Environmental pawprints

Consumers are increasingly aware of the environmental impacts of their diets and lifestyles, with everything from transport to dinner coming under scrutiny for its footprint. Pets are also coming under the microscope, principally for the role of their diets in the wider food system.

Most research to date has focused on cats and dogs, due to their high domesticated populations globally and industrial food production systems. Both also consume food with a relatively high content of animal-sourced ingredients: around a third of the energy in cat and dog food is animal-sourced, compared to a fifth for people. In the US, cats and dogs consume around 20% as much food energy as the human population.

Quantifying the environmental impact of cat and dog food is challenging since the majority of ingredients are by-products of human food production, e.g., bone meal or grain leftovers. In the DELTA Model®, some of these ingredients are classified under “Other uses”, while some fit in the “Inedible portion” class, showing some of the challenges around assessing these commodities. Some studies allocate all impacts of production to the primary product, making the by-product footprint-free, while others allocate impact based on the mass or economic value of the ingredients.

A recent study used the economic approach to calculate that 1-3% of global agricultural emissions are on account of pet food production, with lower percentages for land and water use. Another calculated the impact of the US pet population’s diet as around 25-30% of the human population’s, including land, water, and fossil fuel use.

One estimate stated that around 140 million people could be nourished using the energy currently entering the US pet food system. However, this was purely an energy calculation, and did not include full human nutritional requirements. Moreover, it does not account for the fact that the food sources demanded by people do not match the lower quality ingredients used in pet food. However, there are increasing purchasing trends towards premium products that do include substantial proportions of human edible food.

As the impact of pet food is not negligible, there have been calls to reduce this pawprint. This impact is affected by many of the same issues as the impact of the human diet: food waste, overconsumption (and consequent non-communicable disease), and the differing impacts of different food sources. Thus, similar solutions can be tried, such as minimising waste, correct portion sizing, and inclusion of environmental impact alongside nutrition in ingredient selection.

Pet ownership is on the rise globally. While the benefits of pets are clear to any pet owner, and have measurable benefits for human wellbeing, they cannot be left out of any holistic approach to measuring or reducing environmental impact.


Nutrition research using smartphone apps

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Tracking population dietary habits is notoriously difficult, from cohort recruitment to the patchy recollections of what someone ate 24 hours ago. A recent article in Nature Communications approached diet studies via a freely available smartphone app, allowing a large cohort to be assessed with minimal commitment from the participants.

Data from over a million app users, who added on average nine entries to their digital food record each day for an average 197 days, was matched up with demographic and location data to understand the consumption habits of a US cohort.

Their results matched existing knowledge on food environments and dietary habits: high income, higher education, high supermarket access and low fast-food access (the latter two determined by location), all correlated with lower BMI, higher fruit and vegetable consumption, and lower fast-food consumption. One exception was a slight association between high income and high BMI.

The authors also matched their location data to the predominant ethnic group, which was possible due to the zip code level resolution of the data. Again, these results reinforced existing data on the prevalence of consumption of specific foods, and the prevalence of obesity, but across a broader area than previously possible.

This paper shows the power of repurposing existing digitalised data for nutrition research. Such large, long-term, detailed sampling of the US cohort would have been extremely challenging without the availability of an already popular app. Moreover, the privacy of individuals was protected, and the app developers donated the data from the research, facilitating a more refined understanding of their nutrition.

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Comparing the environmental cost of foods: Nutritional LCAs

The environmental impact of a food, be that carbon footprint, water use, land use or some other factor, can be estimated by life cycle analysis (LCA). With the environmental impact of food an increasingly important consideration for many consumers, industry and policymakers, the FAO have recently published a report on the challenges and opportunities of nutritional LCAs – those that attempt to capture the nutritional value of food alongside its environmental impact.

LCAs are strongest when used to identify hotspots or areas for improvement within the supply chain for a single item. They can be used to answer industry questions like: where should we act first to lower the footprint of our product? They can also be used in comparisons between two otherwise identical products for consumers: which one should I buy? However, challenges arise when LCAs are used to compare the impacts of very different products.

