How to Feed the World Population Sustainably by the End of the Century
The Western world lives in an abundant society where expenditure on food only constitutes a small portion of the disposable family income, e.g. having fallen from 25% to 10% over the past 80 years in USA; instead, more money is spent on consumer goods and leisure. The developing world aspires to this life style but still finds itself on the other side of a divide. However, feeding the world cheaply now and in the future, with a growing world population, comes at a price: nature, the very foundation our civilisation is built upon.
The objective of this story is to articulate some considerations on how to feed the world sustainably and equitably towards the end of this century. The total amount of agricultural land available is subject to a balanced portfolio of food production systems such that every person in the year 2100 is afforded a healthy diet within the means of the planet. This story tries to communicate an understanding of the order of magnitude of all quantities involved as well as the consequences for sustainable agriculture and our diet.
Taking Stock — Some Basic Numbers
As a first step, let’s take stock of the energy demand for food consumption given the expected world population on one side, and the natural resources available for food production on the other.
Numbers on Food Energy Consumption
Humans need to consume a certain amount of energy from food to sustain the body, per day between 1000kcal and 3000kcal depending on age, gender and activity level; here an average is used, 2000kcal or 8370kJ which is equivalent to 2.3kWh. The ingested food and the therein contained carbohydrates, fatty acids and proteins are metabolised in complex processes to become eventually water, CO₂ and useful energy which in the end will be released as heat and hot air. Expressed differently, the resulting average power consumption (and heat generation) of a human is about 100 Watts, as much as a classic incandescent light bulb. Over a year, the consumed energy would amount to 0.7*10⁶ kcal or 3.1*10⁶ kJ which is equivalent to 848 kWh (about £146 in the UK if the human body was run on electricity alone).
At the end of this century, in 2100, when the world population is projected to reach about 11 billion, the total amount of food energy needed per day would amount to 22.0*10¹² kcal or 92.1*10¹² kJ which is equivalent to 25.6*10⁹ kWh or 25.6 TWh. This figure is a result of affording every person on average 2000kcal/day. The accumulated food energy over a year would be 8.0*10¹⁵ kcal or 33.6*10¹⁵ kJ which is equivalent to 9.3*10¹² kWh or 9,300 TWh. The average human power consumption through food would be of the order of 1.1 TW. To put these numbers in perspective, the current world power consumption according to theworldcounts.com is approximately 17.7 TW.
Numbers on Food Energy Production
On the production side we have to look at the land available for food production, directly to produce staples such as maize, potatoes, rice or wheat, indirectly to produce animal feed, or as grazing land for animals. According to Our World in Data the earth’s surface counts 149 million km² land of which 71% or 104 million km² are habitable. 50% of the latter or 51 million km² is currently used for agriculture, comprising both arable land in direct or indirect use for food production (cropland) as well as land used for grazing (pastureland). The split between cropland and pastureland differs per country. The average amount of cropland is assumed to be about 10% of the land surface or about 15 million km², i.e. about 30% of the agricultural land, or 15*10¹² m². As a remainder, the amount of pastureland is of the order of 36 million km², or 36*10¹² m².
As far as the status quo is concerned, Our World in Data provides an excellent source on food supply, agricultural production, meat and dairy production, environmental impacts of food, as well as many other aspects of food systems such as crop yields. For instance, the yields have tripled per land surface in the past 60 years through various aspects: mechanisation, seed development, industrial fertiliser, pesticides, and herbicides. Cropland has therefore become in many areas a live-less substrate for production resulting in soil erosion, loss of bio-diversity and a significant contribution to climate change (through the release of CO₂ and methane in various ways). Consequently, the basis of our civilisation may soon be removed by our own doing.
Sustainable production & consumption
The question now is: how can the world use the land available to produce food for everybody in a sustainable and equitable fashion. Let’s start with an average land use of foods to work out which diet looks sustainable given all agricultural land and the total amount of food energy needed. For the sake of this analysis we assumed that the amount and allocation of land does change significantly within the next few decades.
