The role of livestock in a sustainable diet: a land-use perspective

In 2000, the Food and Agricultural Organisation (FAO) projected that global demand for animal-source food (ASF) would double by 2050. Those projections, however, are based on global trends for a growing population and increasing incomes and urbanization, but not based on ensuring global nutrition security in a sustainable way. Currently, the world’s livestock sector add to the total anthropogenic emissions of greenhouse gases and competes for scarce resources, such as land, water, and fossil energy. Because especially land is a strict limitation of nutrition security, we took a land-use perspective. No matter how efficiently food is produced, direct consumption of cereals by humans is more efficient ecologically than consumption of livestock fed these cereals, and, therefore, it is often indicated that vegan diets are most land efficient. Should we shift, therefore, to vegan diets? Not necessarily! Because livestock has a potential to convert co-products from human food, food waste, and biomass from marginal land, referred to as ‘leftover streams’, into high quality ASF. Livestock that eat these leftover streams do not compete with humans for cropland, and, therefore, contribute to sustainable nutrition security. By feeding only leftover streams to livestock, the number of humans fed per hectare is maximized. How much ASF can we consume, however, when we only feed leftover steams to livestock? We calculated, that based on leftovers only, about 21 g of protein from ASF can be produced person per day. The daily recommended intake of protein is about 60 g per person per day, from which about a third must be from AFS. These 21 g from AFS is produced without competing with food crops from arable land. We can almost satisfy, therefore the daily recommended intake of protein of an average global person while avoiding competition for land between feed and food production.