Take Energy Rating labels on electrical appliances as an example. Analogous to LCAs, these are an indication of the relative energy usage of a particular model compared with other appliances of the same type. These are useful for comparing two refrigerators, but do not really help when comparing refrigerators with freezers. They are even less useful when comparing a refrigerator with a washing machine: the appliances have completely different functions, and a purchaser would be unlikely to use them to choose which of the two to take home.

Even within the category of refrigerators, ratings become less relevant when comparing different size models, as they provide a different level of service. Without considering the service or benefit provided by the product we do not have a fair basis on which to compare the footprint or cost of providing that service.

The same problem exists when comparing foods. When we look at the footprint of food products and start making comparisons, we need to be clear on the service or benefit being provided by the products to ensure we are making a valid comparison. However, the service provided by a food item depends on the purpose for which it is consumed.

Food is consumed for a variety of reasons: as a source of nutrition, for sensory experience or pleasure, or for social and cultural purposes. Accounting for these different purposes is not straightforward. For example, from a nutritional perspective, alcoholic beverages provide very little benefit, but many consumers may still place high value on their sensory or social purposes.

The FAO report focuses on nutrition, rather than the other services provided by food, and looks at how nutritional information can be combined with environmental impact data.

One approach is to try and bring together the “benefit” and “cost” into a single analysis: the development of a nutritional LCA (nLCA), a life cycle analysis that includes nutrition.

There are two different methods by which this can be done:

  • As part of the definition of the functional unit (e.g., land use per 100 kcal)
  • As part of the human impact assessment, what is often thought of as the cost side of the analysis (e.g., likely impact on human health)

Neither of these approaches is easy.

Shifting functional units

Often, an LCA uses mass as the functional unit. For example, if considering the water use needed to grow rice, an LCA might report results as “litres of water used per kg of rice”. In this case, the functional unit is “1 kg of rice”.

Putting nutrition into the functional unit moves away from just using mass. In the simplest form, this may be evaluating a set of foods based on the amount of a particular nutrient they contain. Protein is often used for this purpose. Our rice example would then change to “litres of water used per kg protein in rice”.

However, protein is not a single nutrient needed by the body, but rather a collection of amino acids, which are the essential nutrients. Not all proteins are created equal, having both different concentrations of these amino acids and varying in their digestibility. Rice protein is therefore different to soy protein, for example. Thus, comparing water use per kg protein does not capture this information. Sophisticated methods that include protein quality exist, but are challenging and rarely used.

Most food items provide more than one nutrient, and we need a broad range of nutrients to remain healthy. The DELTA Model® estimates the ability of the global food system to supply a basket of 29 nutrients, and would include more given suitable data. Evaluating a food item based on only one target nutrient misses this complexity.

An alternative to selection of a single nutrient as the functional unit is to use a basket of nutrients to create some form of nutrient reference score. The intention of this score would be to provide a more “balanced” view of the nutrition provided by foods. However, what nutrients should make up this score? Do they all have equal weighting? Or are some more important than others? And how does this relate to the needs of an individual? The scientific literature contains many different suggestions, each with their strengths and weaknesses. Each is at risk of introducing some form of bias into the assessment.

Another important consideration is portion size. Once we move away from a functional unit based on mass, we lose some of the context around the amount of food that needs to be consumed to deliver a particular nutrient or group of nutrients, and how that relates to the size of a normal serving. Functional units “per serving” have also been explored, but face the same problems as mass based units.

Bringing human health into the assessment

The alternative approach is to leave the functional unit as the mass of the food item and build the nutritional assessment into the impact side of the LCA. This requires having data on the expected impact of consuming a food for human nutrition or health. The main approach that has been considered to date uses epidemiological data on diets, health, and mortality. This is usually of the kind captured in the Global Burden of Disease (GBD) study, which calculates statistical links between consumption of food groups and expected lifespan or quality of life.

Unfortunately, this data is limited to comparatively coarse effects. The GBD study reports statistical measures for 15 health aspects related to diet and 3 related to nutrient deficiency. The statistical associations are the result of a complex analysis that attempts to isolate the impact of individual food factors on overall outcomes. Changes in assumptions used in the analysis between the 2017 and 2019 data sets resulted in significant changes in the apparent impact of several food groups. These have been highlighted in a recent letter to The Lancet, and would have a major effect on any nLCA employing this data.

