Is a Haber-Bosch world sustainable? Population, nutrition, cereals, nitrogen and environment.

Gilland, Bernard

Nutrition

To measure the adequacy of a diet at least two indicators are needed: a quantitative and a qualitative. The quantitative is the energy content of the daily food supply Per capita. The qualitative is the daily supply of animal protein: protein from meat, marine products, dairy products and eggs (1).

A substantial amount of animal protein in a national average diet is desirable for several reasons:

1. It is universally preferred; per capita animal protein consumption exceeds 40 g per day in almost all countries classified by the UN as "developed", and also in Mexico, Brazil, Argentina, Chile, South Korea, Taiwan, Malaysia, Singapore, Israel, United Arab Emirates and Kuwait.

2. Feeding cereal grain to cattle, pigs and poultry is a safety buffer in the event of a sudden fall in grain production. Recent history confirms this. Until 1991, over half the Soviet Union's grain was fed to livestock. When grain production in the former Soviet Union fell drastically in the 1990s, there was a decline in the consumption of animal protein, but only a slight fall in the consumption of vegetal calories. There was no famine. In contrast, almost all grain in China in the 1950s was consumed by humans. When grain production fell drastically in 1959-61, 30 million people died of starvation (Ashton et al., 1984).

3. Animal products contain on average three times as much protein per calorie as vegetal products (60 g protein per 1000 kcal for animal products; 20 g per 1000 kcal for vegetal products), which makes them especially suitable for children. Countries with a low intake of animal protein per capita have a high incidence of child undernourishment.

4. Proteins from animal products have an amino acid composition closer to human requirements than vegetal protein, and thus have higher uptake efficiency. 1g animal protein is worth 1.4 g vegetal protein.

5. Animal foods have higher biologically utilizable contents of minerals (including calcium, phosphorus, iron, zinc, and iodine) and vitamins of the B group than most plant products. Livestock products are the primary source of vitamin [B.sub.12] (cobalamin).

Based on the recommendations of Randoin et al (1989), a diet ratios are:

Bovine meat 12, pigmeat 23, poultry meat 9, milk 10, eggs 12. that includes 40 g animal protein per capita per day (a level midway between the averages in the developed and the developing countries) can be considered as satisfactory. Madrigal (1994) considers that half the protein should be of animal origin. As the supply of vegetal protein exceeds 37 g per day in almost all countries, this implies that the supply of animal protein should be close to 40 g. With this protein consumption, the average daily food supply per capita would be approx. 3000 kcal, of which approx. 650 kcal would be of animal origin.

In 2009, the world average daily food supply was 2831 kcal per capita, of which 501 kcal was of animal origin (FAO, 2014). Animal food contained 31 g protein, vegetal food 48 g. A projection for 2050 is 3070 kcal, of which 550 kcal is of animal origin (Alexandratos and Bruinsma, 2012). The latter corresponds to 34 g animal protein, a 10 percent increase relative to 2009. The global average food wastage is estimated at 12 percent of supply, varying from 5 to 21 percent in different countries (Porkka et al, 2013).

Approximately one-third of global cereal production is fed to livestock (2). Of every 1000 kcal of grain harvested, 350 kcal is fed to livestock. The feed grain, together with feeds not edible by humans, produces 150 kcal meat, milk and eggs. The similarity to generating electricity by burning fossil fuels is striking: of every 1000 tons oil equivalent of fossil fuel consumed, 280 tons are consumed in power plants, and the thermal equivalent of the electricity output is 110 tons oil equivalent. As Robert Socolow (1999) stated, "meat is the electricity of food."

The crux of the population food supply problem is not the difference between the 40 g animal protein supply and the 2009 global average of 31g, but the difference between the 61 g average in the developed countries and the 24 g average in the developing countries. There is no prospect of a major reduction of this difference, as the developing countries have 12 inhabitants per hectare cereal area and the developed countries only 6. The difference in population per hectare is increasing due to the difference in population growth rates. In 2050 the developing countries are almost certain to have at least 15 inhabitants per hectare cereal area, while the developed countries will remain close to 6.

