Understanding Global Warming Potential of meat, milk, and eggs to illustrate How Feed Additives are Sustainable by Design.

Virginie Blanvillain, Global Services Manager, AB Vista, UK

Sanami Tatekura, NIR Application Specialist – ASPAC, AB Vista, Singapore

Sustainability relies on three pillars, which are 1) economical profitability, 2) social responsibility, and 3) environmental stewardship.From the 1950s, the agriculture sector had a high intensification period, with tremendous improvements in genetic, nutrition and management practices, thus improving animal productivity and economical profitability. This intensification period enabled betteraccessibility to animal products (i.e., meat, milk, and eggs), as the battle for feeding a growing population was just starting.Back in the early 1920s, high-yield dairy cowshardly produced 2,000 kg of milk per year, while today’s records average an annual milk yield greater than 10,000kg per year in several countries. In simple words, this also means that 100 years ago, we would have neededfive times more cows to produce the same amount of milk as today.Because greater productivity often results in better feed conversion and/or yield,efficiency wasalso key to improve farmers’ profitability, while reducing the environmental footprint of agricultural activities. Along with genetic selection, more precise estimations of nutrient requirementshave enabled the refinement offeeding strategies to make more from less, and thus improve nutrient utilisation efficiency. The reduction of phosphorus and nitrogen excretion in the environment has been a top priority for some time now to reduce eutrophication impact,as an indicator of water contamination. This commitment has spread to a much broader sense where we are now facing global pledges for reducing climate change impact to limit global temperature increase.

Greenhouse gas emissions and global warming potential

Despite the greater efficiency in producing animal products, it is expected that greenhouse gas (GHG) emissions associated with livestock production will keep increasing with the growing population and the increasing demand in animal products. Although intensification has strongly contributed to reducing the impact on climate change by reducing GHGemissions per unit of animal product, more efforts are still required to meet the Paris Agreement (2015) of limiting global warming to less than 1.5oC above pre-industrial levels. Especially so, when GHG emissions would have to be cut down by 45% over the 15 years since the agreement was made, as we strive towards net zero by 2050 to achieve this goal.

Carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) are the three GHGused to quantify climate change impact. Global Warming Potential (GWP) is a metric used to calculate the effect of the GHGs on global warming to a 100-year lifespan. The GWP100 is expressed in kilograms or metric tons of carbon dioxide equivalent gases (CO2e), where N2O and CH4 emissions correspond to 298 and 25 times that of CO2, respectively, as defined in the 5thIntergovernmental Panel on Climate Change (IPCC) report (2014). In other words, 1 t of N2O dissipated in the atmosphere is equivalent to releasing 298 t of CO2in the atmosphere during the span of 100 years.

A substantial proportion of the total GHG emissions from agricultural land results from livestock and crop production. In the livestock industry, GWP100 is calculated at the farm gate (i.e., when the product leaves the farm) per reference unit. Most of the time, the reference unit is a kilogram of meat, egg or fat and protein corrected milk. In 2020, the livestock sector contributed to 57% (4.2 Gt CO2e) of the total farm gate emissions, where 66% of the sector was generated by methane from enteric fermentation alone (2.8 Gt CO2e) (FAO, 2022). Looking at a regional level, the top emitters in 2020 were Asia (3.8 Gt CO2e), followed closely by the Americas (3.1 Gt CO2e), and then Africa (2.4 Gt CO2e) (Figure 1).

Total agricultural GHG emissions:10.5 Gt CO2e
Figure 1: Agricultural GHG emissions by region in 2020 (FAO, 2022)

How is GWP100 calculated at farm gate

GWP at farm gate refers to the CO2e/kg of milk, meat, or eggs, depending on the product leaving the farm. The GWP100 is calculatedfor a one-year baseline, and for every production segment, or farm unit system. At farm gate, one would first evaluate the number of farm units making the system boundaries. While an independent broiler producer may only own a few barns with commercial broiler chickens making one single farm unit system (i.e., commercial broiler chicken barns), integrated companies must partition the production system into different farm units, where each one inherits from the other, until making the finished product.

