Mitigating agricultural emissions

Greenhouse gas emissions from agriculture (almost entirely non-CO2 emissions as defined in IPCC Sector 3) fell slightly in the EU-27 in 2018 but are still above their lowest level in 2012. Net emissions from cropland and grassland reported in the LULUCF sector also appear to have stabilised after some years of decline (EEA GHG Data Viewer). Further, projections of agricultural emissions by Member States, as I reported in this post, indicate that no significant reduction in emissions from agriculture is projected in the period up to 2030 even with additional measures in place.

Agricultural non-CO2 emissions are driven mainly by livestock numbers (particularly ruminants such as cattle and sheep) and nitrogen (N) fertiliser use. The emissions sectors included in the IPCC inventories (with the associated gases shown in brackets) cover 3A. enteric fermentation (CH4); 3B. manure management (CH4, N2O); 3C. rice cultivation (CH4); 3D. direct emissions from managed soils resulting from the application of synthetic fertiliers (N2O), manure applied to soils (N2O), manure applied to pastures (N2O), crop residues (N2O), and the cultivation of organic soils (histosols) (N2O). This category also includes indirect N20 emissions from the atmospheric deposition of nitrogen (N) volatilised from agricultural inputs of N (N2O) as well as from N leaching and run-off (N2O); 3E. Prescribed burning of savannahs (CH4, N2O); 3F. Field burning of agricultural residues (CH4, N2O); 3G. Liming (CO2); and 3H. Urea application (CO2). Only the last two categories are directly responsible for CO2 emissions and their contribution to overall agricultural emissions is very small.

Agricultural non-CO2 emissions arise from microbial activity in the soil (N2O), in the digestive tracts of livestock (CH4), in manure (CH4 and N2O), and from the anaerobic decomposition of organic matter in flooded rice fields (CH4). This microbial activity takes place throughout the year and is often episodic, occurring mainly as a direct response to manure or fertiliser application or weather. There are actions that can be taken to reduce emissions of N2O and CH4 from agriculture but measuring and quantifying their effectiveness can be challenging.

In a previous post in 2016 I reviewed estimates of the mitigation potential in agriculture in the context of the EU’s Reference Scenario 2016 and the impact assessment accompanying the Commission’s proposal for the Effort Sharing Directive.  I concluded there that “significant agricultural mitigation is costly and that (for a given carbon price) the agricultural mitigation potential is lower than in other sectors. However, it also suggests that there is a relevant potential for abatement in agriculture which could be taken up with a value on carbon similar to that in place in other sectors of the economy.”

In studies of the mitigation potential in agriculture there is often a tendency to conflate the separate roles of agriculture and land. The IPCC Fourth Assessment Report (Working Group III, Chapter 8 Agriculture, 2007, p. 499). highlighted that 90% of the technical mitigation potential in agriculture that it calculated arose from soil carbon sequestration, with mitigation of CH4 emissions and N2O emissions from soils only accounting for 9% and 2%, respectively (a figure repeated in the IPCC Land and Climate 2019 report’s chapter on food security).  But mitigation arising from soil carbon sequestration is not credited to agriculture in the IPCC inventories but to the LULUCF sector. The latter is also governed by a different regime in the EU climate architecture.

In this post, I look at these microbial emissions from agriculture and how they might be addressed. There is potential both in technological innovations to reduce emissions factors as well as measures that directly address activity levels (i.e., ruminant livestock numbers and use of nitrogen fertiliser). I do not address the potential for offsetting emissions through sequestration arising from changes in land management and land use.

I conclude that there is no silver bullet to reduce agricultural emissions and that action must take place across a wide range of interventions simultaneously. This action will require clear communication and education, sensible regulation, the smart use of CAP subsidies, and significant investment in research and innovation.

Reducing microbial emissions from agriculture

Methane inhibitors. Feed additives have primarily been used to increase animal productivity, but recent advances in understanding methanogenesis in the rumen have resulted in their development to mitigate CH4 emissions. Methanogens prevent the accumulation of hydrogen in the rumen, which otherwise may lead to adverse effects on fibre degradability and animal performance. The use of methane inhibitors must balance between reducing methane production and avoiding negative impacts on animal performance and welfare. Honan et al. (2021) provide a concise summary of feed additives currently available, or in development, with some potential to reduce CH4 emissions from ruminants. Their review also summarises information on mode of action, efficacy, safety and readiness for adoption of anti-methanogenic feed additives.