Only about 25 percent of the world's population live in countries in which the supply of animal protein exceeds 40 g per capita per day. Iceland has the world's highest supply of animal protein per capita: 95 g per day (FAO, 2014). Life expectancy (82 years) is among the highest, and infant mortality (1 per thousand in 2011) is the world's lowest (SI, 2012). The other side of the coin is that globally, 34 percent of adults were overweight or obese in 2008. The proportion varied from 70 percent in North America and 60 percent in Europe to 25 percent in China, 23 percent in Sub-Saharan Africa and 12 percent in South Asia. Under-nutrition and obesity can exist side-by-side within the same country, the same region and even the same family. The primary cause is excessive consumption of oils, fats and sugar (Keats and Wiggins, 2014). The Japanese and South Koreans have a relatively low incidence of overweight and obesity. Their per capita consumption of seafood is several times the world average, and Japan's food supply--2723 kcal per capita per day--is lower than that of any other affluent country.

A diet that includes 40 g animal protein (of which 35 g is from meat, milk and eggs, 5 g from marine products) requires as a global average a feed grain consumption of at least 150 kg per capita per year; the current level is 110 kg. The amount of feed grain needed for a given animal protein supply per capita depends on the proportions of beef, pork, poultry meat, milk and eggs in the livestock protein supply (1), and the amount of protein obtained from pasture and fisheries. Cereal feed consumption in 2009 varied from 568 kg per capita in Canada to 6 kg in India (FAO, 2013). As cereal consumption by humans and for industrial purposes is approx. 240 kg per capita as a world average, achievement of an average 40 g animal protein supply per capita means a total cereal consumption of approx. 400 kg per capita, about 10 percent above the current global average.

Food security

The Economist Intelligence Unit has assessed the level of food security in 107 countries by developing a Food Security Index (FSI) based on affordability, availability and quality (EIU, 2013). The top twenty countries are (in descending order) the U.S., Norway, France, Austria, Switzerland, Netherlands, Belgium, Canada, New Zealand, Denmark, Ireland, Germany, Finland, Sweden, Australia, Singapore, Israel, Japan, Spain and UK. All have a daily animal protein supply exceeding 50 g per capita. They include major food exporters and countries heavily dependent on food imports. On a per capita basis, Australia exported 72% of its food production of 11,336 kcal per day in 2005; New Zealand exported 66% of its production of 9135 kcal; Canada exported 61% of its production of 8929 kcal; the U.S. exported 46% of its production of 7210 kcal (Porkka et al, 2013). In contrast, Japan imported 61% of its food supply in 2012. The EIU considers that a high degree of dependence on food imports is compatible with a high level of food security. This view is not shared by several Asian countries (including China), which have leased tracts of agricultural land in Africa.

In countries with a low level of food security, diets are quasi-vegetarian and from 30 to 90 percent of the labor force is in agriculture. The average size of agricultural holdings is such that even a tripling of crop yields would not bring the peasants out of poverty. For comparison, the average size of agricultural holdings in India is 1.3 ha, the EU-27 average is 14 ha, in France and Germany it is over 50 ha, and in the UK 90 ha. Transfer of roughly 90% of the peasants to the industrial and service sectors would take a century or more. Of the 20 countries with the lowest FSI, all but four are in Sub-Saharan Africa. The population of Sub-Saharan Africa, 926 million in 2013, is projected to be 2185 million in 2050 (PRB, 2013). If fertility in the region does not decline more rapidly than assumed in the projection, a rise in mortality is virtually certain, as the countries in question will be unable to pay for the imports needed to compensate for their grain production shortfalls.