Furthermore, let’s establish 4 groups or baskets of foods with an average group land use (m²/1000 kcal) or group land efficiency (kcal/m²):
- Basket #1: Plants only — at 1.5m²/1000kcal land use or 666.7 kcal/m² land efficiency: a balanced mix in terms of energy in protein, fat and carbohydrates as well as nutrients by containing a varied diet of maize, rice, potatoes, lentils, beans, wheat & rye¹, various nuts as well as derived products such as tofu;
- Basket #2: White meats & eggs — at 6m²/1000kcal land use or 166.7kcal/m² land efficiency: an assortment of meats that are relatively efficient to produce in terms of energy and protein such as poultry, pork and eggs as well as fish from aquaculture;
- Basket #3: Dairy products — at 18m²/1000kcal land use or 55.6kcal/m² land efficiency: dairy milk and all its derivatives, from milk over butter and yoghurt to the finest cheeses;
- Basket #4: Red meats — at 120m²/1000kcal land use or 8.3kcal/m² land efficiency: this comprises beef, lamb and mutton.
If the plant only based basked is used as a reference, it is 4 times less efficient to produce the same amount of energy through white meat, 12 times less efficient through dairy products and a staggering 80 times less efficient through red meats. Following simple maths, it is easy to see that, in order to get 2000kcal a day per person, the land per person needed per day for every day of the year would be: 3m², 12m², 36m² and 240m² when consuming respectively only plants, white meat, dairy and red meat.
These numbers on land use show that producing red meat in particular is a very energy intensive process; a lot of input is needed per kcal produced. From an energetic standpoint, it does not make much sense to feed crops produced on prime land to large mammals such as cattle. They are simply not efficient converters of food; they do not even synthesise any proteins but merely accumulate the ingested proteins. In addition they need lots of energy to maintain their own body and temperature. Why not cut out the middle-man all together?
Premise: do not to use precious cropland to produce animal feed for red meat or dairy production but only pastureland; on the side, no cropland for bio-fuel production at all².
Pastureland is the agricultural land that in most cases is not suitable for growing crops which may include mountainous areas, and in particular areas of intermittent humidity (in many cases facing desertification). Rearing cow herds there for dairy and red meat production does make sense, e.g. the hilly areas of the European Alps or in Wales, UK. Cattle convert food energy from a source (grass) that does not compete with humans. Therefore, the following dietary composition is proposed:
- 80% of cropland to produce a plant based baseline,
- 20% of cropland to produce white meat and eggs,
- 20% of pastureland to produce milk & dairy,
- 80% of pastureland to produce red meat.
These numbers are not cast in stone but should be a good starting point.
Plant Based Baseline
Suppose all cropland is exclusively used to produce food for people, every speck of land out of the 15 million km², or 15*10¹² m². At an average land use or land efficiency for a balanced food based basket #1 above of 1.5m²/1000kcals or 666.7 kcal/m², respectively, the entire cropland would be able to produce an astounding 10*10¹⁵ kcal per year, about 120% of the projected 8*10¹⁵ kcal/year needed in 2100. Even though the 20% margin sounds reassuring, there is no allowance for waste and loss in the production chain. More importantly, however, this figure assumes that food is still being produced in a non-sustainable fashion using current farming practices including artificial fertiliser and other chemical inputs.
However, I am quite confident that over the next 80 years another revolution in agriculture will happen, after the mechanisation phase, the chemical and the biological era, a new way of farming systems will be established: knowledge based farming and Regenerative Agriculture, with at large scale “no-till” and/or “reduced till” practices as portrayed in the documentary Kiss The Ground. Critics might say that these techniques won’t produce as much food per land surface. However, already in the 1980ies I have seen farms to operate that way with comparable yields. Many technologies can be applied to make that happen nowadays such as but not limited to smart & precision farming. There is some time left to transition to the new paradigm.
From what I hear from my farming family’s neighbours who tried out no-till farming, a main issue in no-till farming is weed management which then is mitigated with more chemicals. The EU has commissioned a project investigating what would be needed; the results are available on Non-chemical weed management in arable cropping systems. This paper lists to name but a few: redesigning cropping systems, precision non-chemical weed control, equipment for precise weed management, autonomous robots for weeding, breeding for weed-suppressive and tolerant varieties/crops, etc.
Bottom line: it should be possible to produce the amount of food to feed every person in the world on a plant based diet (2000kcal/person/day) using sustainable techniques with an additional benefit of sequestering large amounts of carbon into the soil. 80% of the total cropland is sufficient to produce this baseline energy need by the end of this century.