The leading candidate in Europe is Bovaer®, a 3-nitrooxypropanol (3-NOP) compound developed by DSM, the Dutch health and nutrition company. Trials have shown that Bovaer® can reduce methane emissions by around 30% depending on the quality of the feed intake. DSM filed for authorisation of the additive in the EU in July 2019 so a decision should be imminent. Bovaer® will be available first for indoor-fed confinement production systems in countries like the Netherlands and Finland, where the Finnish dairy cooperative Valio has signed a collaboration agreement. DSM has begun to cooperate with Fonterra in New Zealand to modify the product for use in pasture-based livestock systems where the trick will be to develop a system to ensure that the additive is in the cow’s rumen at all times to inhibit methane production.

Seaweed (macroalgae) has also been shown to an effective methane inhibitor in ruminants. Seaweed contains high concentrations of halogenic compounds that disrupt the methanogenesis process. Red seaweed (Asparagopsis taxiformis) supplementation has been shown to reduce enteric methane by over 80 percent in beef steers and could potentially also increase production efficiency. Sustainable sourcing of red seaweed would be a problem as harvesting wild seaweed would soon deplete available stocks and cause ecological problems of its own. Nonetheless, understanding the mechanisms at work may open other avenues for this approach that might be more sustainable.

An alternative approach is to modify the rumen environment with feed additives to limit the growth of methanogens without targeting the specific methanogenesis pathway. These feed additives include lipids, plant secondary compounds and essential oils. An example is Mootral® which is made up of two natural ingredients: garlic powder and citrus extracts. Mootral® has also shown it can deliver methane reductions of 30% in farm conditions. Unlike DSM which is a multinational business with a turnover of about €10 billion and 23,000 employees, Mootral is a small start-up that emerged from an EU-funded collaborative research project, SMEthane, an initiative started in 2010 by the UK Department of Food, Environment and Rural Affairs. It is still in the process of conducting scientific validation trials to confirm the effectiveness of its product under different farming and feed conditions.

In the Farm to Fork Strategy, the Commission has undertaken to facilitate the placing on the market of sustainable and innovative feed additives to help reduce the environmental and climate impact of animal production, avoid carbon leakage through imports and to support the ongoing transition towards more sustainable livestock farming.

Nitrogen inhibitors. Nitrogen inhibitors can focus either on urease activity or nitrification. Urease is an enzyme produced by soil bacteria and found in soil as well as plant residues. It can break down or hydrolyse urea fertiliser, the dominant N fertiliser type in the EU, into ammonia. More than 50% of applied N fertiliser can be lost to the atmosphere as a result although on average losses are about half this level. Urease inhibitors protect against ammonia volatilisation by preventing urea from hydrolysing. Urea fertilisers combined with urease inhibitors are referred to as inhibited or protected urea and are a well-known technology within the fertiliser industry.

Nitrification inhibitors are chemical compounds that temporarily reduce populations of the Nitrosomonas and Nitrobacter bacteria in soil that are responsible for converting ammonium to nitrite (Nitrosomonas) and nitrite to nitrate (Nitrobacter). These compounds protect against both denitrification (losses of N2O) and leaching by retaining fertiliser N in the ammonium form. By delaying the transformation of ammonium to nitrite for a period by reducing the activity of nitrifying bacteria in the soil, inhibitors can reduce N2O emissions by up to 50%. At the end of the inhibition time, the original activity of nitrifying bacteria is ongoing again.

Several nitrification inhibitors have been approved for use in the EU. Their cost-effectiveness in terms of the cost per tonne of CO2e abated is generally reckoned to be high, but there is a very wide range in the estimates available in the literature (see Table 9 in this OECD 2015 report).

Manure management. Methane is emitted from manure during the anaerobic decomposition of organic matter during storage, especially in liquid waste (slurry), while N2O is emitted via the nitrification of ammonium and partial denitrification of nitrates during storage of solid manure. The acidification of manures and slurries using compounds such as alum, ferric chloride or sulphuric acid has been shown to reduce methane and ammonia emissions during storage. The ammonia abatement reduces indirect N2O emissions that arise when emitted ammonia settles on soil and causes further N2O emissions. Reductions in excess of 80% in emissions of methane and ammonia have been documented for these slurry amendments. One study estimated that their use would be cost neutral at a price of €27 per tonne of CO2e (Kavanagh et al, 2019), implying that a subsidy of this size would be required in the absence of any charge on emissions.

