Energy in Global Agriculture as the Human Population Peaks
Philip Eckhoff[1] and Lowell Wood[2]
Introduction
Provision of adequate nutrition to a population that is forecasted to grow to 9 billion individuals by the year 2050 is a major challenge facing humanity. When consideringrequisitemajor improvement in the nutrition level of the existing population, net global agricultural production will have to at least double over the next four decades. This growth necessarily will be driven primarily by increases in agricultural productivity rather than by major increases in land under cultivation. If dietary preferences continue to develop globally towards those more characteristic of developed world settings, global food productivity may have to rise even further.
A major component of previous improvements in agricultural productivity and a key requirement for further increase is the availability and cost of energy. Energy is a key input for chemical fertilizer generation-&-utilization, planting, harvesting, transportation, storage, water supply, and many other aspects of modern agriculture. Unfortunately, the areas of the globe with the largest nutritional shortfalls today– and the largest projected shortfalls in 2050– are also the regions with the least effective access to energy today.
For much of human history, human-supplied power, fueled by food intake, was the primary source-term in agricultural energy accounts. The available food supply determined not only the supported population, but the anthropometrics of the supported population and the fraction of the population required for agricultural work. These factors would settle into an equilibrium determined by population, population anthropometrics, labor market, and food supply. Animal labor was the other key input, but this too required either diversion of food supply or allocationof land for grazing. Baseline human metabolism depends on body size, and thus available food calories determine how much excess energy for work will be available for a given body size[1]. A lower food supply supports smaller people –who are less absolutely productiveagricultural workers –so that they will have sufficient excess energy to perform the work of bringing in the harvest. Smaller, less-nourished body sizes also spent relatively more time-and-energyin coping with acute and chronic illnesses, further limiting productivity. Net,low excess per capita caloriesclampedtheamount of agricultural work that could be performed for nearly all of history prior to the 20th century.
As agricultural productivity increased, human anthropometry was able to improve as well, resulting in more productive body sizes, healthier populations, and a lower fraction of the population required to perform essentialagricultural labor. As development continued, several key factors improved agricultural productivity, made the food supply more robust, and changed the sources of energy central to agricultural output. Early mechanization made available human and farm animal energy more efficient in driving crop production. As mechanization progressed, human and farm animal energy, which were in turn dependent on agricultural land and the food supply, were replaced to ever-greater extents by fossil fuels. Existing soil levels of fixed nitrogen, which had been dependent on natural processes such as lightning, crop rotations with legumes, or mined and transported nitrates, were supplemented drasticallywith outputs of the Haber-Bosch ammonia-synthesis process [2]. This technology has made giant strides in efficiency, but such fertilizer production and distribution requires energy inputs. These inputs have enabled tremendous increases in food productivity per cultivated hectare over the past 9 decades, so much so that over half of humanity is presently ‘carried’ nutritionally by Haber-Bosch process outputs.
Modern agriculture is extensively and intensively intertwined with energy production and availability. Energy is required for fertilizer production in Haber-Bosch plants throughout the world, as well as for the transportation and distribution of fertilizer of all types. Energy, primarily as fossil fuels, is required for transportation of crops from sites of production through processing points and on to sites of consumption. Separation of these sites is often inevitable due to the differences in agricultural productivity between the most productive regions and the regions with the highest populations, with efforts to move production closer to the population centers often resulting in higher net energy cost per output-unitthan the nominal transportation savings. Regardless, energy remains a key requirement for transportation of crops. Once transported, crops and agricultural products must be stored until use, e.g., via both standard refrigeration of perishables and the operation of modern granaries to buffer food supply both prior to and following processing steps. Fossil fueled-energized mechanization is now synonymous with high-productivity agriculture in most locales. Energy also is often required in substantial quantities for the sourcing and transportation/distribution of agriculturally-required water.
In the present context of doubling agricultural production, severe energy challenges arise. First and foremost, energy availability is lowest and prices are often highest in areas with the most severe malnutrition. These regions are often also the ones with the highest anticipated population increases during the next four decades. Moreover, these areas generally have low present-day agricultural productivity and tend to face the worst issues with food security and stability. The concatenation of these challenges is formidable.