Poultry & Eggs
Suppose further that the 20% surplus production or margin is now used to produce animal feed as input to the basket #2, a mix of poultry, pork and eggs. In other words, 1/5 of the cropland is used for the the production of items in this basket, i.e. 3 million km² or 3*10¹² m². Given its average 6m²/1000kcal land use or 166.7kcal/m² land efficiency, using this land would add 500*10¹² kcal to the total food energy production, or approximately 120 kcal/person/day in form of 50g of poultry or 50g pork or 2 eggs per day. Comparing with today’s average consumption of poultry and pork combined of about 80g/person/day (from Meat and Dairy Production), the estimated white meat consumption is only about 62% of today’s; this is perhaps not too much of a sacrifice if the survival of the planet is at stake.
Bottom line: 20% of cropland is diverted to produce animal feed for poultry & pork, both very efficient converters of plant energy to meat.
Cheese on Toast
In the proposed scenario, cows used for dairy production are only feed with grass or hay which in some cases is even a condition for producing certain types of cheese like real Swiss Emmental or French Comté. The land use for the dairy basked #3 was about 18m²/1000kcal land use or 55.6kcal/m² land efficiency which may be a bit on the low side if milk was produced using only pastureland, i.e. with no supplement from feed being produced on cropland such as maize silage, barley or soy. Given the average 55.6kcal/m² land efficiency, using 20% of the total pastureland would add 400*10¹² kcal to the total food energy production, or approximately 100 kcal/person/day in form of 200g of half fat milk, or 14g butter or 25g cheddar per day. Comparing to the average consumption of dairy today, this would be less, depending on the source and country, but palatable.
Bottom line: 20% of pastureland is used to produce dairy products, a moderately efficient conversion of plant energy.
The Sunday Roast
The land use for the red meat basked #4 was about 120m²/1000kcal land use or 8.3kcal/m² land efficiency which may be a bit on the low side if red meat was produced using only pastureland, i.e. with no supplement from feed being produced on cropland such as maize silage or soy. Given the average 8.3 kcal/m² land efficiency, using 80% of the total pastureland would add 240*10¹² kcal to the total food energy production, or approximately 60 kcal/person/day in form of 18g beef or 25 g lamb per day, or 125g beef or 175g lamb per week. The good news is that the traditional Sunday roast is still on the menu, but not much more. Comparing to the average consumption of beef today of about 27g/person/day, this would be less, but should be acceptable for the majority of people in the world. For people of countries like the USA with an average consumption of 37kg/year or about 100g/day, this reduction to 18% would be more difficult to digest.
Bottom line: 80% of pastureland is used to produce red meat as a treat, as its production is an inefficient conversion of plant energy.
What about the Vegetables?
A human needs more than just energy to function, the body needs nutrients, too. Vegetables are out of scope for this analysis, but I reckon that some land needs to be set aside for their production if it has to happen on soil such as for most root vegetables such as carrots. With regards to our greens, indoor farming looks like an interesting proposition with many companies offering production solutions such as OptimalLabs. There, the environment and all necessary inputs can be controlled very tightly, removing the need for pesticides and herbicides. Another aspect is that they can be grown very close to the place of consumption, so little transport meaning fresh salads and herbs at every city’s doorstep.
Thanks for All the Fish
According to Seafood and Overfishing, about 100*10⁶t are currently fished per year, or 100*10⁹kg/year, and has remained rather constant over the past decades. This would translate into 25g/person/day or 100kcal/person/day for the projected population in 2100, assuming that the amount fished remains the same. However, it appears that the current amount is beyond a sustainable amount and is expected to be lower. Therefore, this kind of fish falls into the same category as beef, a treat once a week.
Consequences for Agriculture
So far, the analysis was based on pure energy conversion, without any consideration for the economic side of the proposal and the consequences for agriculture. A few thoughts.
As far as the production of the baseline amount plant-based foodstuff is concerned, this is most likely to happen on a larger scale, but using regenerative farming techniques such as no-till farming, but without any chemical support, neither fertiliser nor pesticides or herbicides, thus reducing production inputs. However, smart machines will be required such as weeding robots that will be able to work down to an individual plant, and a host of supporting technologies for smart farming such as satellite/drone monitoring of soil properties, all of which is knowledge and capital intensive.
Animal husbandry can be much less intensive when only used on pastureland, but needs to be supported by technology, e.g. dynamically geo-fencing of herds through GPS tracked collars. One message conveyed by the documentary Kiss The Ground is: use more cattle in a well managed manner to achieve various targets: cover the land with vegetation to sequester CO₂; produce meat in a sustainable way; and lift the affected countries out of poverty. Perhaps those countries would become main meat producers and contribute at some point themselves to feeding the world. Most importantly, using pastureland does not compete with other crops on cropland. Both the cropland and the pastureland energy/protein streams are not mutually exclusive but complementary, and both help mitigate climate change.