Anaerobic digestion (AD) of livestock manure can also reduce emissions, both directly and through substituting for fossil fuel emissions in the energy sector. Technologies range from on-farm covers of pits or lagoons to centralised reactors, and often organic co-digestates are included to boost gas production. Due to the moderate methanogenic potential of manure, profitability of AD is low, but the environmental benefits should also be taken into account.  As well as producing energy and lowering emissions, the solid residues (digestate) can be used as fertiliser, just like manure, as it has the same level of nutrients.

Germany is considered the world leader in farm-based digesters subsidised through attractive feed-in tariffs but mainly based on energy crops such as maize silage as the feedstock. Of particular relevance is the potential for small-scale AD plants suitable for the small-scale farming structure in many parts of Europe. An Irish study (O’Connor et al., 2020) demonstrated the economic feasibility of small-scale AD plants on dairy farms with more than 100 cows, using both manure and grass silage as the co-digestate and based on the subsidised feed-in tariffs available for electricity in Ireland. Continued technological innovation will likely improve the economic attractiveness of this technology over time.

The mitigation potential for microbial emissions

The Commission’s impact assessment in connection with its Communication ‘Stepping up Europe’s 2030 climate ambition’ projected baseline agricultural emissions (prior to new initiatives that might be included in the CAP Strategic Plans) would fall from 409 MtCO2e in 2005 and 388 MtCO2e in 2020 to 375 MtCO2e in 2030 using IPCC AR5 weights to convert non-CO2 gases to CO2 equivalents (CO2e) (a reduction of 3% between 2020 and 2030). This is in line with the projections I reported in this previous post.

The modelling work associated with the Commission’s impact assessment of revising the EU’s 2030 reduction target estimated the likely additional mitigation potential at different assumed carbon prices. This modelling work was based on the GAINS model, which builds on a database of mitigation technologies including the economic costs of adoption and their likely mitigation effectiveness. As we have seen, there can be a wide range of estimates of these parameter values in the literature. The mitigation potential assessed using GAINS will be sensitive to the assumptions made regarding these individual technologies. The dotted lines in the figure below indicate marginal mitigation costs of €10/tCO2e and €55/tCO2e, respectively. At these prices, agricultural emissions would be further reduced by between 3% and 8% compared to the baseline in 2030. As the current price of allowances in the ETS has just risen above €40/t CO2, its highest level since its introduction, these modelling results suggest that the mitigation potential for non-CO2 emissions from agricultural production in the period up to 2030 is modest.

The modelling identifies some win-win options where there are negative costs to reduce emissions. Farm-scale anaerobic digestion with biogas recovery on dairy cow and cattle farms, both small and large, is one such measure highlighted in GAINS. Other low-cost mitigation options include breeding through selection to enhance productivity, fertility, and longevity to minimise the methane intensity of dairy and meat products for dairy cows and sheep, as well as feed additives combined with changed feed management practices to reduce methane emissions, again in large and small farms.  Explicitly reducing activity levels (such as reducing N fertiliser use or reducing ruminant animal numbers) does not appear to be captured in these GAINS model results.

Source: Impact Assessment for the Commission’s 2030 Climate Target Plan.

Incorporating changes into the national inventory

An often-overlooked issue for measures that reduce microbial emissions from agriculture (and indeed also the removal of carbon in land) is getting recognition for these efforts in national inventories. The biogenic nature of these emissions/removals makes them much more complex to measure because they will vary with soil type, precipitation and temperature. While mitigation that affects the amount of an activity can be counted relatively easily (e.g. reduced livestock numbers, lower fertiliser sales, etc.), much greater effort is needed to capture mitigation resulting from changes in emission factors (e.g. timing of fertiliser application, the use of chemical amendments to reduce methane and/or nitrous oxide and altering animal breeds to reduce methane). Where countries use IPCC Tier 1 (i.e., default) or even Tier 2 emission factors such potential mitigation will not be included in national inventories (these points are made in the presentation of the Irish marginal abatement cost curve by Lanigan and Donnellan, 2018). Given the need to justify their inclusion, there is a pressing need for better activity data recording particularly in terms of farm facilities and documenting of behavioural change. Such recording will also be needed in any case to back up sustainability claims, to justify payments under the CAP, or to comply with private certification standards and requirements. Efforts to simplify data input and to facilitate data sharing with due regard for ownership and privacy concerns will be required.