China and India are Nos. 43 and 70 respectively in the FSI table. Food availability in China is 3036 kcal/capita/day, including 37 g animal protein; in India it is 2321 kcal and 11 g animal protein. The number of children under age 5 who are moderately or severely wasted in China is estimated at 2 million; in India the number is 25 million (UNICEF, 2013). China's economic growth since 1980 is unprecedented. Few economists would have believed it possible. In 1984, environmentalist Lester Brown stated: "In China, which has only one-tenth of a hectare of cropland per person, there simply is no room for cars" (Brown et al, 1984). By mid-2011, the number of passenger cars in China had reached 68 million.

World population and cereal production

World average cereal production (counting rice in unmilled form) in 2012 was 2545 million metric tons, grown on 703 million hectares (Mha) with a yield of 3619 kg/ha (FAO, 2014). With a world population in 2012 of 7021 million (USBC, 2014), per capita production was 362 kg. An optimistic estimate for world cereal production in 2050 can be made by assuming that the harvested area in that year will be 700 Mha, and that the global yield will increase at the 1961-2012 average rate of 45 kg/ha/year (from 1442 kg/ha in 1961-1965). The yield in 2050 would then be 5360 kg/ha, and production 3750 million tons. However, the analysis of Grassini et al (2013) shows that wheat, rice and maize yields have plateaued or shown an abrupt decrease in the rate of yield gain on areas that account for 31 percent of global rice-wheat-maize production, and conclude that a linear extrapolation of the 1961-2012 rate of global yield increase to 2050 is too optimistic. The effect is apparent in the global yield of paddy rice: The rate of yield increase, 54 kg/ha/yr in 1961-1995, fell to 43 kg/ha/yr in 1996-2012 (FAO, 2014). N. Alexandratos and J. Bruinsma (2012) project a cereal yield in 2050 of 4300 kg/ha on 763 Mha, giving a production of 3280 million metric tons. Fischer (2012) estimates global cereal production in 2050 at 3500 million tons.

World population in 2050 is projected by the UN Population Division to be 9.55 billion, with a "high" variant of 10.87 billion and a "low" variant of 8.34 billion (UN 2013), by the U.S. Bureau of the Census 9.38 billion (USBC, 2014), and by the Population Reference Bureau 9.73 billion (PRB, 2013). Global population projections for 2050 have changed little over the past 30 years: Demographer T. Frejka (1981) estimated that a plausible "low" projection for 2050 is 8.76 billion, and a plausible "high" projection 11.02 billion; the mean of the two projections is 9.89 billion. Based on the Alexandratos-Bruinsma production projection and the UN "Medium" population projection, global average cereal production per capita in 2050 would be 343 kg. On the linear yield extrapolation projection of 3750 million tons, production per capita would be 393 kg.

Nitrogen fertilizer

Nitrogen (N) constitutes 16% of protein, and the protein content of cereal grain averages 10%. The average nitrogen content of cereal grain is thus 1.6 percent. The total amount of nitrogen in the plant is approximately 1.4 times that in the grain. Nitrogen in a form utilizable by crop plants is fixed by soil micro-organisms, released by crop residues and deposited by rainfall (from lightning and fossil fuel emission) and farmyard manure. The use of chemical fertilizers enables much higher yields to be obtained than from the other sources alone (3). Agronomist Norman Borlaug bred wheat and maize varieties that respond to heavy applications of chemical fertilizers, earning him the Nobel Prize in 1970. In his acceptance speech, Borlaug expressed his disapproval of the global urbanization trend, with increasing numbers living in "the poisoned and clangorous environment of pathologically hypertrophied megalopoles". A statue of Borlaug was unveiled at the National Statuary Hall in Washington, DC on what would have been Borlaug's 100th birthday--25 March 2014.

