Why pig housing upgrades could unlock major efficiency gains

A fresh look at pig housing will be essential if producers are to meet the environmental, welfare and labour pressures increasingly facing the sector, according to a new report.

Rethinking Farm Buildings, published in May by The Royal Agricultural Society of England (Rase), raises the point that livestock housing will play a far greater role in the future sustainability and profitability of UK farming than has perhaps been traditionally recognised.

See also: Farmer Focus: Westerwolds crop of choice on pig ground

And this is particularly so for pig systems, where heating, ventilation and slurry management all contribute significantly to energy use and harmful emissions.

Findings were presented at the recent Pig & Poultry Fair, held at the NEC, Birmingham.

Experts warned that many pig units, which may once have been energy efficient, are now wasting energy, thanks to wear and tear of ageing buildings.

Zanita Markham, AHDB’s sustainability and engagement manager, said that housing remains a major challenge for overall pig emissions.

The levy board’s own figures suggest it accounts for about 80% of emissions linked to pig farms.

Scope for upgrades and renewables

Analysis from 115 farms found heating, lighting and ventilation remain the largest on-farm energy demands within pig systems, particularly in farrowing and weaner accommodation where controlled environments are essential.

On a typical 500-sow unit, electricity consumption averaged 278kWh/t of pigmeat produced, while heat use stood at about 75kWh/t.

And only a relatively small proportion of that currently comes from renewable sources.

For Zanita, that highlights clear scope for improvement.

“It shows where the opportunities are – both to reduce emissions and improve efficiency,” she said.

© Tim Scrivener

Practical changes

The report highlighted several key practical areas for farmers to consider:

• Heating This remains one of the biggest energy demands within pig units, particularly in nursery accommodation. A “fabric-first” approach – improving insulation in roofs, walls and floors – alongside reducing air leaks, can significantly cut fuel use while helping maintain more stable conditions for young pigs. There is increasing interest in lower-carbon heating systems, including heat pumps and recovered heat.
• Ventilation Poorly calibrated fans, damaged sensors and inefficient airflow can all drive unnecessary electricity consumption, while also creating inconsistent conditions within buildings. Fitting variable speed systems and electronically commutated (EC) fans can help improve efficiency, with industry figures suggesting electricity use for ventilation can be reduced by more than 50% in some buildings (see table, below).
• Environmental control Modern environmental control systems can allow producers to manage temperature, airflow, humidity and ammonia levels more precisely. Better control not only reduces wasted energy but can also improve pig performance and general housing conditions.
• Heat recovery This technology presents one of the most significant opportunities to reduce heating demand within pig buildings. The NFU Energy technology review for AHDB Pork suggests some ventilation heat-recovery systems can recover up to 77kW of heat from just 1kW of pumping energy (although this relates to specific exchanger-based systems). Where heat pumps are integrated, recovered low-grade heat can then be upgraded to more usable temperatures of about 45C, with reported coefficients of performance of about 4 (where one unit of electricity produces four units of heat).
• Slurry cooling This offers dual environmental benefits by reducing both methane and ammonia emissions, while also generating reusable low-grade heat. Cooling slurry below 15C has been shown to reduce methane and ammonia emissions by about 30%, particularly during warmer periods.
• Renewable energy Solar photovoltaics (PV) continue to be viewed as one of the most practical renewable technologies for pig units. Falling installation costs mean solar systems can generate electricity at about 3-4p/kWh under favourable conditions, with payback periods of six to seven years when the electricity is used on-site.
• Water efficiency Water losses remain an overlooked issue on many units, with even relatively small leaks substantially increasing both water use and slurry volumes. AHDB figures cited in the report suggest a leak of just 1 litre/min wastes the same amount of water as adding about 22.5 sows to the herd.

Refit or rebuild?

Given the need for these improvements, would producers be better off retrofitting existing buildings or investing in complete rebuilds?

NFU Energy’s Roger Stones said the first step is understanding where energy is being lost.

He pointed out that uncontrolled airflow and outdated ventilation systems are places where energy – and money – are frequently being wasted.

He also recommended asking three key questions to determine the best approach:

• Can I stop the waste?
• Can I control the environment?
• Can I get the value back?

If the answer is “yes”, this signals an opportunity to retrofit. Answering “no” means there is likely to be a bigger benefit from rebuilding.

“[Remember] the best shed equals the best performance per square metre, but this doesn’t always mean the newest shed,” he said.

Roger added that, in many cases, relatively simple upgrades could deliver significant improvements.

He said variable speed drives on farms and pumps, improved insulation and better environmental monitoring are examples of good retrofit options.

For those considering investing in completely new buildings, the thinking and design should be centred on the long-term view, Zanita advised.

“You don’t have to commit to every innovation straight away. But if you think you may want it in future, put the infrastructure in while you’re building.”

See the full Rethinking Farm Buildings report (opens as PDF).