Reducing activity levels

Agricultural non-CO2 emissions are primarily driven by livestock numbers (particularly ruminants such as cattle, sheep and goats) and N fertiliser use. In addition to reducing the emissions factors associated with these activities, further emissions reductions could be achieved by reducing these activity levels.

Improving efficiency. The approach to date has focused on technological options through improved nutrition, genetics, technology, health and management to improve production efficiency, so that final food demand can be met using fewer animals and fewer inputs. The focus here is on improvements in the emissions intensity of production, rather than reductions in absolute emissions. As the productivity of dairy and beef cattle improves, emissions efficiency improves via the dilution of the maintenance effect. US data is the most useful here because of its long and consistent time series. For example, Capper (2011) reported that US beef production in 2007 required 19% less feed, 33% less land, and 12% less water and had a 16% reduction in GHG emissions per kilogram of beef compared with production in 1977.

But these performance improvements have come at a cost, in terms of animal health and welfare and increased food-feed competition. Performance-enhancing technologies such as growth hormones in beef animals or bovine somatotrophin in dairy cows have not been acceptable in the EU. There is criticism of beef feedlots and indoor feeding confinement systems for dairy cattle on animal welfare grounds. Also productivity improvements may cause a rebound effect if some of the benefits are passed on to consumers in lower prices, thus stimulating demand and ultimately increasing production. The importance of this rebound effect will diminish as food consumption levels reach satiation and the price elasticity of demand tends towards zero. However, increasing global demand and the growing import dependence of many developing countries means that improved production efficiency in exporting countries often translates into increased exports. Emissions intensity may fall, but total emissions do not follow suit. In this situation, additional ways to reduce activity levels must be examined. The potential loss of agricultural output, and the consequential adverse effect on farmer incomes, then becomes a critical countervailing force.

Reducing N fertiliser use.  While reducing livestock numbers will have a direct negative effect on agricultural output, the effect of reducing N fertiliser use is more ambiguous. This is because we know that much of the fertiliser spread by farmers is not taken up by plants (a low nitrogen use efficiency). Reducing this loss could lower fertiliser use without affecting production. Substituting mixed swards (grasses and legumes) for monocultural ryegrass pastures can also lower N fertiliser use without affecting production, though possibly at the cost of greater management input. But in other cases, yields and output would be adversely affected, either by restricting N fertiliser use in conventional farming or by eliminating it by conversion to organic farming.

In the Farm to Fork Strategy, the Commission has proposed to reduce nutrient losses by at least 50% while ensuring no deterioration in soil fertility. It estimates that this would reduce the use of fertilisers by at least 20% by 2030. Both nitrogen and phosphorus are included in this overall target. In addition, it proposes that 25% of the utilised agricultural area would be farmed organically by 2030 which would also reduce the use of chemical fertiliser. It is not clear from the Communication whether these two targets are intended to be separate and cumulative, or whether the organic target is to be considered as a way of reaching the 20% target for reduced fertiliser use. INRAE in its report to the European Parliament on the Farm to Fork Strategy chose the latter interpretation. By comparing the differences in fertiliser use on organic and conventional farms in the FADN farm database, they assess that the organic target alone would reduce expenditure on fertilisers by 12.7% by 2030, thus requiring a further 9.2% reduction on conventional farms (assuming no change in input prices so that the expenditure reductions are equal to reductions in use).

As indicated, increased nitrogen use efficiency can play an important role. This can be achieved by better timing and positioning of fertiliser applications making use of precision agriculture techniques. Low-emission slurry spreading techniques can also make a contribution. On grassland farms, nitrogen use efficiency can be improved by optimizing soil pH and extending use of clover in pasture swards. On arable land, an increase in the proportion of leguminous crops and temporary grasslands will reduce the need for nitrogen fertilisation though this will be at the cost of reduced output. Managing nitrogen better in these ways will lead to reduced N20 emissions.

EU Member States in their CAP Strategic Plans will need to consider the optimal way to incentivise these changes, whether through stricter regulation (for example, tightening the implementation of the Nitrates Directive), encouraging the use of the Farm Sustainability Tool for Nutrients proposed by the Commission, subsidising the planting of leguminous crops, or levying a tax on fertiliser use to recognise the potential environmental damage that it can cause.