Globally, chemical fertilizer applied in 2012 had a nitrogen content of 107.5 million tons (Heffer and Prud'homme, 2013). It is produced as ammonia using Haber-Bosch synthesis. The feedstock is natural gas except in China, where coal is used. The most efficient ammonia plants consume 33 megajoules (MJ) of energy per kg N. The theoretical minimum energy requirement is 23 MJ per kg N. Conversion of ammonia to urea (easier to use than ammonia) adds 10 MJ per kg N (Smil, 2008). Nitrogen fertilizer production currently consumes the equivalent of 4% of the world's natural gas, and its application accounts for more than half of world cereal production. Erisman et al (2008) estimate that without Haber-Bosch ammonia, world population would now be about 3.5 billion. The Nobel Prize was awarded to Fritz Haber in 1918 and to Carl Bosch in 1931. Haber's subsequent work included a contribution to the use of poison gas in the First World War and fruitless research on methods of extracting gold from seawater, which contains 4 kg gold per [km.sub.3.] Haber's research may have inspired biochemist J.B.S. Haldane to write the short story "The Gold-Makers" ("The Inequality of Man", 1932).

Ammonia can also be produced electrically by combining atmospheric nitrogen with electrolytic hydrogen. The electricity consumption at the Glomfjord plant in Norway around 1980 was 13 kWh (47 MJ) per kg N. To produce 100 million tons of nitrogen fertilizer electrically would require 1300 terawatt-hours (TWh), or 6 percent of world electricity generation in 2012 (22,500 TWh). The price of nitrogen produced by this method would be in the same ballpark as the U.S. price in March 2014, $750 per ton N as urea. Ammonia was produced electrically in Norway from 1929 to the 1980s, using extremely cheap hydroelectricity, but natural gas has replaced it. It has been claimed that solid state ammonia technology could reduce the electricity requirement to 9 kWh per kg N, and the production cost (assuming an electricity cost of 5 U.S. cents per kWh) to $550 per ton N (Holbrook and Leighty, 2012).

Electricity

It is virtually certain that global electricity generation will increase more rapidly than primary energy consumption in the next few decades, and that fossil fuels will account for over 50% of generation in 2050. World electricity generation in 2040 is projected by the EIA (2013) at 39,000 TWh, of which fossil fuels account for 61%, nuclear 14%, and renewables 25%. The IEA (2012) projection for 2035 is 32,000 TWh, of which fossil fuels account for 57%, nuclear 12% and renewables 31%. The BP (2013) projection for 2030 is 35,000 TWh, of which 63% is fossil, 12% nuclear and 25% renewable. The Shell (2008) "Blueprints" scenario for 2030 is 30,000 TWh, of which 56% is fossil, 11% nuclear and 33% renewable.

Theoretically, nuclear fission could meet global electricity demand for several thousand years, but this would require large-scale conversion of uranium-238 and thorium-232 to the fissile isotopes plutonium-239 and uranium-233, respectively, by means of breeder reactors. Nuclear fission is currently based on uranium-235, the only natural fissile isotope, present in natural uranium at a concentration of 0.7%. The present nuclear generation of 2500 TWh per year is projected to rise to 5492 TWh by 2040 (EIA, 2013). If fusion reactors (based on the fusion of deuterium atoms to form helium) ever become practical, they would produce energy in discontinuous bursts, and therefore be unsuited for continuous electricity generation; however, they could be used as breeders for producing fissile isotopes. The complete replacement of nuclear fission by nuclear fusion cannot be ruled out, but is highly improbable.

Theoretically, solar energy could meet global electricity demand as long as humanity exists, but solar power plants, both thermal and photovoltaic, have a high construction cost in relation to annual electricity generation. Producing 10,000 TWh per year by concentrated solar power (CSP) plants in favorable locations would involve a capital cost on the order of $20 trillion at current prices, or almost one-third of the Gross World Product. This estimate is based on the cost and expected production of the Ivanpah CSP plant in California, due for completion in 2014. The plant will cost $2.2 billion and the expected production is 1.04 TWh per year. The rival type of solar power plant is based on photovoltaic (PV) cells. The Topaz PV plant in San Luis Obispo County, California is due for completion in 2015. The construction cost will exceed $2 billion and the expected production is 1.10 TWh per year. Future improvements in efficiency will probably substantially reduce the cost per TWh, but many solar plants will be built at locations less favorable than south-eastern California. According to the EIA Reference Case (2013), generation by solar power plants will rise from 34 TWh in 2010 to 452 TWh in 2040. This can be compared with 6232 TWh from hydropower and 1839 TWh from windpower in the same year.

