The climate-friendly cow
Wageningen Climate Solutions
Photo: Wageningen University & Research, Eddy Teenstra
BY Albert Sikkema - September 2019
Dutch cows produce a lot of milk but they also produce a lot of methane. The impact of cows on the environment could be halved through targeted breeding, changes to the feed and the separation of manure, says Wageningen researcher Theun Vellinga. But he warns that fancy technical solutions will not be enough. “The climate-friendly cow needs to be part of a broader picture.”
Cows are notorious for their contribution to greenhouse gases. When they burp, fart and poo, they release methane. And when manure is used in fields, it produces nitrous oxide. As a global average, the production of one kilo of milk involves emissions equivalent to 2400 grams of CO2. ‘CO2 equivalents’ are a way of comparing the impact of the greenhouse gases nitrous oxide and methane with carbon dioxide. The figure for the Netherlands, which has very efficient milk production, is much lower: 1150 grams of CO2 equivalents. But Dutch emissions also need to come down — to 1020 grams by 2030 — to satisfy the climate agreements. We can manage that easily, reckons Theun Vellinga, who specializes in agricultural systems, animal production systems and climate change. But what levers do we need to pull to get there?
Changing the type of feed can reduce methane production. Photo: Jeroen Bouman
When cows digest grass in the rumen, they release methane. If you feed a cow less grass and more maize, its methane production drops, says Vellinga. “You can reduce methane emissions considerably if you stuff a cow full of maize, but do you want that? The farmer then has to grow a lot of maize. To do that, grassland has to be converted into arable fields, with organic compounds in the soil evaporating into the air as a result. Maize cultivation can also be a blot on the landscape, and peatland meadows can’t be used to grow maize anyway. So you can only replace grass with maize to a certain extent.”
There are now also additives for feed that inhibit the production of methane in cows. “Lots of ingredients have been tried, including various herbs,” says Vellinga. “They had an effect on the ecosystem in the rumen for a while, but the effect was gone after a few weeks. However, adding nitrate has a lasting impact.” The experimental farm De Marke, part of Wageningen University & Research, has conducted tests with low concentrations of nitrate in animal feed. Adding this to a mixture of silage plus some maize led to a reduction of 30 to 40 per cent in methane emissions.
You can breed cows that produce less methane, says Vellinga. To do that, you need to find out how well cows can digest their feed. That varies from cow to cow, variation that cattle breeders can exploit. Researchers estimate that a targeted breeding programme could reduce methane production by one per cent per annum over the next few years. You could then cut methane emissions by 20 per cent in the space of 20 years.
Targeted breeding can help reduce the production of methane in cows. Photo: Jeroen Bouman
Theoretically you could increase Dutch cows’ milk yields further still, whereby they produce more milk per kilo of feed and therefore less methane per kilo of milk. But you need to be careful with that, says Vellinga. For years, Dutch cows have been bred mainly to maximize production, a strategy that has resulted in cows with low resistance and little meat on their bones. “We mustn’t repeat the mistake of focusing too much on one property of the cow. We want sturdy cows in our fields that don’t fall ill easily.”
In relation to this, Vellinga is a proponent of the dual-purpose cow, one that produces both milk and meat. Dual-purpose cows have slightly lower milk yields per cow, which does mean that more greenhouse gases are produced per kilo of milk. But you also end up producing more meat in the Netherlands, so you are not importing so much meat with a high ecological footprint. That in turn benefits the climate. All in all, dual-purpose cows do not help the climate a great deal but they do make for more robust cattle, thinks Vellinga.
Cows’ welfare is important. These special matrasses can help. Photo: Jeroen Bouman
The strong greenhouse gases nitrous oxide and methane are released when animal manure is stored. Farmers currently gather the manure and urine from the cows in slurry pits, where ammonia is generated, which is toxic to humans and animals at high concentrations. Storing manure and urine separately would reduce ammonia emissions by 75 per cent, says Vellinga. It might also cut greenhouse gas emissions too as the solid manure and the urine would no longer interact. “Further research is needed on that last point.”
Separating out the manure has other benefits on top of a potential reduction in greenhouse gases. It will help farmers apply precision fertilization because the urine mainly contains nitrogen and the solid manure consists mainly of phosphate.
The cows’ manure is examined frequently. Photo: Marije Kuipers
“This is a tricky one,” says Vellinga. “In theory you could reduce the impact cows have on the climate further by keeping them in hermetically sealed barns with equipment to safely remove the methane and nitrous oxide emissions. But such a hermetically sealed barn is expensive and it would mean keeping the cows indoors all the time.”
Many cows are currently kept in open barns with natural ventilation and lots of room for the cows to move around. The cows also spend part of the year in fields. Those circumstances limit the extent to which we can capture or prevent greenhouse gas emissions. But we value having cows in the fields as well. “There are some things you can’t control as a farmer,” says Vellinga, “but there is no cheaper way of removing grass from the land than a cow.”
Many cows are kept in open barns with natural ventilation. Photo: Jeroen Bouman
In short, it should be possible to halve climate emissions from cows in the next few years. Cattle farmers can achieve this reduction through a combination of changes to the feed, breeding and manure separation, argues Vellinga.
Note: don’t forget the full picture!
Dutch livestock farming is caught in the trap of optimization: how can we maximize production with as few inputs as possible and with minimum impact on the environment? Animal manure legislation is a key determining factor. The phosphate rules reward farmers for producing as much milk per kilo of phosphate as possible. Similarly, reducing phosphate excretion per kilo of milk gives livestock farmers scope for more milk and more cows.
We need to wean ourselves off this optimization approach, says Vellinga, because it comes at the expense of other aspects such as the landscape, biodiversity and animal welfare. “Dutch livestock farming makes full use of the phosphate quota but at the same time field birds and insects are disappearing.” The climate-friendly cow needs to be part of a broader picture. “We need to look for a kind of livestock farming that does justice to nature and the landscape, and we need closed cycles.”
DUTCH LIVESTOCK FARMING IS CAUGHT IN THE TRAP OF OPTIMIZATION
That broader picture should also encompass a business model for farmers, says the researcher. “We should pay farmers for their services to the landscape and ecosystem. That is possible for the climate-friendly cow too. You can set requirements for the reduction of greenhouse gases in livestock farming, identify appropriate measures and then reward farmers who implement those measures. The guiding principle is giving the cow room rather than getting the most out of the beast. It is not about one all-encompassing answer; you need to combine perspectives.”
For more information about how WUR is putting climate-smart livestock farming into practice, please visit our website.