Agriculture is a key driver of human demand for water, and as water becomes scarcer and more in demand with growing populations and stepped-up agriculture, supplying of water will be a key driver of agricultural energy requirements. Sourcing may have to resort to such energetically-expensive means as desalination or similar enhancement of local low-quality water supplies, and more water will need to be transported to regions at risk of drought, or without access to water supply levels required for near-optimal productivity.
Increasing agricultural production demands energy of several other major types. More fertilizer will be produced as it becomes more utilized in developing world agricultural areas currently working at subsistence levels, as intensive fertilizer usage can result in order-of-magnitude yield-gains. Many regions of sub-Saharan Africa have difficult (e.g., weather-impaired),costly and long-latency transportation, so that fertilizer typically is not readily available and is much more expensive – often, 2X or more –at farmgatesthan at source-points in best-case. These transportation challenges doubly impact farmers in such areas, as they do not receive major fractions of the ultimate sales-prices of their crops due to high costs involved in moving products from farmgates to urban marketplaces or ports, moreover in transiently market-saturated circumstances arising from minimal crop-storage capabilities. Construction of all-weather roads requires petroleum, and improved transportation of fertilizer and crops requiresmajor energy sources as well.
We explore a variety of routes towards meeting these energy demands in the contexts ofdoublingglobal agricultural production over the next four decades, especially in areas most in need of such large-&-swift gains. Precision planting and water and fertilizer usage combined with deployment of sharply performance-enhanced, locally-optimized seedstockswill attain and maintain productivity gainswith significantly lower inputs and thus less energy, capital and labor than would otherwise be required. Waste and water management in cities and transportation of food to cities will be key drivers of overall use-efficiency as urbanization advancesglobally, and strategies for mitigating energy demand for each sector will all benefit the food supply outlook. Finally, new cultivar strains have the increasingly-tangible potential to require less water and fertilizer while concurrently providing large yield-gains, thereby engenderingnotably nonlinear energy savings. [We are aware of a number of thoughtful studies[3-5] documenting the feasibility-in-principle of adequately nourishing ~50% more people by large-scale redistributions of presently-employed quantities of fertilizers and water supplies concatenated with major shifts in dietary practices, e.g., abandonment of preferences for meat intakes in favor of high-yield cereal grains and uniform distribution of foodstuffs. However, our present focus is on identification of ways-&-means for practically evolving human food generation-&-use in less centrally guided and implicitly coercive manners, according greater respect to national sovereignties, unequal resource distributions, extant-&-evolving dietary tastes of individuals and sub-populations, etc. – i.e., taking note of the salient features and working within the constraints of the quite non-ideal world in which we find ourselves.]
Facilitating the increases in agricultural productivity indicated as required over the next four decades will have dramatic impacts on human health and well-being. Nutritional status is a key factor in many types of disease and chronic illness[6]. Most notably, adequate macro and micro-nutrition for humans in their first half-dozen years of lifeis essential for cognitive development, andhas been demonstrated to dramatically improve the health, productivity and overall outlook for future individuals and nations alike; seeing to such nutrition will provide the single greatest return-on-investment in agricultural productivity in the developing world, especially when the relatively very modest demands – of the order of 2-3% –placed on total human food supply are considered. Finally, mitigating stresses on food supply, water, and energy can dramatically boundmajor triggers for large-scale conflict, as the global population swiftly crests.
The Challenge of Adequate Nutrition
All of human civilization rests on an agricultural base, the source of all food and most fiber. Farming is the traditional occupation of 70-90 percent of humanity, and 50 percent of all people still live in rural areas, engaged in predominantly agricultural occupations. The fraction of the human population involved in agriculture has declined remarkably over the past two centuries as productivity gains have allowed a smaller agricultural labor force to feed humanity. As the global population grows beyond 9 billion individuals by 2050 --with a UN-estimated eventual peak at approximately 10 billion – still more food will need to be produced to feed the planet.
