As Rock Phosphate Runs Out, What is More Important - Food Crops or Fuel Crops?

World rock phosphate production is set to peak by 2030. Since the material provides fertilizer for agriculture, the consequences are likely to be severe, and worsened by the increased production of biofuels, including those from algae.

Introduction.

The depletion of world rock phosphate reserves will restrict the amount of food that can be grown across the world, a situation that can only be compounded by the production of biofuels, including the potential large-scale generation of biodiesel from algae. The world population has risen to its present number of 7 billion in consequence of cheap fertilizers, pesticides and energy sources, particularly oil. Almost all modern farming has been engineered to depend on phosphate fertilizers, and those made from natural gas, e.g. ammonium nitrate, and on oil to run farm machinery and to distribute the final produce. A peak in worldwide production of rock phosphate is expected by 2030, which lends fears over how much food the world will be able to grow in the future, against a rising number of mouths to feed. Consensus of opinion is that we are close to the peak in world oil production too. Phosphorus is an essential element in all living things, along with nitrogen and potassium. These are known collectively as, P, N, K, to describe micronutrients that drive growth in all plants and animal species, including humans. Global demand for phosphate rock is predicted to rise at 2.3% per year, but this is likely to increase in order to produce crops for biofuel production. As a rider to this, if the transition is made to cellulosic ethanol production, more phosphorus will be required still since there is less of the plant (the "chaff") available to return as plant rubble after the harvest, which is a traditional and natural provider of K and P to the soil.

World rock phosphate production amounts to around 140 million tonnes. In comparison, we would need 352 million tonnes of the mineral to grow sufficient algae to replace all the oil-derived fuels used in the world. The US produces less than 40 million tonnes of rock phosphate annually, but to become self-sufficient in algal diesel would require around 88 million tonnes of the mineral. Hence, for the US, security of fuel supply could not be met by algae-to-diesel production using even all its indigenous rock phosphate output, and significant further imports would be needed. This is in addition to the amount of the mineral necessary to maintain existing agriculture. In principle, phosphate could be recycled from one batch of algae to the next, but how exactly this might be done remains a matter of some deliberation. e.g. The algae could be dried and burned, and the phosphate extracted from the resulting “ash”, or the algae could be converted to methane in a biodigester, releasing phosphate in the process. Clearly there are engineering and energy costs attendant to any and all such schemes and none has been adopted as yet.

Cleaning-up the Environment.

There is the further issue of the demand on freshwater, of which agriculture already struggles to secure enough to meet its needs, and in a sustainable picture of the future, supplies of water appear uncertain against the countenance of climate change. It is in the light of these considerations that algae/algal fuels have begun to look very appealing, especially given the claimed very high yields that can be obtained per hectare as compared say with rapeseed and biodiesel. Conventional algae production can be combined with water clean-up strategies3, to remove N and P from agricultural run-off water and sewage effluent, both to prevent eutrophication (nutrient build-up in water), which causes algal blooms, and to conserve the precious resource of phosphate. Algae might also be “fed” with CO2 from the smokestacks of power stations to reduce carbon emissions. The implementation of integrated strategies such as these, where the creation of a “carbon neutral” fuel is combined with pollution-reduction is thought to be the only way that the price of algal fuels can be brought down to a level comparable with conventional fuels refined from crude oil. As the price of oil rises inexorably, they are likely to become even more attractive. “Peak phosphate” is connected to “peak oil” since phosphate is mined using oil-powered machinery, and in the absence of sufficient phosphorus, we will be unable to feed the rising global human population, since modern industrialised farming depends on heavy inputs of phosphate, along with nitrogen fertilizers.
Pesticides, too, derived chemically from crude oil, are essential, along with oil-refined fuels for farm machinery. It is, nonetheless, doubtful that the world’s liquid transportation fuel requirements can be met through standard methods of algae cultivation entirely, though fuel production on a smaller scale seems thus feasible. An analogy for the latter might be as growing algae in a “village pond” for use by a community of limited numbers.

No solution to “fuel crops versus food crops” problem.

It is salutary that there remains a competition between growing crops (algae) for fuel and those for food, even if not directly in terms of land, for the fertilizers that both depend upon. This illustrates for me the complex and interconnected nature of, indeed Nature, and which like any stressed chain, will ultimately converge its forces onto the weakest link in the “it takes energy to extract energy” sequence. It seems quite clear that with food production already stressed, the production of (algal) biofuels will never be accomplished on a scale anywhere close to matching current world petroleum fuel use (>20 billion barrels/annum). Thus, the days of a society based around personalized transport run on liquid fuels are numbered. We must reconsider too our methods of farming, to reduce inputs of fertilisers, pesticides and fuel. Freshwater supplies are also at issue, in the complex transition to a more localised age that uses its resources much more efficiently.

In contrast to fossil fuels, say, phosphorus can be recycled, but if phosphorus is wasted, there is no substitute for it. The evidence is that the world is using up its relatively limited supplies of phosphates in concentrated form. In Asia, agriculture has been enabled through returning animal and human manure to the soil, for example in the form of sewage sludge, and it is suggested that by the use of composting toilets, urine diversion, more efficient ways of using fertilizer and more efficient technology, the potential problem of phosphorus depletion might be circumvented. It all seems to add up to the same thing, that we will need to use less and more efficiently, whether that be fossil resources, or food products, including our own human waste. We are all taking a ride on spaceship earth, and depend mutually on her various provisions to us. Our number is now so great that we cannot maintain our current global profligacy. In the form of localised communities as the global village will devolve into by the inevitable reduction in transportation, such strategies would seem sensible to food (and some fuel) production at the local level. "Small is beautiful" as Schumacher wrote those many years ago, emphasising a system of "economics as if people mattered".

And if we try to continue with business as usual?

There is a Hubbert-type analysis of human population growth which indicates that rather than rising to the putative “9 billion by 2050″ scenario, it will instead peak around the year 2025 at 7.3 billion, and then fall. It is probably significant too that that population growth curve fits very closely both with that for world phosphate production and another for world oil production. It seems to me highly indicative that it is the decline in resources that will underpin our decline in numbers as is true of any species: from a colony of human beings growing on the Earth, to a colony of bacteria growing on agar nutrient in a Petri-dish.

By. Professor Chris Rhodes

Professor Chris Rhodes is a writer and researcher. He studied chemistry at Sussex University, earning both a B.Sc and a Doctoral degree (D.Phil.); rising to become the youngest professor of physical chemistry in the U.K. at the age of 34.

A prolific author, Chris has published more than 400 research and popular science articles (some in national newspapers: The Independent and The Daily Telegraph)
He has recently published his first novel, "University Shambles" was published in April 2009 (Melrose Books). http://universityshambles.com