Harnessing Solar Energy for Food Production Sustainability

2. Food production and the food chain: The main numbers: • Solar radiation impacting on Earth • 178,000 terawatts (a terawatt is 1012 watts) annually • Capture of this energy by plants and algae (both terrestrial and marine) • 100 to 120 terawatts annually • 6 terawatts on arable land • 12 terawatts on grassland or savanna • 50 terawatts in forest • Question: • What can we therefore say about plant productivity in terms of its ability to supply the total energy used by humankind?

3. Food production and the food chain: The main numbers: >120,000 terawatts ~ 55,000 terawatts left ~ 40,000 terawatts in Hydrological cycle Of which 0.01 - 0.1% “could” be captured by hydro Capture by plants: 120 terawatts Global energy consumption by man: 15 terawatts

4. Food production and the food chain: Photosynthetic conversion by plants • Photosynthetic conversion by plants • More energy is landing on the plant than is captured by it. • 3-6% of incoming solar radiation impacting on the plant is captured. • Perhaps 1/3 to 1/5 of this is stored by the plant (grain, tuber, stem, root etc.) giving an overall conversion efficiency of about 1%. • The hidden energy needed by plants • Approx 1000kg of water is transpired for each kg of biomass produced by a plant. This energy also comes from the sun via the hydrologic cycle. • The solar energy from the hydrologic cycle needed to produce this transpiration is more than 100 times the energy contained in the plant biomass. • Question: • In terms of the energy required by a plant to produce biomass, which is greater; photosynthetic or hydrologic?

5. What proportion of total energy consumption is actually used in food production? • Global energy consumption by man • 15 terawatts (~475 exajoules) • Direct Agricultural use: • Only 1-2 % of this globally (e.g. ~1.2 exajoules in USA) • Question: • What can we say about total plant productivity and its ability to provide energy used in primary agriculture?

6. How does global food requirement compare with photosynthetic output? • Each human requires about 10MJ of food energy per day • This is about 22 exajoules planet-wide per year • On an annual basis this is currently equivalent to 0.7 terawatts • Or less than 1/20 of total global energy use by humans • Or ~0.7% of global photosynthesis • Or ~12% of the photosynthetic product captured by plants on arable land worldwide

7. How much of the World’s photosynthetically active land base is agricultural? • Total land: • 13 billion hectares • Agricultural land • 5 billion hectares • Arable: 1.5 billion ha (potentially more productive) • Grassland: 3.5 billion ha (for feeding animals which we can then consume) • Question: • Where does this leave agricultural capacity in terms of its ability to produce enough food now and in the future? • To answer this we need more information

8. Photosynthetically active land base and soil degradation

9. Enough food for now and into the future: Population • Current world population: • 6 billion • Projected population for 2050: • 7.7 (L) • 9.4 (M) • 11.2 (H) • Question: • Assuming medium growth, how much more food will be required by 2050?

10. Enough food for now and into the future: Diet • Global food requirement expressed in grain equivalents (billion tons d.w. per year). • Vegetarian diet • Today’s population: 2.9 • 2050 (M): 4.5 • Moderate diet • Today’s population: 5.2 • 2050 (M): 8.2 • Affluent diet • Today’s population: 9.1 • 2050 (M): 14.4 • Question: How does this compare with current food production? • Answer: 4.5 currently

11. What is the potential food production? • If all current agricultural land were operated using maximum inputs (including irrigation), to a level equivalent to the most productive European fields: • Then (theoretically) actual productivity could be ten times higher than now • If potentially productive non-agricultural land were brought into agriculture, this would increase by a further 50% • Even using low inputs, potential agricultural productivity could be four times higher than now. • But if this potential is there, why is there no sign of it being realized?

12. Need for food: Theory versus practice • From slide 5: • 22 exajoules needed (in theory) to feed current population • In reality, more is needed, to allow for waste, after-harvest losses, distribution inequalities etc. • From slide 9: • 4.5 billion tons grain equivalent of food produced each year. • Very broadly, this equates to 45 - 60 exajoules annual production. • So currently, at least twice the theoretical need is being produced to feed World population. • From slide 2: • Energy capture on agricultural land: 500 exajoules • Existing productivity is much lower than indicated on slide 2.

13. Efficiency in food: Developing versus developed World?

14. And what of energy used in food; is this sustainable?

15. So if the whole World moves to an affluent diet and high input systems, do we have enough fuel? • From slide 5: • 22 exajoules needed (in theory) to feed current population • But, if everyone on the planet needed 10 units of fossil fuel energy for each unit of food energy we consume, then the real energy need is 220 exajoules • And, if everyone on the planet over-fed themselves to the extent that Western society now does, then the real energy need rises to 330 exajoules • And if the population increases by 50%, this brings the total energy need to 445 exajoules • Question: • Is there enough fossil fuel for this? • Could biofuels be the answer?

16. Is there enough fossil fuel; how much of current fossil fuel use is devoted to food production? • Assume 450 exajoules (EJ) of fossil fuels are needed for food production, distribution etc. in a year (i.e. everyone follows the western model) • This is in excess of current total energy from oil extracted annually (which is about 150 EJ per year) • Energy from gas constitutes 100 EJ per year • Energy from coal contributes an extra 125 EJ per year • Renewables and nuclear contribute another 60 (about 50/50) • However, remember that right now 80% of fossil fuel use in the developed World is not used for food production or the food chain. • If this rate were applied to the figures above, then 2000 EJ per year would be required for World use; more than four times the current use. • Compare this to the current figure of 90EJ fossil fuel used in the food production system.

17. Is there enough potential biofuel? • Large variations in estimates of biomass biofuels: • IPCC (2000) 334million ha @ 24t/ha/yr. = 107 EJ/yr. • (assuming 18MJ/kg dry matter) • Higher estimates pre-date this one, mostly based on more available land, but lower yields. • The IPCC yield estimate seems very optimistic. • The amount of land available for biofuel could be increased by making existing farmland more productive. • However, this typically requires further energy inputs.

18. This is just energy sustainability – what about other considerations? • Water depletion • Water from many aquifers is being used more quickly than it is being replaced. • Water pollution • Groundwater contamination with fertilisers, agrochemicals. • Tolyfluanid plus ozone treatment creates nitrosamines • Glyphosate in ground water • Simazine • 45% of wells in potato and fruit growing area of Portugal • Soil erosion • The dust bowl • Atmospheric pollution • CO2 and climate change • Destruction of habitats

19. Some examples… ‘Dust Bowl’ USA 1930’s NOAA Photo Library

20. 500,000 homeless ‘environmental refugees’

21. CO2 in the atmosphere

22. Carbon flows 1 petagram = 1 billion tonnes

23. Integrated into an Ecological footprint Kitzes et al. 2008. Shrink and share: humanity’s present and future ecological footprint. Phil. Trans. R. Soc. B. 363, 467-475.

24. Ecological footprint: why the Western World needs to act Kitzes et al. 2008. Shrink and share: humanity’s present and future ecological footprint. Phil. Trans. R. Soc. B. 363, 467-475.

25. Silver bullet: What about new food production technologies? • The current proposition is that GM technology may lead to the next “great leap forward” in plant productivity • Thus far, despite 20 years of trying, GM crops produce lower yields than conventionally bred. • GM crops modified to resist herbicides have resulted in significant increases in herbicide usage. • Environmental damage due to GM technology and the monocultures it promotes has been reported, but not studied in depth. • Like any technology, genetic modification of plants can be used for the benefit of many or few. The privatisation of this technology via plant patents and de-regulation has meant only benefits for the companies involved, and not for humanity.

26. A warning Easter Island