Karen Trebilcock

It seems the politically correct thing to do is to declare yourself carbon neutral. Marks and Spencer in the United Kingdom did it years ago, Copenhagen Airport has done it this year and Danone’s milk plant near Balclutha plan to do it by 2021.

So can your farm also declare itself to be carbon neutral? It would be a nice sign to put up at the farm gate wouldn’t it?

To be carbon neutral, also known as having a net zero carbon footprint, your farm’s total emissions expressed as CO2 equivalents must be neutral or zero.

This includes all the greenhouse gasses (GHGs) not just ones with a C in them, so CH4 (methane), CO2 (carbon dioxide) and N2O (nitrous oxide) are converted to CO2 equivalents based on their warming potential.

Farms produce carbon (C) mainly through livestock. Sheep, cattle and deer belch and fart methane, your tractor and motorbikes emit carbon dioxide in the exhaust fumes and the nitrogen cycle provides lots of nitrous oxide.

But your grass, trees and anything else that grows on your farm absorbs CO2 through photosynthesis – that amazing chemical process that lets plants use sunlight to grow. The carbon is taken from the air and is used to build more plant matter.

Grass also releases carbon out of its root tips to fungi in the soil and when grass dies, or the fungi dies, it’s often eaten by a microbe or a worm and the carbon is stabilised in the soil meaning the organic matter in your paddocks is actually one huge carbon sink.

So how much carbon does a hectare of pasture and the soil underneath it capture?

Unfortunately, the answer is, it doesn’t matter.

Farms are not making or taking carbon out of the environment because of what is known as the carbon cycle. Carbon is absorbed by plants which are eaten by cows which release it back into the atmosphere to be absorbed by plants again.

What farms do is change the form of carbon from carbon dioxide to methane.

And methane is a far nastier global warming gas than carbon dioxide as it absorbs more heat from the sun’s rays. And although it is mostly short-lived, breaking down in decades (CO2 stays around for thousands of years), we’re replacing it all the time so it’s not good.

And permanent pasture, just like mature trees, is always absorbing the same amount of carbon from the atmosphere. What the world needs is more of it doing it.

And don’t think that by decreasing your stocking rate you are decreasing your carbon footprint. If the same amount of grass is being eaten there will be little difference in the amount of methane your cows are producing.

So if the carbon stores in our grasses and soils can’t be used to offset methane produced, what can we do to be carbon neutral?

Well, there is always a needy country to help.

Copenhagen Airport is carbon neutral partly because it has teamed up with international NGO Nexus for Development to provide energy-efficient stoves in Laos.

In much of the Asian country, meals are cooked on open fires with the wood sourced from their native forests. The new stoves use 22% less firewood or charcoal and so far 270,000 have been distributed and thousands of hectares of forests therefore have been saved.

Or, if you’re not keen on that you could follow the example of British retail chain Marks and Spencer which does it by owning a portfolio of carbon credits which include reforestation projects.

Reforestation projects? We can do those ourselves!

Current thinking, and this seem to be changing all the time as scientists try to figure it out, is the average forest captures about 26.7 tonnes of CO2 equivalent per year and the average dairy farm produces about 11.25t of CO2 equivalent per year so, very roughly, for every hectare we farm as dairy, we need nearly half a hectare of trees to offset it.

And if those trees are in a nice forestry block, not strung out along a waterway or your tanker track, you might be eligible for carbon credits as well under New Zealand’s Emissions Trading Scheme.

If you were farming in parts of the United States you could get carbon credits just with grass.

To stop the carbon emissions from your motorbike, tractor and ute you could soon be able to go electric.

With no hydraulics, the experts are saying electric tractors will be more powerful, more accurate (in precision sowing and other applications) and they won’t wear out as quickly.

Then there is the power to run your dairy.

Here you could follow what Danone near Balclutha is doing to declare itself carbon neutral. It is changing its boiler to run on biomass instead of gas. Biomass is the world’s hot word for energy created from everything from wood to cereals to rubbish.

In Scotland, cereal silage pits as big as rugby fields feed biomass plants which supply gas to thousands of homes. In Denmark they create electricity and hot water by burning rubbish, importing it from other European countries because the Danes don’t make enough rubbish themselves.

Danone is planning to burn forest waste from Otago’s commercial forests – in other words the branches from the trees which are made into logs.

Burning them produces CO2 but it is carbon neutral as the smoke is offset by the CO2 absorbed in the original growth of the forest or will be captured when the forest is replanted.

And if that doesn’t make any sense don’t worry about it. Remember we’re living in the world of the climate emergency and politics is more important than reality.

If that wood waste was left lying in the forest it would still retain its carbon. As it decomposes it would give off CO2 slowly, but not like burning it.

Growing cereals to produce gas to heat homes in Scotland just doesn’t make sense either, especially when the world goes hungry. And burning rubbish? Surely some of it could be recycled?

At least Danone is fronting up with the $30 million for the biomass boiler near Balclutha itself. In the Netherlands it would probably get a European Union subsidy to do it.

We also could run a wood chip boiler onfarm to heat the hot water for the dairy and use the methane coming from the silage pit and the effluent pond to generate electricity to run the milking machines.

Except most dairies in NZ are powered by electricity from the national grid which is already close to carbon neutral – mostly created through hydro and wind. So no carbon savings there.

Maybe stick with just planting a few trees in the gully which has never grown much grass anyway.

Because forgetting the politics and the hype, becoming carbon neutral even in our small corner of the world is important.

The carbon in the atmosphere is reaching new record levels, reaching 415 parts per million (ppm) this year and increasing rapidly – 100 years ago it was steady at about 275ppm. Some projections see it reaching 550ppm or more by 2050.

Carbon traps heat – directly responsible for global warming. And as carbon in the atmosphere rises, more of it is absorbed by the oceans making them more acidic and less able to support current marine life.

Whether we are in Europe or NZ, it is going to affect us and doing our bit, however small, can only help.

More? go to www.dairynz.co.nz/