Friday 10 September 2021A Greener Future for Pig Systems

The effects of climate change are upon us, and we know we must work hard and fast to tackle their causes. Agriculture – and livestock farming in particular – is regularly portrayed as a villain in the global warming story. But, of course, it’s not as simple as that. So, what can pig farming do to make tangible improvements, and is there hope for the future?

When we think about reducing the environmental impact of agriculture, we usually come at the puzzle exclusively from the perspective of carbon reduction. In reality, carbon dioxide (CO²) isn’t the only gas that’s implicated in climate change. But we need a common denominator to measure the Global Warming Potential (GWP) of other gases, so carbon equivalents (CO²e) are used.

Methane and nitrous oxide are agriculture’s most emitted gases. Scientists have assessed their Global Warming Potential against carbon, giving methane a rating of 25 and nitrous oxide a rating of 298. Simply put, that means 1 kg of methane released into the atmosphere is the equivalent of 25 kg of carbon. When you think about it that way, it’s clear the pig industry needs to focus on reducing methane and nitrous oxide, not just on cutting carbon.

How we manage these gases may seem like a challenge, but it’s also an area where potential opportunity lies. And there are two very good places to start – feed and muck.

Successful systems are built on feed

In pig systems, feed accounts for around 60% of carbon (CO²e) use. That means there’s a huge opportunity to reduce carbon (CO²e) just by rethinking what the national herd eats. Unlike changing your power source (which comes with installation costs), changing your ration to one with a lighter carbon footprint needn’t carry any additional cost at all.

Of course, farmers know that nutrition efficiency is key – the more meat produced per tonne of feed means a healthy bottom line and reduced carbon usage. When formulating feeds, we should be taking a holistic approach and making feed choices based on a combination of factors. These include nutritional value and effectiveness, price and profitability, as well as carbon cost. If factoring carbon into the equation became standard practice, it’s not outlandish to foresee it being incentivised by government as part of the public-funds-for-public-good philosophy. This is already done for green energy, with 20-year minimum price guarantees. And in the same way as a higher price is accepted by the consumer for high-welfare meat, the pig industry could take the lead and levy a premium on low-carbon meat.

But what feeds are classed as low carbon? Generally, they’re feeds that require low land use or minimal energy inputs for their production. Co-product feeds tick the box for low land use, and they’re just as nutritious as cereal-based alternatives. Because they piggyback off human food production systems, the land they’re produced on is technically being used to grow human food, not animal food. There are internationally accepted ways of calculating carbon share for foodstuffs, and co-products are often assigned no carbon responsibility at all, as the primary product carries it all. All of which means you can wipe out a good chunk of your carbon use with a simple switch of ration.    

As an example of how co-products can reduce land use, take a system using 533Ha to grow the 4000 tonnes of feed needed to feed 500 sows and grow their progeny to bacon weight. If it replaces 30% of the feed with co-products, then 1200 tonnes less crop is required and 160Ha of land is freed up. That area could be planted with trees (if there were government incentives to do so) but would most likely be used to grow grain to sell, increasing farm productivity and further reducing the carbon share.

Where there’s muck there’s gas

Manure management is vital to greenhouse gas reduction in agriculture. Amazingly, we manage muck in broadly the same way today as we did thousands of years ago when farming was first formalized. Now’s the time to use scientific advances to unlock the potential held within manure and do more than just spread it on our fields.

Slurry is abundant in pig systems. It’s 90% water, which can be separated off, leaving a concentrate that makes an immensely useful product. The key to that usefulness is the hydrogen found in ammonia (NH³), methane (CH⁴) and urea (NH⁴). Scientists calculate that if these hydrogen stores could be exploited as an alternative fuel, we could offset the combined emissions of both the UK agricultural and transport sectors, which amount to 28% of the UK’s total.

The possible wins from this energy source are both commercial and environmental. The methane in the pig manure can be used as an energy source to evaporate out the liquid, leaving hydrogen-rich urea as a co-product. This can then have its hydrogen extracted, before it’s made into a fertilizer pellet for more accurate field spreading. Vegetables and grain need fertilizer, and the more efficient we can be in using the manure from livestock systems, the less reliant we’ll be on unsustainable (and expensive) chemical alternatives.

It’s also increasingly well known that pig manure can be fermented – a bit like biogas – to make the nutrients break down and become about 30% more available to plants. That means you need to put 30% less on the land to get the same crop yield. It also means the plant removes more from the soil and there’s less residual build-up. With modern technology, you don’t need an expensive biogas plant, an engine or a grid connection – just a small fermentation vessel.

Ammonia from urine is getting a lot of scientific attention, with new techniques using wind power being developed to split apart the hydrogen and nitrogen, leaving the hydrogen to be exploited as fuel. Hydrogen-powered vehicles, from cars and tractors to aeroplanes, aren’t the stuff of science fiction. They’re in development, currently running off hydrogen reaped from fossil sources. The logical next step is to fuel them with the hydrogen that’s a co-product from our livestock industry. Pig power? It’s something to look forward to. 

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