Food To 2050  

Stuart Staniford (often known simply as "Staniford") has another one of his excellent "2050" series of posts up at The Oil Drum, this one looking at trends in global food production (one of my favourite topics).

In Powering Civilization to 2050 I argued it was potentially feasible to transition to power civilization with a mix of solar, wind, and nuclear energy, with the transition well on the way to completion by 2050. (Luis de Sousa made a broadly similar argument in Olduvai Revisited 2008). This would require a period of belt tightening and conservation in the next couple of decades, but once the transition had overcome the critical threshold (as solar energy in particular became cheap), I suggested energy in general would get cheap again. I adopted the UN medium population projection which has population at about 9 billion by 2050, with growth slowing sharply. Making plausible assumptions for economic growth between now and 2050 if energy was available, we got to a world GDP of about $350 trillion in 2050 (in 2006 purchasing power parity dollars), versus about $70 trillion in 2007

If the average global citizen was significantly wealthier in 2050, they would undoubtedly want to drive more. The switch to primarily electrical energy sources for civilization would preclude doing this with all liquid fuels. In Four Billion Cars in 2050? I argued that, given that the average citizen will be living in a dense third world city by 2050, we can assume rates of ownership typical of the most car-free corners of western Europe at the moment (Holland), which gives rise to a few billion cars in 2050. I further argued that it seems feasible that this many plugin-hybrids could be built - there appears to be enough lithium for the batteries - and run on less than 10mbd of liquid fuels.

In this piece I want to look at another area that many people think is likely to be a critical bottleneck to civilization continuing - the area of food, agriculture, and soil. I am of course not an expert in these areas, but happily there is a lot of excellent scholarship and scenario building that I can lean on. My task is reduced to reporting of the existing science, with some modest adjustments to reflect where my assumptions differ from those of published scenarios (most especially the assumption of a near-term peak in oil supply, and a full-speed effort to convert society to carbon-free energy sources.)

Let's begin with two very helpful UN Food and Agriculture Organization reports: World agriculture: towards 2015/2030, and the sequel World Agriculture: Towards 2030/2050. What these reports do is basically look at projections for population and economic growth and then estimate how much food people would want in the future, and what quantity of agricultural commodities would be required to fulfill that demand. The first report focuses a lot more on the supply-side factors of how this could be done, while the second report extends the analysis out further in time but confines itself much more to demand side considerations.

The input assumptions about population and world GDP are slightly different than mine, but close enough that I am just going to adopt their food scenario wholesale, rather than trying to construct my own from first principles. The differences would be small - much smaller than the other uncertainties in the problem. Let me first summarize their scenario, and then we will start to explore the potential bottlenecks that might prevent achievement of this much food production. (However, I strongly encourage readers that care about where their food is going to be coming from in the future to take the time and read the FAO reports themselves.)

Let's start with a look at what the FAO scenario has for average nutrition. This next graph shows both history and projections to 2050 for daily dietary energy (in Kilocalories/day/person) in various regions of the world, as well as the global average. ...

Another way to try to get at the issue is to look at how current yields compare to the theoretical potential of photosynthesis. This is generally expressed as net primary productivity (NPP) - the amount of carbon that plants can fix, exclusive of that used to power their own respiration. The net primary productivity is the photosynthetic product that is available to be eaten by people and other animals, rot into the soil, etc. Here is a map of the fraction of net primary productivity appropriated by humans published by Haberl et al last year in the Proceedings of the National Academy of Sciences, which I take to be a decent representative of the state-of-the-art in this kind of calculation:

You might look at the red - 60%-80% appropriation of NPP in many of the world's key crop growing areas, and think there wasn't enough head room for another 50%+ increase in yield in those areas. However, it's important to understand exactly how the accounting in these calculations is done. Let's consider a piece of the US midwest that used to be tall-grass prairie and is now under corn. What Haberl et al would do is first use a vegetation model (specifically, this one) to establish that it would be a prairie there absent human intervention, and figure out how much carbon the prairie would have fixed as NPP. ...

