Pre-pandemic it was estimated in the UK that 24% of adults owned a dog and 26% of adults owned a cat (Gallizi, 2021), since then this figure has increased to 33% and 27% respectively (Pet Food Manufacturers' Association (PFMA), 2021). Owning a pet has a number of benefits — they reduce illness such as heart disease and stress, increase fitness, reduce allergies and asthma in children, and increase social interactions (Swanson et al, 2013) Their environmental impact, however, is, to some owners, an important consideration. While larger pets and those with a meat-based diet have the highest cumulative environmental impact (Acuff et al, 2021; Gallizi, 2021), eco-friendly and environmentally sustainable choices have been shown to have increased in popularity in the pet food industry (Horton, 2021). The PFMA agreed in 2018 that various environmental sustainability areas needed to be focused on, including packaging recyclability, animal welfare, sustainability of ingredients, and the environmental impact of food production (PFMA, 2021). In addition, the European Pet Food Industry Federation (FEDIAF) developed the Product Environmental Footprint Category Rules (PEFCR), a scale for measuring the environmental footprint of pet foods from ‘cradle to grave’, including considerations such as ecosystems, human health, climate change, natural resources and water use (FEDIAF, 2022a). This PEFCR document was endorsed by the European Commission and details the environmental footprint of each stage of production; it deems the ingredient sourcing and distribution as having the greatest impact on the environment, while the manufacturing process and packaging is the least impactful part in the pet food journey (FEDIAF, 2018).
Impacts of pet food
Rearing livestock has a cost to the planet; in addition to requiring more land than plant crops to produce equivalent energy, livestock rearing contributes to more soil erosion, has a considerably greater impact on water use, fossil fuel use, greenhouse gas emission and pesticide use (Okin, 2017) than crop growth.
This has been succinctly summarised by Acuff et al (2021) in Table 1 as a carbon footprint comparison.
Table 1. Carbon footprint of protein sources
| Protein | Black soldier fly larvae | Beef | Lamb | Salmon | Pork | Chicken | Soy |
|---|---|---|---|---|---|---|---|
| Carbon Footprint (kg Co2 eq/kg) | 1.36–15.1 | 14.8–23.2 | 10.9–19 | 2.1–2.7 | 2.01–3.02 | 1.99 | 0.3–0.7 |
While meat production is responsible for approximately 25–30% of the world's greenhouse gases (Espinosa-Marrón et al, 2022; Kerwin, 2022), FEDIAF highlights that the majority of pet food meat content is a by-product of the human food production system (FEDIAF, 2022b). This equates to approximately 20% of all meat production (Horton, 2021), while claiming almost no land use or water use as a separate industry. This implies that the only true environmental costs of the industry itself is the processing facility, packaging and distribution impact on the environment (Okin, 2017). Alternatively, it can be viewed as the pet food industry offsetting some of the costs of the human food production industry, as fewer of these by-products such as offal are discarded to landfill if they are utilised as pet food sources (Berry, 2021).
The environmental impact of the aquaculture industry is estimated to be comparable to that of the agricultural industry because of the space required and use of biocides, among other factors (Swanson et al, 2013); however, this has been somewhat resolved by the introduction of the Marine Stewardship Council (MSC) which insisted on regulated standards of more sustainable initiatives. Not all manufacturers attain this certification, although the MSC has seen an increase in companies choosing to achieve certification of 57% in the UK during the last 5 years (Horton, 2021).
Animal-based diets
Meat production as an industry creates around a quarter of the world's greenhouse gases, and is the main reason that dog ownership is deemed the environmental equivalent to driving two 4x4 cars (Woodmansey, 2019; Omni, 2022). However, the impact of pet food is increased if owners are purchasing meat intended for human consumption, such as from butchers or meat counters of supermarkets to feed to their dogs (Perkins, 2021). Beef or red meat production has a greater cost to the environment than chickens, however both have an impact (Figure 1) (González et al, 2020; Yora, 2022).
Depending on the individual farming methods, fish, eggs and chicken are the least impactful on the environment, while ruminants have the biggest carbon footprint (Swanson et al, 2013). In addition to the cost of the production itself, only 7% of cattle mass is deemed by-product, and therefore not a competitor for human food production. In chicken rearing there is over 34% by-product, and in fish aquaculture this accounts for 55% (FEDIAF, 2018), so clearly the protein ingredient as well as grade chosen has a huge impact on the food's sustainability.
In some scenarios, current practices are not as sustainable as possible, for example one study found Scottish fisheries could increase their by-product profitability by 803% and their food production by 60% without using more marine resources (Stevens et al, 2018).
Collecting evidence of sustainability on current fishing practices on a larger scale would be informative. There is the potential to utilise human food production by-products, or mitigate the environmental impact of rearing fishstock.
Commercial diets
Many commercial pet food companies, including Mars owned Royal Canin and Colgate owned Hills have made pledges towards sustainability. This includes Hills' aims to improve water efficiency, CO2 emissions, recyclable packaging and greener buildings (Hills, 2020), while Royal Canin pledges to achieve net zero greenhouse emissions by 2050, become carbon neutral by 2025, and have a carbon neutral pet food range by 2022 (Royal Canin, 2021).
