Frysa livsmedelsrester eller kassera dem för biogasproduktion
En studie, ur livscykelperspektiv, av energianvändning och växthusgasutsläpp
Food is widely consumed and in 2011 an average American devoured approximately one ton of food. The production of these goods requires large amounts of energy and contributes to 22-31 % of all greenhouse gas emissions occurring in Europe. More than one third of the produced food is discarded instead of consumed, and food waste make up about 30 % of the waste generated by households. 60 % of this food waste could be avoided if the eatables were handled in a better way.Avoidable food waste arises partly because residues from food are not taken care of, and because the food is not stored in a way that optimise its durability. Residues arises part- ly because of the contradictory and complex demands of everyday life and are, because of our busy lifestyle, difficult to avoid. To reduce the environmental impact of food con- sumption the focus should be on managing residues in the most environmentally friend- ly way, rather than to prevent residues from arising.To prolong the shelf life of food residues freezing it is an alternative method. The free- zer is one of the most energy consuming appliances in the household. Therefore this method requires energy consumption, which contributes to the generation of greenhouse gases. The food must also be thawed if this method is used, which may require additio- nal energy. The residues may also be disposed and used as a feedstock for biogas pro- duction. Biogas is an energy rich gas that can be used as vehicle fuel, as a replacement for fossil fuels. This handling of residues therefore has the potential for both energy gain and a reduction in greenhouse gas emissions.This report examines which management method of residues that is the most energy ef- ficient one, and which method that generates the least GHG emissions. The survey was carried out for residues of beef, rice, bread, tomato, carrot and apple. Energy consump- tion for production, freezing and thawing of food were weighed against potential energy gain from biogas production. The same calculation was used for greenhouse gas emis- sions from the described activities.The result shows that the method which is the most energy efficient, and causes the least greenhouse gas emissions, is dependent on several factors, including the source of the food, the residence in the freezer and packing at the time of the freezing. Knowledge regarding the specific food, and the handling of it, must be possessed to answer how food residues should be handled. It is clear that there are cases when it could be more energy efficient, and produce less greenhouse gas emissions, to dispose food residues to produce biogas than to freeze them for later consumption.