Unfortunately, these required gains are not starting at food adequacy today, as extensive malnutrition still persists in many human populations [7]. This current malnutrition leads to stunting and wasting of growing young people – approximately a half-billion of whom have already been irrevocably ruined and another billion of whom are at risk between now and 2050, if current conditions persist. There has been tremendous progress in certain regions of the world since 1985, especially East Asia and South Asia, but sub-Saharan Africa is just recently catching up to its nutritional standards of 1985 after over a decade of decline through the mid-1990’s [7]. Figure 1 shows the trends in height-for-age Z-score (HAZ) by region over the past 3 decades relative to 2006 WHO child growth standards.
Figure 1: Trends in height for age Z-scores (HAZ) by region. Each panel plots estimated distributions of HAZ at 5-year intervals. The more of the distribution below -2, the higher the prevalence of malnutrition in a region’s children. The more of the distribution below -3, the higher the prevalence of severe malnutrition. South Asia started with the worst malnutrition in 1985 but has made dramatic progress in each 5-year interval. East and southeast Asia have made tremendous progress as well. Southern and tropical Latin America are actually approaching the WHO child growth standards. Sub-Saharan Africa, on the other hand, had a decade of increasing malnutrition from 1985 to 1995 and is just now getting back to the HAZ distribution of 1985. Figure from [7].
South Asia still dominates in total numbers of children with HAZ and WAZ (weight-to-age Z-score) below 3 standard deviations of the mean of the WHO standard distributions, but this region has made great progress in both mean Z-scores and in total numbers of children most at risk since the mid-‘80s. East Asia has raised its mean Z scores from ones statistically similar to sub-Saharan Africa to scores closer to Latin America. The mean Z-scores in sub-Saharan Africa are similar to those in 1985, and the increase in population there means that the total number of children with Z-scores below -3 has actually risen while the globe’s corresponding numbers have fallen. These trends and patterns are displayed in Figure 2.
Figure 2: Trends in mean Z-scores and numbers of severely malnourished children by region. South Asia still has more children with HAZ and WAZ below -3 than any other region, but the prevalence has been decreasing even faster than populations have been growing. So even the absolute number of severely malnourished children is decreasing. In contrast, the prevalence in sub-Saharan Africa is similar to 1985 but populations have increased, resulting in an increase in the absolute number of severely malnourished children. East Asia used to represent a sizable fraction of the absolute number of severely malnourished children in 1985, but the situation has changed dramatically for the better. Figure from [7].
The first Millennium Development Goal – MDG-1 – focuses on a two-fold reduction in malnutrition (specifically defined as reducing the prevalence of children with WAZ < -2 by a factor of 2 or attaining a low target prevalence), but the estimated probability of attaining MDG-1 is quite low across much of sub-Saharan Africa and South Asia (Figure 3)[7].
Figure 3: Estimates of the likelihood of attaining MDG-1 by 2015. Figure from [7].
In addition to improving nutritional standards for existing populations and increasing food production for future populations, agriculture is necessarily responding to a large-scale evolution in dietary preferences. Dietary preferences across the developing world are changing towards the less crop-efficient, more meat-intensive diets characteristic of the developed world. The diets of more economically developed countries exhibit higher total per capita caloric inputs to diets and more upgraded dietary protein sources such as eggs, milk, and meat. Figure 4 exhibits trends over the past half-century in total dietary caloric demand and protein demand for a variety of economic categories [8].
Figure 4: Trends in caloric and protein demand with changes in GDP. Figure from [8].
As much of the readily arable land of our planet has already been enlisted in crop production, these necessary gains in crop production will have to come primarily from gains in agricultural productivity. Increasing total land area under cultivation will become increasingly difficult, and urbanization in many regions may be expected to even reduce total arable land. Concatenating all these factors, agricultural production will have to at least double in the next four decades, and the average productivity per unit of cultivated area will have to more than double.