Fossil fuels and carbon dioxide

A rapid phase-out of fossil fuels, asserted by Ehrlich and Ehrlich (2013) to be necessary to prevent a collapse of global civilization, would precipitate a global economic collapse. The most extreme climate alarmists fear that anthropogenic global warming, if unchecked, will render the planet uninhabitable. An anonymous reviewer replied that scientific and industrial society has made life far more comfortable for everyone, and added: "It is unfortunate that the price we may have to pay for this comfort is the extinction of the species, but this reviewer for one would sooner be extinct than go back to the horrors of the Middle Ages, or the high civilization of the Aztecs" ("Send for the elite", a review of biologist Sir Macfarlane Burnet's "Dominant Mammal" in the Times Literary Supplement, 7 April 1972). The reviewer's standpoint is discussed by Gilland (1995).

Atmospheric carbon dioxide concentration, 396 parts per million volume (ppmv) in 2013 and increasing by 2.1 ppmv per year, cannot be stabilized at a level lower than double the pre-industrial concentration of 280 ppmv, be the consequences what they may. In 1906, the Swedish scientist S.A. Arrhenius calculated that a doubling of the atmospheric carbon dioxide concentration would result in a global temperature rise of 2.1 [degrees] Celsius. According to the Intergovernmental Panel on Climate Change (IPCC 2013), the transient climate response, defined as the change in global mean surface temperature at the time when atmospheric carbon dioxide concentration has doubled after increasing at 1 percent annually, is likely to be in the range 1.0 [degrees]C to 2.5 [degrees]C and extremely unlikely to exceed 3 [degrees] C.

Data from climate monitoring stations show that the scenarios of climate alarmists are not plausible. An example: In the period 19932013, sea level rose at a constant rate of 3.2 mm per year, despite rising atmospheric carbon dioxide concentration throughout the period and rising global surface temperature during the first half of the period (Humlum, 2014). Part of the rise is undoubtedly caused by human activity, but this activity is not confined to fossil fuel combustion. It is estimated that depletion of aquifers and lowering of groundwater levels account for 25 percent of the 1150 [km.sup.3] annual increase in the volume of the oceans. This component of hydrospheric expansion is the result of population increase, not carbon dioxide emission. Thermal expansion accounts for 35 percent of recent sea level rise, and 40 percent is due to melting glaciers, mainly the Greenland and Antarctic ice sheets (IPCC, 2013).

The discovery of an exploitable oil or gas field always gives rise to jubilation, but unless it results in a decision to let the oil or gas remain underground, stabilization of atmospheric carbon dioxide concentration will remain a distant prospect. The proven reserves of fossil fuels have an estimated carbon content of 900 billion tons, corresponding to approx. 1000 billion tons oil equivalent. Burning the entire reserves would bring atmospheric carbon dioxide concentration up to approx. 650 ppmv. Extraction of oil and gas from shale and tar sands could result in a much higher concentration.

Future nitrogen demand and environment

The global nitrogen demand for agriculture in 2050 can be estimated conservatively at 155 million tons (4). Galloway et al (2004) have estimated nitrogen consumption in world agriculture in 2050 at 135 million tons. Sutton et al (2013) cite a "high" projection for 2050 of 190 million tons, a "mid" projection of 140 million tons, and a "low" projection of 80 million tons.

Increasing nitrogen fertilizer application would further increase nitrogen runoff to rivers, thereby increasing the pollution of river estuaries and coastal waters and creating hypoxic zones ("dead zones") that cannot support marine life. These zones now number over 400, with a total area of 250,000 [km.sup.2] (Diaz, 2008). Another problem with intensive cultivation is that pesticides are needed to protect the crop, but pesticides generate resistant pests, making it necessary to develop new pesticides to keep one jump ahead of the pests. Pesticides also cause ecological damage and high incidences of farmer poisoning and chronic health effects (Pretty, 2005).