Generally, the utilisation of human food production by-product waste is beneficial to the environment (Okin, 2017; Berry, 2021), however, commercial pet foods often label their meat source as ‘human grade’ in an effort to entice owners — this could mean there is direct competition with the human food production system, livestock production and will increase its environmental impact (Swanson et al, 2013), particularly if the ‘human grade’ meat is diverted from human consumption rather than utilising the by-products available. This is influenced by social-economic and cultural norms, in terms of which meat by-products are seen as desirable by the consumers in that specific area (Okin, 2017). It is also important to remember that the protein levels within many pet foods is much higher than the pet's requirement (Swanson et al, 2013; Bittel, 2021), which contributes to higher production and waste costs. The rendering process used to provide safe livestock and pet foods processes approximately 25 million tonnes of animal by-products in America each year — this is livestock biological waste that would otherwise end in landfill, be burned or buried, adding pollutants to the air and waters (Meeker and Meisinger, 2015). Annually in the EU 12 million tonnes of Category 3 livestock by-products are produced. These are by-products with a very low risk of disease transmission that are edible, often containing higher levels of macro and micronutrients than the dressed carcass at the slaughter-house (Galanakis, 2019) and that are therefore an ideal nutrient source for any omnivore or carnivore.
Comparative data on the sustainability of the processing of both wet and dry commercial food is hard to find, and if displayed on pet foods would allowing for transparency from manufacturers (Swanson et al, 2013). Overall, it has been estimated that an average 15 kg dog creates an approximate 631 kg CO2 equivalent in 1 year if eating commercial diet wet food, or 139 kg CO2 equivalent if eating commercial diet dry food (Acuff et al, 2021). Total pet food globally is equated to producing 1.1–2.9% of all global agriculture emissions (Alexander et al, 2020).
Homemade diets
While homemade diets risk being deficient in nutrients (FEDIAF, 2022c), the environmental impact is difficult to assess as it depends on the resourcing of ingredients. If the protein sourced is human grade, then the pet potentially has the same carbon footprint sources as their owner (Swanson et al, 2013), and fails to utilise the nutrient rich animal by-products discarded by the human food production system (FEDIAF, 2018; Swanson et al, 2013; Meeker and Meisinger, 2015).
Insect diets
While the introduction of insect-based foods raised noteable support, there was also some consideration of ecological risk (Berggren et al, 2019) if the live species were to escape into the local area. However farming insects for protein considerably reduces land use, greenhouse emissions, carbon footprint, and water usage compared with other pet food sources (Table 2) (Yora, 2022; Acuff et al, 2021). As a comparison, 10 kg protein gained from Black Soldier fly larvae (Figure 2) only requires 45 m² land mass and has a carbon footprint up to 1/10th of beef production by weight (Acuff et al, 2021).
Table 2. Table of carbon footprint of protein sources
| Beef (10 kg) | Chicken (10 kg) | Insect | |
|---|---|---|---|
| Greenhouse gases | 1500 e.kg | 375 kg | 60 kg |
| Water use (litres) | 1 120 000 | 340 000 | 54 000 |
| Land use | 2100 m2 | 300 m2 | 45 m2 |
Yora (Yora, 2022) is one brand of pet food offering an insect-based dry or wet diet for dogs and a dry cat food, with more yet to be released in 2022. Another brand venturing into the insect protein market in Europe is Purina who have launched two diets using the black soldier fly larvae as the protein source, which is the same source as Yora, for both dogs and cats (PFMA, 2015a,b). Other manufacturers using insect protein sources, such as soldier fly larvae and crickets, include Jiminy's (Berry, 2021) and Percuro (Percuro, 2022) for dogs and Lovebug for cats (Natusan, 2022) — these companies are all using the relatively small amount of space and water needed for insects compared with that required for livestock, to create volumes of highly nutritious protein (Hawkey et al, 2020; Bittel, 2021), although the protein levels differ according to sources and processing methods (Veldkamp and Vernooij, 2021). There are also the added benefit of reducing the prevalent protein allergens (Natusan, 2022; Yora 2022).
Vegetarian/vegan diets
Soy production for food uses up to 26 times less water, and is up to 20 times more fossil fuel efficient, than live-stock sustenance and is 14 times more efficient in fossil fuel use than trawling for fish (Swanson et al, 2013). Cats are obligate carnivores, with blindness and heart failure recognised as just two of the risks associated with taurine deficiency (FEDIAF, 2022d), so any vegetarian diet must be carefully supplemented with the recommendations of a board certified veterinary nutritionist (FEDIAF, 2022d). Dogs however are omnivores and can process nutrients from vegetables and carbohydrates, thanks to their three key genes: AMY2B, MGAM and SGLT1 (Perkins, 2021). However, they do require vitamin D, which can only be sourced from animal proteins (Loeb, 2021). Any pet food diet should ideally be formulated under the consideration of a board certified veterinary nutrionist, and considerations should include age, breed, comorbidities and neutering status. Omni (2022), a pet food manufacturer, claims to have created a vegetarian dog food that increases pet longevity, and contains a higher protein content than many meat-based diets on the market, increasing sustainability. Other vegetarian diets for dogs include Yarrah (Yarrah, 2022) and a range from Lily's Kitchen (Lily's Kitchen, 2021) and Barking Heads (Barking Heads, 2022), which all advocate for either use as an occasional meal to reduce meat consumption, or as a complete diet. Some companies creating vegetarian treats, such as Shameless Pets (Berry, 2021) use vegetable products that are usually wasted from human food production. Use of overripe, bruised or sub-standard looking vegetables from agricultural production, post-harvest leftovers and food processing stages, provides another way the pet food industry can positively impact the environment by reducing food waste (Berry, 2021). In the US alone, it is estimated that 19% of fruit and vegetable foods are wasted (Swanson et al, 2013).