In general, the benefits of consumption of food or nutrients follow a curve. Initially there is a positive impact on health, with increasing consumption providing nutrients essential to bodily functions and growth. This benefit is reduced once daily requirements are met, and, if consumption continues to increase, may eventually have negative health outcomes.

This is illustrated with the energy content of diets: eating insufficient calories leads to wasting, but eating too many leads to obesity and a range of related health conditions, and just how much is too few or too many depends upon the need of the individual. Sodium is another example: a diet deficient in sodium can have serious health consequences. However, many diets contain a considerable excess of sodium, carrying health risks for many individuals.

Putting food and nutrients in context

Food items are consumed as part of meals and diets, and it is at this level that we need to apply considerations of nutritional sufficiency. The relative nutritional benefit of consuming a food item varies based on the dietary context of the individual. For example, the protein or amino acid content of a food item may be of limited value in a diet that is otherwise oversupplied with this nutrient, but of immense value in a diet that is deficient.

Within the DELTA Model we have implemented a simple nutrient contribution measure for food items. This is based on the sum of the relative contribution the food item makes to each of the nutrients captured in the model. As such, it gives a higher weighting to nutrients that have low global availability and a lower weighting to nutrients that are abundant.

For example, the default 2018 DELTA Model scenario has a 34% deficiency for calcium against global requirements (achieving 66% of target), whereas phosphorous has a 150% excess (250% of target). Thus, a food that provides 33% of the daily target for calcium gets a score of 0.5, whereas 33% of the daily target of potassium scores only 0.13 – approximately ¼ the importance. A similar approach has recently been published for the individual dietary context.

The right use of nLCA

The challenges described above stem from trying to compare refrigerators with washing machines, and lead us to the fact that nutrition does not easily collapse into a single score.

The scope of comparisons, or the grouping of foods into groups becomes important. If food items are grouped with others that provide or purport to provide similar nutritional benefits, we can make more realistic comparisons that better reflect the real choices facing us.

As an example, we might compare the nutritional LCA of milk with that of a plant beverage and use a nutritional functional unit that reflects the role of these items within the overall diet. Milk products make a significant contribution to the global supply of calcium, phosphorous, and potassium, six indispensable amino acids, dietary fat, overall protein, and vitamins A, B2, B5, and B12. A nutritional functional unit could be designed that reflects this nutritional value to enable us to compare milks and milk-alternatives when consumed as a source of nutrients. However, this same approach would not necessarily be appropriate if the purpose of the product was simply to whiten a cup of coffee. The intended service or benefit of foods must be understood when deciding how to compare costs.

Whilst the concept of a universal nutritional LCA that provides all the information necessary to support a wide range of decisions is attractive in its apparent simplicity, the reality is that nutrition and environmental impacts are too complex, and too important, to be reduced to a single number.

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“Local” food and sustainability

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Local food supply chains are often touted as more sustainable than international food trade. A recent review aimed at decision makers in the food system has emphasised that this is not a rule of thumb.

The review provides a clear explanation for why the purchase and consumption of food produced locally is not necessarily more sustainable than food that has travelled longer distances.  For example, a food product’s carbon footprint is determined much more by land use and production efficiencies than by the distance it has travelled.

Transport-related emissions account for only 5-6% of global food system emissions. As exemplified by the authors: “cargo ships or trains can exploit economies of scale and be relatively less polluting over longer distances than small trucks over shorter distances.  Similarly, if consumers visit individual local producers, their carbon emissions can be greater than the emissions from the systems of large-scale suppliers.” 

The authors provide strong arguments for the need for strategic diversification of food supply via international trade to create food security. The food demands of less than one-third of the global population could be met from local crop production, even with dietary adjustment, reductions of yield gaps and reduced food waste. Depending upon location, 26-64% of the population could not meet their demands for specific crops within a radius of 1000 km.  This distance could become even larger if all essential nutrient requirements were considered. Less than 50% of people worldwide could sustain their existing dietary compositions from the continents they live in. 

