Energy efficiency is a growing concern for all businesses and farming is no exception. More end users are trying to reduce the carbon footprint of their products, and inevitably that focus comes back to the farmgate. Pepsico – the company behind Walkers crisps – recently issued best practice guidelines to its potato growers on cutting carbon and water use, while Arla Foods will roll out a voluntary carbon reduction programme for its milk suppliers this spring.
Farmers may not necessarily receive higher prices for being “greener”, but there are some potentially big financial savings from relatively simple improvements, says former Farmer Focus writer turned consultant, Patrick Godwin.
As part of his work with the Sherborne branch of the Farm Consultancy Group in Dorset, he undertakes farm energy and resource efficiency audits as part of the Southwest Regional Development Agency’s Agricultural Resource Management (SWARM) initiative.
SWARM offers farmers in the southwest free advice and possible grant funding in two key areas. Soils for Profit (S4P) covers nutrient management, while Resource Efficiency for Farmers (R4F) focuses on improving energy efficiency and identifying opportunities for renewable energy generation.
The following information is based on an R4F energy audit at Trent Manor Farm in Dorset. Figures are specific to this farm, but the principles of the audit can be applied elsewhere.
Trent Manor is a tenanted 146-cow dairy farm in the village of Trent, near Sherborne. Total farm size is 181ha of sandy clay loam soils, comprising 92ha grazing/silage, plus 18ha maize and 71ha rented out on arable contract.
The herd is housed from October to March on straw-bedded cubicles and is currently moving from all-year-round to autumn calving. Milk yields average 7,600 litres a cow a year and there are 80 youngstock. Milk is sold to Barbers and is collected every day.
The farm is not in a Nitrate Vulnerable Zone and is part of the Entry Level Stewardship scheme.
Cooling milk is one of the most energy-intensive operations on a dairy farm. Trent Manor currently uses a plate cooler for pre-cooling the milk, then an ice bank bulk tank. Mr Godwin suggests installing a Direct Expansion (DX) tank could cut total energy use by 15%, as DX tanks run the cooling system only when milk is added, while ice bank tanks run for longer to build up the ice layer.
However, upgrading the bulk tank is a major task that could cost £10-12,000, so it may be more appropriate to focus on maximising efficiency of the existing system, he says. “You’ve got to look a long way forward to justify putting a new tank in while the old one works.” Also, ice bank tanks do offer some advantages over DX systems, he says. “Compressors are running longer than a DX system, but at least you can use off-peak electricity to build up the ice bank.”
Compressors and pumps
Any compressor condensers, such as those for the ice bank tank, should be regularly cleaned and positioned so they draw cool, clean air from outside, keeping fins dirt and dust-free. “It’s a bit like looking after the radiator in a car,” says Mr Godwin. “Ideally they should be on the north side of the building, drawing the maximum volume of clean air. But relocating them can be expensive and it may be better to incorporate this with other major works as required.”
There are opportunities to recover heat generated from condensers, especially on ice bank tanks. This recovered heat can significantly cut water heating costs elsewhere.
For example, if heating a full tank of water from 10C to 90C costs £1.34 a day or £490 a year (at night rates), using heat recovery means water only needs to be heated from 60C to 90C, costing 50p a day or £182 a year – an annual saving of £308. Such systems typically cost about £2,500, which gives a reasonable payback period, Mr Godwin says.
Vacuum pumps are another area to look at. Trent Manor’s existing pump produces a constant vacuum, drawing 3.5kWh. It runs seven hours a day, costing £2.19 a day or £800 a year. Installing a variable-rate vacuum pump for around £3,000 could save 40% or £320 a year – payback of less than 10 years, he says.
Heating water for parlour cleaning is another energy-intensive task, so switching to cheaper night-rate electricity and ensuring equipment is well maintained could save money, says Mr Godwin. He reckons about 10kW of electricity is needed to heat 20 gallons of water from 12C to 90C, costing about 90p a day on peak-rate electricity, but only 57p on off-peak tariffs. Using timer switches to heat water at night could therefore save the farm £120 a year.
Some farms may be able to switch to one hot wash of milking equipment a day rather than two, he says.
Like many farms, Trent Manor uses bore hole water, which can be very hard, resulting in scale build-up on heating elements and less efficient electricity use. In such cases it may be worth installing a water softener, he adds.
The water heater and all exposed pipework – hot and cold – in the dairy and pump house should be insulated. Refrigerant pipework to and from the compressors should also be lagged.
“The amount of energy needed to heat a tank of water can be quite frightening and farmers often don’t realise how much energy is lost by not insulating pipes,” says Mr Godwin. “Equally, if you’ve used energy cooling water, cold water pipes need to be lagged to keep the water cool.”
Potential savings from lighting are relatively small, but it is still worth looking at, says Mr Godwin. Generally strip lights are best for longer periods of all-round lighting, such as in the parlour, as they are relatively cheap to run and provide decent illumination.
Low-intensity sodium lights take longer to warm up, but are cheap to run and more appropriate in livestock sheds. Higher-intensity halogen lights on motion sensors can be fitted outside in the yard if needed.
Know what you use
One of the simplest things anyone can do is to make sure they regularly read water and electricity meters to track exactly how much is used, advises Mr Godwin. “It’s surprising how many still don’t do this enough.”
Those on monthly-billed accounts should read meters weekly and quarterly-billed accounts should be read monthly, he suggests. “Keep a note of all readings and note anomalies. Certainly don’t pay on estimated bills.”
He also advises farmers to make sure they are on a competitive electricity tariff and watch out for “tariff creep”. “This situation occurs when the current agreement falls beyond its life and the supplier can suddenly increase the tariff to an assumed level. Check the contract and renew as appropriate – brokers or buying groups can be used to get a good deal.”
Working out the average electricity use per 100 litres of milk sold can provide a useful quick reference to see if efficiency improvements are needed, he says. In the case of Trent Manor, total annual electricity use is 46,480 units, which divided by total milk production of just over 1.1m litres, equates to 4.19kWh/100 litres milk sold (see table). Efficient systems may be nearer 3.5kWh/100 litres, while the worst could be up nearer 9kWh/100 litres, he says.