New Zealand and its Green House Gas dilemma

By Brook Wright

New Zealand is unique among its global counterparts when it comes greenhouse gas (GHG) emissions. It’s carbon budget is dominated by the agricultural sector, which represents around 49% of gross emissions. According to the OECD, this is the highest ratio in the western world.

The key sources of these GHGs are nitrous oxide (N₂O) from soil bacteria and methane (CH₄) from sheep and cattle (ruminants). These gases are particularly troublesome because of their comparative impact, not because they are emitted in significantly large quantities. A single tonne of methane is roughly equivalent to the release of between 25-30 tonnes of CO₂. Nitrous Oxide, while being the lesser of the two evils is more than 300 times as potent.

The nature and origin of these gases makes cessation or mitigation rather tricky when compared to other sectors including manufacturing, energy and construction. Put it this way: it’s harder to alter the biochemistry of a cow, than it is to augment a well understood and sequenced industrial process.

This begs the question: What can be done to limit or reduce emissions in the agricultural sector? Well, there are currently two options for mitigating the carbon that ruminants/microbes emit. The first of these involves artificial selection, where cows can be sired by bulls that are known to have low carbon daughters. This relies on the assumption that the genes responsible for controlling gut flora are heritable and have no impact on other more desirable characteristics. In other words, you wouldn’t want a low carbon cow that produced no milk.

There appears to be a growing body of research that supports the notion that ruminant host genetics – the cow –  impacts microbial composition in the gut. The most important factor seems to be the ratio of bacteria to archaea (methanogens). Finding the right equilibrium may one day lead to clean fuel cows and farmers might be able to look through their next bull catalogue to find that carbon intensity has been added alongside other performance-based indices like BW, live weight and total production.

The second of these approaches involves manipulating the activity of the microbes themselves. Methods of inhibiting methanogens (methane producing bacteria) could include:

• The use of antibiotics;
• Promoting viruses/bacteriophages that target methanogen species (yet to be developed);
• Use of feed additives such as fats, oils and/or nitrate salts (already in trail);
• Vaccination against methanogens; and or
• Defaunation (physically getting rid of selected bacterium species).

It is likely that there ways of artificially altering the internal gut flora of ruminants to suppress the activity of methanogens. The Hunggate1000 project initiated by Ag-research is part of collaborative effort to sequence 1000 gut microbiota species and is certainly on its way of achieving its goal. This will paint a fantastic genetic picture of these microbes and provide much needed insights. It is hoped that through understanding the life history of these little guys we can hope to prevent or limit their bacterial colonies in the gut.

Seaweed is one of the up and coming solutions that could really deliver on limiting GHG emission in ruminants. Several in-vitro (that’s in the lab for the uninitiated) studies have already indicated that some red seaweed species can limit methane production in the gut by as much as 99%. The issue here seems to be lack of studies involving cows (in-vivo), and replication studies.

There are also concerns that this effect might be temporary. Only time will tell, but it seems to be a promising road to explore, considering that seaweed is highly palatable and nutritious.

AgriSea is one New Zealand’s leading businesses when it comes to the development of seaweed based nutritional products and their supplements are used nationwide. Although, the company has yet to lay claim that the ingredients assist in limiting carbon emission.

It is safe to say that many of the technologies suggested remain firmly in the early stages of development and it will be some years before these become available to the consumer. The New Zealand agricultural industry will have to look at more immediate measures if it wishes to tackle climate change in the short term. There is the uncomfortable suggestion of stock density limitations, and the lowering of farm inputs. This goes against the general convention of many farmers and there will certainly be a kick back it becomes a popular policy option.

The reversion of farmers to once-a-day farming might also be an option, and there are some examples of farms where this switch has proven to be more cost effective than traditional high input twice-a-day (TAD) models; this tends only to prove profitable in times where farm-gate prices are low. We seem to be at the tail end of the dairy slump with Fonterra (https://www.fonterra.com/nz/en.html) forecasting a pay-out of $7.00 kg/milk solids., so it is unlikely that the incentive is there to switch to less intensive models, especially considering that farmers will most likely need to pay down debt.

As technology progresses we are likely to see progress in this space and New Zealand will always be a ready testing ground for these innovations. We should remain optimistic that our primary sector will remain robust, competitive and resilient, so it can adapt to the risks and challenges presented by climate change.