Reducing ruminant animal numbers

Reducing ruminant livestock numbers is among the more complex and controversial approaches to reducing agricultural emissions. This is due to the wide variety of production and management systems with different emissions footprints, their role in upgrading inedible raw material to contribute to human nutrition, the variety of ecosystem services livestock can provide and the trade-offs between them, different understandings of the way in which to account for the contribution of methane to global warming, and the importance of their contribution to farm livelihoods (ruminant livestock account for 22% of the value of EU-27 agricultural output, of which 14% is due to milk production).

There are two ways to approach a reduction in ruminant livestock numbers. One is indirectly through demand-side measures, and the other is directly through supply-side measures.

Demand-side measures. Demand-side measures assume that a lower demand will lead to lower prices and in turn lower production and therefore lower emissions. There is widespread agreement in the scientific literature that a shift away from ruminant meat consumption towards more plant-based diets with greater consumption of fruits and vegetables would not only help to improve public health by reducing the incidence of certain non-communicable diseases but would also reduce the environmental impact of the food system including by lowering emissions. This evidence was summarised in the 2019 report of the EAT-Lancet Commission on healthy diets from sustainable food systems. The IPCC’s 5th Assessment Report chapter on agriculture, forestry and land use in 2014 also underlined the importance of demand side measures in mitigating climate change, while conceding that they can be difficult to implement. This message was repeated in the IPCC’s 2019 Land and Climate report which summarised the global technical mitigation potential of different dietary options in 2050 in the following chart.

There are significant differences in per capita consumption of beef and lamb across Europe. The DG AGRI DataM database reports that apparent consumption of beef (in carcass weight equivalent) varied from 44 kg in Ireland to less than 5 kg in many Central European countries. Consumption of sheep and goat meat varies from over 8 kg in Greece and Cyprus to less than half a kilo in most Central European countries.

Per capita beef and lamb consumption has been falling in the EU. Per capita beef consumption in retail weight equivalent (also referred to as product weight) was 11.9 kg in 2005, had fallen to 10.4 kg in 2020 and is projected to fall to 9.7 kg in 2030 according to the latest DG AGRI market outlook projections. This is an annual rate of decline of 1% per annum. The fall in lamb consumption has been steeper, from 2.1 kg in 2005 to 1.3 kg in 2020 but is expected to stabilise at this figure up to 2030. On the other hand, per capita consumption of milk in dairy products has been increasing. These changes in the quantity demanded likely reflect both changes in eating habits as well as substitution towards other meats as the relative prices of pigmeat and especially poultrymeat have fallen. Reliable statistics on the numbers of people who have adopted vegetarian or vegan lifestyles in the EU are missing so the contribution of changes in dietary preferences to the fall in meat consumption to date cannot be properly assessed.

Prices of ruminant meat products in the EU are already high due to heavy import protection. Average tariffs on beef and lamb amount to around 45%. While these high tariffs encourage production (and thus emissions) in the EU, they also discourage consumption. Based on FAOSTAT data (reported in carcass weight equivalent rather than product weight so including the weight of bones and fat that are removed for retail sale), average per capita availability of beef in the EU-27 was 13.8 kg in 2018. This figure is much lower than for other major beef producers such as Argentina (55.4 kg), Australia (28.2 kg), Brazil (37.5 kg), Canada (26.8 kg) and the US (37.2 kg). Given the role of international trade, if attempts to further reduce beef consumption in Europe were successful, the impact on production (and thus emissions) would be partially offset by the diversion of some EU production to export markets. Even within the EU, demand management policies are of limited direct relevance to countries (like Ireland) with export-oriented production. Their production will be affected more by demand shifts in the importing countries than by shifts in their domestic demand.

Achieving a more rapid reduction in ruminant meat consumption will require behavioural change by consumers that can be challenging to achieve. The Farm to Fork Strategy recognised that moving to a more plant-based diet with less red and processed meat (where red meat includes pigmeat in addition to ruminant meat) with more fruits and vegetables would reduce not only risks of life-threatening disease but also the environmental impact of the food system. However, the Strategy proposes few new instruments to accelerate this transition. It proposes that the Commission will seek commitments from food companies to avoid marketing campaigns advertising meat at very low prices and holds open the possibility of legislative measures if such commitments are not sufficient. The proposed shift to organic farming will also lower production given that stocking densities on organic farms tend to be lower than on conventional farms.

