P.O.V.: Food versus fuel

P.O.V.: Food versus fuel McGill University

| Skip to search Skip to navigation Skip to page content

User Tools (skip):

Sign in | Friday, July 11, 2014
Sister Sites: McGill website | myMcGill

McGill Reporter
May 15, 2008 - Volume 40 Number 17
| Help
Page Options (skip): Larger
Home > McGill Reporter > Volume 40: 2007-2008 > May 15, 2008 > P.O.V.: Food versus fuel

P.O.V.

Food versus fuel

Food versus fuel

Three of the great challenges for the 21st century will be energy, climate change and security of the food supply. Biofuels are where these overlap.

As the extent of the global food crisis has become apparent, biofulels have suddenly become the unwanted guest at the party. And, certainly, biofuels made from cereal grains that might otherwise feed hungry people, aren't the best way to cope with dwindling energy supplies or the need to curb greenhouse gases.

But not all biofuels are created equal, so we should not rush to write them out of our energy repertoire just yet. Let me explain. Biofuels come in a number of forms. There can be simple direct combustion of biomass for energy and, in the long run, this may be the most efficient approach. There are numerous other possibilities, such as fermentation of sugars (derived from free sugars, starch or cellulose) into ethanol or butanol, the conversion of plant or animal lipids into biodiesel, the production of bio-methane from waste materials or the conversion of biomass into hydrogen. The use of waste biomass is always a good approach as it converts a waste stream into a resource stream.

There are a number of potential benefits to biofuels, notably the production of a renewable energy source and a net reduction in CO2 emissions, compared with fossil fuels. However, the crop plants we initially turned to for biofuels were developed as food crops, with little consideration for energy or greenhouse gas balance. Both are strongly affected by nitrogen fertilizer as it takes a lot of fossil fuel (usually natural gas) energy to produce it and its use promotes nitrous oxide emissions. Nitrous oxide is, like CO2, a greenhouse gas, but it is 310 times more effective at heat trapping than CO2.

The federal government has mandated five per cent ethanol in gasoline by 2010 and two per cent biodiesel by 2012, but given all that needs to be done to reach these goals, we are unlikely to meet them. In addition, Canada is a major producer of fossil fuels and so needs methods to offset greenhouse gas emissions.

How do biofuels differ? The energy balance (the amount of biofuel energy output divided by the amount of fossil fuel energy input) varies substantially. The energy balance for corn-based ethanol/butanol is generally given to be in the range of 1.3-1.4, because of the large amount of energy-intensive nitrogen fertilizer required as well as the amount of energy needed for the distillation process. For biodiesel, the values are often about 3; this is better than corn-ethanol/butanol because some of the oil-producing crops are legumes (soybean) and don't require nitrogen fertilizer, and because the process to convert plant oils into biodiesel is less energy demanding than ethanol production.

For sugar cane ethanol/butanol, the value is generally given to be about 8, because associated bacteria supplies the crop with nitrogen and because the biomass remaining after sugar extraction is burned as an energy source for distillation.

But the newer process of developing ethanol/butanol from cellulosic material (fast-growing grasses and trees and forestry waste) produces values that range from 2-40, with most above 10. These crops, which require little nitrogen fertilizer, may offer the best long-term prospects of all. They can be produced on less-than-prime agricultural land, so would compete minimally with food crops.

Global grain stores have been in decline for the last decade. This has been driven, in large measure, by increasing populations and increasing per person consumption. The increasing consumption has been strongly affected by increasing meat consumption, particularly in China. There are clear inefficiencies and energy losses associated with going from one trophic level to another (in this case plants to animals, where it can take 2-10 kilograms of plant material to make 1 kilogram of meat, depending on the livestock species and growth conditions). Global grain stores have slid fairly steadily from about 130 days in the 1980s to about 40 days now.

The diversion of corn and other food crops into biofuel production has coincided with roughly a doubling of the price of corn, rice and other food commodities over the last 12-18 months. This has even affected the biofuels industry; the sharp rise in the price of corn has halted the construction of some corn-ethanol plants, as the feedstock material (corn) is now too expensive for the plant to be profitable. Adding biofuels onto current crop production capacity and crop stores, along with a sudden increase in energy costs, has tripped this price rise. As often happens when it becomes clear that a commodity has reached a critically limiting level, speculators have entered the fray. This has steepened the rise in food prices.

A gradual rise might have been useful in many ways: allowing restoration of viability to the agricultural sectors of many nations, reducing the pressure for subsidies, and even causing calories to be somewhat more expensive leading to reduced obesity in western countries. However, for the poor of developing nations, and especially the urban poor, things will be much more difficult in the near future.

If we are to successfully tackle the challenges facing us at the start of the 21st century, we will need to increase levels of agricultural training and research to improve food production everywhere, and shift to second-generation biofuel crops (non-food crops) so we can reduce greenhouse gases without taking food off the table.

We can produce biofuels that won't exacerbate the global food crisis. We should be working as hard as we can right now to do just that.

Dr. Donald Smith is a James McGill Professor, the Chair of McGill University Department of Plant Science, and the Head of Canada's Green Crop Network.

view sidebar content | back to top of page

Search