The Challenge of Agriculture Productivity is a Challenge of Energy Supply-&-Utilization
Cheaper and more plentiful energy has been a major driver of previously documented major improvements in agricultural productivity. Energy is a key component driving generation-&-transport of fertilizers, crop planting and tending, water supply, harvesting, transportation, and processing and storage. Of special note is the water supply, as agricultural uses dominate the human-controlled global water budget, currently accounting for ~69% of human water use.
Unfortunately, the regions with nutritional shortfalls and thus behind their commitments on attainment of MDG-1 often have less effective energy access. Table 1 shows the annual electric power consumption per capita (in kW-hr/year) for a variety of countries, with data from IEA [9].
Country / Consumption / Country / Consumption / Country / ConsumptionHaiti / 36 / Bangladesh / 252 / China / 2631
Ethiopia / 46 / Cameroon / 271 / Argentina / 2759
Tanzania / 86 / Pakistan / 449 / Malaysia / 3614
Benin / 91 / Mozambique / 453 / Libya / 4170
Nepal / 91 / India / 571 / UK / 5692
DRC / 104 / Zambia / 635 / Russian Fed. / 6133
Togo / 111 / Vietnam / 918 / Germany / 6779
Kenya / 147 / Algeria / 971 / France / 7468
Senegal / 196 / Zimbabwe / 1026 / Belgium / 7903
Angola / 202 / Botswana / 1503 / Australia / 11113
Cote d’Ivoire / 203 / Namibia / 1576 / USA / 12914
Yemen / 219 / Thailand / 2045 / Norway / 23550
Table 1: Electric power consumption per capita (kW-hr/year). Data from [9].
Transportation and mechanization are other drivers of energy consumption in agriculture, and here too effective access to energy is more limited in regions most in need of productivity increases. Table 2 shows the distribution of vehicles, diesel consumption, and the cost of gasoline normalized by local GDP (PPP) for a range of countries.
Country / Motor vehicles per 1000 [10] / Diesel fuel consumed (road sector, kg oil equiv. per capita) [10] / Cost of gallon of gas in June 2010 [11] / Gallon of gasoline normalized by per capitaGDP (PPP) per day [12]Eritrea / 11 (2007) / 6 (2009) / 9.59 USD / 4.76
Senegal / 22 (2008) / 41 (2009)
Kenya / 23 (2009) / 21 (2009) / 4.31 USD / 0.9
India / 18 (2009) / 26 (2009) / 4.25 USD / 0.42
Pakistan / 13 (2009) / 38 (2009) / 3.02 USD / 0.39
Nigeria / 31 (2007) / 4 (2009) / 1.62 USD / 0.23
Indonesia / 79 (2009) / 44 (2009)
Brazil / 209 (2008) / 149 (2009) / 5.69 USD / 0.18
U.K. / 523 (2009) / 351 (2009) / 6.60 USD / 0.067
France / 598 (2009) / 470 (2009) / 6.04 USD / 0.063
U.S. / 802 (2009) / 384 (2009) / 2.85 USD / 0.02
Table 2: Data for motor vehicles per 1000, diesel fuel consumed, and the cost of gasoline normalized by per capita GDP indicate that normalized costs are higher and availability is lower for transportation in countries requiring the largest increases in food supply. Data from [10-12].
Trends in Energy Usage over the History of Agriculture
For most of human history, human-supplied power, fueled by food intake, was the primary source of agricultural energy. People prepared fields, planted, tended, harvested, and threshed their crops with energy supplied by ingestion of fractions of their previous agricultural output. Available food supply determined both the number of the supported population and its anthropometrics, which determined the labor effectivelyavailable to produce the next season’s food supply. Energy exertion in various activities can be measured as a multiple of the Basal Metabolic Rate. Including the necessary functions of eating, digestion, hygiene, etc,, abare-survival diet requiresapproximately 1.27 x BMR [6]. Work, e.g., the production-&-processing of food, requires additional food energy beyond this modest BMR-multiple (see Table 3 for typical required BMR multiples for various agricultural activities central to food-&-fiber production).