The Strategy mentions meat substitutes are a key area for research. Plant-based meat and milk substitutes are already on the market and significant resources are being allocated to research into cellular meat. The main aim here is to deliver a product to consumers that is similar in taste to conventional meat and milk products and does not cost more, so making it easier for consumers to choose what is seen as a more environmentally-sustainable alternative. There are various projections for how fast the market for alternative proteins will grow in Europe. At the moment, their market share is small – one estimate puts average per capita consumption in Western Europe at 0.2 kg in 2018 compared to total meat consumption of 54.0 kg (Rabobank, 2019), but the consumption growth rate is high.

The pace of change will be influenced by the regulatory landscape in Europe. EU regulation and policy has been characterised as largely supportive of investments in alternative proteins (Froggatt and Wellesley, 2019). The 2018 revision of the Novel Food Regulation is perceived as generally supportive of innovation, although there remains some doubt over whether plant-based ‘meat’ products are considered as novel foods under the regulation. A particular issue arises around product labelling and marketing, given that this is an important determinant of consumer demand. Under the Food Information to Consumers Regulation, labels have to be clear, precise and not misleading. In 2017, the European Court of Justice banned terms like “soy milk” and “vegan cheese”, ruling that words such as milk, butter, cheese and yoghurt cannot be used for non-dairy products. Lawmakers in the European Parliament attempted to extend this ban to using meat terms to describe plant-based foods when preparing the Parliament’s position on the legislative package on the post 2022 CAP. This attempt was defeated. However, the Parliament did adopt an amendment that could make it more difficult to market plant-based dairy alternatives. The fate of this amendment remains to be decided in the ongoing trilogues.  

Supply-side measures. An alternative approach to limiting livestock numbers is to take direct action on the supply side. This could take the form of limits on the use of fertilisers or stocking densities, or by including agricultural emissions within an emissions trading scheme as is proposed in New Zealand. Limiting supply would tend to raise the EU price for meat and dairy products and thus also limit consumption. Higher prices for meat and dairy products would fall most heavily on lower-income households. Once again, international trade plays a role. In the absence of any change in consumption preferences, reduced domestic supply would be partially substituted by a reduction in net exports/increase in net imports. This would result in carbon leakage as emissions from domestic production would be replaced by emissions from imported products. If imports come from countries that have a higher emissions intensity per unit of product than in the EU, it is theoretically possible that global emissions could even increase as a result.

There are at least two scenarios where reductions in EU ruminant animal numbers would still be justified even with the risk of carbon leakage. One is where ruminant production is associated with significant non-climate environmental costs, as in the case of phosphate pollution in the Netherlands in recent years. Activities where the returns from production (including the value of any public goods provided by that production) do not cover both the private and social costs of production should be wound down because they imply a net loss to European society. Second, there are examples where the private returns from production are less than the private costs of production. In this case, livestock farmers are producing at a loss, and their income is entirely dependent on the CAP payments that they receive. Linking these payments to an extensification requirement would safeguard these farmers’ income, maintain the value of any public goods supplied, while also helping to reduce emissions. Such farmers would get an additional bonus from the tightening of supply as this would also lead to a lift in market prices.

Discussion

There are several key messages in this post examining the mitigation potential in EU agriculture. First, projections of EU agricultural emissions (as measured by IPCC Category 3 in national inventories) tend to show only a limited reduction up to 2030. Furthermore, expectations of the potential for further reductions with additional measures, based on the Commission’s impact assessment for the 2030 Climate Target Plan, also seem modest.

This partly reflects the way emissions are reported in national inventories. Mitigation actions that farmers can take in the land sector to reduce emissions (e.g. by rewetting organic soils) or to increase removals (e.g. by incorporating more organic matter into soils or planting trees) are not reported in the Agriculture sector in the inventories but in the LULUCF sector. Not only does this reduce the visibility of these actions, but the value of these actions is also capped under the EU’s existing climate architecture. The Commission’s suggestion in its 2030 Climate Target Plan that it is prepared to consider creating a combined AFOLU sector as well as to change the accounting rules for LULUCF emissions/removals would help to give a more holistic and accurate account of net emissions from farming activity.

Second, agricultural emissions are largely non-CO2 gases that arise from microbial activity in livestock rumen, soils, rice fields and manure. Because the sources of these emissions are biological in nature, the prospect for technical mitigation options to date has been seen as limited. However, advances in understanding the rumen microbiome, the soil microbiome and in manure management are opening promising avenues to reduce these emissions. This research and innovation work should be strongly supported with a view to greater deployment later in this decade. These efforts will need to be accompanied by improved data collection of management practices on farms to ensure that appropriate credit for mitigation actions can be included in national inventories.

