Written evidence submitted by Mr Alejandro Moure Abelenda (ELM0015)

Highlighting the importance of the chemical amendments to tackle greenhouse gas (GHG) emissions from manure and slurry


This policy briefing addresses to fourth question of the terms of reference: “How can ELM be made an attractive business choice for farmers and land managers while effectively delivering its policy goals?”. The aim is to foster the use chemical amendments of slurry by including more details of this technology in the next document of the Agricultural Transition Plan (ATP), which will be published in the second quarter of this year. In the Code of Good Agricultural Practice (COGAP) for reducing ammonia (NH3) emissions it is stated that this kind of processing requires of professional equipment and advice(DEFRA, 2018). However, the slurry investment scheme, which is part of the ATP, will only promote the implementation of the measurements stablished in the Clean Air Strategy to cover all slurry stores (UK government, 2020a). In this regulation, the low emission slurry spreading (LESS) equipment and closed stores are presented as solutions for reducing ammonia emissions (UK government, 2019). It is expected the complete adoption of LESS techniques by 2025 and covered slurry stores by 2027.

The Agriculture and Food Development Authority of Ireland (Teagasc), which plays the leadership role in the development of policy internationally, is at the forefront of the R&D of chemical amendments in the British islands. Teagasc compared these three measurements in the Marginal Abatement Cost Curve (MACC; Figure 1) for the period 2020 to 2030 (Buckley et al., 2020). Figure 1 does not included the price of carbon credits in international markets, which could be assumed between €25 and €150 per ton of CO2-equivalent. For the calculation of the cost of ammonia emissions it is necessary to consider that 1 % of the emissions of NH3-N and NOx-N are converted to N2O after dry and wet depositions (IPCC, 2019). The N2O is a greenhouse gas with 298 times greater global warming potential than the CO2 (Kavanagh et al., 2019). Since each kg of ammonia emitted correspond to 2.98 kg CO2-equivalent, the Y axis of Figure 1 goes up to €13,423/ton CO2-eq. In the same way, an affordable carbon credit of €150/ton CO2-eq translates to €0.45/Kg NH3.

Figure 1 – MACC of NH3 prepared by Teagasc for the period 2020 to 2030 (Buckley et al., 2020)

According to Figure 1, the 85 % of the mitigation potential comprises two measures, the use of protected (i.e. with stabilisers such as nbpt, dcd, and dmpp) urea and LESS (i.e. low emission slurry spreading) technology. Covering the pig slurry might be cost-effective and even cost-beneficial (i.e. in addition to reduce the ammonia emissions, this measurement saves farmers’ money in the long term). Handling the manure from cattle and dairy via ceiling stores, chemically amending, and LESS appears as cost-prohibitive (i.e. these measures are expensive in the long-term).

The Environmental Agency has stablished that for slurry pig and poultry slurry stores, instead of covering, the acidification is also possible (UK government, 2020b). The additives which are recommended in the COGAP for reducing ammonia emissions are sulphuric acid and nitric acid (DEFRA, 2018) but alternatives are needed to improve the management of this organic wastes (Regueiro et al., 2016). It should be noted that the acids are a type of chemical amendment but there are others (e.g. aluminium sulphate, iron (III) chloride, lime, gypsum, calcium chloride, biochar, ashes, etc.) that might be able to reduce sources of pollution different from ammonia as well (Moure Abelenda et al., 2020).

For the mitigation of GHG gases CH4 and N2O, Teagasc did not included the covered facilities (Figure 2). The reason might be that this technology (i.e. covered stores) does not tackle the emission of these gases or, if it does it, the pollution swapping (Brennan et al., 2015) or trade-off cannot be prevented (i.e. the emissions savings due to the covered storage are inevitably lost after land application). It should be noted that currently chemical amendments and LESS are not economically viable technologies for minimising the emission of these gases.

Figure 2 – MACC of CH4 and N2O prepared by Teagasc for the period 2020 to 2030 (Lanigan et al., 2018)

Covering stores, chemically amending manure, and LESS are regarded as the best available techniques (BAT) that can be implemented to reduce ammonia and GHG emissions from management of manure. The chemical amendments has the potential to prevent the contamination of underground water due to the leaching of phosphates (Brennan et al., 2011) and nitrates, in addition to decrease the CAPEX and OPEX of farms (Moure Abelenda et al., 2020) while minimising gaseous emissions. In combination with closed stores and LESS, chemically amending could make even more effective the management of nutrients in animal slurry.