The key things to note are these:

* Rates of soil production and erosion under native vegetation are roughly similar, suggesting soil depths are naturally in equilibrium.
* Rates of "agricultural" erosion are a couple of orders of magnitude higher, suggesting that ploughing is not a long-term proposition.
* Rates of "Conservation" erosion are roughly comparable to to natural erosion rates under native vegetation. This covers more sustainable management regimes such as terracing and no-till agriculture.

This suggests that the long-term sustainability of industrial agriculture requires the use of no-till farming systems in which ploughing is not done, crop residues are left on the field, and weeds are managed another way (primarily via herbicides today).

Fertilizer

The three major fertilizer nutrients applied in industrial agriculture are Nitrogen (N), Phosphorus (P), and Potassium (K). None appear to be a critical constraint on agriculture to the 2050 timeframe, though there are significant issues with nitrogen in the short term.

Nitrogen fertilizer is manufactured via the Haber-Bosch process in which nitrogen gas (which forms almost 80% of the atmosphere) is heated with hydrogen over an iron catalyst at high temperatures and pressures to form ammonia (NH3) which is subsequently reacted with other compounds to form urea, ammonium sulphate, and other compounds used as fertilizer. Presently, almost all the hydrogen input to this process is produced by steam reformation of natural gas, and this is the cause of the short term problem since natural gas supplies are problematic, and likely to worsen with both Europe and North America probably at or past peak natural gas. Fertilizer manufacture is exiting these regions and moving to the Middle East, Trinidad, and other places with more natural gas.

However, in the long term, there's no reason nitrogen fertilizer has to be made from natural gas. In my scenario in which energy production is dominated by renewable/nuclear electricity by 2050, the natural source of hydrogen for Haber-Bosch is by electrolyzing water. Producing nitrogen fertilizer is unproblematic as long as society has ample energy.

The reserves and reserve-base for phosphorus are enormous. According to the USGS, 2006 global production of phosphate rock was 145 million tons, while reserves were 18 billion tons, and the reserve base was 50 billion tons. For the 2050 timeframe, I consider reserve base to be the more appropriate number for the same reasons discussed under lithium. The reserve base for phosphate rock is 350 times larger than 2006 production, so there is no evidence of a problem at present.

Some bloggers are concerned that the Hubbert linearization suggests peak phosphorus has already past. However, Hubbert linearization is not very reliable if there is no independent evidence to suggest peak is at hand, due to the problem of dual peak structures giving rise to misleading linear regions (eg see the UK oil linearization). In this case, with enormous reserves, and stable phosphorus prices (they haven't varied outside the range of $27-$28/ton from 2002-2006), it seems very unlikely that phosphorus is in trouble. JD has made a similar point (snark warning).

Potassium comes from the mining of potash. The USGS estimates the global reserve base to be 550 times larger than current usage. So potassium is unlikely to limit civilization any time soon. ...

Shipping is extremely energy efficient - two orders of magnitude better per ton-mile than air freight. Thus, long-haul shipping of food will be cost effective long after oil has peaked. Ships can also be run on nuclear power, as the US navy has been demonstrating for decades.

In Conclusion

There seems to be reason for cautious optimism that if other global problems can be solved, food production will not be a critical constraint on civilization to 2050. If industrial agricultural yields maintain their historical trajectory, there will be enough food without needing much more land. In case yields fail to continue increasing, more land is potentially available globally, though likely of poor quality. Soil erosion is an important problem, but not a critical emergency, and can seemingly be solved permanently with no-till farming methods. Fertilizer does not appear to be seriously constrained in the long-term, though nitrogen fertilizer needs to be transitioned away from reliance on natural gas. Agriculture only needs a tiny fraction of global liquid fuel use to operate, and this can be maintained for a long time, since food production is a critical infrastructure.

However, if we were to keep growing the conversion of food into biofuels, all bets would be off.