A life cycle comparison between processed ready meals and their home-made equivalent were published in a special edition of the journal Ambio (Ambio: A Journal of the Human Environment, vol. xxxiv number 4-5 June 2005). The conclusions are that there's not a lot to choose between the two. The home cooked meal used slightly less energy but generated slightly more GHG emissions (a result of different waste disposal assumptions).
Processed vs home made meals - Findings: The study compared three possible ways of producing a meal of meatballs and mashed potatoes served with carrots and milK:
- Entirely home cooked
- Instant mashed potato powder and chilled meatballs
Ready to eat all-in-one meal.
The following points are worth noting:
It was assumed that the meal was consumed on the day of purchase and therefore energy for home storage was not included.
- The study, being Swedish, quantified energy emissions based on the Swedish energy mix. 45% of Sweden's electricity is produced from HEP and 45% from nuclear with the remaining 10% from coal, oil and gas. This is of course different from the UK situation. This point is worth noting since slightly more electricity was used in the production of the ready meal than in the production of the home cooked equivalent; the balance might therefore be different if the UK electricity mix were factored in instead.
- The meat (pig and cattle) and dairy element of the meal contributed about 70% of the GHG emissions - with the remainder resulting from transport, processing, potato, carrot and wheat farming and the production of packaging. The implication of this finding might be that it's not how you eat what you eat but it's what you eat in the first place.
No allowance was made for the fact that a home-cook might cook enough for two days worth, nor that they might cook enough for the whole family. This could affect the conclusions.
This is of course just one type of meal out of infinite possibilities as the paper stresses.
Another relevant paper in the journal is Sonesson U, Anteson F, Davis J and Sjödén P-O. (2005). Home Transport and Wastage: Environmentally Relevant Household Activities in the Life Cycle of Food, Ulf Sonesson, Frida Anteson, Jennifer Davis and Per-Olow, Ambio Vol. 34, No. 4–5, June 2005 This focuses on the environmental significance of shopper transport and food waste in the food life cycle.
There are a few comments about the ready-meal vs processed foods question in the Wise Moves report, section 6.5, pages 78-80.