Third, a significant reduction in the two main drivers of agricultural emissions, nitrogen fertiliser use and ruminant livestock numbers, will still be required. Increasing production efficiency has become a dirty word because of the way intensification in the past has been associated with harmful environmental and animal welfare effects. But pursuing increased production efficiency while avoiding these harmful environmental and animal welfare outcomes must remain an important tool in the toolbox.

Improved production efficiency will not on its own lead to reductions in total emissions in a world where the global demand for animal protein is increasing, where fast-growing markets have a growing demand for imports, and where these imports will be met by the most efficient producers, including those in Europe.

Fourth, therefore, more direct ways to reduce the two main drivers of agricultural emissions must be found. In the case of nitrogen use there is low-hanging fruit given the possibility to reduce losses to the air and water by improving nitrogen use efficiency. In the case of livestock emissions, there is low-hanging fruit where strong synergies exist with improvements in other environmental indicators, notably water quality but also reductions in ammonia emissions, and by using CAP payments to restructure unprofitable production to focus more on public goods and more extensive production systems. The growing availability of more attractive and competitive meat and dairy plant-based alternatives during this decade will also help to drive a reduction in agricultural emissions and should be encouraged by a supportive regulatory environment.

If the sole policy objective were to reduce domestic greenhouse gas emissions, then slaughtering the cattle herd would be an effective way to reach this goal. But ruminant livestock production produces more than simply greenhouse gases. It adds to the human food supply by converting otherwise inedible roughage into high-quality nutrition that humans can eat; grazing and browsing livestock can have a positive effect on the composition of vegetation and biodiversity and help to maintain valuable grasslands; grazing livestock can help to sequester carbon in grassland soils depending on management practices; methane, the most important greenhouse gas produced by ruminants, is a short-lived climate gas and its different role in climate warming compared to more long-lived gases should be reflected in policy; and livestock are an important source of livelihoods for rural communities.

Policymakers need to be aware of these multiple trade-offs in reducing agricultural emissions. Agricultural emissions cannot be reduced to zero. But this should not be taken as an excuse for inaction, or for unambitious targets. The previous discussion suggests that there is no silver bullet (such as the electrification of passenger cars in the case of transport emissions) and that action must take place across a wide range of interventions simultaneously. This action will require clear communication and education, sensible regulation, the smart use of CAP subsidies, and significant investment in research and innovation.

This post was written by Alan Matthews.

Update 28 March 2021: Minor corrections made to update references to rice cultivation and methane from rice cultivation.

Photo credit: Patty’s-photos via Flickr, used under a Creative Commons licence.

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11 Replies to “Mitigating agricultural emissions”

  1. As always, a balanced and objective assessment of the problem. As an outsider to the complexity of carbon accounting, my suspicion is that a significant factor in the overall carbon contribution from the agri and forestry sectors is increasing mechanisation of production. I see woods harvested in days and the timber shipped from one end of Ireland to the other for processing and back again as finished products. Silage is cut and processed with huge specialist machines and brought in using 4-5 tractors. Tank loads of slurry are spread similarly. Machinery used in the arable sector has similarly become huge. Do the accounting methods factor these in, or the carbon-based energy making fertilisers, drying crops, etc?
    Surely the problem is one of energy intensity of the industry as well as the stocking intensity?

    1. @Peter
      Many thanks for highlighting this question of energy use in agriculture and forestry which I should have mentioned. The reason I did not is that this energy use is not reported under Agriculture (Sector 3 in the inventory accounts) but under Other emissions in Sector 1 Energy where it is reported under heading 1.A.4.C. Specifically, this heading covers emissions from fuel combustion in agriculture, forestry, or domestic inland, coastal and deep-sea fishing. This includes traction vehicles (tractors, combines, etc.), pump fuel use, grain drying, horticultural greenhouses and other agriculture, forestry or fishing related fuel use. Highway agricultural transportation is excluded.
      To give an idea of its relative importance in Ireland, these fuel combustion emissions were around 0.625 MtCO2 in 2018 compared to total Agriculture emissions (including fuel combustion) of 20.5MtCO2e, or 3% of the total.