The article also draws a distinction between “local” based on distance, and “short” based on number of actors in the supply chain. Both of these qualities have an impact on sustainability. Purchase of local food can provide localised economic and social benefits, but there is little evidence that localised production systems make food more affordable for consumers.  The fact that “local” and “sustainable” are not equivalent when it comes to food is accepted in the scientific field, but is still a widely leveraged concept for retail and consumers.

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Commentary on nutritional LCAs

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Dr Bradley Ridoutt, Principal Research Scientist at Australia’s CSIRO and agricultural sustainability researcher, has recently published a commentary on the challenges and opportunities for combining nutritional information with the environmental impacts of food.

Recent years have seen increased efforts to compare the environmental impacts via life cycle analysis (LCA) of food to lead diets and production down more environmentally sustainable paths. Dr Ridoutt highlights that, as yet, no universal definition or best practice for nutritional LCA exist, leading to discussion (including by the FAO) on what the best approach might be.

In a previous article, we discussed the use of LCA in food sustainability research. The main limitations of the nutritional LCA approach were reiterated in the commentary article. A key question remains: what is the function of food? And thus, how should we compare foods?

As stated by Dr Ridoutt, “Foods contain a variety of nutrients, and a healthy diet requires a variety of foods.” Defining an appropriate way to compare the worth of different foods is challenging, which makes incorporating this with environmental impact (fraught with its own challenges of what factors to include), nearly impossible. Dr Ridoutt notes that the further inclusion of the health outcomes of food, often contested, adds to this challenge.

A key quote in the article is “…wrapping environmental LCA results together with nutritional epidemiological findings would appear unlikely to inform wise decision-making and will most likely only benefit individuals and organisations with a social or commercial agenda to promote.” The author concludes that only through separate reporting of the nutritional and environmental impacts of food can trade-offs be identified and assessed. Given that the relative importance of these two impact categories will vary between individual perspectives, this area seems likely to be highly discussed for the foreseeable future.

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More about what you eat, and less about how much

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A recent article in The American Journal of Clinical Nutrition has highlighted the inconsistency of rising obesity rates despite focused efforts to eat less and exercise more. The paper critiques the current energy balance model (EBM) and offers a review of an alternative model that considers the underlying biological processes at play. It suggests weight gain is as much about what we eat as it is about how much.

According to the EBM, obesity is understood as an imbalance of energy. If an individual consumes more energy than expended, the surplus energy is stored as body fat. This has led to the common approach of eating less and moving more to achieve weight loss. EBM assumes all calories are metabolically alike, thus excluding the causal mechanisms of food quality, structure, or composition on processes that may impact weight gain. This simplistic approach to a complex biological system faces the risk of inaccuracies and may cause misguided obesity management practices.

The present paper reviews an alternative model: the Carbohydrate Insulin Model (CIM), against various hypotheses and advocates for the accuracy of this model over the EBM. CIM considers the source of calories, versus the calorie content exclusively. It suggests calorie-independent mechanisms are at play where the compounds in food can impact hormonal and metabolic responses. Among these factors, glycaemic load (GL) plays a significant role: hormonal responses to high glycaemic foods (easily digested, high sugar) drive an increased energy positive imbalance resulting in weight gain. A focus on the quality of the calorie sources should be considered, where consuming lower GL foods is favourable over attaining a calorie deficit.

CIM is not without criticisms of its own, as the authors identify claims by previous research challenging the validity of CIM. This has caused misinterpretations of the model, such as “Energy expenditure is not increased by low- compared with high-carbohydrate diets in some feeding studies”. The review provides explanations to these misleading statements, often due to weak evidence or trial errors.

Whether CIM offers a more accurate representation of weight management or not, this paper highlights the importance of considering the types of foods we consume and their impact on our hormones and metabolism for a more sustainable pathway toward healthier living. Taking a wider lens, it also exemplifies the need for researchers to consider multiple models to improve our understanding of complex systems, an idea that can be applied to modelling the global food system.

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Changes to diet can be a win-win for nutrition and environment, but not all changes

Individuals are increasingly concerned about the environmental impacts of their food choices. A recent paper in Sustainability quantifies the global warming impact of several NZ diets over the entire lifetime of the consumer, providing context for the role of diet in an individual’s overall contribution to global warming.