Phosphorus and potassium

Phosphorus is an essential plant nutrient and a non-renewable resource. It has been asserted that production of phosphorus fertilizer will peak by mid-century, but this is not the case: "IFDC estimates of world phosphate rock reserves and resources indicate that phosphate rock of suitable quality to produce phosphoric acid will be available far into the future. Based on the data reviewed, and assuming current rates of production, phosphate rock concentrate reserves to produce fertilizer will be available for the next 300-400 years" (Van Kauwenbergh, 2010).

Physicist Charles Galton Darwin (1952) was aware of the importance of phosphorus in the long term: ".... the future numbers of humanity will depend on the abundance in the surface of the earth of the chemical elements which are necessary for life...... Two only deserve comment, nitrogen and phosphorus..... The question of phosphorus is far more serious [than that of nitrogen], though less of it is needed. There are great tracts of land, in particular in Africa, which are permanently deficient in phosphorus, and these can never be raised to the fertility of the more favoured regions, unless large quantities of it can be supplied to them. So it may well be that the future numbers of the human race will depend on the abundance of phosphorus in the earth's surface".

Reserves of potash (mainly in the form of potassium chloride) amount to approx. 250 years consumption at the 2011 rate. When the reserves have been exhausted, potassium can be extracted from seawater, in which the concentration is 380 g/[m.sup.3] (6000 times higher than the concentration of phosphorus).

Population limits

Writing in 1948, mathematician Michael Roberts (1951) concluded: "Within a century or so, the world's population will almost certainly be stabilized at something like three thousand millions, which is the utmost that the earth is likely to be able to feed." He had no inkling of the coming Green Revolution, and did not believe that inorganic fertilizers could be more than a short-term palliative.

Economist Nicholas Georgescu-Roegen (1979) pointed out that industrial society is based on a "unique mineralogical bonanza", and concluded that "at all times population must remain near the level at which it can be maintained biologically by organic agriculture." The global population that can be maintained by organic agriculture is approximately 2.5 billion (based on an average grain yield of 1500 kg/ha on 700 Mha, and a per capita grain production of 400 kg per year). On the highly improbable UN "Low" variant projection, world population will have declined to 3.2 billion in 2200 (UN, 2004). In a few countries, a drastic population decline will take place if current fertility rates continue and immigration is negligible. An example is Japan, whose population was 44 million in 1900, peaked at 128 million in 2010. and could decline to 50 million by 2100 (Yomiuri Shimbun, 2014).

Entrepreneur Arwind Bondre (2014) makes an important point: "All through their lives the same people are both consumers and producers. In their role as consumers they condemn the ever-increasing population, and when acting as producers or in some way being involved as producers, they welcome it. This is the most intriguing paradox of our time".

China introduced the one-child policy in 1979. It applies only to the urban population. In rural areas a second child is permitted if the first is a girl. China's population is projected to peak around 2030, and to decline thereafter. In Dec. 2013, the one-child policy was relaxed to permit couples to have a second child if either parent is an only child. An editorial in the South China Morning Post (14 Nov. 2013) comments: "The one-child policy may get some credit for China's economic miracle. But it remains divisive, with a painful legacy of sex determination and abortion, distortion of the birth ratio in favour of boys, an ageing society and the prospect of millions of men without partners." The birth ratio is 118 males per 100 females, far above the normal 105. To discuss whether the aim of China's demographic policy justifies the human costs of its implementation is outside the scope of this paper.

Other developing countries are either unable or unwilling to follow in the wake of China. Many of them will pay a high price for their future population growth, especially those in Sub-Saharan Africa, where the Green Revolution is unlikely to increase crop yields as it has done in Asia (Frison, 2008). The poorest countries will not have sufficient foreign exchange for a major increase in food imports, and will become increasingly dependent on foreign aid and emigrants' remittances (Alexandratos, 2005).

