3.3 How important is transport?
3.3.1 GHG contributions from transport depend on the mode of transport.
Food Miles: Is nearer better?
Not necessarily: depends on
Mode of transport
Efficiency of transport vehicles
The trade offs
- e.g. energy use in storing something vs. energy in transporting it – both cold stores and transport uses energy
- Growing in heated greenhouses can be more energy intensive than importing
localised food systems can have other social & environmental benefits
Globally food transport is growing
Solvability: decarbonising transport energy use may be harder to address than stationary energy use (e.g. very limited renewable alternatives to aviation fuel).
GHG impacts arising food transport are not particularly significant, although they have increased in recent years.
The mode of transport is important, with air-freight having a much higher impact (see below).
This impact cannot, however, be assessed in isolation from impacts at other stages.
There are trade-offs to consider regarding energy use for both storage and transport, because both emit GHGs. This underlines the point that the whole system needs to be considered.
There may be other social, economic and environmental benefits arising from more localised food systems.
3.3.2 Air freighting food generates high GHG impacts.
Air freighting food generates high GHG impacts
Source: Sim (2007).
Airfreighting is the most GHG-intensive mode of transport.
This study shows how the impact from long-distance transport via air as compared with other modes (in this case road), can be very high.
However a full life cycle approach needs to be taken. A comparison between roses grown in heated conditions in the Netherlands and then transported the short journey to the UK versus those grown in Kenya and airfreighted to to the UK found that the airfreighted roses had lower overall emissions.
This is because the heating and lighting requirements to grow roses are extremely high, and therefore highly energy intensive.
3.3.3 We cannot consider “food miles” in isolation of other life cycle impacts.
Further isn’t always worse
|Green = Lower in comparison
Red = Higher in comparison
GWP t CO2 eq. t-1
|Tomatoes, UK vs Spain||2.2||0.7|
|Strawberries, UK vs Spain||1.0||0.9|
|Potatoes, UK vs Israel||0.3||0.5|
|Poultry, UK vs Brazil||2.8||2.6|
|Beef, UK vs Brazil||24.0||32.2|
|Apples, UK vs New Zealand||0.3||0.9|
|Lamb, UK vs New Zealand||14.1||11.6|
Webb, et al. (2013)
The above table illustrates that different products have different GHGs when imported to the UK vs. produced in the UK. “Food miles” cannot reliably indicate the total GHG emissions arising from a particular food product.
Different regions and countries have better growing conditions for certain foods; this may mean that, even after transport, the total GHG emissions of imported food can be lower than home-grown food.
However assessing the sustainability of products requires a wider consideration of other environmental, social, ethical and economic factors. In short, “food miles” are not a good indicator of sustainability.
3.3.4 Seasonal food choices can make a difference.
Relative importance of transport can depend on seasons
Edwards-Jones, G., et al. (2008).
This study illustrates the difference in GHGs for lettuce consumed in the UK for different seasons.
In winter, lettuce grown in the UK (grown indoors with fossil-fuel based heating and lighting) has a higher GHG footprint than field-grown Spanish imported lettuce, despite the shorter transport distances for UK lettuce.
In the summer, more UK lettuce can be grown outdoors, resulting in lower comparative GHGs for UK lettuce produce.
In other words, in winter the lowest GHG option is Spanish lettuce; in summer UK field-grown lettuce has (generally) lower GHGs.
There are other important issues to consider however, such as water scarcity and pesticide use.
3.3.5 Positive developmental effects of export horticulture.
Export horticulture in low income countries can contribute positively to development
- High-value products with modern supply chains can contribute positively to incomes and jobs in poorer countries.
- Employment and supplier rights are important conditions of these successes and need to be present.
- Ethical trading initiatives can contribute to positive outcomes.
Products that are air-freighted may have high relative GHGs, but they also contribute positively to economic development in less developed countries. Well-managed production with modern supply chains and strong suppler/employee rights and gender equality has been shown to positively influence welfare in these situations. Standards can be strengthened following involvement in ethical trading initiatives.
The developmental benefits of export horticulture are good example of the kind of trade-offs first mentioned in Chapter 1, where some GHG mitigation initiatives (a switch away from air transport) may potentially have negative socio-economic consequences (the loss of employment and livelihoods in less developed countries). Note that perishable products such as green beans that are commonly grown in Sub Saharan Africa for export are too perishable to be transported the longer journey by sea.
3.3.6 Transport impacts in the USA.
Transport impacts in different regions – USA as an example
This USA study found transport to contribute 11% of food related GHGs. The production stage contributed 83%, although their definition includes food processing, manufacture and preparation, not just agricultural production.
Note that the 11% is similar to the figure for food transport in the UK (12%) – see earlier in this chapter.
3.3.7 Transport impacts in India.
Transport impacts in different regions – India as an example
Pathak, et al. (2010)
This study in India found that agricultural production accounted for 87% of food system GHGs, while transport and other stages such as processing have a very small relative impact. This reflects the fact that food systems in India tend to be more localised and less mechanised than in countries such as the US or UK. More locally produced food is consumed, so transport impacts are very low.
In general, there is a lack of research in for Asia, and it is unclear how this might change over time.
It is unclear how the relative impact of non-agricultural stages might change over time, as diets and production systems shift as a result of industrialisation and economic development.