Mon 13 Jan 2020

Seaweed: the agricultural superfood in the fight to reduce carbon emissions?

I grew up in a fishing village in the North East of Scotland. My father was a trawlerman and all his side of the family were from the Moray Firth or from the Northern Isles. 

From a very early age, I was made aware of the importance of seaweed. My grandmother swore that it was the seaweed raked through her vegetable beds that made the kale and tatties grow strong. 

An abundance of seaweed was a huge bonus to farmers, from Highland crofts to lowland farms. Interesting, in the 1960s, a proposed seaweed processing plant in East Lothian had to be shelved as it would have used up all the seaweed the farmers needed. 

There is a record of a historic civil court case which illustrates the importance - an action brought against one Thomas Maule by two complainants for (amongst other things):

“Stoopping of Thame fra taking of wair of the sey to lay apone the sadis landis for the gudeing thairof as was usit and wont in tymes bigane”

“Stopping [the complainants] from taking seaweed from the sea, preventing [the complainants] using it as a fertiliser as has been the past custom”

‘Acts of the Lords of Council in Civic Causes II’ (1496 - 1501) p. 350 - NMS.

My grandfather provided regular reminders that it was seaweed that got the islanders through the lean times as an abundant and nutritious food source - I can still hear the refrain of "If you're still hungry, bain da beach wi ye" from him. The islanders cultivated it, such was its importance.

It is not just an excellent food source for humans either, it has been used for years as animal fodder. There are many accounts of early farmers having noted deer and cattle happily grazing on seaweed from the foreshore. It used to be collected by Hebridean crofters and farmers direct form the beach as fodder for cows throughout the winter months.

My favourite example has always been the North Ronaldsay Sheep  - as an aside, there is an excellent article about them and the new warden, Sian Tarrant on the BBC website.

However studies carried out in Australia and New Zealand have shown that algavory (the consumption of seaweed) may actually reduce greenhouse gas emissions from livestock.

Australia's main science agency, CSIRO, co-ordinated the research, which looked into the types of microbes which line the stomachs of ruminating animals - such as sheep and cattle. It is these bacteria which break down the fibre in the animals food into molecules, which they can then absorb.

One molecule that is not capable of being absorbed, however, is methane, which the animals "evacuate" into the atmosphere. This causes us a bit of a problem.

Methane is a greenhouse gas with a warming effect 28 times as powerful as carbon dioxide’s and given recent estimates that 60% of all mammals on the planet are livestock (a figure rising around 2.4% year on year) the volume of methane being released is huge. To put it into perspective, a cow has around about the same greenhouse effect as a car, cutting the emissions of even a portion of the world’s 1.5bn cattle would be massively beneficial.

The most recent study, published in October 2019, showed that dairy cows eating a diet containing a small element (1% of their overall feed) of a specific type of seaweed (Asparagopsis) produced a third of the volume of methane produced by their non-seaweed eating compatriots.

Whether or not this takes off as a concept and makes its way into everyday feedstock, remains to be seen. However given the Climate Emergency and the push on farmers to reduce their overall carbon emissions it would seem a very straightforward way to make a difference. As an aside, it has the potential to add seaweed as a crop to be cultivated and harvested on a commercial scale. I think that notion would have made my grandparents very happy indeed.

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