Conclusion

The dependence of the global food supply on nitrogen fertilizer will continue to increase as long as world population continues to increase. Agronomist Ken Cassman et al. (2002) conclude that "the dual goals of meeting food demand while protecting the environment from excess reactive nitrogen is one of the greatest ecological challenges facing humankind." It is fashionable to say that almost any economic or social problem is a "challenge" to which there is a "smart" solution, but there are problems that cannot be solved. Restoration of the pre-Haber-Bosch nitrogen cycle while maintaining a satisfactory nutritional standard worldwide is not possible until world population has declined to roughly one-third of the present number, and it is extremely unlikely that this will happen as a result of fertility decline. But it is certain that the Haber-Bosch nitrogen era and the fossil hydrocarbon era are "blips" in the course of human history. It is highly probable that the post-1950 population explosion will also be a blip.

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Bernard Gilland, Address for correspondence: bernardgilland1@gmail.com

(1) The global daily per capita supply of animal protein in 2009 was 31.2 g, of which meat supplied 14.1 g (including 3.6 g from bovine meat, 4.6 g from pigmeat and 4.7 g from poultry meat), dairy products 8.0 g, marine products 5.1 g, eggs 2.7 g, offals 1.1 g and animal fats 0.1 g (FAO, 2013).

The global average consumption of cereal feed for livestock in 2009 was 307 g per capita per day. It is estimated that the cereal feed is distributed as follows: pigs 35%, dairy cows 26%, beef cattle 14%, meat chickens 14% and laying hens 11% (Bradford et al., 1999).

On the basis of these data, the global cereal feed-livestock product protein ratios are:

Bovine meat 12, pigmeat 23, poultry meat 9, milk 10, eggs 12.

(2) There is no loss of protein utilizable by humans in the conversion of feed grain to meat, milk and eggs. This was pointed out by Bradford et al., 1999.

The following data refer to 2009:

Cereal grain for livestock feed: 746 million tons Protein content of feed grain: approx. 75 million tons

Global supply of protein from meat, milk and eggs: 26 g per capita per day = 64 million tons

Ratio of animal protein utilization efficiency to grain protein utilization efficiency = 1.4

The livestock product protein supply is equivalent to 1.4 x 64 = 90 million

tons grain protein. Equivalent animal protein output / grain protein input = 90 / 75 = 1.2

The bulk of the feed grain energy, however, is lost in the conversion to livestock product energy:

Feed grain energy : 112 kg per capita per year = 1043 kcal per capita per day

Animal product energy: 501 kcal per capita per day

As marine product energy is 33 kcal per capita, livestock product energy =

501-33 = 468 kcal per capita per day

Energy output / feed grain energy input = 468 / 1043 = 0.45

Production of one kcal meat, milk and eggs costs, as a global average, 1 / 0.45 = 2.2 kcal cereals (plus 5 or 6 kcal non-cereal feed, chiefly grass, oilseed cakes and by-products of the milling, brewing, distilling and starch industries).

(3) The incremental yield/nitrogen ratio in 2011 is calculated as follows:

Global cereal yield (2010-2012): 3620 kg/ha. Basal cereal yield (1948-1952 average + 25 percent): 1500 kg/ha. Yield from N fertilizer: 3620-1500 = 2120 kg/ha. Global nitrogen application on cereals (2011): 107.8 x 0.55 = 59.3 million tons. Cereal area: 701 million ha. Average nitrogen application on cereals: 84.6 kg/ha. Incremental yield/nitrogen ratio: 2120/84.6 = 25.

Cereal yields of up to 2500 kg/ha were obtained in the Netherlands as far back as 1850, but the world average yield without inorganic fertilizer would be much lower, chiefly due to variation in soil quality and moisture availability (Smil, 1994).

Incremental yield/nitrogen ratios for maize cultivation at three levels of aggregation can be calculated as follows:

Global maize, 2010:

Yield: 5180 kg/ha (FAO, 2014).

