Biofuels: Use With Caution

As Peak Oil looms over the horizon, the race to develop alternative transportation fuels is heating up.  A main contender for a replacement or at least a supplement is the general class of biofuels - liquid fuels made from live organic material.  This race has prompted much technical analysis and speculation on production processes for fuels like ethanol, methanol, bio-butanol and biodiesel.  While I was initially extremely enthusiastic about these developments, my position had gradually shifted over time.

I am now utterly opposed to biofuels from food sources in general, and corn ethanol and biodiesel made from soy or canola in particular..  My opposition has both technical and ethical foundations.  The technical objection is that  they return far too little net energy to make them a sustainable process in a period of overall energy decline.  My ethical objection is that they compete with food for land, fertilizer and water - all of which are currently under threat in both the developed and developing worlds.  These concerns overlap substantially: the low net energy of biofuels means that more and more fuel production will be required to replace declining supplies of petroleum fuels that have higher net energy, and any increase in fuel production disproportionately threatens food production as well as other aspects of the biosystem such as forest cover.

Obtaining biofuels from non food sources seems a reasonable approach, subject to certain caveats.  First, I think cellulosic ethanol and algal biodiesel are dead ends.  Because the processes have not yet been commercialized, the technical questions of EROEI (Energy Returned on Energy Invested, or net energy) and the need for fossil fuel inputs to the manufacturing process remain unknown.  Second, even if we do get those processes sorted out (and that is far from a sure thing at this point), they are likely to require such a high level of technology as to make them unsustainable in a time of overall energy decline. Third, if we try to produce them on a scale large enough to offset the decline in the world's petroleum supply, we rink further topsoil depletion, as material that is normally returned to the soil is hauled away and converted into fuel.

I do like the various biomass gasification proposals that are being worked on - processes that are a minor elaboration of charcoal-making have a higher probability of being maintainable over the long term.  Terra Preta is one such approach that has caught my attention, because it has the ability to address three major concerns of fuel, food scarcity and carbon sequestration using a single relatively low-tech process.  If it can be commercialized and retain its positive attributes in the face of hard reality, it could be very useful over the medium and long terms.

Issues of Scale
How much oil-equivalent biofuel could we actually make if we turned all the world's major grain and oilseed crops into automobile fuel, leaving none whatever for food?  In other words, what are humanity's relative energy requirements for food and transportation?  Would their scales of use allow us to easily and effectively substitute a portion of our food energy use for transportation fuel?

To answer this question I considered ethanol from corn, wheat, rice, sugar cane and sugar beets, and biodiesel from soybeans and rapeseed (canola), plus palm&sunflower oils.  In each case I converted the entire world crop into fuel, discounted the ethanol by 1/3 for its lower energy content, and converted the annual production in litres to the oil-industry standard measure of millions of barrels of oil equivalent per day.  Here are the results:

Ethanol

Corn:
World crop (Million tonnes): 700
Litres per tonne: 400
MBOE/day: 3.2

Wheat:
World crop (Million tonnes): 600
Litres per tonne: 370
MBOE/day: 2.5

Rice:
World crop (Million tonnes): 600
Litres per tonne: 400
MBOE/day: 2.7

Sugar Cane:
World crop (Million tonnes): 1324
Litres per tonne: 100
MBOE/day: 2.5

Sugar Beets:
World crop (Million tonnes): 250
Litres per tonne: 108
MBOE/day: 0.3

Biodiesel

Soybeans:
World crop (Million tonnes): 270
Litres per tonne: 140
MBOE/day: 0.5

Rapeseed (Canola):
World crop (Million tonnes): 55
Litres per tonne: 400
MBOE/day: 0.4

Palm&Sunflower oils:
World crop (Million tonnes): 42
Litres per tonne: 900
MBOE/day: 0.7

The total from turning virtually all of our food into fuel is 12.8 MBOE/day - only 15% of the current world oil consumption of  84 million barrels per day.  To make matters worse, it takes a lot more energy to make biofuels than it does to simply pump oil from the ground and refine it.  A rough estimate is that it takes at least twice as much.  Accounting for this necessary energy outlay reduces the available net energy of our biofuels to less than 8% of the world's oil consumption.

I'm not saying we should turn all our food into fuel. Nobody is saying that, or claiming that biofuels can replace all petroleum. What people are hoping is that biofuels will be able to replace some useful fraction of petroleum. This calculation shows that to be a forlorn hope.  We are being systematically oversold on the potential utility of biofuels, and this is creating unreasonable expectations of the degree to which biofuels will be able to replace petroleum.  The hope is that such substitution will address both climate change and dwindling post-peak fuel supplies.

Every percent of petroleum we replace by crop-sourced biofuels implies a 12%+ reduction in the food supply. While this might be acceptable in very small, localized applications, it will not (must not) be part of the global solution set if we begin to see multi-percent declines in fossil fuels. Trying to make it play such a role would amount to doing what some farmers were forced to do in the depths of the Great Depression:  burn their seed corn for heat.  We need to be aware that at some point in the deployment of biofuels we might cross the line from "small-scale petroleum extender" to "burning the seed corn".  We need to be aware of the issues surrounding biofuels so we can resist crossing that line, because the pressure to cross it will become enormous.

This is one of the reasons why using crop-sourced biofuels for transportation is such a horrifically bad idea.  We strip mine our top soil, we deplete our water tables, we starve everyone and we still have only an 8% solution.  We all - individuals, countries and our whole civilization - need to be very, very cautious in promoting the use of biofuels, lest our thirst for transportation fuel overrun our common sense..  And we must always remember to crunch the numbers.
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© Copyright 2007, Paul Chefurka

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