After much speculation among farmers, Teagasc has moved to outline the “inventory carbon values” for Irish hedgerows and grasslands.
In an interview with Agriland, Teagasc’s gaseous emissions research officer, Gary Lanigan gave an overview of the current state of land use emissions in Ireland.
He explained: “The land use emissions are emissions associated with changing land use from crops to grass, grass to forestry, grass to wetland, grass to settlement, and are predominantly CO2 emissions.
“The Intergovernmental Panel on Climate Change (IPCC) recommended a number of years ago that land use emissions be treated as one sector, which is called Agriculture, Forestry, and Other Land Use (AFOLU), so, from 2030 the EU is going to treat them as a single sector.”
“The reason they’re not treated as a single sector at the moment is because the agricultural emissions and the land use emissions are reported in a different way.”
“So, the agricultural emissions, the energy emissions and all the rest of the non Land Use, Land-Use Change, and Forestry (LULUCF) emissions are reported on a gross-net basis. So that means all of the emissions are counted,” Lanigan explained.
However, Lanigan outlined: “Land-use change is different. It’s reported on what’s called a net-net basis.
“It’s reported relative to a baseline which means it is far more favorable for us [agriculture] because it doesn’t take into account all the emissions from the peatlands.
“However, the government, for the Climate Action Plan, is reporting land use on a gross-net basis,” he explained.
Teagasc figures – grassland
Commenting on the carbon values of grassland in Ireland, Lanigan said: “At the moment, grasslands on a gross-net basis are a source of about seven million tonnes of CO2 per year.
“That’s made up of two million tonnes of removals (of carbon sequestration) from our four million hectares of mineral grassland and in the inventories they’re assumed to be sequestering at the rate of half a tonne of CO2/ha per year.”
Despite this, Lanigan explained: “Our grasslands that are on peat soils (between 325,000ha and 350,000ha) are emitting at about 23t/CO2/ha.”
Lanigan said that Teagasc estimates peat soils in Ireland to be “emitting nine million tonnes (CO2) in total”.
Teagasc’s figures – hedgerows
In relation to hedgerows, Lanigan explained: “The best management to sequester carbon is to allow your hedges to grow up and out, so don’t keep them nicely clipped.”
“They’re [hedgerows] sequestering somewhere between 400-800kg of carbon per kilometre and we have got about 680,000km [of hedgerows].
“We estimate the amount of sequestration of all the hedgerows is somewhere in the region of about 300,000kg up to about one million tonnes.
“The best best guesstimate would be about 600,000 tones of carbon, ” Lanigan explained.
“If you cut a hedge, some of it goes into the soil and some of it goes into the atmosphere. Now, the rule of thumb is about 10% of it stays in the soil.”
He explained that Teagasc is currently carrying out extensive research on the “figures in the inventories” for the sequestration values of mineral soils and hedgerows, noting that the agricultural research body believes the sequestration values for hedges and grassland “is too low”.