How can we eat healthier diets that still satisfy us, which don’t cause excessive damage to the environment, without breaking the bank? Questions like this have arisen in the minds of most conscientious consumers at some stage, but there is little consensus on what such a diet might look like in the nutrition field.

Prioritising any factor – health, taste, price, or environmental impact – depends on the values of the individual. However, when we fail to adequately consider health and nutrition, the risk to the individual is high.

On this topic, the Riddet Institute’s Sustainable Nutrition Initiative team were recently involved in a multi-organisation international project calculating the global warming impact of various New Zealand diets.

The research took the current average NZ diet and calculated what the global warming impact of this diet would be. In a point of difference to much other work in the field, the cumulative warming impact was calculated over the entire lifetime of an individual, rather than shorter term impacts. The calculation was repeated for a NZ diet that follows the national dietary guidelines, and a vegetarian NZ diet with no meat content. Each was designed to reflect realistic choices that a NZ consumer might make.

The results show that a move from the average diet to one that adheres to the NZ dietary guidelines would have benefits both to nutrition and global warming impact. Similar results have been found in many other studies (see here, here, and here), so this was not surprising. In this research, the reduction in the global warming impact of the dietary guidelines diet was 7-9% compared to the current average diet.

Transitioning to the no meat diet showed a reduction of 12-15% in the global warming impact of the diet compared to the average NZ diet, so an additional reduction of 3-8% compared to the dietary guidelines diet. However, in the context of an individual’s total warming impact from all consumption (i.e. including things like transport and heating), switching to the no meat diet at age 25 was calculated to result in a 2-4% reduction overall. This relatively small result is because diet is only one part of our global warming impact, accounting for about a quarter of consumption-based emissions for the average New Zealander. As a comparison, transport is on average around 35% of NZ consumption-based emissions.

Consumption-based emissions differ to production-based emissions. Production-based emissions are those produced within a country, without accounting for how goods are traded across the world. Consumption-based emissions take account of the trade of goods, allocating emissions to the end user based on the products they consume. This choice is particularly important in countries like NZ, which export and import large proportions of the food they produce and consume.

Bringing in the cost side, other NZ research has also shown that dietary guidelines, flexitarian and vegan diets can have reduced greenhouse gas emissions, but that the price also rises as the diet moves further from the current average NZ diet. Thus, such changes will be less achievable for individuals with less to spend on their food.

Clearly, there are a number of ways that concerned individuals can reduce their warming impact, such as changes to transport, heating and recreational choices. Diet is one of these options, but these choices must be evaluated on their efficacy.

This research is important in providing context for the contribution of diet to an individual’s global warming footprint. Most importantly, a transition towards the recommendations of the dietary guidelines was a win-win for both nutrition and global warming footprint.

However, in the context of an individual’s overall lifetime global warming impact, it is important to realise that changes to diet made only a minor difference.

The NZ context of this work is also influential. Over 80% of NZ electricity generation is from renewable sources, which reduces the global warming impact of the NZ energy sector. As such, many activities in NZ (such as heating or manufacturing) have a lower warming impact than they would in other parts of the world. Similarly, many parts of the NZ agriculture sector have lower carbon emissions per kg of product than seen in other parts of the world. Therefore, the percentages above are likely to differ in different parts of the world.

A key takeaway emphasised by this research is the need to prioritise considerations of nutrition and health when thinking about our own diets. One of the important things to note from this paper is that the diets considered were not nutritionally equivalent. Moving from the average NZ diet to the dietary guidelines diet largely meant increasing fruit and vegetable content and reducing discretionary foods. There were some smaller increases in certain dairy products and decreases in some meat products. The result was a diet with improved availability of calcium, fibre, folate, and magnesium.

The no meat diet was not equally win-win: while it had a reduced warming footprint and was broadly similar in its nutrient availability to the dietary guidelines diet, its iron content fell short of the average adult’s daily requirement.

The nutrient differences are more pertinent to consumers than the small calculated global warming impact. Changes to the foods in an individual’s diet result in changes to the amount and sources of the nutrients they consume. It is essential that, when considering changes to diet motivated by external factors such as global warming impact, individuals are aware of the nutritional changes they will also be making. These changes may have large positive or negative impacts on health and wellbeing.

