Reducing carbon footprints in food supply chains

Abstract

Dear Editor, Over the last three years we have carried out over 150 carbon footprints of supply chains from across the world, mainly in horticulture. Very few of these data have been published due to their commercial sensitivity. However the process of developing these footprints has provided us with knowledge on patterns of greenhouse gas emissions (GHGs) from different food supply chains. It is from this experience that I draw the following observations. While there is great variation in the source of GHGs from horticultural supply chains, generally mitigation opportunities during production are limited. While there is scope to reduce use of on-farm energy, and to make more efficient use of inputs such as fertilisers, in reality these factors tend to contribute relatively little to the overall footprint of fresh produce. Processes such as packing, storage and transport make much greater contributions. Indeed storage can account for over 50 per cent of emissions for produce that are stored for many months, such as potatoes. These emissions are largely from energy use in the buildings, and the design and structure of the building has a large impact on levels of energy use. Redesign of stores and packhouses, and their internal processes offers potential to reduce the footprint of fresh produce. The same is true for protected crops where typically 90 per cent of the footprint comes from heating the glasshouse. Analysis of 23 of the UK’s 35 large tomato growers shows a strong positive relationship between the age of the glasshouse and the overall carbon footprint of the tomatoes. Newer glasshouses have lower footprints because of a combination of better internal processes, their structural design and the thermal properties of their constituent materials. The current advice to farmers on how to reduce GHGs through on-farm strategies such as enhancing yields and reducing on-farm energy use are useful starting points, but none of these will get anywhere near the levels of GHG reductions required to stabilise the climate. Radical redesign of ‘big ticket’ items at least offers some hope of approaching the necessary targets. However, achieving this is not simple. First we need better understanding of emissions from buildings in the food supply chain. Then we need to design new buildings and processes that have fewer emissions. Finally, we will need to persuade food businesses to make the extra investment required in new capital. Indeed ideally, technologically obsolete buildings would be replaced in the short term, even if this was ahead of their scheduled renewal time. A carbon tax, or massive increase in energy costs, would provide some incentive for new investment, but would not be welcome by many. Pressure from civil society and supermarkets is another option, but it will need a lot of pressure to encourage the early replacement of a million Euro glasshouse! Grants for capital investments are always well received by farmers, but tend not to be popular with policymakers, even when they offer genuine social goods, such as in pollution control. If none of these options is possible or palatable, then regulation is an option. One of the main drivers of enhanced energy efficiency in the UK’s housing stock has been the building regulations that require certain materials and designs to be used in all new houses, e.g. minimum thresholds for the quality of insulation in walls. Are radical building regulations for agricultural buildings a possibility? As with much in the climate change arena, ideas are cheap and solutions are not. However, the benefit of focusing thought and resources on buildings and other capital items in the food chain is that at least they are big enough users of energy to offer some hope of achieving meaningful reductions in GHGs.