For example, the calculation steps for determining the GWP100 of a finisher pig at farm gate (kg CO2e/kg dead weight) may be partitioned into three successive steps in an integrated company (Figure 2).First, the sow farm unit allows to calculate the GWP100 of weaned piglets. Then, the GWP100 calculated per weaned piglet (kgCO2e/kg weaned piglet) is used as an input into the nursery units, for which every weaned piglet entering the nursery farms is assigned the inherited GWP100 of the weaned piglet. In a similar manner, the GWP100 of the grower pigs (kgCO2e/kg grower pig) leaving the nursery farm units can be calculated, and then inherited by the grow-to-finish farm units to calculate the final GWP100 of the finisher pigs ready to market (kgCO2e/kg finisher pig or kgCO2e/kg dead weight). Also, in a situation where the company breeds replacement gilts, a system unit for these replacement gilts should be considered, where some piglets would be purchased externally, and others would be inherited from the sow farm unit.

In addition to the movements of the animals into and from one farm unit system to the other, the inventory of other categorised inputs must be performed to calculate the GWP100 of every farm unit system. While litter, water and electricity usageshould be recorded, they represent a minor portion of the GWP100. On the contrary, feed ingredient usage contributes to the large majority of the GWP100. For each feed ingredient, a carbon emission factor (CEF), expressed in kgCO2e/t ofthe ingredient, is assigned. While one may obtain the CEF from their supplier directly, the GFLI database (www.globalfeedlca.org) is commonly used worldwide as a reference for the determination of the CEF of feed ingredients, while taking into account the manufacturing process and country of origin.

Figure 2: Diagram of the system boundaries of an integrated swine producer, composed of four farm units: sow farm units, nursery farm units, grow-to-finish farm units, and the replacement gilts farm units. All other animals purchased out of the system boundaries will be coming into the system with their own GWP100 (kgCO2e/animal).

Our emissions database illustrates thatthe GWP100 of weaned piglets is typically close to 50kg CO2e/piglet, while in comparison, the GWP100 of finisher pigs mainly vary between 3 and 5 kgCO2e/kgof carcass, depending on final live weight and age, breed, feed ingredient usage profile, and country/production system. In addition, since feed ingredients typically represent more than 70% of the GWP100 of swine and poultry, and 30% to 40% of the GWP100 of dairy milk and beef, it appears clear now that evaluating and understanding the impact of feeding strategies on GWP100 can help identify opportunities for reducing GHG emissions.

While the selection of the right ingredient matters and contributes to the final feed carbon footprint most of the feed additives available on the market provide environmentally and economically favourable outcomesthat are sustainable by design. At AB Vista, this is where our Emissions Reporting Services (ERS) comes into play, as we are committedto 1) helping our customers measure their GWP100 score, and understand what they already do to support sustainability, and 2) what they can do further to be more sustainable on the three pillars.

In the next section, we explain how big of an impact ingredient sourcing can have on the final GWP100, and how feed additives, with a focus on enzymes, have demonstrated their sustainability by design.

Selection of by-product ingredients that reduce feed carbon footprint

The CEFsare estimated for every feed ingredient incorporated into a feed diet. The CEF refers to the amount of CO2e emitted to produce one metric ton of that same ingredient. Since one metric ton of ingredient may result in different products and by-products, different methodologies may be used to calculate the CEFof a feed ingredient. As an example, when corn is used for the bioethanol industry, one metric ton of corn would result in bioethanol, corn oil, and corn distillers dried grains with soluble (DDGs). To determine the CEF of each product resulting from the bioethanol industry, different allocation methods would give rise to different results.

