Can agriculture meet its methane targets?

New Zealand agrculture is required to achieve a ten percent reduction in its methane emissions by 2030.  This is set down in legislation. The subsequent 2050 target, also laid out in legislation, has been set in the range of 24-47 percent, with the specific requirement within this range still to be determined. The question addressed here is whether these targets are realistic and what do they mean for the future of pastoral agriculture?

The reason this is such an important question is that pastoral exports from dairy, sheep, beef and venison comprise some 50 percent of New Zealand’s merchandise exports. Add in horticulture, fish and forestry, and the overall primary industries contribution to exports rises to over 80 percent. These export percentages have been increasing each year for the last ten years.

Looked at another way, non-primary-industry exports have been steadily declining as share of total exports, something very poorly understood within broader society.

Without exports, New Zealand cannot fund imports.  And without imports, the whole economy falls over.

Approximately half of the pastoral-sourced methane is generated on dairy farms and just under half on sheep and beef farms. However, the impact of a methane levy will be felt most fiercely by sheep and beef. This is because there is less economic resilience in the sheep and beef industries to withstand the levies.

To understand the reduction pathways, the starting point is to recognise that methane production is a direct function of the total amount of feed eaten by pastoral animals, which in turn is driven by the amount of feed grown. Accordingly, the amount of feed grown and eaten has to decline by about ten percent by 2030.

Unless new technologies become available that reduce the amount of methane from each kilogram of feed that is eaten, there is no other alternative way to meet the reduction.

There is one possible caveat to the above statement. About five percent of the methane on dairy farms is associated with effluent ponds, and there is a new technology, already close to commercialisation, that can totally smash these effluent pond emissions. Trademarked as the ‘Ecopond’ technology, it is based on adding controlled levels of ferric sulphate to effluent ponds, with this making the effluent pond an unsuitable environment for methane-producing bacteria, and no environmental downsides.

The Ecopond science has been developed and proven at Lincoln University. Ravensdown is now proceeding with commercialisation. Already installed on two pilot farms, hopefully the system will be commercially available within the next year.

If the Ecopond systems are fully implemented, then methane from dairy farms would reduce by about 5 percent. Across the total pastoral system, that would mean savings of about 2.5 percent.

So, even assuming full implementation, that still leaves 7.5 percent further reduction required by 2030. This can only be done by reducing the amount of feed consumed by dairy, sheep and beef. The pathway to that lies in converting some sheep and beef land to forestry, together with a likely decrease in the number of dairy cows in response to regulatory constraints.

However, this does not necessarily mean that the volume of pastoral products has to decline.   This is because increasing the biological efficiency of production, with less feed consumed per unit of product, also leads directly to less methane emissions per unit of product. In essence, it is all about production systems that reduce the amount of feed required for maintenance, thereby leaving more feed available to drive production.

I mentioned in a recent article that methane emissions per kg of New Zealand lamb meat are estimated to have decreased by 31 percent since 1990/91. This has been a direct result of much higher carcass weights and much higher lambing percentages, with ewe size only increasing marginally.   These biological efficiency gains then flow through directly to the same efficiency gains in terms of lower methane emissions per unit of product.

About seven years ago I was adviser for a PhD study by Peter Klaassen that explored the potential for further increases in biological efficiency within sheep farming. Peter demonstrated how there was no one factor. Rather, it was going to be a case of working on multiple factors including further increases in lambing percentage, plus lower death rates, perhaps more lambing as hoggets, and perhaps even higher carcass weights. But with each progressive step, further improvement becomes increasingly challenging.

Some weeks back, I spent a morning with Professor Derrick Moot at Lincoln discussing what further improvements we could see forthcoming from known technologies in regard to methane emissions from sheep. We both think that a further ten percent is realistic, but getting there by 2030 could be a very big ask.

In contrast to sheep, productivity improvements in cattle, and hence lower intensity of methane production, have been modest at about eight percent over the last 30 years. This is largely because cattle are not designed to produce twins, and they cannot be convinced otherwise. Also, cattle have always been slaughtered at close to their mature liveweight. But further reductions in methane intensity can still occur as better use is made of the surplus calves from the dairy industry. Use of sex-selected semen to produce dairy females and crossbred-beef males will be fundamental to this occurring. Although already widely used, some fine tuning of the technology is still needed.

I then went digging to see what I could find about reduced methane intensity in New Zealand dairying, using the key performance indicator of feed eaten per kg of Milksolids (fat plus protein). I found a DairyNZ paper prepared for MPI in 2021 estimating that in 1990/91 the average cow weighed 470 kg, produced 243 kg Milksolids, and ate 3.87 tonnes of dry matter. By 2019/20, the average cow still weighed 470 kg (by coincidence) but produced 376 kg Milksolids and ate 4.76 tonnes of dry matter.  I then did some calculations to come up with an estimate that the biological efficiency increase had been 21 percent, with this flowing through to the same improvement in terms of reduced intensity of methane production.  Although not quite as spectacular as the improvements with sheep, it has still been a remarkable improvement.

I then looked at what would happen if Milksolids production per kg of liveweight increased from the 2019/20 figure of 0.8 kg of Milksolids per kg liveweight to 1.0 kg Milksolids for each kg of liveweight. The biological efficiency would increase by a further 9 percent and methane emission intensity would drop by a similar amount.

Most of the farmers that I work with are already operating with Milksolids production per cow at between 0.9 and 1.2 kg of Milksolids per kg of liveweight. So, getting the average for the industry up to a 1:1 ratio would seem a worthy goal.

Bringing this all together, achieving ten percent reduction in methane emissions by 2030 looks feasible but challenging. It can only happen if some of the marginal sheep and beef country is converted to forestry – something in excess of 500,000 hectares. My key concern is that this occurs on the genuinely steep marginal country, and with a focus on non-harvested forests, rather than short-cycle production forests of which we already have close to two million hectares.

As part of the equation, New Zealand has to decide whether it is serious about the Paris commitment that all countries made as to the importance of maintaining food production. Also, if New Zealand is to avoid shooting itself in the foot in regard to export industries, then in taking a step forward there has to be a focus on what is already known in regard to driving further efficiencies in farming systems.

When I started writing this article, I planned to extend the analysis through to the post-2030 years leading to the much tougher 2050 target range of 24-47 percent. However, that will have to wait for another time. What I will say here is that it is going to be exceptionally difficult to retain vibrant export industries and still get within that target range, unless some commercial technologies applicable to pastoral conditions become available. These technologies would need to inhibit methane-producing bacteria in the rumen but without reducing animal productivity.

The extent of the challenge should be a concern for all New Zealanders. The export alternatives to pastoral agriculture on hilly lands exposed to a South Pacific maritime climate are far from obvious.