Adequately nourishing the global population is a key component of sustainability. A food system that does not deliver nutritious diets to all cannot be considered sustainable, regardless of its social, economic or environmental sustainability. It is essential that, when we are considering the environmental aspects of diet, such as the lifetime global warming impacts (as calculated in this paper), that we do not ignore the nutritional adequacy of different diets.

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Feed Our Future event to bring science, government and industry together

The Riddet Institute is this week hosting an event to bring together food system stakeholders and decision makers for accessible evidence-based discussion of the key global issues and the local decisions that we need to make.

Sustainably feeding a growing population is a global problem, but also one for New Zealand to consider. Where does our reputation for high quality, premium food products fit in a hungrier world? How can kiwi innovation and ingenuity make a difference to the global future of food?

The event will explore the current conversation of sustainable food, bringing moderation and balance to what is often a debate of extremes. National and international experts in the fields of nutrition, food waste, food systems, life cycle analysis and consumer science will speak on these important issues, with open discussion from the attendees.

This dialogue will inspire our future decisions and put New Zealand at the front of the sustainable food systems debate.

The life of your food: A discussion of LCAs

A low impact lifestyle has become desirable as the consequences of our excessive consumption are exposed. However, how do we assess the environmental impacts that our product choices have? Here, we discuss the use of life cycle analyses (LCAs) and the challenges and opportunities these pose in estimating the environmental impact of our food systems.

LCAs are an assessment method used to estimate the environmental impact of items over their lifetime. Such impacts can include water use, land use and greenhouse gas emissions (GHGs). When used correctly, they can be an effective comparative tool between similar items and highlight points in the value chain for improvement.

LCAs have a number of stages, and there are a range of types of LCA. Lifecycle inventories (LCIs) are first collected, which take account of all inputs and outputs within a system. This is followed by LCIAs (lifecycle impact assessment) where the impacts of LCIs are quantified and often differentiated into ecosystem impacts, human impacts and resource depletion. The commonly used term ‘footprint’ can represent a partial or full LCA, but only focuses on one aspect of the system. For example, a water footprint assesses the impact on water availability and quality across the entire life cycle of the product, but this would not include the impact on carbon emissions or land use.

LCAs are recognised as a useful impact assessment tool and as such have standardised methods set by ISO (International Organization for Standardisation). These guidelines have been interpreted differently throughout the literature, especially when applied to a system requiring the allocation of upstream products and inputs that serve in more than one system. For example, water used to irrigate rice paddies would form part of the water footprint of the rice. However, if the rice straw is also used as animal feed, how should the water footprint be allocated between the rice and animal production? Another issue with the methodology when applied to GHGs is that it typically only uses the GWP100 climate change metric, which can misinterpret short lived gas potentials e.g. methane. These limitations highlight the complexities of LCAs and the need for consistent methodology to improve the reliability of the assessment.

Using LCAs for the estimate of a product’s impact provides a landscape where the products can be compared. Although this can see misinterpretation, which will be discussed later, the complexities of this process can also offer up informative results for consumers and producers that may not seem obvious at first glance. This can be best used when comparing products that are similar in their final output (i.e. provide an equivalent user benefit), but may differ in their production chain e.g. competitor products, items produced in different regions and countries, or comparing similar products manufactured by the same company.

One product may have a variety of impact levels dependent on its origin, where it was purchased, right down to the practices of the individual farmer. Simple consumer choices may significantly decrease an individual’s impact. When choosing a discretionary food like chocolate, the choice of dark chocolate over milk or white chocolate significantly reduces the environmental impact. A difference in the nutritional composition of these products should be noted, although it is not a product we eat for its nutritional benefit. Furthermore, it has also been found using LCAs that a change to using 100% recyclables will result in minor reductions in an individual’s carbon footprint, and rather a focus on simply reducing consumption of packaging would see better results.

