable Future Group
- Cleveland Biotech 01642 606606
- Hobart UK 0700 2101101
- Meiko UK 01753 215120
- Miele Professional 08453 303618
- Winterhalter 01908 359000
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