N application: 17.6 million tons on 164.3 million ha =107 kg/ha (Heffer, 2013; FAO, 2014).

N content of protein: 16%. Protein content of grain: 8.4% (Nafziger, 2013).

Total N uptake: 1.33 times grain N (Oklahoma State, 2010).

N requirement: 5180 x 0.084 x 1.33 x 0.16 = 93 kg/ha.

N fertilizer utilized: 107 x 0.50 = 54 kg/ha (estimated).

N from other sources: 93-54 = 39 kg/ha.

Yield from other sources: 39/0.084 x 1.33 x 0.16 = 2180 kg/ha

Incremental yield/nitrogen ratio (IYNR): (5180-2180)/107 = 28

United States maize, 2010:

Yield: 9592 kg/ha (FAO, 2014)

N application: 157 kg/ha

N requirement: 9592 x 0.084 x 1.33 x 0.16 = 171 kg/ha

N fertilizer utilized: 157 x 0.70 = 110 kg/ha (estimated)

N from other sources: 171-110 = 61 kg/ha

Yield from other sources: 3410 kg/ha

Incremental yield/nitrogen ratio: (9592-3410)/157 = 39

Average of 522 State winners in the 2010 NCGA Corn Yield Contest:

Yield: 18,940 kg/ha (NCGA, 2010)

N application: 290 kg/ha (NCGA, 2010)

N requirement: 18,940 x 0.084 x 1.33 x 0.16 = 339 kg/ha

N fertilizer utilized: 290 x 0.80 = 232 kg/ha (estimated)

N from other sources: 339-232 = 107 kg/ha

Yield from other sources: 5980 kg/ha

Incremental yield/nitrogen ratio: (18940-5980)/290 = 45

If the efficiency of the applied nitrogen fertilizer were 100%, and the amount applied was equal to the nitrogen uptake, the IYNR would be 1/(0.084 x 0.16 x 1.33) = 56. The recommended nitrogen application in U.S. maize cultivation is one pound of nitrogen per targeted bushel (56 pounds).

Approx. 40% of the U.S. maize harvest is converted to ethanol. The 2011 yield of 9200 kg/ha contains 5700 kg starch, which is converted to 2700 kg ethanol. The ethanol energy is equal to that of 1700 kg gasoline (2250 liters). The average American automobile consumes 1900 liters gasoline per year (19,000 km, 10 km per liter). One hectare maize thus fuels 1.2 automobiles; 40% of the 32 million hectares U.S. maize area is 13 million hectares, sufficient to fuel 16 million automobiles. The U.S. has approx. 190 million passenger cars. Ethanol therefore provides approx. 8 percent of the fuel energy consumed by U.S. automobiles.

Ethanol production raised the price of U.S. maize to a peak of $8.50 per bushel in 2012; the price in March 2014 was $5.68. The USDA estimates the average production cost of U.S. maize at $4.20 per bushel in 2011 and $5.56 in 2012.

(4) The global nitrogen demand for agriculture in 2050 can be estimated as follows:

Basal global cereal yield = 1500 kg/ha (Erisman et al., 2008)

Global incremental yield/nitrogen ratio 2011: 25 [Note 3]

Cereal area 2050: 763 million ha (Alexandratos and Bruinsma, 2012)

Total nitrogen consumption: 1.82 times the amount applied to cereals (Heffer, 2013)

Global cereal yield 2050: 4300 kg/ha (Alexandratos and Bruinsma, 2012)

Nitrogen application on cereals 2050: (4300-1500)/25 = 112 kg/ha

Total nitrogen application on cereals 2050: 0.112 x 763 = 85 million tons

Total nitrogen consumption 2050: 85 x 1.82 = 155 million tons

A global cereal production in 2050 of 3500 million tons (220 million tons higher than the Alexandratos-Bruinsma projection) would involve a total nitrogen consumption of:

155 + 1.82 x (220/25) = 171 million tons.