Energy Use for Cooking and Other Stages in the Life Cycle of Food

Abstract
In this study, electricity use for cooking wheat, spaghetti, pasta, barley, rice, potatoes,
couscous and mashed potatoes from potatoes mashed powder was measured. The
measurements were made with cooking appliances and number of portions relevant for
households. Hotplates, electric kettles and microwave ovens were used for measuring
electricity use for cooking. We also estimated the energy use in the life cycle stages before
cooking.
Energy use for cooking can be a large or dominating part in the energy use for some food
products’ life cycle. Such food products are of vegetable origin with low to medium degree of
processing. Electricity use per portion for cooking varied between 0.11 MJ and 5.1 MJ and
was greatly influenced by the choice of cooking appliance and the number of portions cooked.
Cooking in a microwave oven with a sensor regulated simmering function was 36 % to 92 %
more energy demanding compared to cooking on a hotplate. An electric kettle was 35 % to 60
% more energy efficient than a hotplate for boiling the water needed for cooking couscous
and mashed potatoes from mashed potato powder. The electricity use for boiling water in an
electric kettle was similar to the specific heat for water. A microwave oven was up to ten
times more energy efficient than a conventional oven for baking potatoes. It was always more
energy efficient to cook several portions at the same time. The differences were in the order of
a factor two to three for wheat, barley, rice, potatoes, couscous and mashed potatoes. For
spaghetti and fresh pasta the differences were smaller.
Electricity use for households’ cooking matches’ energy use for industrial food processing.
There seem to be great possibilities for improving the energy efficiency of diets with respect
to choice of ingredient and cooking method. Our study indicates that one portion of food
commonly served as part of hot meals can be produced with life cycle energy inputs ranging
from 0.33 MJ to 6.0 MJ per portion. Wheat and barley had the lowest energy inputs while
fresh pasta, imported spaghetti and potatoes baked in a conventional oven had the highest
energy inputs.
2