How much meat should we eat – the environmental benefit of feeding food waste to pigs

In the years to come global pressure on land use will intensify. Livestock production currently uses about 70% of the agricultural land, mainly for pasture and production of feed crops. Feeding nine billion people the required protein content of 57 g/day in 2050, is only possible when resources are used efficiently. From a land use perspective, this implies that we should ensure that the production of animal proteins results in the same amount or more human digestible protein produced per m2 compared to crops. This can be achieved by feeding waste products from human diets to pigs. The aim of this study was two-fold: to assess how much pork can be produced based on waste products from a vegan diet and to determine the environmental benefit related to this. Based on a vegan diet of an average European person, 158 kg waste is available per year, for example from the production of margarine or bread. A pig diet based on waste products only did not meet the nutritional requirements of the pig, and therefore, the pig diet was supplemented to prevent health and welfare issues. The amount of waste products in the pig diet was optimized such that the amount of human digestible pork protein produced per m2 is similar to crop cultivation (i.e. 0.18 m2), resulting in a pig diet with 70% waste products. These waste products were used in the fraction of availability originating from the human vegan diet. Preliminary results showed that 114 g meat, containing 36 g of protein, can be consumed per day. The production of the daily required 57 g protein based on these waste-fed pigs, resulted in a global warming potential of 0.56 g CO2-e and a land use of 0.18 m2, whereas based on plant protein this was 38 g CO2-e and 0.18 m2. We, therefore, concluded that pigs fed with human food waste can have a role in future protein supply in human diets.