So where does that leave the revenue stream for farmers, small or large? Unfortunately, most consumers do not necessarily put their money where their mouth is and accept higher local food prices as a consequence of the pressure they exert on the farmers. So the choices are:
- Part-time farming: since smaller family farms won’t be able to make a living from growing commodity crops, protein rich or other, the farm has to be run part-time, with the main family income from other employment;
- Land and farm consolidation: the minimum size for a commercially viable farm will result into concentration of farms, first through renting and working more land, eventually through acquisition;
- Niche products: for a small number of farms only, as niche products are usually for a limit market with higher purchasing power.
Last but not least: farmers do more than just producing food. Traditionally, at least in Austria, they look after the landscape, fields and their boarders and hedges, etc., the maintenance of which takes time and adds cost. If the population values a beautiful landscape and bio-diversity, which in turn is needed to maintain the basis of our civilisation, then this comes at a price. It has to be quantified and added to production as external cost. Alternatively, other means to generate additional revenue streams for farmers have to be devised, like farming-as-a-service, payments commensurate with the effort on land stewardship (and not proportional to land ownership). One part of such service could be sequestration of CO₂ perhaps monitored by satellites.
Societal impact
By the time you have reached this part it will be obvious that the only sustainable diet will be mostly plant based, with some addition of white meat, eggs and dairy during the week, and some red meat once a week for non-vegetarians/vegans. Cooking meat is easy in terms of taste, vegan and vegetarian cuisine is more demanding if flavour matters. But then, tastes are not innate, I reckon; so it is a matter of time that the whole of mankind learns to prepare and appreciate plant based dishes. In the meanwhile, lots of companies try to replicate the meat eating experience based on plant inputs.
In the end, evolution is still in progress. As long as a civilisation does not learn to live within its limits, it will fail and nature will prevail. It has happened through history which demonstrates the power of evolution: species with detrimental properties disappear. Mankind might be eliminated unless some of its traits disappear.
Notes
- As a personal check of the figures in the chart Land use of foods per 1000 kilocalories, let’s look at wheat & rye at 1.44m²/1000kcals, or its inverse, ~700kcals/m². At an energy density of 3.4kcal/g for wheat this would translate into roughly 206g/m² or 2,060kg/ha. On our family farm in Austria we used to harvest about 6,000kg wheat per hectare, so about 3 times more. I suppose the values given by Our-World-In-Data are averages across the globe including areas with poorer soil and less input such as fertiliser; the latter are expected to produce much less and will naturally decrease the average weighted by land surface.
- A short remark on bio-fuels. Suppose rapeseed is used as an input to the production of bio-fuel. Rapeseed yield can be up to 3,000kg/ha per harvest, i.e. 0.3kg/m²; 1kg rapeseed contains about 0.5kg oil; with oil containing 38MJ/kg the energy gained is consequently 5.7MJ/m². This energy spread over one year (1 harvest per year) results in 5,700,000J /365/24/60/60 s = 0.180W/m² average power. Conversion to bio-diesel incurs certainly some additional losses. In contrast, the solar irradiation at sea level is about 1kW. With on average 4h/day and an efficiency of 20%, a 1m² solar panel would produce an about 1000*4/24*0.20 = 33W average power. Therefore, a factor of 184 more power can harvested from solar panels than from growing rapeseed to produce bio-fuels. Consequently, bio-fuels from crops are indeed questionable in terms of efficiency.
- A short remark on vegan or vegetarian diet. Life on earth appears to be an intricate and intertwined system of living entities, transforming in essence an-organic matter into complex beings through many interactions, during evolution and at any time of the day. Such transformations need energy as well as other organic compounds as inputs, i.e. food at different levels of complexity. For some beings, ingesting other another living being is the easiest and most efficient way to live and grow. Some carnivores such as cats need to eat meat and the contained protein in order to survive; Omnivores like humans can live off all sorts of inputs at various levels of complexity. Cats have little choice, biologically and probably mentally; humans do have a choice, biologically and through their consciousness: ingesting food of lower complexity and let the body do the work, or ingest beings at a higher stage of the food chain, i.e. mammals. It does not need to be one or the other extreme, however, but a sustainable combination.