Plant-based diets use up to 92% less land, 61% less water and create 85% less greenhouse gases than meat-based dogs foods (Blanco-Gutiérrez et al, 2020; Mishyna et al, 2021; Omni, 2022).
So far, studies have found little evidence of palatability difference between meat-based and vegetarian pet diets (Debnath and Patil, 2018; Knight and Satchell, 2021) or their digestibility (El-Wahab et al, 2021), although one study did find a significant increase in weight gain in groups of growing dogs fed a meat-based diet, although dry matter intake was no different (Debnath and Patil, 2018). The study failed to mention the body condition score (BCS) of these dogs, to ascertain which group of dogs had the healthier weight, or proportion of muscle mass at either the beginning or end of the study.
Vegan diets are likely to be deficient in many essential amino acids as well as macro and microminerals for both cats and dogs. These include arginine, lysine, methionine, tryptophan, taurine, iron, calcium, zinc, vitamin A and some B vitamins, and as such are not widely recommended (FEDIAF, 2022d). Vegan diets, for this reason, raise a question on the subject of negligence under the Animal Welfare Act for cats (Loeb, 2021). Research on the long-term effects of these diets is lacking, although early studies have found significant nutrient deficiencies in both cat and dog vegan diets (Zafalon et al, 2020).
A number of companies make vegan dog food, and the manufacturers encourage owners to either feed the diet as an occasional treat, or as a complete diet (Hownd, 2020; DoGood; 2021; The Pack, 2022). Ami (2012) is one company making vegan cat food that it claims is supplemented and nutritionally complete, although caution in the long-term use of non-meat based diets for cats has been expressed (Cats Protection, 2019).
The future of pet food
Other possibilities for the future of dog and cat food include the use of cultured or lab grown meat products (FE-DIAF, 2022b) or algae, which contain double the protein content of beef and absorbs CO2 during growth. Yeast cultured proteins, the Koji mushroom (Berry, 2021) and single celled organisms (Acuff et al, 2021) may well become the future options for sustainable pet foods.
Processing and packaging
Comparable data on manufacturing processes required to take raw ingredients to the finished form of pet foods are not available (Swanson et al, 2013), although they would likely be similar for different companies that use the same processing techniques. While the PEFCRs do estimate that packaging and manufacturing to be the lowest environmental impact stages, the inclusion of these data for sustainability comparisons on packaging or websites would give more clarity on the accurate environmental impacts of pet foods (FEDIAF, 2018).
While many companies are slowly introducing recycling schemes or recyclable packaging, pouches, polyethylene, PET and mixed plastic still end their life in landfill in the majority of cases (FEDIAF, 2018) and influence some owners' food choices for their pet. New brands that concentrate on sustainable pet foods are choosing eco-friendly packaging from the start of production (Hownd, 2020; Dogood, 2021; Omni, 2022; Yarrah, 2022).
Conclusions
Feeding pets more sustainably can be simply a matter of feeding the correct volume of food for the pet; lowering the likelihood of obesity and the food waste production (Gallizi, 2021), with the correct type of food for the age, breed and sex (Swanson et al, 2013). The change in human dietary choice has had a two-fold influence on the pet food industry; if fewer livestock are raised for human meat production, the by-products and co-products available to the pet food industry will be lower, and more livestock will be raised purely for pet food. In addition, if more people choose to waste less, and lower volumes of by-products, coproducts and disposed nutritious foods are available, the companies relying on these sources will have to search for a suitable alternative.
Any environmental consequence of pets must be considered in balance with their benefits, and this makes the overall assessment of their socio-environmental impact challenging to ascertain. VN
KEY POINTS
- Pet ownership has been increasing year on year, and many owners consider the environmental impact of owning a pet as greatly important.
- Rearing of red meat protein has the highest production impact on the environment, including CO2 emmissons, land use and water consumption when compared with white meat, tofu or insect alternatives.
- While vegetarian diets are not currently reccomended by many veterinary clinics or for cats, they are gaining traction and popularity because of their proposed benefits.
- Insect-based protein diets provide a varied amino acid profile and nutrient dense diet with lower use of space, carbon production and water use than meat production.
- Manufacturing, production and processing costs of various food sources are difficult to assess and have an impact on the ecological impact of the final product.
- The sustainability impact of utilising human food by-products for pet food is an area that would benefit from wider research.