Feeding asparagopsis armata to cattle reduces methane by up to 99% when fed at 2% of total feed (by dry matter) and by up to 80% when fed at 0.6% of dry matter. It’s invasive in the UK, partly due to it being farmed in the Irish Sea to make wrinkle cream. As part of our Culm Restoration project, we’re going to get a house cow, so we want some asparagopsis to feed to the cow. We can collect it from the beach, but we’re also going to try to grow some.
This is a work in progress and the methodology of the experiment may well change as we proceed. If you have any information that you feel would be useful, please do contact us to let us know.
Asparagopsis Armata is a red macroalgae which reduces methane by 99% when fed to cattle at 2% and by 80% when fed at 0.6% of their feed as dry matter(DM).
Asparagopsis armata grows fastest at temperatures between 15°c and 24°c. It is damaged by temperatures of over 29°c.
There are 2 stages to Asparagopsis in British waters. The 2 stages were previously thought to be different species, so the stage that exists in winter has its own name: Falkenbergia rufolanosa. During this stage it is a small fluffy looking macroalgae. It is during the summer, that it grows the majority of its mass. The change between stages of growth are based on day length.
We intend to grow the seaweed in a 1M³ Individual Bulk Container (IBC) with translucent sides in a polytunnel. The IBC will be at one end of the polytunnel, allowing us to open the doors of the polytunnel to cool it down to prevent it overheating. It may need to be shaded with wet cloths if there is a heatwave. Asparagopsis uses the green part of the spectrum for photosynthesis. This makes it a good addition to a polytunnel as it uses the light that is reflected by and filtered through green vegetation and will do well in the shade of green plants. To increase the length of the summer stage of its growth, we will use a green led light to increase day-length. The other energy inputs are an air pump to aerate the tank and a water pump to create water movement. This will be powered from a solar panel. We’re hoping to find a second hand panel to power the system. The 1,000 litre water container will have an added bonus of acting as thermal mass, decreasing temperature fluctuations within the polytunnel.
The top of the IBC will be cut out to create an open topped tank. We are currently looking at the “tumble culture” method of seaweed cultivation. This is a method where the seaweed is tumbled around the tank using an air pump to create the movement. This method exposes all parts of the seaweed to the light, whilst not leaving any of it in direct light for too long.
We are assuming (partly for ease of calculations) that our cow with a calf will require 10kg of DM per day. We therefore require between 21.9kg (@0.6% DM) and 73kg (@2% DM) of seaweed by dry matter per year. It’s hard to find figures for tank grown seaweed production per M³, but anecdotal evidence shows that 140kg (fresh weight) per m3 is possible. Water content of asparagopsis armata is around 70%. This therefore equates to 42kg DM. In practice, if we could get half of this yield so required 2M³ to grow 42kg, we’d be quite happy.