Go green with red

One of the solutions to our agricultural greenhouse gas emissions problems could already be here and it doesn’t require any genetic modification or breakthrough vaccines. I’m not talking about culling a significant portion of the country’s 10-million-strong dairy cow and beef cattle herd, though I am a proponent of the late Sir Paul Callaghan’s call to ‘‘get off the grass’’.

Kiwi scientists have known for a long time that feeding red seaweed, (Asparagopsis taxiformis) to cows can lead to them burping out much less methane gas. Methane is a potent greenhouse gas that can trap heat up to 28 times as effectively as carbon dioxide, even if it doesn’t hang around in the atmosphere for as long.

Nasa estimates that nearly a quarter of the climate change measured last century was from methane emissions, which can emerge naturally from wetlands, ponds and lakes, from oil, gas and coal extraction and intensive agriculture, which accounts for around 20 per cent of global methane emissions. A study published last week in the journal PLoS One adds to the evidence base for red seaweed as a means of lowering cow emissions. Scientists at the University of California fed varying quantities of red seaweed to beef cattle mixed in with hay, grain and corn.

Over 21 weeks, the researchers measured the methane, carbon dioxide and hydrogen emissions from the Angus-Hereford bullocks. They found that the red seaweed supplement reduced methane emissions by between 45 and

68 per cent. That gels with the results of previous studies, including ones involving dairy cows. The best results were achieved with a high red seaweed, low forage diet, where methane was reduced by up to 80 per cent. Forage is plantbased material, like the grass most of our cows rely on for sustenance. A high seaweed diet amounted to just

0.5 per cent of the feed the bullocks consumed.

The researchers claim the study is the first to show sustained reductions in greenhouse emissions from cattle due to feeding them red seaweed. They also found that the bullocks grew at the normal rate while eating less food. By grading the beef and tastetesting it with consumers, they found no difference in quality or preference compared to cattle fed their usual diet.

It’s another promising result and one that should bolster local efforts to use red seaweed as a feed supplement. But it isn’t an instant solution. Red seaweed grows in abundance around New Zealand, but we can’t just harvest red seaweed in the wild. Taking the quantities required to make a difference, we’d quickly deplete the ocean of it, potentially causing all sorts of carnage for marine ecosystems in the process.

We need to figure out how to grow it in large quantities, sustainably. Our world-class aquaculture industry can play a role there and gear up to serve our cows a seaweed diet.

Red seaweed supplement reduced methane emissions by between 45 and 68 per cent.