Following the approach proposed by Teagasc (Figure 3) for the promulgation of regulations, the outcomes of relevant research might be considered for the transfer of knowledge (KT). The author wants to express their concern about how the slurry investment scheme takes advantage of the research related with the chemical amendments. Teagasc highlighted that the adoption of amendments will require significant KT effort to educate the farmers to what the benefits of these additives are.

Figure 3 – Role of knowledge transfer and research in reducing the carbon footprint (Lanigan et al., 2018)


Brennan, R.B., Fenton, O., Rodgers, M., Healy, M.G., 2011. Evaluation of chemical amendments to control phosphorus losses from dairy slurry. Soil Use Manag. 27, 238–246. https://doi.org/10.1111/j.1475-2743.2011.00326.x

Brennan, R.B., Healy, M.G., Fenton, O., Lanigan, G.J., 2015. The effect of chemical amendments used for phosphorus abatement on greenhouse gas and ammonia emissions from dairy cattle slurry: Synergies and pollution swapping. PLoS One 10, 1–20. https://doi.org/10.1371/journal.pone.0111965

Buckley, C., Krol, D., Lanigan, G., Donnellan, T., Spink, J., Hanrahan, K., Boland, A., Forrestal, P., Humphreys, J., Murphy, P., NiFhlatharta, N., O’Brien, D., O’Dwyer, T., O’Mara, F., Richards, K., Shalloo, L., Wall, D., Waters, S., 2020. An analysis of the cost of the abatement of ammonia emissions in Irish agriculture to 2030. https://www.teagasc.ie/media/website/publications/2020/NH3-Ammonia-MACC.pdf

DEFRA, 2018. Code of good agricultural practice (COGAP) for reducing ammonia emissions 1–25. https://www.gov.uk/government/publications/code-of-good-agricultural-practice-for-reducing-ammonia-emissions

IPCC, 2019. Chapter 11: N2O Emissions From Managed Soils, and CO2 Emissions From Lime and Urea Application, 2019 Refinement to the 2006 IPCC Guidelines for National Greenhouse Gas Inventories. Volume 4: Agriculture, Forestry and Other Land Use. https://www.ipcc-nggip.iges.or.jp/public/2019rf/pdf/4_Volume4/19R_V4_Ch11_Soils_N2O_CO2.pdf

Kavanagh, I., Burchill, W., Healy, M.G., Fenton, O., Krol, D.J., Lanigan, G.J., 2019. Mitigation of ammonia and greenhouse gas emissions from stored cattle slurry using acidifiers and chemical amendments. J. Clean. Prod. 237, 117822. https://doi.org/10.1016/j.jclepro.2019.117822

Lanigan, G.J., Donnellan, T., Lanigan, G.J., Hanrahan, K., Paul, C., Shalloo, L., Krol, D., Forrestal, P., Farrelly, N., O’brien, D., Ryan, M., Murphy, P., Caslin, B., Spink, J., Finnan, J., Boland, A., Upton, J., Richards, K., 2018. An Analysis of Abatement Potential of Greenhouse Gas Emissions in Irish Agriculture 2021-2030 Prepared by the Teagasc Greenhouse Gas Working Group Authors 1–80. https://www.teagasc.ie/media/website/publications/2018/An-Analysis-of-Abatement-Potential-of-Greenhouse-Gas-Emissions-in-Irish-Agriculture-2021-2030.pdf

Moure Abelenda, A., Semple, K.T., Lag-Brotons, A.J., Herbert, B.M.J., Aggidis, G., Aiouache, F., 2020. Impact of sulphuric, hydrochloric, nitric, and lactic acids in the preparation of a blend of agro-industrial digestate and wood ash to produce a novel fertiliser. J. Environ. Chem. Eng. 9, 105021. https://doi.org/10.1016/j.jece.2020.105021

Regueiro, I., Coutinho, J., Fangueiro, D., 2016. Alternatives to sulfuric acid for slurry acidification: Impact on slurry composition and ammonia emissions during storage. J. Clean. Prod. 131, 296–307. https://doi.org/10.1016/j.jclepro.2016.05.032

UK government, 2020a. Farming is Changing. https://www.gov.uk/government/publications/future-farming-changes-to-farming-in-england

UK government, 2020b. Slurry stores on permitted pig and poultry farms with less than 1% dry matter. Regul. Position Statement. https://www.gov.uk/government/publications/slurry-stores-on-permitted-pig-and-poultry-farms-with-less-than-1-dry-matter/slurry-stores-on-permitted-pig-and-poultry-farms-with-less-than-1-dry-matter#when-this-rps-expires

UK government, 2019. Clean air strategy 2019, Department for Environment, Food & Rural Affairs. https://www.gov.uk/government/publications/clean-air-strategy-2019