One of the most robust uses of LCAs is in the optimisation of company production lines. An internal LCA can pinpoint both the area with the most opportunity to reduce impact (e.g. manufacture, shipping, retail) or highlight one product having less impact than another, signifying its value for the company. Having numerical figures produced by LCAs can also provide tangible options for tracking improvements through regular analyses. For example, following its first LCA in 2009, Nespresso committed to reducing the carbon footprint of a cup of its coffee by 28% by 2020. Through these LCAs, Nespresso also investigated the impact between coffee systems to show the use of Nespresso was equal in carbon footprint with three other common coffee systems, while fully automated coffee systems had the highest carbon footprint. Not only does the direct product hold opportunity for more sustainable consumption choices; so too do the processes used to extract the coffee.

The benefits of the accurate use and awareness of LCAs go further than educating individuals or companies. As the literature on LCAs increases across a broader range of products, processes and end-of-life options, it allows consumers to make informed decisions in their quest for a truly low impact life. This also provides critical data to modelling platforms such as the DELTA Model.

With the complexities of LCAs comes the opportunity for misleading comparisons. This can be through comparing two products that have little similarity in characteristics, comparing different parts of the value chain (cradle-to-farmgate versus cradle-to-grave), or only using one footprint to pull conclusions on an item’s entire impact. These have led to some misconceptions, especially when inappropriately exploited by commercial interests to promote one product over another. For example, plant-based milks being touted by some as better for the environment than dairy.

The environmental impact of bovine milk has shown significant variation between different countries, right down to differences inter-regionally. This variation allows the impact assessment outputs to be picked in favour of marketing claims by competitors. When used to compare bovine milk to plant-based alternatives, LCAs can create oversimplified and misinterpreted conclusions such as assuming nutritional equivalence between products, or using global average impacts not representative of the variation between production systems. More appropriate use of LCAs in milk comparisons would be to compare plant-based milks with one another, or compare different farming systems and practises between countries.

This scenario exemplifies the potential misuse of the tool, and highlights a gap in the literature that LCAs are yet to fill when applied to delivery of nutrition. A focus has been placed on whole products and macronutrients, where LCAs give footprints per kg of product or, less commonly, per kg of protein. Micronutrients are yet to be explored and would be an instrumental addition when considering the entire impact of food. This has become even more critical as deficiencies in specific nutrients when feeding the global population have been suggested by the DELTA Model. This gap can be demonstrated in LCA comparisons of protein sources that claim protein powders are more efficient protein sources than cheeses, grains and beef when considering their environmental impacts. This study does not include the numerous micronutrients also received from the ‘less efficient’ protein sources.

Taking a holistic view, you could argue that given the interconnectivity of complex systems such as the food system, even seemingly unrelated factors can have indirect impacts on one another. LCAs can provide an excellent measurement tool when estimating the impact of products on individual environmental factors. However, the examples of misinterpretation and the opportunity for further research demonstrate how the application of LCAs can fall victim to tunnel vision when estimating a product’s true impact. This absence of a holistic view can produce results misleading for consumers. Narrow LCAs provide one piece of the puzzle and consideration should be made of the broader impacts the product has on our planet, our bank accounts, our health and our livelihoods.

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What the global population thinks about climate change

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The United Nations Development Programme has conducted an online survey of 1.2 million people from 50 countries to hear their views on climate change. Food waste emerged as an important theme worldwide.

Renewable energy, conserving forest and land, and a transition to more sustainable transport were high on the list of policies that the surveyed population wanted to see prioritised. Also high was the adoption of climate-friendly farming techniques, though less so in countries dependent on large agricultural sectors.

Targeting food waste received more support than targeting energy waste. Plant-based diets received the least support of the policies posed in the survey, with 30% of respondents supportive.

The importance of climate change was greater in the minds of young people and decreased with age, but even in older age groups around 60% of respondents felt that climate change was a global emergency. Notably, almost half of the respondents were under the age of 18, the age group most likely to say that climate change is a global emergency in the survey. Thus, the overall results of the survey strongly reflect the feelings of younger generations.

The survey results largely reflect common discourse on climate change. The low popularity of plant-based diets to counter climate change, although often a feature in the scientific literature on sustainable nutrition, was unsurprising given the social importance of current omnivorous diets. More surprising and encouraging was the high popularity of reducing food waste, an area that shows great potential for improvement.

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