Is cow manure the answer to European farming’s diesel problem, and what do chickens and supermodels have in common?

How much diesel does farming actually use?

European agriculture is spectacularly dependent on diesel. Tractors, combines, forage harvesters, irrigation pumps, grain dryers, if it moves, spins or rattles loudly in a field, it probably runs on red diesel.

Best estimates put on-farm agricultural diesel use at around 15 million tonnes per year across the EU. That excludes upstream inputs like fertiliser manufacture and downstream food transport; 15 million tons is just the fuel burned directly on farms.

Diesel contains about 11.9 MWh per tonne, so agriculture consumes roughly:

15 million tonnes × 11.9 MWh = ~180 TWh per year

That’s the target amount of energy we need.

How much biomethane from how many plants would we need?

Biomethane contains about 10 kWh per cubic metre. So, to replace 180 TWh of agricultural diesel, we’d need:

180 TWh ÷ 10 kWh/m³ = 18 billion m³ of biomethane per year

That’s a big number, but not an absurd one. Europe currently produces around 7 billion m³, so we’re talking about a 2.5× scale-up — not a moonshot, more a stiff climb.

A large modern biomethane plant might produce 40 million m³ per year, so:

18 billion ÷ 40 million ≈ 450 plants, so 18 billion m³ and 450 plants are our key numbers.

The obvious next question is whether Europe has enough feedstock to support them. Which brings us neatly to manure.

Cows first (because they always go first)

Europe has around 85 million cows. Each produces roughly 65 kg of manure per day, or 23 tonnes per year. That’s a lot of poo.

A tonne of cow manure yields around 13–16 m³ of biomethane, so assuming 14 m³/t as a mid-point, we get

322 m³ x 85 million equals 27 billion m³of biomethane, which is all we need.

The snag, of course, is collection. Manure is only easily captured when animals are housed, and cows don’t live in sheds all year. If we conservatively assume we can collect one-third of available manure, cows could still deliver 9 billion m³of biomethane, which is about ½ of what we need.  

What about chickens?

Europe has around 1.8 billion chickens, which equates to just over four chickens per European. If chickens could vote, European politics would look very different.

Chickens are a bit like supermodels. They don’t want bloated stomachs because they still harbour delusions of flight and don’t want to feel weighed down by food (the chickens, not the supermodels). As a result, they extract less energy from what they eat and quickly pass the rest through. Which means their manure is still full of energy. (This probably applies to both)

Each chicken produces about 50 kg of manure per year, yielding roughly 2.75 m³ of biomethane per chicken per year. Individually unimpressive. Collectively not.

So, we have a three-part problem: many more chickens than cows, less manure per bird, but higher energy content. Using the same conservative one-third collection assumption as for cows, European chickens could contribute 1.6 billion m³.

NB: “Chickens with delusions of flying” would be an excellent name for an indie band.

Finally, the pigs

Europe has about 132 million pigs, each producing around 7 kg of manure per day. Pig manure has a slightly higher gas yield than cow manure, thanks to pigs having a less efficient digestive system. They don’t dream of flying, but they have only one stomach instead of four.

Europe has about 132 million pigs, each producing roughly 2.5 tonnes of manure per year (or 7 kg/day), with a biomethane yield around 20 m³/t, so 50 m³ per pig per year. Applying a collection of one-third and following the same maths, you get 132 million x 50m³ x 1/3^rd equals 2.2 billion m³ per year.

Putting the numbers together

After all that arithmetic, here’s the payoff:

• Cows: 9 billion m³
• Chickens: 1.6 billion m³
• Pigs: 2.2 billion m³

Total: ~12.8 billion m³ of biomethane

That’s 71% give or take of the 18 billion m³ required to replace all agricultural diesel use in Europe. We could probably source the remaining by increasing the amount of poo collected from 1/3^rd to more like 40% or 50%.

What would that actually achieve?

If we could get to 18 billion m³, we could replace 15 million tonnes of diesel and avoid roughly:15 million × 3.2 tCO₂ = ~48 million tonnes of CO₂ per year.

And that’s before you account for the fact that manure-based biomethane often delivers net-negative emissions, because collecting manure and putting it into AD plants avoids methane that would otherwise leak into the atmosphere.

In climate terms, this is one of the highest-leverage interventions available to European agriculture. It’s obviously not as sexy as wind or solar, but in practical day-to-day terms, it is a very effective policy with an almost instantaneous payback in terms of avoided CO2.

Making it happen (the awkward bit)

The maths works. The physics works. Three challenges remain.

1. Animal housing

Collecting manure means housing animals — more sheds, more covered yards, more slurry management. In my experience of visiting farms, the cows, chickens and pigs don’t seem overly bothered about being kept in sheds out of the rain. City people, however, are.

Try saying this at a dinner party:
“I’ve been thinking we need to house more livestock to decarbonise European agriculture.”

Suddenly, it’s not Animal Farm, it’s 1984. Vegans get shouty. Hurtful things get said about foie gras.  Your partner reminds you, once again, Michael, please don’t talk about your job at parties.

2. Plant investment

Roughly 450 biomethane plants at perhaps €40–50 million each, requiring between €20–25 billion of capital investment – that sounds large until you remember that Europe spends maybe EUR 400 billion annually on fossil fuel imports.  

Infrastructure investors, meanwhile, have developed a remarkable fondness for biomethane, so this may be the least problematic hurdle.

3. Machinery adoption

Agriculture replaces machinery slowly. Tractors last decades, not years. But gas-ready engines already exist for heavy-duty applications, and many stationary uses, such as grain drying, irrigation pumping, and on-farm CHP, can switch far faster than a mobile kit.

This is less a chicken-and-egg problem than a tractor-and-tank one. If fuel is available, equipment follows. If it isn’t, it won’t.

Conclusion

It is technically feasible to replace all agricultural diesel use in Europe with biomethane produced largely from livestock manure. The feedstock exists. The technology exists. The emissions savings are enormous.

The main resistance isn’t engineering -it’s aesthetics, politics, and dinner-party acceptability. The main pushback is animal housing, so you can collect the manure, but we already do much of this; we just don’t mention it to people who live in cities and go to dinner parties.

My LEGO tractor will never plough a field and will spend its retirement gathering dust in my home office. But in the real world, its biomethane-powered cousin could quietly remove 15 million tonnes of CO₂ from European agriculture, powered, improbably, by cows, chickens, pigs, and a great deal of poo.