The IPCC guidelines are the international reference for calculating CEFs of feed ingredients, and these guidelines recommend that the CEF of the by-products from a crop should be allocated based ontheir economic value. Economic allocation implies that the GHG emissions resulting from the production of one metric ton of carbon should be assigned to each by-product as a pro-rated function of their economic value. In the case of corn for the bioethanol industry, thisis mainly manufacturedfor the purpose of producing bioethanol, and corn DDGs are a by-product of that industry. Therefore, since corn DDGs resulting from the bioethanol industry represents a small economic value relative to the other products (i.e., bioethanol and corn oil), the GWP100 allocated relative to the economic value of corn DDGs is proportionally minimal as compared to the economic value of bioethanol. In a similar manner, meat and bone meal and other animal by-products have a lower CEF value as compared to other protein sources such as soybean meal.

In general, the use of by-products offers an interesting leverage to reduce the GHG emissions associated with feed. For example, we estimated that formulating diets with no animal by-products result in a 28% increase of the carbon footprint per kilogram of live broiler at farm gate, when compared to a feeding strategy using meat and bone meal as a source of proteinand poultry fat as a source of fat,in replacement of soybean meal and soya oil, respectively (Blanvillain Rivera, 2022).

Use of feed additivesto make more from less

Enzymes have grown to be essential to the livestock industry, particularlyto monogastrics. Over time, phytases and non-starch polysaccharide enzymes (NSPase) have become common additives to feed rations as they allow to improve production cost.

At AB Vista, the Maximum Matrix Nutrition (MMN) strategy allows to reduce the need to incorporate inorganic phosphorus, amino acids, and energy to compensate for the release of phytate-P, amino acids and undigested fibres present in the feed. While the MMN strategy allows to reduce feed cost and maintain performance, it also reduces feed carbon footprint (Figure 3). By reducing phosphorus and nitrogen excretion, as well as energy (carbon) wastage, phytase and NSPase are sustainable by design, and enable one to mitigate the impacts of animal production on both eutrophication andclimate change.

Figure 3:The potential impact on feed cost and emissions usingan MMN feeding strategywith the monogastric species.

In ruminants, a fermentation extractfrom Trichodermareesimay be used to release more energy from the fibre contained in forages. In 2021, a 44-day trial of adding VistaPre-T to dairy diets, taking an energy matrix approach, resulted in a significant 15%reduction in methane emissions; and a 65-day trial of VistaPre-T in beef led to a 4%reduction in GHG emissions per kilogram of carcass.


Sustainability is about being economically profitable, as well as socially and environmentally responsible. There is a clear and pressing need for the livestock sector to reduce its environmental footprint, given its impact on GHG emissions. Based on how the GWP100 of livestockproductsarecalculated at the farm gate, it is apparent that feed forms a significant portion of the total emissions.This indicates that conscious feed ingredient sourcing, smartfeeding strategies, and the use of feed additives to improve nutrient utilisation efficiency, offers a way for farmers to cut their emissions with the greatestmitigation potential.

Through the Emissions Reporting Service (ERS) and our holistic approach, we can support farmers on their sustainability journey by capturing and analysing data to identifyareas in the farm’s activities in which the greatest impact on GHG emissions can be made.Bycarefully craftingwhat-if-scenarios, we can not only report on where the best opportunities lie in implementing mitigation strategies, but alsosuggestthe relevant products and services we have available to cut GHG emissions at farm gate.With the goal of reducing the overall carbon footprint of the farm, there is the added benefit of improving general farm management without losing competitiveness.

Working towards the 2050 goal to battle climate change is a global and continuous effort. Over the years, we are seeing more individuals, companies and government bodies showing commitment in making these changes that impact the environment. The growth towards a sustainable future is not an uncommon subject in the media and serves as motivation for others to follow. We each have a personal responsibility in putting in the efforts to reduce our carbon footprint, and it is important to emphasise that any small change adds up to the bigger picture. As a global company supplying the feed industry, we are proud to bring to feed and livestock producers around the world,our technical and nutritional expertise alongside innovative solutions to help them get one-step closer in achieving their sustainabilitygoals.