  2. Fascinating.
    Very helpful to the non-specialist.
    The issue of emissions avoided, eg land use change, is clearly captured in your blog in so far as: ‘mitigation arising from soil carbon sequestration is not credited to agriculture in the IPCC inventories but to the LULUCF sector. The latter is also governed by a different regime in the EU climate architecture’. BUT this seems to be a massive opportunity for Irish agriculture and the environment – in the climate & biodiversity context ? Is there any useful analysis and commentary out there that looks at this? I know forestry commentary is full of contradictory positions, etc but in orders of magnitude, if 10% or 20% of agricultural land was shifted (out of farming) towards long term guaranteed (ie locked in) emissions avoided and sequestering use would that offer a serious contribution to GHG reduction goals?

    1. @Mark
      You are right that I deliberately left the potential land mitigation potential out of this blog post, partly because this is the way agricultural emissions are currently measured and partly because it was already a very long post ! The best estimates I am aware of are still those made in the Teagasc MAC curve (the Lanigan and Donnellan link in the post). While that report saw the potential for 3.07 Mt CO2e abatement in agricultural emissions in 2030, it estimated land use mitigation at 3.89 Mt CO2 in 2030 from better grassland management, afforestation at a rate of 7,000 ha per year, rewetting of 40,000 ha of organic grassland soils, and cover crops and straw incorporation in tillage systems.

  3. Would a recognition of soil carbon from the eu emission trading scheme not be the best foot forward. Australia has a model where it pays 25$ for 1 tone of soil c sequestered each year considering average farm emits 4t/ha and there have been various examples in Australia of 13t/ha other research in states texas a&m berkley and michigan state showed 8t/ha 7t/ha 3.59t/ha and 3t/ha now we would need deeper rooting grasses like mixed species swards they require less nitrogen and herbs such as plantian chicory and clover lower methane emitted plus boost biodiversity. Throw hedgerows and tress into that we arent far away but that all depends on eu policy considering f2f mentions carbon farming but is arguing over mearsurements doesnt bode too well

    1. @Matthew
      Many thanks for this comment. As I note in my reply to @Mark, the Teagasc MAC curve does include an estimate of the potential for soil carbon sequestration in Irish conditions based on extra liming and use of clover. The potential rate of sequestration in Irish soils is estimated at 0.55t C per ha per year on average which is a good deal lower than the rates that you quote. Including LULUCF emissions/removals in the ETS is probably a step too far for the EU at this stage, but the Commission has floated the idea of a separate Agriculture/LULUCF (AFOLU) sector where an emissions trading scheme could be trialled.

      1. Really frustrated that eu doesn’t recognise the soil carbon why is this and other countries do? I’ve seen an ippc comment about the potential of it. My quotes are from a adaptive multi paddock grazing system and they have deep roots which clover and prg dont have and we would need to overseed them, but certainly can be done on some farms. I know looking at teagasc signpost farm webinar they are going to deep soil sample and identitfy mixed species as an abatement but have to be investigated.

        1. @Matthew
          There are moves afoot at EU level to recognise soil carbon. The Farm to Fork Strategy includes a carbon farming initiative which the Commission intends to announce later this year. It is better to ‘make haste slowly’ on this and get it right. Any suggestion that soil carbon credits are not credible or verifiable and are used as ‘greenwashing’ would kill the idea stone dead. And there are many practical problems to be resolved. You as a farmer may have looked after your soil while your neighbour may have mined it for years. Your neighbour’s potential for sequestration may therefore be greater, should they get more support from the CAP because of poor management in the past? And if the taxpayer is paying a farmer to sequester carbon, should the farmer be asked to pay back that support if management practices or land use changes and some of that carbon is subsequently released? These are not easy questions to resolve.

  4. soil carbon far better and secure storage of c02 rather than short rotation forestry as we see it is a net emitter in ireland but can displace carbon heavy materials. silvopasture could be an option

    1. @Matthew
      We will have to wait until the CAP negotiations are completed to find this out. The Parliament had proposed an amendment that would have allowed Member States, at their discretion, to include landscape features and biotopes such as trees, bushes, field copses and wet areas, provided they did not cover more than one third of the area but, according to the latest report of the trilogues, this amendment does not appear to have been accepted. It appears that only non-productive areas required to meet the minimum non-productive area on arable farms under GAEC 9 will be allowed as eligible area in the next CAP. However, this remains to be confirmed in the final agreement.

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